DOCTORAL DISSERTATION SERIES

n n r 7H£ fA bdLO B O Ll M LM & U M i O f
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AUTHOR. M mtm smm
UNIVERSITY.

DEGREE

MltH' STfifi CiLitdate
PUBLICATION NO._

Jiil

3

y UNIVERSITY MICROFILMS
AKIKI A D R f l D

.

MirUlftAM

THE

FAT-GLOBULE

MEMBRANE

AND SOME

OF

RELATED

HOMOGENIZED MILK

FACTORS

By
JAY

ROBERT

BRUNNER

A THESIS
S u b m i tt e d
State

to the
College

in p a r t i a l

School

of G r a d u a t e

of A g r i c u l t u r e
fulfillment
for

the

DOCTOR OF

and Applied

of the

degree

Studies

Science

requirem ents

of

PHILOSOPHY

Department

of Michigan

of D a i r y

ACKNOWLEDGMENTS

The
to Dr.

author wishes

G. M.

Trout,

to e x p r e s s

his

assistance

a p p r e c i a ti o n

Duncan,

A s s o c ia t e

istry,

for

his

for

service

much of the

essential

The
Professor

w riter

i s,

of Dairying

a lso

study and

manuscript.

The

extended to C.

of A g r i c u l t u r a l

W.

Ch e m ­
of this

microbiological analyses.

als o

to P .

due

to Dr.

H. A.

and to Dr.

G.

S.

Lil—

Djang

Coleman f o r the

Dolores

and to o t h e r s

m o s t gra t e fu l

and Head of the

study p o s s i b l e .

of this

his

Abbott for

who have

helped

work p o s s i b l e .

indeed,

College

for

in the p r e p a r a t i o n

to M r s .

work;

this

ment Station f o r providing
this

is

the

is

a n alyses;

art

of this

of C h e m i s t r y ,

re n d e r e d ;

to make

to Michigan State

make

for

acknowledgment

photographic

course

(Research)

arranging

electrophoretic

in many ways

the

and a s s i s t a n c e

Assistant P ro fe s so r

the

w riter

Professor

m a n u s c r i p t and f o r

levik,

of the

advice

G r a t e fu l

during

in the p r e p a r a t i o n

sincere

deepest appreciation

R e s e a r c h P r o f e s s o r of Dairying,

e n c o u r a g em e n t and i n t e r e s t
f or

his

to Dr.

Earl

Da iry D e p a r t m e n t ,

and the Michigan A g r i c u l t u r e
the funds

Weaver,

and f a c i l i t i e s

and

Experi­

n e c e s s a r y to

TABLE

OF

CONTENTS

Page
I N T R O D U C T I O N ....................................................................................................................

1

SECTION I
The

E f f e c t of V a r i a t i o n s

Procedure

and in the

in the

Composition,

E f f i c ie n c y of Ho m o ge ni z at io n
ment

of High

H o m o ge ni z at io n
of Milk on the

and on the

Develop­

V i s c o s i t y .........................................................................................

REVIEW

OF

4

L I T E R A T U R E ............................................

5

V i s c o s i t y .............................................................................................................................

5

Definition of
Viscosity

of Milk,

Sk im m i lk
Some

F actors

Milk

Viscosity

and

.............................................................

Ho mo ge ni z ed

Milk,

W h e y ...............................................................

Affecting

the

Viscosity

and R e l a t e d P r o d u c t s

Pasteurization

5

5

of

....................................

and h e a t t r e a t m e n t

.

.

.

9
9

Ho m o g e n i z a t io n p r o c e d u r e s ....................................

11

Variations

14

F at—
globule
Theories

in the

c lu ste rin g

Proposed

G ravitation

c o m p o s i t i o n of m i l k

to

of f a t

.

E x pl a in

.

.

.

.

Clustering

.

.

.
.

.

16
.

21

g l o b u l e s .............................................

21

iv
Page
E lectrostatic

charge

......................................................................

glo bu le s
Interfacial

on fat

tension

Stickiness

22

...............................................................

23

......................................................

24

A g g l u t i n a t i o n .....................................................
H o m o g e n i z a t io n

E f f i c i e n c y .......................................................................

27

of H o m o g e n i z a t io n

.

27

M e a s u r e m e n t ................................................................................

28

F at—
globule

28

Expression
Reported

Values

and Methods

F actors

Influencing

ef f ic ie n cy
the

Ho m o g e n i z a t io n
Summary

of the

EX PE R I M E N T A L
.

Influence

.

.

tests

.

.

.

.

30

of

.......................................................................

32

Review of L i t e r a t u r e ....................................

34

.

...............................................................

.

37
40

of Ho m o ge ni z at io n

Double—
s ta ge

.

of

Efficiency

PROCEDURE
.

E f f i c ie n c y

s i z e .......................................................................

H o m o g e n i z at io n

RESULTS

25

Procedures

Ho m o ge ni z at io n

.

.

.

.

40

....................................

42

C o m p o s i t i o n ....................................................................................................................

42

D I S C U S S I O N .............................................................................................................................

56

V i s c o s i t y .............................................................................................................................

56

H o m o g e n i z a t io n E f f i c i e n c y

61

.

V

Page
SUMMARY OF

SECTION I

................................................................................

65

SECTION II
The

Relationship

Fat

Existing

the

Ten den cy

Viscosity

at

Between the

H o m o ge ni z at io n

T o w a r d the

of G l o b u l a r

Tem peratures

and

D e v e lo p m en t of High
......................................................

66

L I T E R A T U R E ................................................................................

67

in Ho m o g e n i z e d

REVIEW OF

Equilibria

EXPERIMENTAL

Milk

PROCEDURE

...............................................................

71

R E S U L T S .....................................................................................................................................

77

D I S C U S S I O N ...............................................................................

86

SUMMARY OF

90

SECTION I I ............................................

SECTION III
A Prelim in ary
Manifested
Membrane
S u r fa c e

in the

Nature

M aterials

of the

mogenization
REVIEW OF
Nature

R e p o r t on Some

Fat

of the

Closely

Globule

as

of the

Changes

Proteinaceous

Associated

with the

a R e s u l t of Ho­

............................................................................................................................

91

L I T E R A T U R E ................................................................................

92

of the

Normal

Photographic

brane

.

92

M e m b r a n e ......................................................

92

C haracteristics

F at—
globule
C o m p o s i ti o n

Fat-g lo bu le

of the

M em brane

.

of the

Fat-globule

Mem­

of Nonhomogenized Milk

.

.

.

.

93

vi
Page
Lacto-fibrin

and haptogenic

m e m b r a n e .................................................................................

93

P r o t e i n s ..................................................................................................

94

Ph ospho lipid-protein

96

complex

..

.

.

.

Phospholipid-p rote in -g ly ce rid e
c o m p le x

•.
........................................................................

102

F l a v o p r o t e i n .................................................................................

102

Copper—
containing

103

Serum

proteins

proteins

.

.

.

.

A g g l u t i n i n ................................................................................................
Carotenoids

103
104

Phosphatases

104

Changes

From

and l i p a s e s ...................................................

c o m m e n t s ...............................................................

in the

Fat

Globule

in the

Ph ysical

Com po ne nts

105

R e s u l ti n g
.■ ................................................

H o m o ge ni zat io n

Changes
Milk

................................................................................

103

L e u c o c y t e s ...............................................................................................

General
Some

100

Dimensions.

.

.

.

105
105

A d s o r b e d on the

I n c r e a s e d Surface

of Ho mo ge ni z ed

F a t ..........................................................................................................................

106

Phospholipids

106

.....................................................................

P r o t e i n s .......................................................................................
M i n o r - p r o t e i n f r a c t i o n ............................................................

107
107

V ll

Page
Manifestations
Various

of the A d s o r p t i o n

Milk

Surface

C o m po ne nt s

of

on the

of Ho m o g e n i z e d F a t ....................................

108

L i p o l y s i s ..................................................................................................

108

O x i d a t i o n ..................................................................................................

108

m o b i l i t y ......................................................

109

Electrokinetic
Surface

tension

Protein

stability

Methods

........................................................................
*

U s e d to Study the

..........................................................

Protein

b rane

Respective

Fat-globule

A n a l y s i s ........................................................................

Amino Ac i ds

of the

Nature

the
EX PE R I M E N T A L

113

C h a r a c t e r i s t i c s ....................................

114

Review of L i t e r a t u r e ....................................

118

Fat-globule

of H o m o ge ni z at io n

Methods

Ill

114

of the

the

Ill

........................................................................

E lectropho retic

Ef fe c t

Mem­

D i s t r i b u t i o n ........................................................................

Elem entary

Summary

Milk

P r o t e i n s .........................................................................................

N itrogen

110

Co mponents

of Nonh om og en ize d and H o m o ge ni zed
and T h e i r

109

C haracteristics
A v a il abl e f o r
Fat-g lo bu le

Membrane

of M
the

.

118

i l k ....................................

119

on Some

Analysis

.

.

of

of

M e m b r a n e .............................................

PRO CEDURE

...............................................................

120
121

V lll

Page
Preparation

and D e t e r m i n a t i o n of N i t r o g e n

Fractions
P reparation

and M i n e r a l s

from

e ni z ed M
Preparation

i l k ........................................

and

Washed C r e a m

of the

and

Washed—

Nonhomogenized

and

........................................................

Fat-globule

124

Membrane

P r o te i n s for E le c tro p h o re tic , Microbio­
lo g ic a l and G e n e r a l C h a r a c t e r i z a t i o n

.

125

............................................................................................................................

134

N i t r o g e n D i s t r i b u t i o n in Homogenized
Distribution
M inerals

of Milk Solids,

Nitrogen

in Skimm ilk

and C r e a m

Nonhomogenized
Distribution

Milk

and

.

.

.

.

.

134

.

.

.

135

and

and Homogenized

of Milk Solids

Washed C r e a m

from
Milk

and N i t ro g e n

Washed—
cream

in

Serum

f r o m Nonhomogenized and Homogenized
M i l k ...........................................................................................................................
Some

C haracteristics

Proteins

Isolated

and Homogenized
Some

E l ec tro ph ore tic

Fat-m em brane
Some

123

D e t e r m i n a t i o n of Milk Solids

Serum from

P reparation

in S k im m i lk and

i l k ..................................................................................................

Ho m ogenized Milk

RESULTS

121

Nonhomogenized and Homog­

and N i t r o g e n in
cream

M

and D e t e r m i n a t i o n of Milk Solids,

Nitrogen
Cream

inHomogenized

of F a t —
membrane
from
M

Nonhomogenized

i l k ..............................................................

Characteristics

C haracteristics

141

of the

P r o t e i n s ............................................................

M i c r o b i o l o g ic a l

Fat-m em brane

138

141

of the

P r o t e i n s ...........................................................

143

ix
Page
D I S C U S S I O N ............................................................................................................................

179

G e n e r a l ............................................................................................................................

179

Discussion

180

of E x p e r i m e n t a l

Influence

R e s u l t s ....................................

of Homogenization

N i t ro g e n
Influence

on the

D i s t r i b u t i o n in Milk

of Homogenization

Distribution
in C r e a m

,

180

on the

of Milk Components

and S k i m m i l k .............................................

182

S o l i d s - n o t - f a t ................................................................................

182

N i t r o g e n d i s t r i b u t i o n ..............................................................

183

M inerals

184

..............................................................

Influence of Homogenization on the
D i s t r i b u t i o n of Milk Components
in Washed
cream
Influence

Cream

Concentration
N i t ro g e n

from

Chemical

istics

Washings

of F a t ,

Total—
protein

M i l k .......................................................................

and P h y s i c a l

E lec tro ph o re tic

Proteins
patterns

186

C haracter­
P roteins

C haracteristics

Fat-m em brane

buffer

in

Homogenized and Non­

of F a t - m e m b r a n e

E le ctro ph ore tic

185

on the

and Li po id P h o s p h o r u s

h omogenized
Some

Washed-

S e r u m ................................................................................

of S u c c e s s i v e

Cream

and

.

.

.

187

.............................................

189

of the

in v a r i o u s

m e d i a .......................................................................

189

X

Page
Mobility—
pH r e l a t i o n s h i p s

of v a r i o u s

m e m b r a n e - p r o t e i n s .....................................................
Influence

of t e m p e r a t u r e

electrophoretic

on the

mobilities

of

m e m b r a n e - p r o t e i n s .....................................................
Influence

of c o n c e n t r a t i o n

electrophoretic

191

193

on the

mobility of

m e m b r a n e - p r o t e i n s .....................................................

194

Amino Acid A s s a y of F a t - m e m b r a n e
P r o t e i n s .....................................................................
SUMMARY

FOR SECTION III

GENERAL

SUMMARY AND CONCLUSIONS

The Influence

.

of V a r i a ti o n s

enization P r o c e d u r e s

.

195

.....................................................

in the

and the

.

.

.

.

199
202

Homog­
Compo­

sition of Milk on the Efficiency of
Homogenization and the

Vis co si t y of

M i l k ..........................................................................................................................
The

Influence

of the

F a t on the
and the
Some

State

of the

Efficiency of Homogenization

Vis co sity

C haracteristics

Proteins

Physical
of M

i l k .....................................................20 3

of the F a t - m e m b r a n e

of Nonhomogenized and Ho­

mogenized M i l k .......................................................................................
LITERATURE

202

C I T E D ................................................................................................

204
207

LIST OF

TABLES

Page

TABLE
1.

The

influence of v ar i ou s

efficiency of homogenization and on

the

v i s c o s i t y of milk homogenized at

ization
The

on

the

2,500 pounds p r e s s u r e

2.

tem peratures

after p a s te u r ­

..............................................................................

influence of v a r i o u s p r e s s u r e s

45

on the

efficiency of homogenization and on

3.

The

the

v is co s it y of milk homogenized at

80

F.

a f t e r p a s t e u r i z a t i o n ...........................................

influence
the

of v ar i ou s

6.6 p e r

v is co s it y

of milk

tion at
s torage

145

F.

at 45

influence

The

3,500

following p a s t e u r i z a ­
and a f t e r

F.

.

.

a 20-hour
..................................................

47

of v ar i ou s t e m p e r a t u r e s

and p r e s s u r e s
the

containing

cent fat homogenized at

pounds p r e s s u r e

The

on

efficiency of homogenization and

on the

4.

tem peratures

46

of homogenization on

efficiency of homogenization and

the v is c o s it y

of milk

fat and

per

11.01

influence

of

and p r e s s u r e s

(2.8 p e r

cent total

v arious

cent

solids)

.

.

48

.

.

.

49

temperatures

of homogenization on

the

efficiency of homogenization and

the

v is co s it y

fat and

.

of milk (4.0 p e r

12.56 p e r

cent total

cent

solids)

X ll

TABLE
6.

Page
The

influence

of v a r i o u s

of h o m o g e n i z a t i o n

on the

efficiency

of h o m o g e n i z a t i o n

and the

and
The

of milk

13.10

influence

cent f a t

t otal solids)

of v a r i o u s

.

tem peratures

.

of h o m o g e n i z a t i o n

on the

e f f ic ie n c y

of h o m o g e n i z a t i o n

and the

of mi lk

15.50

(6.2 p e r

p e r cent

influence

solids—
n ot —
f a t on the
justed

milk

.

50

.

51

cent f at

t otal solids)

of v a r i a t i o n s

.

and

pressures

and
The

(4.4 p e r

p e r c e nt

viscosity

8.

and

pressures
v isco sity

7.

tem peratures

.

.

.

in f a t and

viscosity

homogenized

at

of a d ­

various

p r e s s u r e s ..................................................................................................
9.

The

percentage
500-gram

at

of milk

(6.6 p e r

different p ro c e s s in g

e ff e c t of h o m o g e n i z a t i o n
pressures
in

in a
tem ­

.....................................................................................................

peratu res
The

so l id ifi ed f a t

sample

c e n t fat)

10.

of

on the

at

nitrogen

m i lk p a s t e u r i z e d

at

52

80

various

distribution

143

F.

for

30

m i n u t e s ...................................................................................................
11.

Distribution
cream

and

enized
12.

and

enized

solids—
not-fat

skimmilk f r o m

the

in c r e a m

m i l k .............................

skimmilk from

of a sh ,
and

calcium

148

in

n on homog­
m i l k .............................

149

and p h o s p h o r u s

skim milk f ro m

and h o m o g e n i z e d

in

nonhomog­

n itrogen f ra c tio n s

and h o m o g e n i z e d

Distribution
enized

and

and h o m o g e n i z ed

D i s t r i b u t i o n of
cream

13.

of f a t

147

nonhomog­

m i l k .............................

151

X I 11

TABLE
14.

Page
The

effect of s u c c e s s i v e
re s e p a r a t i o n s
fat,

dilutions

on the

and

concentration

of

n i t r o g e n and lipoid pho sp ho ru s

in c r e a m

from

nonhomogenized and

homogenized m i l k ......................................................................
15.

D i s tri b u ti o n

of f at

wa s hed c r e a m

and

solids-not-fat

153

in

and wa s he d —
cream

serum

of nonhomogenized and homogenized
m i l k ..................................................................................................................
16.

D i s tribution of the n i t r o g e n f r a c t i o n s
the

washed c r e a m

serum

from

in

and w a s h e d - c r e a m

nonhomogenized and ho­

m o genized m i l k ...............................................................................
17.

Some

characteristics

proteins

D i s ta n c e s

isolated from

m i g r a t e d by the

p r o t e i n components
and the

effects

nonhomogenized

in v a r i o u s

19.

ethanol

and

of m e m b r a n e -

................................................................................................

Mobility of peaks
pattern

buffers

p r o d u c e d on m i g r a t i o n

c o n c en t r a t i o n

proteins

in the

as

protein

shown in F i g u r e s

15

to 20
20.

The

161

effect of t e m p e r a t u r e
treatm ent

on the

of ethanol

electrophoretic

bility of the f a t - m e m b r a n e
components
(pH 6.5)

159

electrophoretic

of the f a t - m e m b r a n e

components

158

fat-m embrane

by t r e a t m e n t with w a r m
by the

156

of f a t - m e m b r a n e

and homogenized m i l k .............................................................
18.

155

in phosphate

mo­

protein

buffer
163

xiv
Pa g e

TABLE

21.

The

effect of c o n c e n t r a t i o n of the f a t membrane

p r o t e i n components

m o genized milk on the
mobility in phosphate

22.

A c o m p a r i s o n of
obtained f o r
with the

some
the

in ho­

electrophoretic

buffer

amino

(pH 6.5)

a cid values

fat-m em brane

proteins

m inor—
protein fraction,

lac t al b u m i n ,

lactoglobulin,

casein,

pseudoglob­

ulin and e u g l o b u l i n ....................................................

23.

The

number

of amino

fa t-m e m b ra n e

acid

proteins

cold ethanol t r e a t m e n t

164

residues

165

in the

p r e p a r e d by
.

.

166

LIST O F

FIGURES

FIG U R E
1.

Page
The

e f f e c t of

single-

and d o u b l e - s t a g e

h o m o g e n i z a t i o n on the v i s c o s i t y
high-fat
enized
2.

The

milk

at

80°

influence
pressures
the

(6.6 p e r cent)
F.

data

maintained
of m i l k

(SERIES A)

on m i lk

The

influence
the

80

F.

c ontaining

11 p e r

cent

) ..................................

(SERIES B

maintained

at

80

F.

containing

c e n t f a t p lu s

various

amounts

fat

(SERIES

on m i l k

(SERIES

Schematic
fat

D

6 per

showing

3 per

of

solids—

cent

how the

55

dis­

of h o m o g e n i z e d

a c co u n t f o r

viscosity

an

in­

of h o m o g e n i z e d

...........................................................................................................

5.

C alo rim etric

6.

T herm al-correction
m etric

on

) .....................................................................

in p a r t ,

in the

milk

54

and c o r r e s p o n d i n g

and c l u s t e r i n g

could,

crease

C)

containing

d ra w in g

persion

am o u n t s

and c o r r e s p o n d i n g

of m i l k

data

8 per

various

viscosity

not—
fat

on

of d i f f e r e n t hom o ge ni z in g

pressures

4.

at

containing

solids—
not—
fat
3.

53

solids—
not—
f a t p lu s

of f a t

homog­

of d i f f e r e n t h omogenizing

viscosity

cent

of

assembly

used

curve

assembly

used

in this

for

the

in t h i s

study

64

.

.

75

,

.

76

calori­
study

.

xvi
FIG U R E
7.

Page
Shows

the

effect

of the

tem perature

homogenization on the
of v i s c o s i t y
was

development

when 6.6 p e r

homogenized

at

of

cent

milk

3,500 pounds

p r e s s u r e .......................................................................................................
8.

Shows

the p e r c e n t a g e

of solidified fat

obtained at v a r i o u s
tem peratures
milk)
9.

The

of

milk

cent)

in h ig h-fat

(6.6

homogenized following p a s ­
at t e m p e r a t u r e s

ranging

140° to 60° F .......................................................................

relation

between

the d e g r e e

of

development

of v i s c o s i t y

milk

in high-fat

(6.6 p e r

homogenized at t e m p e r a t u r e s

ranging

from

a 20- ho ur
s he e t

60

to

storage

140

F.

following

p e r i o d at 45

showing the p r o c e d u r e s

F.

.

of fat-globule

membrane

.

proteins

.

effect of s u c c e s s i v e

.

.

.

washings

.

.

.

.

.

.

effect of s u c c e s s i v e
total n it r o g e n

133

on the

f r o m nonhomog­

enized and homogenized m i l k ...................................
The

85

fol­

lowed in the p r e p a r a t i o n

f at content of c r e a m

13.

84

solid­

ification of f at and the

Flow

83

solid­

of v i s c o s i t y

The

The

degree

development

cent)

12.

cent f a t in the

ification of fat and the

from

11.

(6.6 p e r

................................................................................................................

teurization

10.

homogenizing

r e l a t i o n between the

per

82

washings

content of c r e a m

167

on the
from

nonhomogenized and homogenized
m i l k .................................................................................................................

168

X V I1

FIG U R E
14.

Page
The

effect of s u c c e s s i v e
lipoid p h o sp ho ru s
from

washings

on the

content of c r e a m

nonhomogenized and homogenized

m i l k .......................................................................................................................
15.

Electrophoretic
p roteins
milk

patterns

of f a t - m e m b r a n e

isolated from

nonhomogenized

and homogenized milk

persed
buffer

169

and d i s ­

in g l y c i n e - h y d r o c h l o r i c
at pH 1.5 and ionic

acid

strength

of 0.1
16.

Electrophoretic
proteins

patterns

of f a t - m e m b r a n e

i s o l a t e d f r o m nonhomogenized

milk and homogenized milk and d i s ­
p e r s e d in a c e t a t e buffer at pH 3.0 and
s t r e n g t h of 0 . 1 .............................................................

ionic
17.

Electrophoretic
proteins
milk

of f a t - m e m b r a n e

isolated from

and homogenized

persed

in phosphate

and ionic
18.

patterns

proteins

patterns

nonhomogenized
milk and d i s ­

buffer

s t r e n g t h of

Electrophoretic

172

of f a t - m e m b r a n e

i s o l a t e d f r o m nonhomogenized
in v e r o n a l —
citrate

pH 8.0 and ionic
19.

at pH 6.5

0 . 1 ....................................................

milk and homogenized milk
persed

171

and d i s ­

buffer

at
.

173

0 . 1 .................................................................................................................

174

Electrophoretic
proteins
milk

s t r e n g t h of 0.09

patterns

buffer

isolated f ro m

.

nonhomogenized
and d i s ­

in a m m o n i a —
h y d ro c h l o r i c
at pH 9.0

.

of f a t - m e m b r a n e

and homogenized milk

persed

.

and ionic

acid

s t r e n g t h of

XV111

FIG U R E
20.

Page
E lectropho retic
proteins
mi lk
a t pH

isolated from

and

10.8 and ionic

dis­

buffer

strength

of 0.1

.

.

m e d i a ................................................................................

E lectropho retic
m i lk
the

.

175

.

176

milk

showing

with both cold

patterns

showing

in p h o s p h a t e

the

on the
buffer

homogenized
e ff e c t

of p r o t e i n

resulting p atte rn s
a t pH 6.5 and

s t r e n g t h of 0 . 1 ...............................................................

pH—
mobility
p on ents

curves
of the

for

the

m ajor

pH-mobility
p on en ts

curves
of the

178

com­

nonhomogenized—
milk

m e m b r a n e - p r o t e i n s ........................................................................
25.

177

of f a t - m e m b r a n e

isolated from

and

and

e t h a n o l ........................................................................

concen tratio n
ionic

n o n h o m o g e n iz e d

of t r e a t m e n t

Electropho retic
proteins

.

of f a t - m e m b r a n e

and h o m o g e n i z e d

effect

mi lk

patterns

iso la te d f r o m

and w a r m

24.

milk

in v e r o n a l —
e t h y l a m in e

proteins

23.

nonhomogenized

C o m p o s i t e of e l e c t r o p h o r e t i c p a t t e r n s of
f a t - m e m b r a n e p r o t e i n s in v a r i o u s buf­
fer

22.

of f a t - m e m b r a n e

and h o m o g e n i z e d

persed

21.

patterns

for

the

m ajor

197

com­

homogenized—
milk

m em brane-proteins

.

.

198

INTRODUCTION

C ertain

characteristic

homogenization.
procedures,
its
is

When

however,

d esirability
not

carefu lly

viscosity,
cooking

peratures

the

(80

o

factors

believed

viscosity
v aria tio ns

to the
The

a

or

of

at

sharp

associated

presence

45

or

clusters

a v a i la b l e

information

not

consists

in the

vis­

which co n ti n u e d to
o

F.

Some

of the

occurrence
of the

in—

other

of a high

m i lk

of f a t g l o bu le s

and

due,

pos­

the

nature

m aterial.

e x t e n t to which h o m o g e n i z a t i o n
is

established

m i l k wh ich c o n t r i b u t e d to

of p r o t e i n a c e o u s

m em brane

high

when u s e d f o r

increase

with the

of the

as

r e l a t i v e l y low t e m -

in the p r o c e s s i n g

composition

of c l u m p s

at

enha nc e

such

research

of m i l k

s to rag e

changes

curdling

E arlier

rather

a l t e r e d by

recomm ended

qualities,

homogenized milk,

variations

of the f a t - g l o b u l e
the

caused

to be

in the

formation

in f l a v o r

are

homogenization p r o c e s s

undesirable

manifest.

72 h o u r s

were

of t h e s e

If the

homogenization

of the f r e s h l y
up to

sibly,

are

F.)

crease

the

defects

of m i l k

h o m o g e n i z e d by

m ajority

controlled,

various

that

the

is

a beverage.

purposes,

the f a c t

cosity

as

m i lk

properties

modifies

clearly

p rim arily

understood,

because

of c o n j e c t u r e s

and

2

postulations
c ha n g e s
tion.

proposed

that

are

There

is

to

a id in the

known to o c c u r
no c l e a r - c u t

composition o r

the

fat-m em brane

m aterial

the

characteristic

properties

tal

to f oc u s

nature

duced
the

of the

stability

reduction

h om o ge ni z ed ,
to

develop

only

composition
rounding

(c)

ous

factors

and to

curd

the

type

determ ine,

fat-globule

m aterial
m i lk

insofar

m embrane

and

in

A few of

flavors

which have

(a)

the

re­

to high t e m p e r a t u r e s ,
that

suscep tibility
and

(d)

has

been

(b)

e f f ic ie n tly

of h o m o g e n i z e d

the

retardation

in h o m o g e n i z e d

observations

m i lk .

of the

These

inform atio n concerning

homogenized

investigation

has

m i lk

which point to the

of the f a t - g l o b u l e

esp ec ia lly

to the

which o c c u r

include:

of m i l k

of obtaining f u n d a m e n t a l

related

changes

concerning

on the f u n d a m e n ­

reported

o b j e c t of t h i s

evi dence

of i n v e s t i g a t o r s

of o xi dation

and

r e s u l t of h o m o g e n i z a ­

milk

increased

and p r o p e r t i e s

of the

of h o m o g e n i z e d

tension

solar—
activated

the

s ome

to h o m o g e n i z a t i o n .

fat-m em brane

in the

m i lk f a t

The

of the

due

attention

a few of the

importance

nature

of h o m o g e n i z e d

copper-induced
are

the

as

experim ental

the

served

the

e x p l a n a t i o n of

membrane

the

sur­

m i lk f at.

b e e n to

study

vari­

development

of high v i s c o s i t y

in mi lk

as

the

normal

the

possible,
influence

nature

of the

of h o m o g e n i z a t i o n

on

3
the fat-globule

membrane.

ity in the p r e s e n t a t i o n ,
independent
tors

sections.

which influence

enization

efficiency)

composition

of the

For

the

the

sake

investigation

Section I is

milk a r e

varied.

i n f o r m a t io n on the phy sical

use

of

some

development of high v i s c o s i t i e s
a method for

The

in t h r e e

of the f a c ­

state

t e r i z a t i o n of the f a t - m e m b r a n e
chemical

and

fat at
on the

milk.

Section

subsequent

and m a k e s

work

technique

influence

in homogenized

proteins

and the

of glo bu la r

and its

the iso la ti o n

(homog­

experimental

of a c a l o r i m e t r i c

homogenization t e m p e r a t u r e s

of the

presented

when homogenization p r o c e d u r e s

to obtain

son of some

and continu­

the v i s c o s i t y of homogenized milk

in Section II m akes

III p r e s e n t s

is

a study

reported

v ar i ou s

of c l a r i t y

charac­

a com pari­

and p hy si ca l p r o p e r t i e s

of c r e a m s

obtained f r o m nonhomogenized and homogenized milk.
A general

s u m m a r y of the o v e r —
all inv es tiga tio n

some of the p e r t i n e n t
tion.

conclusions

are

and

included in the l a s t

sec­

SE C TIO N

THE

EFFECT

OF

PROCEDURE

VARIATIONS IN THE HOMOGENIZATION

AND IN THE COMPOSITION OF

THE EFFICIENCY
THE

I

OF

MILK ON

HOMOGENIZATION AND ON

DEVELOPMENT

OF

HIGH VISCOSITY

REVIEW O F

L I T ERA TU RE

Viscosity

Definition of V i s c o s i t y

D a v ie s
lows:

"The

resistance
lute

units

quired

and

cm.

to

shear,

the

per

b et w e e n

centipoises,

a

apart.
the

the

viscosity

of a l i q u i d

agitation

poise

1 cm.

1 cm.

defined

viscosity

to p r o d u c e

liquid of
sq.

(1939)

or

its

difference

in the

s e c o n d when this

two p a r a l l e l
. . . The
s ta n d a rd

planes

is

m easurable

defined a s
v el o c i ty
force
each

viscosity

being

internal friction

flow

which m a y be

of a liquid a s

is

or

its

in a b s o ­

force

re­

of flow of a

is

exerted

1 sq.

usually

t h a t of w a t e r

the

fol­

cm.

on

in a r e a

expressed

at

20

1

o

C.

in

(= 1.005

c e n t i p o i s e s ) . 11

Viscosity

of Milk,

Ho mo ge ni z ed

Skimmilk

Soxhlet
in the

(1876)

viscosity

repo rted

values

was

of m i l k
o bt a i n e d

the

due

and

first

Milk,

Whey

to i n v e s t i g a t e

to a l t e r a t i o n s

the

cha n ge s

in t e m p e r a t u r e .

with an O s t w a l t - t y p e

tube

He

viscom eter

6

that

ranged from
o

ing f r o m

0

from

15°

to

t io n s

at

at

37°

20

C.

o

His

in an
the

and

all

effect

to

C.

C.,

obtained

the

to

the

of flow of the

reported

that

Evenson

and

whole

milk

creased

S h a rp
mental

(1928)

of

(1914)

homogenization
(1924)
the

increasing

s tu dy of
was

principles

findings.

reference

viscosity

of m i l k .

raw

resulted

showing

m ilk

milk

(1911)

were

on
was

reported

the

that
and

an i n c l i n e d

(1917)

ho­

also

of m i l k .

homogenization
the

in

glass

u n a f f e c t e d by

viscosity

also,

in­

a decrease

Quagliariello

increased

known

of

viscosity

in­

homogenization p r e s s u r e s .

milk

viscosity

outstanding
for

first

of

skim m ilk

viscosity

experim ents

Soxhlet's

on the

m i l k by

and

determ ina—

that homogenization

homogenized

Wiegner

t he

vary-

a tem perature

and M u r p h y

dem onstrate

of whole

increased

The

Bi sh o p

at

conducted

homogenization

viscosity

F erris

with

is

tem peratures

viscosity

supporting

(1908)

in v i s c o s i t y .

the

(1904)

at

worked

made

of h o m o g e n i z a t i o n

viscosity

mogenization.

data

of B u g l i a

in A m e r i c a

and t h a t

(1908)

(1913)

Cavazzani

the

plate

centipoises

Kobler

creased
rate

1.64

T a y lo r

s howed t h a t

increase

first

o

C.,

report

show the
data

30

18°

and

The
to

to

4.25

reported

in t h a t

determ ining

some

viscosity

by

Bateman

of the
were

m ore

and

funda­

investigated.

7
They u s e d
s ible

to v a r y

ination.
of

a Bingham—
type
the

In t h i s

shearing

theorization
and,

m anner,

pressure

of m i l k v a r i e d

liquid

shearing

with

a

pressure
it was

shearing

g r a d i e n t had l i t t l e

pressure

of about

flow,

the

Ostwald—
type

200

shearing

viscosity

at

pasteurized

milk

at

vidual
tion at
a

rise

about

o

varied,

C.

in the

viscosity

the

viscosities

viscosity

when

whole

is

square

at

skimmilk.

reported

repeatedly

of whole

milk

m ilk,

1.48,

run

was

to the
viscous

an unknown

At a

shearing
a value
gravity -

values

for

r a w whole

some

per

but

and

through

the
mi lk

of t h e i r

whole
in d i ­

n oted t h a t h o m o g e n i z a -

In addition,
m i lk

v iscosity

1.56 and h o m o g e n i z ed

generally

of h o m o g e n i z e d

at

of an o r d i n a r y

and 4,000 pounds p r e s s u r e

of

influence

not a t r u e

centim eter,

Although

of whole

the

exam­

according

value.

at about

m i lk

it was

viscosity

the

constant

skim m ilk

study

m easurem ent

they

1.67 c e n t i p o i s e s .

values
50

of

to

milk

pressure

viscom eter,

relativ e
1.55,

that

per

liq uid u n d e r

i nd ic a ti ng ,

theoretical

gram s

pos­

They found t h a t the

force,

viscosity

shearing

approximating

possible

(1912),

single

with which i t was

on the

on v i s c o s i t y .

of H a t s c h e k
that

viscom eter

square

was

it was

without

effec t on

observed

skimmilk

a capillary,

r e d u c e d by this

inch c a u s e d

that

rem ained
whereas

treatm ent.

the

They

8
attributed

this

regularity

in the

Trout,
homogenized

d ifferen ce

a factor

m i lk .

From

tipoises

after

sim ilar

set

wald-type
water

v al ue

centipoises,
with the
values

centipoises
with a

reported

an

average

the
5°

these

and

effect

homogenization
2,500

Sharp

pounds
m i lk ,

milk

b ut t h a t
in v i s ­

of h e a t

v al ue
and

2.315

was

homogenization

on

for

pressure.

2.142

m ilk.

raw
cen—

In a
the

and

av­
1.814

and

80°

A fter
and

(1927),

v iscosities
C.,

varied

conversion

Jackso n's

values

t hen

for
from

to

the

Ost—

(1918)

60°

2.9b

to

for

6.57

specific—
viscosity

between

5°

and

C.

70

skim m ilk

relative—
viscosity

ranged fro m

varying

1.52 b e t w e e n

employing

in a t e m p e r a t u r e - c o n t r o l l e d

specific

tem p eratu res
of

at

raw

reduced

the

im m ersed

resp ectiv ely .

m inimum

was

to

before

S he rm a n

between

for

that

to the

homogenization.

found t h a t

water,

F.

obtained before

a id of B i n g h a m

for

n o t ed

attrib uted

t he y

viscom eters

tem peratures

145°

and

in h o m o g e n i z e d

in v i s c o s i t y ,

with p a s t e u r i z e d

following

b ath,

at

homogenization

Whitaker,

(1935)

increased

homogenized

centipoises

of f a t —
clumping

f a t globules

was

which t hey

viscosity

centipoises

F.

of t r i a l s

lack

and Gould

12 t r i a l s ,

of 2.152

erage

90°

milk

cosity;

m i lk

of the

Halloran
at

pasteurized

size

to the

1.95
and

to

1.59

80°

C.

S im ilar

results

were

obtained f o r

reported
as
and

relative—
v iscosity

1.27 c e n t i p o i s e s
70°

C.

reported

M ore

the

c os it y
at 40
the

recently,

range

o

(1947)

relative

in g e n e r a l ,

to 40°

of

the

Some

Factors

Pasteurization
that p a s t e u r i z a t i o n

viscosity

at

ported

a reduction

C.

are

referred

the

Dahlberg

and 80

Vuillaume

o

C.,
50

o

(1934)

skimmilk

over

the

1.23 and 2.84

Saal and van d e r
milk
and

to

relative

vis —

1.64 c e n t i p o i s e s

not in a g r e e m e n t

to p r e v i o u s l y ;

tem perature

the

o

who

1.19 between

of fluid m i lk

Affecting

with

because,

and c l o s e l y
is

Viscosity

decreased.

of

and R e la t e d P r o d u c t s

67°

of whey.

(1924),

as

o

5

(1945),

3.44 to

and h e a t t r e a t m e n t .

v iscosity

F erris

as

Eilers,

1.59 at 0

viscosity

increase

Milk

duction in the

C.

c a l c u l a t e d v alues

relative

of

and

the v a l u e s f o r

v i s c o s i t y v al ue s

re la ted products

the

0°

converted

These

whey at

of mi lk

respectively.

and found v a l u e s
C.

for

T a p e r n o u x and

(specific)

from

1.08 c e n t i p o i s e s ,

Waarden

values

and Korff

with a m i n i m u m value

viscosity

tem perature
to

s k i m m i l k by E i l e r s

C.

for

Woll

20 m i n u te s

of m i lk

and c r e a m

Babcock

and R u s s e l l

and Hening

(1925)

in v i s c o s i t y following

(1895)

causes

a

reported
slight

and an i n c r e a s e
(1896),

re­
in

E v e n s o n and

and o t h e r s

a ls o

the p a s t e u r i z a t i o n

re­
of

10
whole

milk

and c r e a m .

o b s e r v a t i o n was

r e p o r t e d by A c h a r d

noted an i n c r e a s e
Wh itaker
cosities

100°

tures

(measured

C.)

crease.

the

Under

the

the

increase
serum

absence

decrease

30 m i n u t e s .

v iscosity

inherent p r o p e r t ie s
v iscosity

sulted f r o m
m aterials.

a

of

C.,

whereas

tem peratures

they noted a m a r k e d
t h ese

their

results

skimmilk

and that

it

of v i s c o s i t y ,
skimmilk

or

respon­

to

resulted

sustain

in a d e c r e a s e

(1928)

consideration

reported
at

of

62

pasteurization
denaturation

o

a

C. f o r

some

they concluded that the

after

slight a l t e r a t i o n

they p o s ­

was

served

re­

coag ulatio n by h ea t

and Sharp

careful

(60

At t e m p e r a ­

of s k i m m i l k p a s t e u r i z e d

a more

vis­

s k i m m i l k continued to in­

( r e n n e t whey)
Bateman

higher

in the

since

in the

and whey p a s t e u r i z e d

in v i s c o s i t y .

From

of c a s e i n

who

m ilk.

a decrease

skimmilk

conditions,

proteins;

Sim ilarly,

A fter

of

in v i s c o s i t y

of c a s e i n

in the

C.)

of whey.

that the p r e s e n c e

for

recorded

general

(1925),

of p a s t e u r i z e d

v i s c o s i t y of

same

v isco sity

in v i s c o s i t y .

in the

24°

exc e ptio n to t h i s

and S t a s s a n o

in an i n c r e a s e

C.

the

c o a g u l at e d

in the

v iscosity

up to 60°

100°

duction in the

sible

at

resulted

above

tulated

in the

e t a l . (1927)

at t e m p e r a t u r e s
to

A noteworthy

of the
decrease

probably

re­

of the p r o t e i n

11
H o m o ge ni z at io n p r o c e d u r e s .
enization on the
however
f e c ts

it

The g e n e r a l

v i s c o s i t y of mi lk has

seems

of c e r t a i n

app rop ria te

variations

effect of homog­

a lre ad y been

to r e v i e w

in

some

in homogenizing

r ev i e w e d ,

detail

procedures

the

ef­

on the

v i s c o s i t y of milk.
Wiegner
made p r i o r
of n o r m a l
per

about
ies

all

m i lk was

was
1.46.

s ize

only

(1912)

of the

a l . (1935)
viscosity
creasing

after

substance

resulting

of a f i l m
reported,

from

a r o u n d the
h ow e v e r ,

of p a s t e u r i z e d

He

and t ha t

is

that

density
with the

of the

milk when it

was

was

p articles.

r e d u c ti o n

was
stu d ­

of the p a r ­
over­

who concluded t h a t

dispersed
a

assum ed

in a c c o r d

hom o ge niz ation

that

25.20

its

viscosity

casein

whereas

im portance

on the

(1912)

of the

globules,

adsorbed

who e m p h a s i z e d the

and with H a t s c h e k

m easurem ents

c e nt

homo ge nization .

d is p e r s e d phase

v iscosity

adsorption

2.27 p e r

The f o r e g oi ng p o s t u l a t i o n

system,

creased

viscosity

a d s o r b e d on the f a t

adsorbed

the

of Od£n

ticle

calculated from

to h o m o ge ni z at i on tha t

c ent was

casein

(1914)

the

due

to the

Trout

occurred

in­

et

in the

homo ge niz ed with in­

pressures.

Evenson
tion p r e s s u r e s

and F e r r i s
increased

(1924)

the

noticed

viscosity

of

that high h o m o g e n i z a ­
" r e m a d e 11 m i l k s .

12
Tretsven

(1939)

concluded that the

v is c o s i t y of homogenized

milk was

a function of the fat content and of the homogeniza­

tion t e m p e r a t u r e ;

low t e m p e r a t u r e s

high v i s c o s i t i e s .

F arrell

(1942)

homogenizing t e m p e r a t u r e s
cessive

viscosities

peratures.

being m o s t conducive to

r e c o m m e n d e d the use

to avoid f a t - c l u s t e r i n g

which a r e

(1928)

milk which had been w a r m e d to 50°

value

respect

that the
but is

o b s e r v e d that r a w whole

C.

and homogenized at

i n c r e a s e d in v is co s i t y

and that the higher

r e m a i n e d constant on r e p e a t e d v is c o s i t y

In this

homogenized milk is

v is c o s i t y

does not change

gradually on s u c c e s s i v e

sim ilar

m easurements.

to skimmilk,

in which the

m easurements.

ity in the v i s c o s i t y of homogenized milk was

v is c o s i t y d e ­
This

u n i fo r m ­

also noted by

Caffyn (1951),

who u sed homogenized milk to study c e r t a i n

herent factors

peculiar

Whitaker
enization at

in­

to milk vis co s it y.

and Hilker

(1937)

3,000 pounds p r e s s u r e

cent milk and 20 p e r

in

on r e p e a t e d m e a s u r e m e n t s ,

unlike nonhomogenized milk,

creases

and the ex­

induced at low homogenizing t e m ­

Bateman and Sharp

4,000 pounds p r e s s u r e

of high

cent c r e a m

studied the
on v ar i ou s

effect of homog­
lots

of 4.0 p e r

which had been handled dif­

f e r e n t l y with r e s p e c t to heat t r e a t m e n t .

The

ave ra ge

size

of

13
the fat g lo bules,
treatm ent

their

tendency to c l u s t e r

and h o m o ge ni z at i on w e r e

but no v i s c o s i t y

determinations

which had b e e n p r e h e a t e d
various

lower

tem peratures

o v e r n i g h t at 40

o

F.

and then

showed no f a t - c l u m p i n g
below
for

100

o

F.

All

30 m i n u t e s

examination;
clumping.
sim ilar

of the

a factor

The

o

cream

warmed

and r a w mi lk

holding p e r i o d

s to red for

samples

h owever,

were

Trout
enization

period

noted when the

milk

at 40°
mi lk

held

m ay not

a t 60
have

o

F.

in c r e a m

at

clumping

80

o

samples

tem perature

after

prior

F.
to

in a

of the f a t

low as

F.

o

influenced

which had b e e n t r e a t e d

as

145

we r e

50

o

F.

was found to
which were
a prelim inary

F.

and Scheid

of ra w

samples

to homo ge niz ation

18 h o u r s

Homogenization

o

Milk

p asteu rized at

showed definite

homogenizing
at 40

consideration,

which had been

warmed p rio r

samples

to f a t - c l u m p i n g

to the

of h ea t

and then h om o ge ni zed at

when h om ogenized a t t e m p e r a t u r e s

be conducive

result

reported.

F.

which may o r

following p r e h e a t i n g .

storage

of p r i m a r y

were

145

the

when h o m o ge ni zat i on t e m p e r a t u r e s

and then

manner,

globules

to

as

(1941)

studied the

at v a r i o u s
F.

was

Some

efficiency of homog­

tem peratures

after

a 24—
hour

homo ge niz ation effec ts

h om o ge ni zed a t

80° F . ,

but

we r e

satisfactory

14
dispersion

of the f at globules

zation t e m p e r a t u r e

reached

a s s u m e d that p a s t e u r i z a t i o n
tion,

no v i s c o s i t y

r e c e n tl y ,

Moore

studies

and

of a p r o g r e s s i v e
F urther

cent p a s t e u r i z e d
pressure,

gregates

markedly

bel ie v ed t ha t the
solids
Ta y lo r

that the

at 45

content,

o

(1913)

solids-not—
fat

F.

80° F.

we r e

of p r o t e i n

Bogdan (1905)

p r o p o r t i o n a l to the

observed

in isotonic

content of milk.

Ba te m a n and Sharp

ing that the

v i s c o s i t y of ski m m il k
s ta te

of the

of the

above

total

samples.

to e s t i m a t e

the

(1928) p r e ­

concepts by

v a r i e d with the

components.

ag­

thickening.

determinations

show the f a l l a c i e s

up to

They also noted that a

u tilize d v i s c o s i t y

to

milk.

and 2,500 pounds

and the p r e s e n c e

sented data

the p h y si ca l

More

v i s c o s i t y of a 4.6 p e r

of milk was

but v a r i a t i o n s

samples.

pasteurized

c omposition of m i l k .

viscosity

it was

and continued to i n c r e a s e

a c co m pa n ie d the p r o g r e s s i v e

in the

Since

r e p o r t e d on the o c c u r r e n c e

in homogenized,

" c h a l k y 11 f la v o r

V a r i a ti o n s

above.

on these

homogenized at

the f o u r th day of s t o r a g e
characteristic

made

revealed

milk,

or

would n o r m a l l y follow h om o ge ni za ­

(1947)

thickening

increased

100° F.

were

Trout

i nv estigation

did not o c c u r until the homogeni­

show­

t r e a t m e n t and

15
Oertel

(1908)

a rise

o r fall

in s olids,

n at ur e

of the f at globules.

phy (1911)
cream

observed

reported

but that it depended on the
At the

an i n c r e a s e

following p a s t e u r i z a t i o n ,

in the v i s c o s i t y of s k i m m il k .
viscosity
G n e ist

(1945)

the

The

diff e r en ce

Tretsven

e niz ed milk

(1939)

in the

investigators,
Hatschek

increase

a ds or p ti on

of the

i n c r e a s e d fat
and Dahle

viscosity

milk.

Spottel and

(1922)

of p r i m e

and ev­

indicated that l a c t o s e

and

of s k i m m il k ,

importance.

but

Nu­

Wiegner

(1914),

Ba te m a n and Sharp

(1928)

Bugattrib ­

v i s c o s i t y of homogenized milk to the

d i s p e r s e d pha se
as

could not

the v i s c o s i t y of homog­

et a l . (1927)

were

(1912),

surface

a change

increased

However,

notably among t he m

in the

and M u r ­

v i s c o s i t y of morning

s t a t e d that

and

of milk and

They a t t r i b u t e d the

over—
all v i s c o s i t y

that the p r o t e i n components

(1908),

Bishop

with

dependent on the fat content.

data of Whitaker
role

s ize

but could not p roduce

in the

was p a r t i a l l y

played a m i n o r

uted the

in the

time,

concluded that the f a t content of milk

ening milk.

merous

s ame

to the fat content of the

account for

l ia

that v i s c o s i t y did not change

the

and l a t e r

(probably p ro te i ns )

on the

r e s u l t of homogenization.

Palm er

cluded that the v i s c o s i t y of milk

and An de r s on

(1926)

Palmer
con­

resulted p rim a rily from

the

16
adsorption of colloidal p r o t e i n s
and not f r o m

the p e r c e n t a g e

Fat—
globule
mechanical
globules

(1896)
ters

were

the f i r s t

of fat globule

milk.

been indicated pre v io us ly ,
to the clumping of fat

role

milk p ro d u c t s .

in d et ermining
Babcock

milk and c r e a m

vis co s it y.

Bishop

tended to d e c r e a s e

explained that the

increase

homogenization depended not only on the
of the fat globule,
Abundant

was

but also on the

clustering

Doan made

and Murphy
at

information concerning
c osity of whole

the

o

r esu ltin g

reduction

F.

F.,

but

Sommer
from

in the

size

contributions

to the

effect of homogenization on the

homogenized milk would c r e a m
but l a t e r

70

o

viscosity,

of noteworthy

milk and c r e a m .

duced to c l u s t e r s ,

140

extent of f a t - c l u s t e r i n g .

would favor h ig he r
a series

clus­

accom­

the vis co s it y.

in v is c o s i t y

v is­

and Ru ss e ll

a higher v i s c o s i t y than homogenization at

that r e p a s t e u r i z a t i o n

the

that a diminution in the

in p a s t e u r i z e d
in the

of the fat globule

o b s e r v e d that the homogenization of c r e a m

produced

(1946)

has

conducive

to o bs er v e

panied by a reduction
(1911)

are

As

and they play an i m p o r t a n t

cosity of f a t —
containing

surface

of fat in the

c lu s te rin g .

manipulations

on the

He

(1927)

speculated that

if the fat globules

o b s e r v a ti o n s

v is­

could be

in­

showed that the fat

17
globules

of h om o g e n i z ed

a f t e r p r o lo n g e d
Brownian

storage

t en s i o n

Excessive
F.

at

(1929a).

m o v e m e n t of the

the f at globules
f a c ia l

mi lk had l i t t l e

in motion,

globules,

greater

in 4.0 p e r

3,500 pounds

pressure

to fat

ever,

the f a t

content w e r e

increased

ratio

became

0.50

whereas

8 and

was

to 0.60;

18 p e r

c e nt

the f o r c e

together

less

raised

than 0.40
to
an

the

of

inter-

in c l u s t e r s .

h omogenized

encountered

serum —
solid s

between

ratio

cent m i l k

was

which s e r v e d to keep

than

tending to d r a w the globules

clumping

even

He b e l i e v e d t h a t the h ei gh te n ed

small
was

t endency to c l u s t e r

at

100

o

only when the
to 0.50.

6 per

cent,

increase
critical

If,

the

how­

critical

in fat content

ratio

to 0.60

to

0.85.
Doan (1929b,
concentration
was

a ls o

protein

of

1929c)

noted that

serum —
s o l id s ,

a c on tr i bu ti ng f a c t o r

stability

the

in addition to an adequate

c alc iu m —
ion c o n c e n t r a t i o n

to both f a t - g l o b u l e

in h omogenized milk.

N evertheless,

concluded t h a t n e i t h e r

the

theories

ade q uate l y explained why the

of c l u s t e r i n g

electrostatic

clustering

eniz ed m i lk f a i l e d to c l u s t e r .
ster

(1933)

observed

ally h i g h - f a t

content

clusters

Doan

charge

(1928)

and

of f a t globules

nor

and

he (1932b)

the

agglutinin

fat in homog­

Doan and Min­

in milk of u nu su ­

which had b een homo geniz ed a t low

18
tem peratures

(100

o

In m o s t i n s t a n c e s ,

F.

and lower)

fat-clu sterin g

and a b n o r m a l l y high p r e s s u r e s .
in h omogenized

e li m i n a t e d by double —
stage

homogenization.

ported

a t low t e m p e r a t u r e s

t ha t h omo genization

clumping,
m aterial
terial

which was
rather

varied

creased

by the

and 65°

C.

use

Whitaker

at 45°

F.

r e t a r d e d between

and

Hilker

(1937)

for

and J a c k

valve,

(1937)

but no clumping

an e x c e s s i v e

and 2,500 pounds
copious
a c eous
the

viscosity

pressure.

amount of clumping
in n a t u r e .

theories

used

and 42°
some

normal
was

valve.
in milk

in­
60

clustering
100

o

F.,

18 h o u r s

clumping

conditions

in

with a

evident

when m i lk was

Moore

and T r o u t

h om o ge ni z ed at

They w e r e
which was

was

between

above

s ome

ma­

C.

and held for

recorded

under

homogenized with a d o u b l e - s t a g e
reported

dispersion

observed

30 m i n u t e s

homo geniz ed m i lk p r o c e s s e d
single-stage

its

37°

re­

r e s u l t e d in f a t -

The f i l m

which had b een p r o c e s s e d

145° F.

Dahle

thus

(1949)

of homo geniz ation t e m p e r a t u r e s

in homogenized milk
at

tem perature,

could be

in the f i l m —
forming

than to the fluidity of the fat.

and was

pasteurized

Wittig

a t t r i b u t e d to a change

with the

milk

a lso

able

(1947)

80°

to d e t e c t

F.
a

b e l i e v e d to be p r o t e i n —

Dunkley and S o m m e r

(1944)

to explain f a t —
clustering

reinvestigated

and the

creaming

of

19
milk

and p o s t u l a t e d that:

tion of a definite
ther

than by

(1940)

clumping

addition

line

and l a t e r

clustering

of milk

in h omogenized

Doan (1927)
hanced c r e a m i n g

Sommer

and

Theophilus

"viscolized"

clusters.

milk,

fat

occur

c o m m o n l y known a s

enized c r e a m . "
which o c c u r r e d

Babcock

tem peratures.

(1931)

as

Doan (1931)

and a d e c r e a s e

or

mi lk

that the

and milk

had b e e n added was
Trout

(1950)

in homo ge niz ed

fa t-

cream
as

was

due

en­

to which
to the

noted that:

10-

or

12—
per

and in homog­

r e p o r t e d t h a t the

well

fat-clumping

increased

by high

by low h omo genization

r e c o g n i z e d t ha t

e ni zat io n of c r e a m f r e q u e n t l y
clusters

observed

'half-and-half,'

in homogenized

h omo genization p r e s s u r e s

on any f r a c t i o n

(1941)

f o r m a t i o n of n u m e r o u s

does

induced by the

milk.

abi li ty of

c lustering

that f a t-

had a t endency to r e d u c e

milk

cent

stated

work of Doan (1929a)

terrperatures

a quantity of homo ge niz ed

"m arked

(1946)

The

serum -solids

ra­

g lo bu les."

(euglobulin).

showed t h a t high p r e h e a t i n g

the f o r m a ­

of euglobulin

in h om o ge ni z ed m i lk could be

of agglutinin

combination

by d e n a t u r a t i o n

sub division of the f a t

Sharp
globule

cream

"homogenization p rev en ts

single-stage

c a u s e d the f o r m a t i o n

in he a t - s t a b i l i t y .

homog­

of fa t- g lo b u le

He found t ha t the

20
addition of h ig h-qu a li ty

serum -solids

stabilizing

sodium c i t r a t e ,

salt

an i n c r e a s e

such as

in he a t - s t a b i l i t y

ing tendency.
was

the

stage)

observations

who likewise

homogenization

(2,000 pounds

was

b eneficial

maximum d ispersion
milk,

In somewhat
Mortenson
Dahle
have

(1925),
reported

protein
were

(1918),

occurrence

induced by
they

mix.

single-stage
reported

r eho m og e niza tio n

detrimental
of c r e a m .

In m o s t

ef­
To in­

recommended

ice

(1926),

Hening

of e x c e s s i v e

on

of s e p a r a t i o n of fat

involving

(1926),

of

of d o u b l e- s ta g e

and a double—
stage

Sherwood and Smallfield

i ns ta bi li t y in the

G e n e r al ly ,

studies

fat-

and 500 pounds

the

Webb and Holm (1939)

Reid and Moseley
the

use

and a m ini m um

sim ilar

in

homogenization

of p r e v e nt in g

heat-stab ility

of high homogenizing p r e s s u r e s

resu lted

a

in a g r e e m e n t with those

in l e s s e n i n g

s ur e

instances,

in the f a t —
clu ster­

total p r e s s u r e

of homogenization on the

in e v a p o r a t e d

are

means

found that the

f e c ts

use

frequently

and a d e c r e a s e

efficient and p r a c t i c a l

The se

Webb (1931),

second

in some

He concluded that d o u b l e - s t a g e

most

clustering.

or,

cream

valve.
m i x e s,

M ar ti n and

(1928)

and o t h e r s

fat—
clustering

instances

the

these

and
defects

homogenization at high p r e s s u r e s .

that agitation

at a low er p r e s s u r e ,

a f t e r homogenization,
or

double-stage

homogenization e li m i n a t e d f a t- c l u m p i n g .
f a t- c lu m pi ng

in s i n g l e - s t a g e

nounced that v a r i a t i o n s

Reid (1927)

homogenized c r e a m

stated

was

in homogenization p r e s s u r e s

that

so p r o ­
had l ittle

effect.
Apparently,
and o t h e r
the

excessive

dairy products

fa t-c lu ste rin g

play an i m p o r t a n t p a r t

ult im ate p h y s i c a l p r o p e r t i e s

clustering
c lo s e l y

which o c c u r s

view b r i e f l y
explain this

some

of t h e se p r o d u c t s .

in some

homogenized

Therefore,

of the t h e o r i e s

milk is

and Bancroft
of r i s e

ters.
greater

of fat

(1926)

greater

would be

s iz ed the

ten de n cie s

appropriate

to

in
re­

which have been advanced to

the

the

i m p o rt a n c e

Both McKay and L a r s e n

c o n j e c t u r e d that

globules

opportunity f o r
The

seems

probably

P r o p o s e d to Explain C l u s t e r i n g

G r a v it a ti o n of fat g l o b u l e s .

essary

it

The f a t -

phenomenon in nonhomogenized milk.

Theories

rates

in d e t e r m i n i n g

a s s o c i a t e d with the n o r m a l f a t - c l u s t e r i n g

nonhomogenized milk.

(1906)

in homogenized milk

of d if ferent

globule

sizes

difference

in the

p r o v i d e d the n e c ­

contact and the f o r m a t i o n of c l u s ­

opportunity f o r

tendency to
of the

the

rise.

absolute

cluster—
f o r m a t io n ,
Sommer

size

(1946)

the

empha­

and the v a r i a t i o n s

in

22
the

size of f at globules

l ar g e

globule with its

globule

in the upward

as

factors

g r e a t e r buoyancy would overtake
sweep,

thus providing

contact and c l u s t e r —
fo rm a t io n .
(1927)

and Theophilius

deep c r e a m i n g
(1929)

of

This

(1941)

as

11v i s c o l i z e d "

concluded that the

most important factor

influencing clumping.

size

milk.

responsible

Dahlberg

for

sm aller

o bs erv e d by Doan

of the fat globule

r e sp on si bl e

the

an opportunity for

fact was

a factor

The

for

the

and M a r q u a r d t
was not the

the difference

in c r e a m ­

ing p r o p e r t i e s .

Electrostatic

charge

on fat glo bu le s .

p o r te d that the e l e c t r o p h o r e t i c
sured

b erg

to the

and M a r q u a r d t

cell,

and that c lu s t e r i n g

results

oppositely c h a r g e d globules.

i n v e s ti g a t o r s

the fat globules

had

Dahl­

(Sirks,

in milk c a r r y opposite

from

However,

supported by e x p e r i m e n t a l data,
several

in milk.

mea­

attempted to explain f a t - c l u s t e r i n g

on the pro po si t io n that the fat globules
charges

re­

v a r i e d and t h e r e f o r e

extent of f a t - c l u s t e r i n g

(1929)

(1923)

mobility of the fat globule,

in a m i c r o e l e c t r o p h o r e t i c

no rela t io ns hi p

Sirks

in milk c a r r y

a t t r a c t i o n of

such a t he or y is not

because

1923;

mutual

Jack

a negative

it has been
and Dahle,
charge

shown by
1937a) that

and t h e r e

is

no r e a s o n
globules

to

suppose

would be p r e s e n t

Schneck and
mer

(1935) found

charge

same

(1931)

system.

and N o r th ,

and its

tendency

on the

to clump.

tendency

g lo bu les.

Sirks

p anied by an i n c r e a s e

from

in the

Furtherm ore,

Dahle

which they concluded that

the fat globules
to the

as

a

fat—
clustering

Interfacial
t ha t the

result

increase

tension.

McKay

accom­
of the fat

presented

in the

data

mobility of

was

and L a r s e n

and c r e a m i n g

at low t e m p e r a t u r e s

surface

sion in cold m i lk has

ten si on

a ls o b een

sky (1939).

Doan (1929a)

enized

might be

milk

mobility

(1937)

change

was

data

not

related

tendency.

stored

in the

presented

of h e a t t r e a t m e n t

improved f a t-c lu s te r in g

that had b e e n

the

milk to an in­

t endency

and J a c k

charge

They a t t r i b u t e d

(1923)

electrokinetic

and Som­

electric

in hea ted

show t h a t a d e c r e a s e d f a t - c l u s t e r i n g

globules.

Courtney

r e l a t i o n s h i p bet we e n the

decreased fat-clustering

creased
to

in the

Brandt

some

on the f a t globule
the

t h a t both p o s i t i v e l y and n e g a ti v e ly c h a r g e d

of milk.

Lower

and

serum .

due

surface

r e p o r t e d by Sharp

postulated

suggested

observed

might be

of the

in milk
to an
ten­

and K r u ko v —

that f a t - c l u m p i n g

e xplained on the b a s i s

ten si on bet we en the fat

(1906)

in homog­

interfacial

Van Dam and S i r k s

(1922)

24
and N o r t h et al.
tween the

(1935)

interfacial

fat-clumping

in m i lk

hanced c l u s t e r i n g
in the

fat globule.
surface
able

Rahn

or

property

1922)

stick in ess

the

another.

that

and van

The

observations

s uc h as

had b een added.

the

The

of an

adsorbed

on the

membrane

when they c a m e
(1922)

in the f o r m a t i o n

en­

on the

an adh e sive

and S i r k s

gel­

adsorbed

c ollo id s

together

of Schneck

Dam and S i rks

colloid,

membrane

formed

Van Dam

pla ye d by p l a s m a

and Muth (1930)

in co n ta c t

emphasized

of f a t —
globule
lend

cap­

the

clusters.

s u p p o r t to

statements.

Brunner

and J a c k

tion which o c c u r s
physical

tha t the fat be
sem i-soft

and the

explained on the b a s i s

of the

globules

part

the foregoing

interface

be­

and i m p r o v e d c r e a m i n g

arabic,

was

of the f at globules

with one

a

gum

Rahn b e l i e v e d

of binding

to the

(1921,

to which a hydrophilic

gum t r a g a c a n t h

increase

relationship

at the f a t / s e r u m

noted i n c r e a s e d f a t - c l u s t e r i n g

properties
atin,

tension

important

tendency.

Stickiness.
(1922)

o b s e r v e d no

or

durin g

s ta te

(1950)
the

of the

neither

believed

that the f a t a g g r e g a ­

churning p r o c e s s

fat.

solid n o r

The

necessary

liquid,

" s t i c k y 11 condition.

was

in p a r t

condition being

but that

Wittig

due

(1949)

it

should be
was

more

in

25
c o n c e r n e d with the
clumping

nature

than with the p h y s i c a l

Ag g l u ti n a ti o n .
p li ed to the
connotation
been

Whether

clustering
is

of f at

to

express

phenomenon:

the

This

" a g g l u t i n a t i o n , 11 as

is

u s e d in i t s

expression

has

agglutination

(1944),

"can

which influenced f a t -

of the fat.

term

bacterial

Dunkley and S o m m e r

c lu ste rin g

s ta te

globules,

q u e s t io n a b le .

reserved

ing to

of the f a t - f i l m

its

use

to

ap ­

proper

generally
and,

accord­

describe

only be j u s t i f i e d on the

the

fat-

basis

of

convenience. ' 1
Babcock
ules

in mi lk was

(1922)

the

Hekma

fat globules
milk.

made

b e l i e v e d that
possible

r e p o r t e d t ha t f i b r i n

therefore,
Dam,

(1889a)

"fibrin"
and S i r k s

could be

Further

that the

as

milk

it was

in agglutination was

of Babcock was

of f i b r i n .

in mi lk

was

agglutinins.

found that the

Hekma

and,

untenable.

Van

clustering

of

by an agglutinin p r e s e n t

by Hekma and S i r k s

bacterial

of f a t glob­

not a c o n s t i t u e n t of milk

(1922) b e l i e v e d t ha t the

substance

tem perature
serum,

theory

c lustering

by the p r e s e n c e

acco un te d f o r

studies

creaming

was

the

(1923)

demonstrated

thermolabile

By the

at the

fractionation

constituent p r i m a r i l y

identified with the

in

globulin f r a c t i o n .

same

of

involved
This

26

o b s e r v a t i o n has
derson

a lso b een

r e p o r t e d by P a l m e r ,

(1926).
Brouwer

(1924)

out by h a l f - s a t u r a t i o n

f r a c t i o n a t e d globulin which had been
with a m m o n iu m

sulfate

pseudoglobulin and d e m o n s t r a t e d that the
ben e f ic ia l to f a t —
clustering
(1937)

noted that the

to the

euglobulin f r a c t i o n

r e d u c ti o n in c r e a m i n g
loss

amount of albumin

salted

into euglobulin and

and c r e a m i n g p r o p e r t i e s .

companied by a c o r r e s p o n d i n g
tional

Hening and An­

ability,

was

Rowland
p robably a c ­

in f a t - c l u s t e r i n g ,

was p r o p o r ­

and globulin tha t was

d e n a tu r e d

by heat.
Sharp
fat globules

and Krukovsky

(1939)

to be an agglutination p r o c e s s

the

agglutinin in milk

is n o r m a l l y

the

solid fat globules

and is

uefaction of the fat.
Sommer
terized
of fat

(1944)
it as

c o n s i d e r e d the

Th ese

euglobulin.

globules

surface

serum

agglutinin m a t e r i a l

place

by the

upon l iq­

and c h a r a c ­

"that

the

same

mechanism

agglutination of b a c t e r i a . "

s e r v e d that in addition to agglutinin,

of

v e r i f i e d by Dunkley and

They concluded,

in milk t ak e s

that involved in the

into the

data w e r e

of

and concluded that

a d s o r b e d on the

released

who i s o l a t e d the

clustering

clustering

They also

com plementary

as

ob­

m aterials

27
in milk,

such as l o w - s a l t

c on c en tr a t io n,

we r e

r e q u i r e d to p r o ­

duce fat- c lu m p i n g .
Hening
(1939),

Burgwald (1940),

Doan (1948)

and o t h e r s

to p r o m o t e
cream

and Dahlberg

have

Nair

tem perature

and F l e m in g

(1941),

Smith and

r e p o r t e d f a v o r a b l y on t h e i r

and i n c r e a s e

11r ebodying11 o r

volved c a r e f u l

Weise,

Skelton and H e r r e i d

fat—
clustering

by a

(1932),

the

ability

v i s c o s i t y of fluid

"reseparatio n"

technique

which in­

ma nipu latio ns.

Homogenization Efficiency

Expression

of Homogenization Efficiency

Efficiently homogenized milk
term s

of the

degree

of d i s p e r s i o n

efficiency with which the p r o c e s s

is

usu al ly e x p r e s s e d

of fat,
was

thus

re l a t i n g

a c c o m p l is h e d .

inition of homogenized milk which has b een g e n e r a l l y
was f u r n i s h e d by the
and is

sta te d

been t r e a t e d
globules

to

no visible
percentage

as

United States

follows:

Public

in such a m a n n e r

as

to i n s u r e

of the

separation occurs
milk in the top

on the

100 ml.

is

The

def­

accep te d
(1947)

milk which has

break-up

such an extent that a f t e r 48 h o u r s
cream

to the

Health Se r vic e

" H o m og en iz e d milk

in

of the fat

quiescent

s to r a g e

milk and the f a t of milk in a q u a r t

28
bottle,

o r of proportionate

does not differ by mo re
percentage of the

volumes

than

remaining

in c ontainers

of o th er

sizes,

10 p e r c e n t of itself f r o m the fat
milk as d et er m in ed after

thorough

mixing.' 1
Other definitions

(Tracy,

1941;

1946) have been offered to d e s c r i b e
and, in general,

they imply the

Babcock,

1947;

Doan,

p r o p e r l y homogenized milk

same

conditions as p r e s c r i b e d

by the definition quoted above.

Reported

Values

Fat-globule
of fat globules
milks

ameters

Van Slyke

(1891)

than 2.4 to mo re

cent were l e s s

of Holstein fat globules
and 88.7 p e r

recently,

of Mea su r e men t

Campbell

(1932)

and that 65 to 80 p e r

in the

in d ia m e te r .

2 -m i c r o n c l a s s .

than

12 mi cr o ns

ranged f r o m l e s s

cent were

smaller

size

and Guernsey

than 7.2 m i c r o n s .

in

The di­

than 2.4 to

than 7.2 m i cr o ns .

r e p o r t e d that the mean f a t -

globule volume for Guernsey milk was

microns

m e a s u r e d the

and r e p o r t e d values for J e r s e y

37.5 p e r

9.6 m i cr o ns ,
More

size.

ranging f r o m l e s s

diameter;

and Methods

18.8 p e r

cent of the globules
The l a r g e s t number

were

cubic
less

micron
than 3.5

of fat globules

He also gave the mean fat-globule

was

29
volume f o r

Hol st ei n

mi lk

as

10.4 p e r

to 94 p e r

c e n t of the f a t globules

diam eter,

whereas

1.5 to 3.5 t i m e s

1—
m icron

class

were

as

Wiegner
was

(1914)

subdivided into

moge ni z at i on .

He

recorded
as

am eter,

would be obtained a f t e r

then only

Rahn and Sharp
of the f a t globules
m icrons
loran

to be

to c r e a m .

Wittig

that in p r o p e r l y

was

homogenized

i z e d , 11 the fat globules

fat

globules

in the

globule

by ho­

of fat globules
with the

other

aid of

hand,

f a t globule

that

milk

are

Som­

were

1 m icron

roughly
are

und er

globules

than 2 m i c r o n s

(1949)

were

in

6

in d i ­

homogenization.

stated

and t ha t all

less

On the

20

3.5 m i c r o n s

size

measured

216 globules,

b e l i e v e d that the f a t

would have

eter.

(1928)

small

average

in homogenized

in d i a m e t e r

(1932)

1,200

m ea n d i a m e t e r

c a l c u l a t e d that if the

and that

many globules

average

microscope.

in d i a m e t e r ,

than

t ha t the

micron,

microns

less

class.

the

0.27

as

micron

3-m icron

observed

a Siedentopf-Zsigmond
(1935)

were

approxim ately

in h omogenized m i lk

mer

in the

cubic

even
milk,

85 p e r

sm aller

3 microns.

Hal—

definite

in o r d e r

than

not

and c l a i m e d

which he l a b e l e d

should be l e s s

2

in homo ge niz ed m i lk

in d i a m e t e r

more

than

c e nt

1 m icron

"m icronin d i a m ­

30
Homogenization efficiency t e s t s .
mended the
an o c u l a r

use

of a h ig h - p o w e r e d

m icrom eter

homogenized milk.

to m e a s u r e

Properly

Walts

and Hanson

m e a s u r e m e n t of the
to c a lc ul a te

sizes

microscope
the

size

(1938)

about

(1941)

of fat globules

utilized the

in d i a m e t e r .

microscopic

in homogenized

an index of homogenization efficiency.

Mykleby (1943) f e l t that the

F arrall

Index was

as

to the

e s t i m a t i o n of homogenization efficiency as

States

Public

Health S e r v i c e ' s

the

opp ortu ni ti e s

for

the

same.

recommend

being
to the
per

They

indicative

error,

well adapted
was

we r e

Index of about

homogenized milk,

Public

the

s e p a r a t i o n method,

a F arrall

Health Se rvic e

milk

Doan and

due to faulty technique,

of p r o p e r l y

United States

g r a v it y

in

should contain

1 micron

of fat globules

recom ­

equipped with

homogenized milk

u nifo rm ly d i s p e r s e d fat globules
F arrall,

Parfitt

United
but
about

12 as

in c o m p a r i s o n

Index of about

8

cent.
According

and Weise

(1914)

to

Trout

were

(1950),

the f i r s t

e s t i m a t i o n of homogenization
of the

milk

after

q u i es c e n t

von Sobbe

investigators

storage.

of p r e s e r v e d

milk be

ated c y l i n d e r s

for

at

and B u r r

to advocate

efficiency by t e s ti n g

250 m i l l i l i t e r s

72 h ours

(1914)

various

They r e c o m m e n d e d
s e t a side

in

the
layers
that

s p e c ia l g r a d u ­

room t e m p e r a t u r e s .

Finally,

two

31
5 0-m illiliter portions

should be

r e ma in in g low er p o r ti o n
fat content we re
p or tion,

after

fat content,

drawn off f r o m

should be

equal to

100,

t e s t e d f o r fat.

top and the
If the

o riginal

then the fat content of the bottom

being c o n v e r t e d to a p e r c e n t a g e

was

the

c a l c u l a t e d to e x p r e s s

of the

o ri g i n a l

the homogenization effi­

ciency.
Procedures
b a s e d on the fat
United States
1947,

45

o

F.

ence

was

exceed

1943)
Public

as

10 p e r

Various

quart

t hese

have

after

the b a s e .
cent

made

involving

were
(1939,

the

top

48 h o u r s

the

value

(Trout

critical

(1939)

and S o m m e r
was

r e c o m m e n d e d by the
1947).

and Scheid,

As

adopted in

100 m i l l i l i t e r s

difference

the

of the

at

differ­
top

100

should not

Health S e r v i ce ,
1942;

and the

s t o r ag e

the p e r c e n t a g e

obtained f r o m

Public

evaluations

of homogenization

of qui es c e nt

The p e r c e n t a g e

(United States

Health Service

c ent r ifug a l f o r c e

degree

two m e a s u r e m e n t s ,

investigators

Snyder

tests

of testing

c a l c u l a t e d using

m illiliters

the

Health Service

consists

of the

From

estimating

s e p a r a t i o n p ri n c i p l e

Public

the t e s t

remainder

for

1947).

Doan and Mykleby,

earlier

United States

procedure.
(1943)

reported

u ti li z e d to h a s t e n the

homogenization

efficiency.

a method in which
separation

of fat in

32
Mayer

(1917)

homogenized milk

thought that the even d is t r i b u t i o n of fat in

should make

density m e a s u r e m e n t s
of homogenization.
this p r i n c i p l e

as

it p o s s i b l e

a means

More

recently,

in p e r f e c t i n g

to utilize

optical

of d e t e r m i n i n g the
A shworth (1949)

a t u r b i d i ty t e s t f o r

deg r e e

applied

d e t e r m in in g the

efficiency of homogenization.

Factors

Influencing

the

Efficiency

of Homogenization

Doan and M i n s t e r
(1943)
the

stressed

homogenizer

the

i m p o rt a n c e

and the

of homogenized milk.
not able

to obtain

rotary-type

as

J os ep hs o n,

mechanical
in the

condition of

efficient production

Doan and Adams

(1941)

efficient homogenization by me a ns

Doan and Mykleby (1943)

by a w i r e - c o r e
(1950),

efficient homogenization p e r
type

valve

after

concluded that

than with the

reviewing the

s ta n d a r d ,

of
conven­
were

pound of p r e s ­

literature

on homog­

was

adequate

milk which would m e e t the

Health Service

were

solid valve.

2,500 pounds p r e s s u r e

a homogenized

Public

system

and Judkins

machines.

sure

States

of the

(1941)

could be obtained with the

to obtain m o r e

Trout

F a r rail

as

able

to produce

valve

homogenizers

tional p i s t o n —
valve

enization,

(1933),

pro vi de d the

United

homo geniz er

33
and v al ve s
excess

were

in good m e c h a n i c a l

of 2,500 pounds

dispersion

of l it tl e

of the f a t mi gh t be

Jones
that milk

we r e

(1929),

should be

tem perature

to

(1932a,

was

1937)

t ha t the fat

were

able

is

at

those

These

r e p o r t e d by

80°

Doan and Mykleby
p a s t e u r i z a t i o n l o w e r e d the
Index on m i lk s
no effect
Wittig

account for
heat-treated
pounds).

(1943)

milk

was

M a xi mum

100 a t m o s p h e r e s

(ca

homogeniza­

obtained

melting point
the

same

as

(19 37).

r e p o r t e d that high—
tem perature

United St a te s

Public

im properly

homogenized at

1,500 pounds).

On the

but had
other

of the f i l m - m a t e r i a l

in homogenization

homogenization

Health Service

homogenized,

samples.

that a l t e r a t i o n

a decrease

the

essentially

and H ilker

t ha t had been

believed

limited

Trout

but no n ot iceable

above

we r e

on e fficiently homo ge nized

(1949)

F.

state.

Good f a t d i s p e r s i o n was

observations

Whitaker

recom mended

about the p a s t e u r i z a t i o n

in a liquid

in milk homo ge niz ed a t t e m p e r a t u r e s
of milk fat.

in

even though a f in e r

and o t h e r s

to d e m o n s t r a t e

recorded.

Pressures

achieved.

in mi lk h omogenized

fat d i s p e r s i o n

value,

h om o ge ni z ed a t o r

insure

and Scheid (1941)
tion effects

Doan

condition.

hand,

could

efficiency when high-

300 a t m o s p h e r e s

efficiency

was

(c a 4,500

obtained with

34
Su m m ary of the

Review of L i t e r a t u r e

The v i s c o s i t y of milk,
viscosity,

has

been

1.56 c e nt ip oi se s .

usually

r e p o r t e d by num e r ou s

This

value d e c r e a s e s

zation at n o r m a l p a s t e u r i z a t i o n
the p a s t e u r i z a t i o n
rum proteins.
cause

temperature

Generally,

an i n c r e a s e

is

as

the

tion,

has

has

p ro ducts

fat

ness

as

well

quantity and n a t u r e

of the

but m o s t g e n e r a l l y to the

milk fat.

containing fat.

and the

enhanced

v is c o s i t y of milk,

of fat-globule

been a s s o c i a t e d with i n c r e a s i n g

sweeping,

se­

in the v is c o s it y of milk following homogeniza­

of the

many t h e o r i e s ,

if

high fat content and low ho­

The b as ic

An unusually high deg r ee
erally

but i n c r e a s e s

in the v is c o s it y of milk which was

been a tt r i b u t e d to both the

state

slightly a f t e r p a s t e u r i ­

high enough to affect the

constituent fat and p l a s m a p r o t e i n s ,
physical

a t about

homogenization has been found to

tem peratures.

increase

relative

investigators

tem peratures,

by high homogenization p r e s s u r e s ,
mogenizing

e x p r e s s e d as

Fa t -c l u m p in g has

m o st of which a r e

electrostatic

charge,

agglutinin theory.

t heory is believed to be

applicable

viscosities

in d airy

been explained by

as follows:
interfacial

Of t h e s e ,

clumping gen­

grav itation al
tension,

or

s ti c k i —

only the agglutinin

in explaining the n o r m a l

35
fat-clumping

in milk.

to explain the
is

violently

However,

some

investigators

a g g r e g a t i o n of f at globules,

agi ta t ed ,

on the b a s i s

as

have

elected

found when mi lk

of the p h y s i c a l

s ta te

of the

g lo b u la r fat.
E f f i c ie n t homo geniz ation
f at globules

in milk f r o m

in d i a m e t e r

and

homogenized fat
increase

in the

Pu bl ic

factors

ones

48 h o u r s

r ange

as

surface

increased

plasm a

proteins

reported

pasteurization

homogenizer

factors

size
the

above

the

separation
F arrall

which influence

of

Index,
The

and

condition

milk.

in the l i t e r a t u r e
the

The

of h o m o g e n i z a ­

m echanical

of the

an

United States

of the f a t globules.

c o m p o s it io n

of

efficiency

homo ge nization t e m p e r a t u r e

reports

area

t ec h n i q u es .

and the

the

micron

approx­

surface

The

the

efficiency

tem perature,

and the

In view of the

storage,

in the

as:

as

of the

and c a u s e s

by n u m e r o u s

which m e a s u r e s

influencing

pressure,

various

the

s ize

to about one

of the f a t

designated

of q u i e s c e n t

the

recognized

are

Index,

been

the

is

b een t e s t e d

tion have

of the

average

v i s c o s i t y of homo ge niz ed m ilk.

important

which m e a s u r e s

it

the

s ix m i c r o n s

area

which a d s o r b s

Health S e r v i c e

fat a f t e r

the

Reputedly,

of h omo genization has
two m o s t

about

increases

i m a t e l y fivefold.

reduces

con c ern in g

efficiency of homogenization

36
and the

deve lo pme nt of a high v i s c o s i t y ,

ducted with m i lk s
study the
the

of v ary in g

effect of v a r i a t i o n s

f at and

experiments

solids-not-fat

in t e m p e r a t u r e

dev e lo pme nt of a high v i s c o s i t y

were

content to

and p r e s s u r e

in hom o ge niz ed

con­

milk.

on

EXPERIMENTAL

The
from

milk u s e d in this

patrons

milk was

of the

filtered

PROCEDURE

study was

Michigan State

upon r e c e i p t

ized at a p p r o x i m a t e l y

143° F .

for

Sa mples

s aved f o r

2.82 to

6.60 p e r

c e nt f a t and f r o m

d e t e r m i n e d by the

were

withdrawn at

single-stage

second

stage)

laboratory

phase

of the

of the

final

per

hour

cooled,

the

140°,

1,500,

model,

data

2,500

were

h omogenization

as

otherwise

ranged from

15.62 t otal

and

80°,

solids

70° and 60° F.

3,500 pounds

In one

after

employed.
was

of c e r t a i n

series

to 45° F.

on

A 2 5- ga l lo n p e r

u s e d during

the f i r s t

inconsistencies,

of t r i a l s

which it was

tem peratures.

pressure.

(500 pounds p r e s s u r e

obtained with a p i s t o n - t y p e ,

following p a s t e u r i z a t i o n ,
24 h o u r s ,

or

v a t - c o o l e d and p o r ­

90°,

homogenizer

but b e c a u s e

homogenizer.

proximately

11.12 to

100°,

and double —
stage

study,

30 m i n u t e s ,

milk was

homogenization w e r e

hour,

The

Mojonnier p r o c e d u r e .

to be homo ge niz ed at
Both

Cream ery.

subsequent analysis

After p a ste uriz atio n
tions

College

selected

and i m m e d i a t e l y h o l d e r —
p aste u r­

noted.

as

h e r d mi lk

and

500-gallon

the

milk was

s to red for

warmed

all

to the

ap­
i nd icated

38
In o r d e r
the

for

sam p le

of the

stored

it was

the

a t 45

of the

o

the

to

save

examination:

were

until

v olumes

cylinder

oil-im m ersion

we r e

determ ined

in the

after

24—
hour

Public

Health S e r v i c e

e ni zat io n

efficiency

of a S p e n c e r

in the

1-quart

determinations

was

s a m p le
we r e

100-

sample.
and

(1947)

top

test

The

microscope

m icrom eter.

o

on the

F.

for

1-pint

stored

size

drop

in

of the
after

25 m i l ­
under

which was
Homogenization

of the

which e x p r e s s e s

100 m i l l i l i t e r s

vol­

determ ined

a hanging

of the p e r c e n t a g e

held at 45

made

sample

the

diluted with

a s c e r t a i n e d by m e a n s

in t e r m s

fat content between the

one

1-pint

by m e a s u r i n g

storage.

w a t e r by examining

further

sam­

in i c e —
water

of d i s p e r s i o n w e r e

w e l l - m i x e d mi lk

lens

sample,

and one

100—
m illiliter

equipped with a c a l i b r a t e d o c u l a r
was

1—
quart

cooled i m m e d i a t e l y

degree

of the

of d i s t i l l e d

efficiency

v i s c o s i t y of the fin ­

the following t h r e e

one

on

examined.

layer

and the

m illiliter

liliters

F.

cream

graduated

fat globules
one

effect of t h e s e p r o c e d u r e s

in a g r a d u a t e d c y l i n d e r

samples

Cream
ume

necessary

s u b se qu e nt

m illiliter
All

the

efficiency of homogenization and the

i sh e d milk,
p le s

to evaluate

United St a te s
the

homog­

difference

and t ha t
48 h o u r s .

samples

in the

remaining
V i s co si t y

with the

aid

39
of a Br o ok fi e ld Sync h ro —
Lectric
the v i s c o s i t y of a fluid p r o d u c t
m easured

at

20

o

C.

in the p r o c e s s e d

In o r d e r

milk,

all

viscom eter,
as

which e x p r e s s e s

" relative

to obtain

samples

the

were

viscosityn
maximum

held at 45

o

when

viscosity
F.

for

72

hours.
Although the
of the
able

variations

to p r e p a r e

ratio

of

samples

t ha t o c c u r
a

series

were

in n o r m a l

probably
milk,

of r e c o m b i n e d

(32—
per

nonfat

milk

cent fat),

solids

skimmilk,

were

representative

seemed

d esir­

in which the

a wider

distilled

u s e d to p r e p a r e

it

m i lk s

solids-not—
fat to f a t v a r i e d o v e r

cream

following

m i lk

range.

water

Fresh

and low—
heat

synthetic

milks

of the

composition:

Series

A.

Eight p e r
from

Series

Series

C. T h r e e
from

Series

D.

solids—
not-fat

and fat

ranging

and fat

ranging

3 to 6 p e r cent.

B, Eleven p e r
from

cent

c e nt

solids-not-fat

3 to 6 p e r cent.
per

cent fat

8 to

11 p e r

Six p e r

cent fat

and s o l i d s —
not—
fat

ranging

cent.
and

ranging f r o m

8 to

11 p e r

cent.
The se
lar

m i lk s

were

processed

to that d e s c r i b e d f o r

and e x a m i ne d in a m a n n e r

the n o r m a l

m i lk

samples.

sim i­

RESULTS

Influence

The
various

data p r e s e n t e d

temperatures

viscosities
pounds

pressure

low—
f a t mi lk

in

on the

of low—
test

representative

Table

1 show the

efficiency

and h i g h - t e s t

milk

experimental

(4.4 to

data

are

6.6 p e r

data

r ange
the

was

of 80

lowered.

o

low -test

to

70

milk,

tendency was

o

F.

was

as

in the

F.

causes

was

c hurning

of

4 to 7 i nc lu si ve .
that the

ef­
tem ­

tem perature
clumping

the

to p r o f u s e .

in

clumping

An i n c r e a s e

recorded

Homogenization at t e m p e r a t u r e s

a partial

trials

homogenizing

in the

a ls o

with

The b alance

1 shows

the

2,500

are

different

h i g h - t e s t mi lk

moderate

and

trials

a c c o m p a n i e d by sli gh t

in the v i s c o s i t y of h i g h - f a t m i l k
tem peratures.

as

Homogenization

whereas

c la ssifie d

and t h r e e

in Table

data

different

in T a b l e s

f ici e n c y of homo ge nization d e c r e a s e d
perature

These

ce nt fat).

recorded

An i n s p e c t i o n of the

three

c e nt fat)

of

h omogenized at

valve.

of that obtained f r o m

influence

of hom o ge niz ation

milk

with a s i n g l e - s t a g e

(2.8 to 4.0 p e r

with h i g h - t e s t
the

of Homogenization P r o c e d u r e s

at t h e s e

lower

of the f a t which was

o

than

70

manifest

as

41
an aggregate

fat m a s s

ple bottles.

Homogenization is not complete

peratures

since

there

or

"cream

was

plug"- a t the top of the

an i n c r e a s e

at the

sam­

lower t e m ­

in the n u m b e r of l a r g e

fat globules.
The beh a vior of h i g h - t e s t p a s t e u r i z e d
s t r a t e d by the data p r e s e n t e d in Table

milk is

demon­

2 by an i n c r e a s e

in the

v i s c o s i t y and by the tendency of the fat to clump when the milk
was

homogenized at

was

ra ise d from

80

F.

1,500 to

When the homogenization p r e s s u r e

3,500 pounds

nounced i n c r e a s e

o c c u r r e d in the

to f o r m

and by an i n c r e a s e

lic

clusters

Health Service

Index,

At

were

that they were

so pro f us e

one f r o m
crease

another

also

in the United States
a decrease

3,500 pounds p r e s s u r e ,
practically

in the v i s c o s i t y

after

Pub­

in homogeniza­

the fat c l u s t e r s
indistinguishable

when o b s e r v e d m i c r o s c o p i c a l l y .

occurred

a pro­

tendency for the fat globules

indicating

tion efficiency.

(si n gl e- s ta g e) ,

the

A sharp

72-hour

in­

storage

period.
The data compiled
methods

of p r e p a r i n g

fic i e n c ie s ,
pasteurized

in Table

3 show the influence

of two

homogenized milk on homogenization ef­

fat-clumping

t en dencies,

and v i s c o s i t i e s

in high-fat,

milk homogenized at 3,500 pounds p r e s s u r e .

42
Single-stage,
conducive

high-pressure

to f a t —
globule

c o s it y when the
p rio r

homogenization of h i g h - f a t

clumping

mi lk had b e e n

to w a r m i n g

in that which has

to the
been

cooled f r o m

t his phenomenon o c c u r r e d
to

70°

F.)

The
was

and h i g h e r f o r

D o u b l e - s ta g e

Data
s tage

illustrating

the

homo ge niz ation a r e

homogenization
clumping
high—
fat

milk

pressures

145° F .

critical

F.

for

lower
the

for

the

and a ls o

to the v a r i o u s

the

warmed

vis—

24 h o u r s

tem perature
cooled

samples

at which

samples
(90°

F.).

influence

of

single-stage

entirely

1.

and d ouble-

Double —
stage

eliminated excessive

occurrence

of high v i s c o s i t y

fatin the

which had been homo ge niz ed at t e m p e r a t u r e s

conducive

to the

ho­

Homogenization

shown in F i g u r e

reduced o r

and p r e v e n t e d

o

s t o r e d a t 45

in the

h omogenization t e m p e r a t u r e ,

mo ge niz ation t e m p e r a t u r e s .

(80°

and an i n c r e a s e

milk was

d ev e lo p m e n t of this

and

characteristic.

Composition

The

literature

tain n a t u r a l l y
milk

on the

citations

occurring

efficiency

c o n c er n in g

variations

in the

the

influence

of c e r ­

c om p o s it io n of h e r d

of homogenization and the p ro d u c ti o n of

43
high v i s c o s i t i e s
resentative
are

samples

presented
The

zation at

have

of p r e p a r e d

in Table

data

on the

B).

Regardless

pressures

of the

c o m p o s it io n ,

v elopment of e x c e s s i v e

and below)
viscosity,

homogenization p r e s s u r e s
increase

m ore

of f at

tem perature
Milk
st a n t

at

effects

effects

6 per

of h om o ge ni ­

p r o d u c e d by v a r y ­

compounded to con­
cent while

11 p e r

ce nt

homogenization
had l ittle

but the

(3,500 pounds

samples
6 per

and

above)

cent,

C and

are

80

o

testing

while

11 p e r
D).

p resented

at n o r m a l
de­

caused

5 per
the

a

cent o r
critical

F.).

compounded to keep

manner

( Se r ie s

to

A and

e m p l o y m e n t of high

homogenized within

o

l evel

effect on the

milk was

(70

the

(Series

when the

8 and

in the

the

of m i lk s

r ange

with r e p ­

3.

viscosity

3 and

trials

2 and

in the

v a r i e d between

these

3 to

trials

of c o n t r o l l e d c o m p o s i t i o n

v i s c o s i t y of m i l k s

m a i n t a i n e d at

(2,500 pounds

sharp

and the

ranging f r o m

of s o l i d s - n o t —
f a t was

m i lk s

2 ill us tr 'a te

a given t e m p e r a t u r e

at l e v e l s

F urth er

8 and in F i g u r e s

in F i g u r e

ing the p r e s s u r e s
tain fat

b een c o n s i d e r e d .

the

the fat

levels

cent w e r e

treated

Representative
in F i g u r e

of

3.

v i s c o s i t y of l o w - f a t m i lk when the

content

con­

solids-not-fat
in a

sim ilar

data obtained f r o m

Little

change

solids-not-fat

was

noted

content

44
varied from
ture

was

c os it y

8 to

11 p e r

maintained

of the

at

high—
test

80

in v i s c o s i t y

e ni z at io n

80° F .

2,500

pounds

o

as

had l i t t l e

e ffect in inhibiting

the f at and

a

noted,

or

in v i s c o s i t y was
3,500 pounds
within the

promoting

viscosity.

h owever,

solids-not-fat

However,

the

when the

contents

were

homog­

apparent

pressure.
r ange

studied,

increase

concentrations
increased.

at

Ap­

fat-clustering

A slight

vis­

D showed

r e s u l t of h i g h - p r e s s u r e

s o l i d s - n o t - f a t content,

d e v e lo pm e nt of an e x c e s s i v e

C).

r e p r e s e n t e d by S e r i e s

and p ro n o u n c e d at

the

h o m o ge ni z at i on t e m p e r a -

(Series

An i n c r e a s e

parently,

v i s c o s i t y was

F.

m i lk s

an i n c r e a s e
at

cent and the

and the
in

of both

45
TABLE
The

influence

of v a r i o u s

tem peratures

h omogenization and on the
2,500 pounds

pressure

1

viscosity

on the

efficiency of

of m i lk h o m o g e n i z ed at

after pasteurization

Homogenization
Ef fi c ie nc y a s
Tem perature

72—
h ou r

Homogenization

Range

in the

Diameter
Fat

(M

milk

of

Globules

(° F.)

Low—
fat

V i s c o s i t y A fte r

Shown by

of

)

(3.51% fat

St or a ge
o
a t 45
F.

USPHS
Index

(ce ntip oise s )

(%>

and

12.18% total

solids)

140

1-2

8.1

2.4

100

1-2

7.4

2.4

90

1-2

9.0

2.4

80

1-4*1

12.1

2.4

70

2-6*

46.2

2.4

60

2-6*

--------++

Hig h- f a t

milk

(6.6% fat

and

2

15.62% total

2.2

solids)

140

1-2

9.8

2.8

100

1-2

8.3

2.8

90

1-3

10.1

2.8

14.0

3.2

80
70

2-6**

68.0+2

3.2

60

2-8*

--------++++

2.8

Degree

of fat -clu m p i n g

2 ^
Cream -lay er

formation

46
TABLE
The

influence

of v a r i o u s

e ni z at io n and on the

2

pressures

v iscosity

on the

e f f iciency of homog­

of m i l k h om o g e n i z ed at

80

F.

after pasteurization

Homogenization
Efficiency

72—
h ou r St orage
Range

in the

Diameter
Fat
(lb. / sq.

in.)

Low—
fat

V i s c o s i t y After

Shown by

Homogenizing
Pressure

as

of

Globules
(M)

milk

(3.5% fat

at 45° F .

USPHS
Index

(centipoises)

(%)

and

12.18% total

solids)
2.4

0

2-9

1,500

2-4

15.2

2.4

2,500

1-4*1

12.1

2.4

3,500

1—
3*

10.2

2.4

High—
fat

milk

(6.6% fat

and

15.62

total

solids)

0

3-12

1,500

2-5*

15.0

2.8

2,500

2-4***

14.0

3.2

3,500

2—
4****

21.4

6.2

Degree

of f a t - c l u m p i n g

2.8

47
TABLE
The

influence

mo ge niz ation

of v a r i o u s

teurization

at

tem peratures

and on the

c e nt fat h omogenized a t
145

F.

3
on the

v i s c o s i t y of milk
3,500 pounds

and a f t e r

a

efficiency of ho­

containing

pressure

20-hour

6.6 p e r

following ^pas­

storage

at 45

F.

Homogenization
Efficie ncy as
Tem perature

Homogenization

Viscosity After

Shown by

of

72-ho ur
Range

in the

140

100

90

80

70

60

(C)

(C)1

1-2

9.1

2.8

<w)2

1-2

8.6

2.8

(C)

1-2

9.3

2.8

( W)

2-4

11.2

2.8

(C)

1-3

10.4

2.8

20.0

4.2

21.4

6.2

C r e a m plug

2.6

36.0

3.0

3

(C)

2-4***

(W)

3-8

(C)

3-5**

(W)

3-9

Cream

layer

2.8

(C)

3-8

Cream

plug

2.8

(W)

3-9

Cream

layer

2.8

-

Milk p a s t e u r i z e d
to homogenization

2

(W)

(centipoises)

(%)

C~)

(W)

—P a s t e u r i z e d

milk,

at

145° F .

for

of f a t —
clumping.

30 m i n u te s

and cooled

tem perature.
stored

20 h o u r s

to homogenization t e m p e r a t u r e .
Degree

F.

Index

F a t Globules
(° F.)

at 45°

USPHS

D i a m e t e r of

St orage

at 45

o

F.,

warmed

TABLE 4
The influence of various tem p eratu res and p r e s s u r e s of hom ogenization on the e fficie n c y of
hom ogenization and the v is c o s it y of m ilk (2.8 per cent fat and 11.01 per cent total solids)

Hom ogenization P r e s s u r e (lb ./s q . in.)

H om ogT em per­
ature

1

1,500

2,500

3,500

Hom ogenization
E fficien cy as
Shown by

Hom ogenization
E fficien cy as
Shown by

Hom ogenization
E fficien cy as
Shown by

Range
in D i­
a m eter
of Fat
Globules

USPHS
Index

(° F.)

(*)

(%)

140
100
90
80
70
60

1-2
1-2
1-2
1-4
2-5
2-6

10.0
10.0
11.0
14.0
20.0

D egree of fat-clu m pin g

V isc o sity
After
72-hour
Storage
at 45° F.

Range
in D i­
a m eter
of Fat
Globules

(cen tip o ises)
2.2
2.2
2.2
2.2
2.2
2.1

USPHS
Index

(%)
1-2
1-2
1-2
1-3
1-4
2 -6

6.5
6.5
7.0
8.4
12.0 .
------++

V isc o sity
After
72-hour
Storage
at 45° F .

(cen tip o ises)
2.2
2.2
2.2
2.2
2.2
2.1

V isc o sity
After
72-hour
Storage
at 45° F .

Range
in Di­
am eter
of Fat
Globules

USPHS
Index

(>u)

(%)

(cen tip o ise s)

1-2
1-2

6.5
6.5
6.5
8.0
11.0

2.2
2.2
2.2
2.2
2.2

------+++ 2

2.0

'-2 1
1-3*
1-4*
2 -6

C r e a m -la y e r form ation

TABLE 5
The influence of various tem peratures and p r e s s u r e s of hom ogenization on the efficie n c y of
hom ogenization and the v is c o s it y of m ilk (4.0 per cent fat and 12.56 per cent total solids)

Hom ogenization P r e s s u r e (lb ./sq . in.)

Hom ogptii T.afinn
T em p er­
ature

1,500

2,500

3,500

Homogenization
E fficien cy as
Shown by

Hom ogenization
E fficien cy as
Shown by

Hom ogenization
E fficien cy as
Shown by

Range
in Di­
am eter
of Fat
Globules

V isc o sity
After
72-hour
Storage
USPHS
at 45° F.
Index

(° F.)

(M)

(%)

(cen tip o ises)

140
100
90
80
70
60

1-2
1-2

13.0
13.0

2.5
2.5

1-3
2-4
2-6

20.2
52.0

2.5
2.5
2.3

--------++

D egree of fat-clum ping

2

Range
in Di­
am eter
of Fat
Globules

USPHS
Index

Cm )

(%)

V isc o sity
After
72-hour
Storage
at 45° F.

Range
in D i­
am eter
of Fat
Globules

(cen tip oises)

1-2
12.0
2.5
1-2
12.2
2.5
no sam p les co llec te d
14.4
2.5
*- 3 1
1-4*
36.5
2.5
2
2 -6 *
2.3
-------- ++

1-2
1-2

U3 1
1-4*
2 -6 *

V isc o sity
A fter
72-hour
Storage
USPHS
at 45° F .
Index

(%)

(cen tip o ises)

7.5
7.5

2.5
2.5

10.0
15.2

2.7

------+++

2

2 ‘6
2.3

C r e a m -la y e r form ation

TABLE 6
The influence of various tem p eratu res and p r e s s u r e s of hom ogenization on the efficien cy of
homogenization and the v is c o s it y of m ilk (4.4 per cent fat and 13.10 p er cent total solids)

Hom ogenization P r e s s u r e (lb ./s q . in.)

H om ogT em p er­
ature

(° F.)

140
100
90
80
70
60

1,500

2,500

3,500

Homogenization
E fficiency as
Shown by

Homogenization
E fficien cy as
Shown by

Hom ogenization
E fficien cy as
Shown by

Range
in Di­
am eter
of Fat
Globules
W

1-2
1-2
1-3
2-5
2-5
2 -6

V isc o sity
After
72-hour
Storage
at 45° F .

USPHS
Index

(%)
8.6
9.0
10.1
20.4
68.2
--------++

D egree of fat-clum ping

-

Range
in Di­
am eter
of Fat
Globules

USPHS
Index

(cen tip o ises)

(M)

(%)

2.6
2.6
2.6
2.6
2.6
2.6

1-2
1-2
1-2
2-4
2 -5
2-6

8.0
8.0
10.0
15.2
50.0

,
--------++ 2

V isc o sity
After
72-hour
Storage
at 45° F .

(cen tip oises)
2.6
2.6
2.6
2.6
2.6
2.5

V isc o sity
After
72-hour
Storage
USPHS
at 45° F.
Index

Range
in Di­
a m eter
of Fat
Globules

(%)

H
1-2
1-2
!- 2

2 -4 **
2-4
2-6

i

7.6
7.6
8.2
14.1
45.6
?
--------4+

(cen tip o ises)
2.6
2.6
2.6
2.8
2 ‘6
2.5

C r e a m -la y e r form ation

TABLE 7
The influence of various tem peratu res and p r e s s u r e s of hom ogenization on the efficie n c y of
hom ogenization and the v is c o s it y of m ilk (6.2 per cent fat and 15.50 per cent total solids)

Hom ogenization P r e s s u r e (lb ./s q . in.)

H om ogT em per­
ature

1,500

2,500

3,500

Homogenization
E fficien cy as
Shown by

Homogenization
E fficien cy as
Shown by

Hom ogenization
E fficien cy as
Shown by

Range
in Di­
am eter
of Fat
Globules

USPHS
Index

(° F.)

\ M)

(%)

140
100
90
80
70
60

1-3
1-3

12.0
12.0
15.0

U3 1
2 -5 *
2 -5 *
2 -8 *

V isc o sity
A fter
72-hour
Storage
at 45° F.

(cen tip o ises)

J

91.5
—

D egree of fat-clum ping

++

L

V isc o sity
After
72-hour
Storage
at 45° F .

Range
in Di­
am eter
of Fat
Globules

USPHS
Index

H

(%)

(cen tip o ises)

Cu)

(%)

(cen tip o ises)

10.0
10.1
12.2

2.8
2.8
2.8

1-2
1-2
1-3

9.2
9.2
11.0

2.8
2.8
2.8

16.0
48.0

7.8
3.0
2.6

2-4**** 1 !6.2
2 -6 * *
70.0+
2 -8 * *
-------- +++

2.8
2.8
2.8
2.8

2 -4 * * *

2.8
2.6

2 -4 * *
2 -8 **

1-2
1-2
!- 3

1

-------- +++

C r e a m -la y e r form ation

Range
in D i­
a m eter
of Fat
Globules

V isc o sity
A fter
72-hour
Storage
USPHS
at 45° F .
Index

22.0
7.0
2.6

Sample was lo s t

52
TABLE
The

influence

of v a r i a t i o n s

v i s c o s i t y of a dj us te d mi lk

Ad­
justed

in f a t

8
and s o l i d s - n o t - f a t on the

homogenized a t v a r i o u s

pressures

V i s c o s i t y of Homogenized
Fat

Milk

(lb./sq.

S o li d s -

in.)

not-fat
0

(%)

Milk

(%>

1,500

2,500

3,500

( c e nt i —

( c e nt i —

( c enti—

( c e nt i —

p o i se s )

poise s)

p o i se s )

p o i se s)

3.10

8.00

2.5

2.5

2.5

2.5

Series

4.15

8.00

2.5

2.5

2.5

2.7

A

5.00

8.00

2.5

2.5

2.7

3.2

5.95

8.00

2.7

2.8

3.2

5.9

3.15

11.00

2.8

2.8

2.8

2.8

Series

4.00

11.00

2.8

2.8

2.8

2.8

B

4.90

11.00

2.9

2.9

3.0

3.2

5.95

11.00

3.0

3.3

3.4

6.5

3.00

8.30

2.5

2.5

2.5

2.5

Series

3.00

7.10

2.5

2.5

2.5

2.5

C

3.00

9.90

2.6

2.6

2.6

2.6

3.00

10.95

2.8

2.8

2.8

2.8

6.00

8.10

2.9

3.0

3.0

3.2

Series

6.00

9.25

3.0

3.0

3.2

3.4

D

6.00

10.00

3.3

3.3

3.4

3.5

6.00

10.95

5.0

4.8

6.0

6.2

(CENTIPOISES)

53

VISCOSITY

SINGLE-STAGE
DOUBLE-STAGE
5 0 0 P O U N D S / S Q . I N.
SECOND STAGE

1,000

2^000
H O M O G E N IZ A T IO N P R E S S U R E
( P O U N D S /S Q . IN .)

O

Figure

1.

The

effect

of

single-

m o g e n i z a t i o n on the v i s c o s i t y
®
o
cent) h o m o g e n i z e d at 80
F.

and

double-stage

of h i g h - f a t

m i lk

ho­

(6.6 p e r

SERIES A
8 % M .S.N .F

SERIES B
U% M . S . N . F

CONTROL
^500 ( POUNDS/SO.IN.)
^500 (POUNDS/SO. IN.)
3,500(P0UNDS/SQ.INJ

*

♦

V IS C O S IT Y

( C E N T IP O IS E S )

8r

/

♦

.

/

♦

J___________ I___________

4

5

6

FAT %

Figure I .
The influence of different homogenizing p r e s s u r e s maintained at 80 F . on the
v isc o sity of milk containing 8 per cent so lid s-n o t-fa t plus various amounts of fat (SERIES
A) and corresponding data on milk containing 11 per cent so lid s-n o t-fa t (SERIES B).

S E R IE S C
3 % FAT

SERIES D
6 % FAT

CONTROL
IJ500 (PO U ND S/SQ.IN .)
£ 5 0 0 ( P 0 U N D S / S Q . IN.)

5-

^ 5 0 0 ( POUNDS/SO.I N.)

VISCOSITY

(C E N T IP O IS E S )

8

8

10

II 8

MILK S O L ID S - NOT*FAT

9

10

II

(% )

F i g u r e 3. The influence of d iffe re n t homogenizing p r e s s u r e s m a in ta in e d at 89° F . on the
v is c o s ity of milk containing 3 p e r cent fat plus v a r io u s am ounts of s o l i d s - n o t - f a t (SERIES
C) and c o r r e s p o n d i n g data on milk containing 6 p e r cent fat (SERIES D).

D ISC U SSIO N

The

results

o bt ained f r o m

the fat c on te n t of m ilk,
enization
or

and the

double-stage

tro ll in g

the

type

valve

systems)

are

state

of the
is

viscosity

apparently

closely

milk

and p r e s s u r e

associated

e m ployed

im portant

at

well

with

as

for

factors

the fat

of homog­

in con­

develop­
The

h omogenization

some

other

that

(single-stage

and on the

d if f e r e n t

responsible
as

indicate

in h om o ge ni z ed milk.

g lo b u l a r fat

noted in h o m o g e n i z e d

cal

tem perature

e f ficiency of homo ge niz ation

tem peratures

nomena

in v es ti g a t io n

of homo ge ni z at i on

ment of an e x c e s s i v e
p h y si ca l

the

this

of the

def e c ts

u ndeterm ined phe­

when it is

in this

criti­

condition.

Viscosity

High homo ge ni z at i on p r e s s u r e s
and low homo ge niz ation
f ic i e n t h o m o ge ni z at i on
per

c ent o r

opment
per

m ore),

of e x c e s s i v e

cent).

tem peratures

(greater
(ca

80°

and high v i s c o s i t i e s

but have

l it tl e

viscosities

Such an o b s e r v a t i o n

or

than

F.)

2,500 pounds)

augment

in h i g h - f a t

no influence

in low—
fat

milk

would l e a d

one

to

m i lk

on the

(less

inef­
(5.0

devel­

than 4.0

suspect

that

57
the

ratio

of

tion t r i a l s

solids—
not—
fat

with p r e p a r e d

that m o d e r a t e
exert little

influence

an e x c e s s i v e
2 and

3).

ever,

for

v aria tion s

A marked

(1929a)
at
tio

repo rted

3,500 pounds

milks

of known c o m p o s i t i o n

in the

solids—
n ot—
fat

in m i l k

increase

containing

enization p r e s s u r e s

no clumping
pressure,

were

varied from
for

on the

reported

2,2 to

basis

in m i lk

in a

s ta te

of

of the

results

represented
in the

liquid

shifting
m i lk
state

Doan (1931)
could be

had been

(100
also

r e d u c e d by

the

clumping

100° F .
to fat

o

F.),

might be

ratio

ac counted
investi­

at which f at was

whereas

homogenized

ra­

and i n c r e a s e d

obtained in the p r e s e n t

(80

homog­

Doan

solids—
not—
f at to fat

differences

how­

while

D oan's

data

the fat was

F„).
showed that the

increasing

in h om o ge ni z ed c r e a m .

recorded,

pressure.

out a t a t e m p e r a t u r e

equilibria

tha t

(Figures

h omogenized a t

howe v e r,

when the
These

carried

was

80° F .

p r o v i d e d the p l a s m a - s o l i d s

1.3.

gation which was

d e v e lo p m e n t of

content p r o v i d e d

2,500 pounds

indicate

content of milk

hom o ge niz ed a t

a high-fat

exceeded

and the

in v i s c o s i t y

r e m a i n e d below 0,3 to 0.5,

viscosities

involved, but h o m o g e n i z a ­

on f a t - c l u m p i n g

viscosity

m i lk

to f a t was

the

degree

amount

Although the

of clumping

of p l a s m a - s o l i d s

data p r e s e n t e d

in F i g u r e

58
3 show s o m e
levels

of

can be

reduction

solids—
not-fat,

disregarded.

surfacing
to c o v e r

in the

m aterial
a ll

of the

of s o l i d s - n o t —
fat

the

(Doan,

Some

of the

effect

Apparently,
present
fat

1929a;

is

so

there

i nconspicuous
was

thus

Wittig,

little

effect

in r e t a r d i n g

in this

paper

are

thickening

o b s e r v e d by Moore

(1947).

Why

such

a phenomenon as

should o c c u r

under

m aterial for

interesting

U n reported
under

conditions

when the

skimmilk

s o l id s ,

any p o t e n ti a l
a sso cia te d
protein

the
for

conditions

was

to those

Trout

in v i s c o s i t y

e xperim e nt furn ishes

or

the

homo ge ni z at i on

reported for
7 2- h o u r

whole

of s k i m m i l k
milk,

has

viscosity values,

but

s u p p l e m e n t e d with additional nonfat d r y

viscosity

a m arked

was

increase

with the f at c ontent of the

s t a b i li ty .

and

spe c u l a ti o n .

imm ediate

b asic

of this

to the

to the p r o g r e s s i v e

an i n c r e a s e

show that the

sim ilar

on the

milk

the

data

no effect

sim ilar

relative

d evelopment of high v i s c o s i t i e s
milk

in the le v e l

1949).

data p r e s e n t e d

of h om o ge ni z ed

t ha t it

solids—
not—
fat

any v a r i a t i o n

m i lk has

at high

enough of the f a t -

in the l o w e s t l e v e l of

surfaces,

in n o r m a l

fat-clumping

ten den cy of fat to clump

raised

slightly.

in v i s c o s i t y
milk

and/or

Therefore,

m u s t be

c lo s e l y

a lteratio ns

in

59
Although the
this

study wa s

ences

(Bateman

The

increase

attributed

in the

in the

from

h om o g e n i z a t i o n
the

viscosity

fat is

a l iq u i d

volume
in the
the f at

state.

study.
m i lk

of the
volume

of the

g l o bu le s

fat

sharp

due

d isp e rs e d phase
of the

the

to

dispersion

in h o m o g e n i z e d

has been

of

serum
fat

proteins

globules

a greater
m ilk,

provided

grounds,

increases

this

medium.
could

phenome­

viscosity

increase

Profuse
cause

and

the

in v i s c o s i t y

in the

ad d it io n a l

of

degree

and an a c co m p a n y i n g

m i lk

m i lk .

high p r e s s u r e s

increase

to an

whole

to

d isp e rs e d phase

dispersed

homogenized

the

not p ossible

milk

of the

c on di ti on s,

Any f u r t h e r

m u s t be

i t was

adsorption

On t h e o r e t i c a l

account fo r

in t h i s

homogenized

these

should d i s p e r s e

increase

non co u ld not

in the

in v i s c o s i t y

of p a s t e u r i z e d

and n u m e r o u s l y

Under

F.,

volume

homogeniza­

homogenization p r e s ­

of h o m o g e n i z e d

in the

in

slight d i ffe r­

t h a t the

increase

100°

viscosity

an i n c r e a s e

1912).

believed

slight

above

method used

to d e t e c t

Under n o rm al

viscosity

to an i n c r e a s e

(Hatschek,

ported

in a

1928).

viscosity

delicate

generally

results

on the n ew ly f o r m e d

in

is

at t e m p e r a t u r e s

a change

resulting

it

and S h a rp ,

and

measure

milk

of the

sufficiently

in v i s c o s i t y ,

tion of whole

sures

not

sensitivity

re­
of

in the

decrease

clumping

of

s u c h a change.

60
The clumps

of fat globules

since

of the d i s p e r s i o n

some

c lusters.
p ersion

Figure

as

individual

medium would be

been p r e p a r e d

in the v i s c o s i t y

examinations

made

t r a p p e d in the

to i l l u s t r a t e

Since
associated

the

of homogenized milk.

on s a m p l e s

r e v e a l e d extensive

observation lends

how the

of homogenized milk of high v i s ­

occurrence

of c l u s t e r s

with the high v i s c o s i t i e s

of homogenization,

fat

is

is

reported

explored.

is

assum ed

surface

layer

a

as

suggested by Rahn and Sharp

or

one of the
and

seru m proteins,
speculation.

not been o v e r - h e a t e d o r

is

study,

specific
(1928),

conditions

and the

smaller

At any r a t e ,

Wittig (1949)

m e cha n ­

subjected to e x t r e m e s

is
a

surfaces.
material,

and o t h e r s ,

of c o n si d e ra b l e

whole

of

globules,

surface-active

a m atter

the

and the d eg r e e

to s u r r o u n d the new fat
is

has been

When the fat globule

homogenized and b r o ke n up into n u m e r o u s

troversy

in this

Under n o r m a l

in the liquid state

ical efficiency of the h om o ge ni z er .

Whether this

Such an

of fat globules

a function of the applied p r e s s u r e

of p r o t e i n

an

support to the above postulation.

should be

dispersion

dis­

Microscopic

clumping of the fat globule.

clumping tendency

layer

globules,

and clumping of homogenized fat could account f o r

increase

cosity

4 has

would act

con­

milk which has
in p r o c e s s i n g

treatment

should contain adequate

to supply the
1931).

requirements

Wittig (1949) has

f iciencies

at high p r e s s u r e s

peratures

were

other

hand,

observed

as

inferior

Doan and

an i n c r e a s e

indicated by the

(Doan,

1929a;

pasteurization tem ­

Mykleby

in the

materials

homogenization ef­

when e xc e s si ve

ciency when high—
heat t r e a t e d
pressures,

of t hese

of the new sur f a c e

reported

employed.

quantities

(1943),

on the

homogenization effi­

milk was

homogenized at n o r m a l

United States

Public

Health S e r ­

vice Index.

Homogenization Efficiency

When t e m p e r a t u r e s
homogenization is
Such evidence
which r e s u l t s

incomplete

from

incomplete

(1937)
was

who

These

o

and 60

regardless

is f u r n i s h e d by the

the homogenized milk.
observ a tion s

below 70

homogenized at

dispersion
data a r e

are

utilized,

of the p r e s s u r e
cream

of the fat

used.
volume

globules

in

in a g r e e m e n t with the
and Whitaker

and Hilker

only slight o r no fat d i s p e r s i o n when milk
80° F.

o r low er .

In fact,

(1941)

d e m o n s t r a t e d that when raw milk was

times

at 40° F.

at

F.

r e la t iv e l y l a r g e

of T r o ut and Scheid (1941)

recorded

o

5,000 pounds p r e s s u r e ,

T rout and Scheid

r ehomogenized five

the fat failed to

62
d isp erse .

T h e ir

of c o a l e s c e d o r
homogenization
In the
to 70

o

F.,

experim ents

c h u r n e d f a t was f o r m e d
was

a l s o b et w ee n

been w a r m e d

from

F.,

layer

ever,

a n on un ifor m

observed.

90

was

c lu s te r.

up to

fact

p rotein

milks,

as

not been

these

increase

the

result

definitely

Overman

and

above

1941;

tem peratures,

solidification

(Sharp

Tracy,

of the

the f a t / s e r u m

plug

interface

1939;

a

volume

fat-clumping

thickening

were
Moore

to be

established from

(Brunner

selective

there

were
always
and

a denatur—

existing

1951b).
is

and J a c k ,

adsorption

enhances

How­

Menefee,

Dunkley and S o m m e r ,

and t h e r e b y

o

although

the

1946;

and S o m m e r ,
that

down

to a p r o t e i n - l i k e

assum ed

Doan,

o

milk has

studies.

in v i s c o s i t y .

1944;

80

p e r i o d at 45

characteristics

it is p o s s i b l e

which would p r o m o t e

when the

of homogenization,

Shahani

g lo b u la r f a t

and Krukovsky,

F.

and p r o f u s e

(Dunkley and S o m m e r ,

1951)

o

between

cold-storage

attributed p ro g re ss ive

has

cream

when l o w - t e m p e r a t u r e

r a nge

noted in c r e a m

evidence

the

100

Such a phenomenon could be

ation of the
this

o

dispersion

In h i g h - f a t

(1947)

tem perature

a prelim inary

a c co m p a n ie d by a m a r k e d
T rout

a definite

employed.

homogenizing

no c r e a m

showed t ha t

At

a partial
1950;

King,

of p r o t e i n
1944)

at

fa t-c lu s te rin g .

63
Or,

according

ner

and J a c k

sults
is

to Hu nz i ke r
(1950), King

when the p h y s i c a l

conducive

f at-globule
of the

to

state

King

ing to the p r e s e n c e
agent

a maximum
According
1938b),

tard

to van Dam

requires

equilibrium

the

of the

at 45

globule

requirement

for

mechanical

action

attrib uted fat—
clump­

occurred,
This

fat

it

developed

behavior

several

p r o b a b ly

in the f a t globule

a given

storage

hours

to

and

temperature.
(1938a,

reach

a condition

F.

when an i n c r e a s e
procedures,

homogenization

second—
stage

as

together.

and Rish oi and Sharp

o

fat

re­

in v i s c o s i t y

it was

possible

accom ­
to

d ev e lo p m e n t of high v i s c o s i t y by using

low -pressure
in a

also

72 h o u r s .

(1923)

processing

or

has

Brun­

which could con c ei va b ly a c t

developed f o r

specific

second,
cess

value

inhibit

fat

within

instances

or

necessary

(1937),

fat-gathering

surface

in v i s c o s i t y

In m o s t
panied

The

s o l id ifi c a t io n of the

g l o b u l a r f at

of p h y s i c a l

of the

to hold the fat globules

value
a

and Der b y

and o t h e r s ,

(1951)

of f r e e

When an i n c r e a s e

resulted from

Bird

would be f u r n i s h e d by the

homogenizer.

to a m a x i m u m

(1951)

11s t i c k i n g . 11

contact

a c ementing

(1940),

valve

either

system.

as

a

separate

re­
a
pro­

ORIGINAL FATGLOBULE MEMBRANE
NONHOMOGENIZED
FAT GLOBULE

/* > j~ N E W FAT-GLOBULE
MEMBRANE

NORMAL
MEMBRANE

HOMOGENIZED
FAT GLOBULE

HOMOGENIZED

B
: ^HOMOGENIZED
y FAT CLUSTER
ENTRAPPED
SERUM

F i g u r e 4. Schem atic draw ing showing how the d i s p e r s i o n and c l u s t e r i n g of h om oge nize d fat
could, in p a r t , account f o r an i n c r e a s e in the v is c o s ity of h o m oge nize d milk.
A - N o r m a l fat globule with its a d s o r b e d m e m b r a n e - l i k e c o v e ri n g s .
B - w e l l - d i s p e r s e d globules r e s u lt in g f r o m efficie nt hom ogenization.
C - F a t - g lo b u le c l u s t e r s f o r m e d by inefficient hom ogenization.

a

SUM M ARY O F SEC TIO N I

High-fat milk

(greater

enization t e m p e r a t u r e s

are

globules

conditions

5.0 p e r

(80° to 70° F.)

homogenization p r e s s u r e s
inch)

than

(greater

cent), low homog­

and high,

s in gle-stage

than 2,500 pounds

which contribute

per

to the c lustering

square

of fat

and to the development of high v isco sity in homogenized

milk.
Normal

v a ri a ti on s

in the

produced insignificant changes

s o l i d s - n o t - f a t content of milk

in the v is co s it y of homogenized

milk.
When the p r o c e s s i n g p r o c e d u r e s
development of high viscosity,
reduced o r

were

the exce s sive

conducive

to the

viscosity could be

completely eliminated by rehomogenization at

pounds p r e s s u r e

or

by s ec o nd-stage

homogenization.

500

SE C TIO N

THE

RELATIONSHIP

GLOBULAR FAT

BETWEEN

EXISTING AT

TEMPERATURES AND THE
THE

II

DEVELOPMENT

OF

THE

EQUILIBRIA OF

HOMOGENIZATION

TENDENCY

TOWARD

HIGH VISCOSITY

IN HOMOGENIZED MILK

R EV IEW O F L IT E R A T U R E

Wittig
peratures

(1949)

r e p o r t e d that homogenization at low t e m ­

r e s u l t e d in the

clumping

in the fluidity of the fat,
forming

s ub s t a n c e s

temperature.
perature

was

temperature
(1939)
ules

The

to 60

The l a t t e r

m a te rial

whose p r e s e n c e

ley and S o m m e r

(1944).

substance

was

when the fat was
thin.

Moore

to 65
o

o

C.

to 42

and d e c r e a s e d when the
o

C.

d e s c r i b e d by them

an agglutinin

i n c r e a s e d the t en­
c o n f irm e d by Dunk­

Skelton (1941) believed that

melted.

mogenization of milk at

solid globules.

as

o b s e r v a t i o n was l a t e r

and T r o ut

and Krukovsky

a d s o r b e d on the liquid fat glob­

a d s o r b e d on solid fat,

adsorption on the fat

Sharp

solidified fat-globule

This

in the f i l m -

v a r i e d with the

that a d s o r b e d on the

was

dency to clump.

cific

o

m a te rial

on the

of changes

He

but was

some

spe­

released

concluded that it could be l e c i ­

(1947)

were

80° F.

surf a c e

of changes

of fat i n c r e a s e d when the tern—

was lo w e r e d to 37

different f r o m

not b ecause

adhesive p r o p e r t i e s

dispersion

believed that the

was

but bec a us e

whose

ra ise d

of fat,

was

of the opinion that the ho­
accompanied by con si de r a bl e

and that

r a pi d c r y s t a l l i z a t i o n within

68
the fat

resulted from

the

v ig o r o u s

a g i t a t i o n acco mpan ying

ho­

mogenization.
A c c o rd i n g

to H u n z i k e r

Dam and B u r g e r s
and J a c k

(1950),

granules

d ur in g

(1935)
the

the

(1940),

and

as

coalescence
c hurning

Bird,

et

of f a t globules

of c r e a m

was

of the

m aterial

a d s o r b e d on the

fat as

it was

on the

physical

state

of the

globule.

ditions,

coalescence

ing t o g e t h e r
studies
them
ical

a t the

by Ri shoi

to f o r m
state

Herreid

a

somewhat

concept

would have

because

these

of the

areas.

and Sharp
c o n c e r n in g

tem perature.

a certain

surface

both solid

and u n d er

semisoft

(1938a)

c hurning

at the

a mou nt of

of the

and

con­
stick­

Churning
(1940)

led

the p h y s ­

Skelton and
s o lid ificatio n

to o c c u r

to p r o d u c e

maximum

thickness

of the f a t globule

in c r e a m .

King
membrane

t he se

sim ilar

b e l i e v e d t ha t

within the f a t globule
viscosity

at

and Sharp

of the f at a t the

(1941)

surface

dependent

surface

conditions,

thought to o c c u r

of f a t globules

made

of the f at

churning

fat-globule

was

van

into b u t t e r

not as

nature

liquid fat e x i s t

(1937),

d i s c u s s e d l a t e r by B r u n n e r

on the

At o p t i m u m

al.

(1950)

as

microscope,

5 to

estim ated

the

10 m i l l i m i c r o n s .

he found t ha t

the

surface

By the
layers

use

of a polyphase

of h i g h - m e l t i n g

69
fats
as

were

the

oriented

s y s t e m a t i c a l l y on the

r e s u l t of p r e s s u r e

He pointed out l a t e r
cence
and 25

occurred
o

C.,

exerted

(King,

most

1951)

of the

globule

on f a t g lobules by clumping.
that f a t —
clumping

satisfactorily

a tem perature

surface

and c o a l e s -

at t e m p e r a t u r e s

a t which the f a t i s

between

15

o

in a t r a n s i t i o n a l

state.
Two p r a c t i c a l
of g lo b u l a r fat
measures
changes
and (2)

are

small

from

differences

e m ployed the

Sharp

(1938a)

made

equ ilibria

In the p r e s e n t
by J a c k

study,

s ec t io n was

from

which the
Van Dam

dilatometer

of the

(1943)

of the

been

amount

fat when m i l k

is

state
which

as

it

solid to a liquid,

q ua nt it ie s
(1922)

the

of solid and

and Rishoi

and

me th od and Rishoi
method

in

and

studying

different t e m p e r a t u r e s .
technique

described

employed.

experimental
the

a

of fat

which m e a s u r e s

calorim etric

has

technique

volume

calorim etric

in m i lk fat at

to d e t e r m i n e

in g lo b u l a r

s pecific

technique

a direct

and B r u n n e r
The p u r p o s e

present

use

the p h y s i c a l

a dilatometric

s olid o r

calculated.

(1938b)

determining

in the

from

Sharp

the p h y s i c a l

(1)

calorim etric

h e a t of the fat,

liquid f at can be

for

a va i la bl e :

a liquid to a

a direct

specific

m e th o d s

of

work

reported

in t his

solidified fat that is

homo ge niz ed efficiently

70
and to indicate

the

variations

enized at t e m p e r a t u r e s
of a high v i s c o s i t y .

that

which a r e

occur

when m i lk

conducive

to the

is

homog­

dev e lo pm e nt

EXPERIMENTAL PROCEDURE

Sa mples
according
for the

of p a s t e u r i z e d

to the

t echniques

calo rim etric

increase

described

s tu dies

because

and high p r e s s u r e s

The

samples

were

was

u se d as

the

p ro x i m a t e l y

divided into two

c o n t r o l and was

20 h o u r s

sam p le

was

prior

in Section I,
of its

to the

Figure

5 shows

vessel

is

the

insulation.

type,

heating

chromalax heater

1—
quart lots.

placed

current.

means

of a t h e r m o m e t e r
was

The

q ua r t

examination.

ap­
The

and then cooled

slowly

d e s i r e d homogenization t e m p e r a t u r e .

calorim eter

e l e m e n t is

tem perature

m easured

One

in ice w a t e r f o r

140° F .

which o p e r a t e s

nating

voltage

than 2,500 pounds).

assembly.

a wide—
mouth vacuum f lask

The

used

s u s c e p ti b i li ty to

(greater

which had b een w r a p pe d with s h e e t a s b e s t o s
the

were

at low t e m p e r a t u r e s

to c a l o r i m e t r i c

w a r m e d up to

in cold running w a t e r

im eter

which had been p r e p a r e d

in v i s c o s i t y when homogenized

(70° to 90° F.)

o th er

milk,

was

1—
liter

and tape

a 30-watt,
from

a

0.1

-10°

calor­
capa c ity

to i n c r e a s e

im m e rsio n

115—
volt a l t e r ­

m easured

calibrated from

to the n e a r e s t

of

The

to 0.02°

to 60°

C.

C. by
The

volt with a c a binet-type

72
voltmeter.
use

The

of J o u l e ’s

input of h e a t g e n e r a t e d

H = calories

_ E_I _t
“ 4.186

generated,

E = the p o t e n t i a l
the

perature
errors
the

heating

t =

time

r a nge

from

0

compensate
ments

Figure

Th e se

v al ues

for

of the

o

to

60

o

6 shows
we r e

(Table

sample

thermal

correction

influences

was

which the

9,

the

due to

and the

experimental

e va p o r a ti o n ,

c a p a c it y of the

set of data to
heat

require—

e
Column H ).

weighed into the

calorim eter

o p e r a t i n g pos it io n.
was

a t ern—

data obtained f or

u s e d to a d j u s t e a ch

adjustment period
after

and the

the

waterover

to d e t e r m i n e

heat lo s se s

friction

calorim eter

determination,

and

C.,

l ea k ag e,

then p l a c e d in the

tem perature

the heating e l e m e n t ,

c a l i b r a t e d with

environmental

A 500-gram
which was

of

J o u l e ’s c on sta nt.

effect of a g i ta t io n a l

water.

through

in s ec o nd s,

to t h e r m a l

calorim eter.

between t e r m i n a l s

element,

c u rr e n t passing

c a l o r i m e t e r was

due

d if f e r e n c e

I =

4.186 =
The

c a l c u l a t e d by the

equation:

tt

wh e r e

was

A 15-minute

allowed b e f o r e

temperature

was

starting

recorded

a

and

73
the heating c u r r e n t was
range

was

minutes
ture

c ov e r ed .

after

was

heating

the

app r ox im a t el y

have been

0.940 and 0.963,

1.5

the

recorded
started

o

C. p e r

e v e r y five

and the t e m p e r a ­

r e sp e c t i v e l y .
were

The

and Johnson

values

The deg re e
following

rate

0.943 at 0

C.

o

(1913)

used in this

r e p o r t e d by Jac k

the heat of fusion was

(Jack and B r u n n e r ,

The

specific heat of ski mm il k at 0

of

and
as

study

and B r u n n e r

to 0.966 a t

heat of liquid and solid fat was

value for

temperature

minute.

r e p o r t e d by H a m m e r

and ranged f r o m

specific
the

for

calculation p u r p o s e s

(1943)

was

heating p e r i o d was

The values

for

The voltage

r e a d at the end of the holding p e r i o d .

was

60° C.

applied until the d e s i r e d

60

C.

The

r e p o r t e d to be 0.5

19.5 c a l o r i e s

per

and

gram

1943).
of fat

solidification was

c alc ul ate d f r o m

the

equationH* -

Percentage

of

(0.5 x t

i~9~5

solid fat =

where

=

heat

input p e r

total heat
from
t j)

=

t^

tj)

X
gram

required

temperature

(0.5 x t^ -

-

of fat o r
to r a i s e

of one g r a m

the

the

of fat

to t ,

amount of heat n e c e s s a r y to r a i s e
the t e m p e r a t u r e f r o m t^ to t , p r o ­
vided no heat is
fat,

and

used for

melting

74
19.5 =

calo ries
1 gram

The

v iscosity

aid of a B r o o k f i e ld

values

were

of h e a t n e c e s s a r y
of

solidified fat.

d ete rm in ed at

Synchro—
Lectric

to m e l t

viscom eter.

20° C.

with the

76
8 0

HEAT

LOST (CALORIES)

70

60

50

40

30

20

30
20
T EM PERATURE C C )

Figure
m etric

6.
T h e r m a l —c o r r e c t i o n c u r v e
a s s e m b l y u s e d in t h is s tu d y .

40

for

the

50

calori-

RESULTS

Typical
of p re v io us
atures

data taken f r o m Section I showing the

temperature

on the

treatm en ts

for

the p e r c e n t a g e s

ity values.

milk was

lowing p a s t e u r i z a t i o n ,

was

of about

cooled to 45

various

o

80

o

F.,

o

temperature
tained for
data a r e

are

plotted agains t v i s c o s ­

homogenized i m m ed ia t e ly fol­
obtained at a

20 hours

and then w a r m e d to

maximum

vis co s ity was

of solidified fat at the homogenization

determined from
s a m p le s

tabulated in Table
The deg r e e

sample

was

F.

each of the

8.

previous

was

the

ca lo rim e tric

represen ted

9 and a r e

milk.

7.

These

shown gra p hi c al ly in

of solidification of the

h e a t - t r e a t m e n t of the

data ob­

in F i g u r e

milk fat in any

depended p ri n c i p a l ly on the t e m p e r a t u r e

had been p a s t e u r i z e d ,

values

but when the p a s t e u r i z e d milk

held for

The p er c e n t a g e

one

e x p e r im e n t a l

maximum v is co s it y

F.,

90

in homogenized milk a r e

The

homogenization t e m p e r a t u r e s ,

obtained at about

Figure

7.

of solidified fat

When the

temperature

and homogenization t e m p e r ­

development of v is c o s it y

p r e s e n t e d g ra p h i c a l ly in F i g u r e

effects

In milk

cooled and held at 45

o

and the

samples
F. f o r

which

20 hours

78
prior

to homogenization,

the m a x i m u m v i s c o s i t y developed when

the homogenization t e m p e r a t u r e
which t e m p e r a t u r e
to 2.0 p e r

cent.

the

deg r e e

Sim il a rl y,

was

o

about 80

and 70

o

F.,

of solidification ra n g e d f r o m

the

s a m p le s

at
0.5

of p a s t e u r i z e d milk

which had been w a r m e d to the homogenization t e m p e r a t u r e ,
following

a 2 0- h o u r

mum v i s c o s i t y
the

degree

cent,

at about

p e r i o d at 45° F . ,

80° to 90° F . ,

exhibited a m a x i ­

at which t e m p e r a t u r e

of solidification d e c r e a s e d f r o m

18.0 to

7.0 p e r

respectively.
The

rela t io ns hi p between v i s c o s i t y

of solidified fat
sures

are

fig ur e s

r e s u lt in g f r o m

show e s s e n t i a l l y

the

F igures

same
7 and

of solidified fat accompanying

between 0.5 and 2.0 p e r
pasteurization

and the p e r c e n t a g e s

different homogenization p r e s ­

shown g ra p h i c al ly in F i g u r e s

duced a l r e a d y f r o m
age

storage

9 and

10.

information as
8, namely,

Th ese two
has been de­

that the p e r c e n t ­

m a x i m u m v is c o s i t y

ranged

cent in milk homogenized following

in c o n t r a s t

to

18.0 and 7.0 p e r

cent in milk which

had been cooled and then w armed to the homogenization t e m p e r ­
atures.
pounds)

At lower homogenization p r e s s u r e s
the

deg r e e

only difference

of solidification

being

(less

r e m a i n e d the

a reduction in the

than 2,500
same,

v is co s it y which

the

79
accompanied the low er homogenization p r e s s u r e .
enization p r e s s u r e s
was
fat

below 2,500 pounds w e r e

developed even though the
r e m a i n e d the

same.

deg r e e

used,

When homog­
no v is c o s i t y

of solidification of the

80
TABLE
The p e r c e n t a g e
(6.6 p e r

of solidified f a t in a 5 0 0 - g r a m

cent fat)

at d ifferent p r o c e s s i n g

Temp,
Heat­

at B e ­

Temp.

ple

ing

ginning

Rise

Volt­

Num­

Pe­

of

During

age

ber

riod

Heating

Period

Homogenized^

Added
From
Circuit

(cal.)

(° c.)

of milk

tem peratures

(H)

Period
(° C.)

sample

Heat

Sa m ­

(sec.)

9

Heat

Effec­

Cor­

tive

rec­

Heat

tions

<HC)

(cal.)

(cal.)

i m m e d i a t e l y following p a s t e u r i z a t i o n

1

450

38.00

10.05

116.0

5,330.3

670.2

4,660.1

2

960

26.74

21.90

116.0

11,358.0

1,268.0

10,090.0

3

1,080

21.01

25.05

116.5

12,885.5

1,319.2

11,566.3

4

1,300

15.52

30.08

116.0

15,430.7

1,468.5

13,962.2

Homogenized following a 20 - h o u r

sto r ag e

period

at 45 °

F.

5

1,320

15.72

29.98

116.0

15,601.0

1,454.0

14,147.0

6

1,120

21.00

25.20

115.8

13,195.7

1,350.0

11,845.7

7

970

26.41

21.79

116.0

11,464.4

1,272.0

10,192.4

8

620

32.00

14.21

116.8

7,430.2

830.0

6,600.2

9

446

38.06

10.04

116.4

5,308.0

659.7

4,648.3

Samples
60

F.,

1,

2,

3 and 4 were

homogenized

at

100°,

80°,

70°

and

respectively.

Samples 5, 6, 7, 8 and 9 were
o
o
90
and 100
F ., respectively.

homogenized a t

60°,

70°,

80°,

81

TABLE

Heat
Sam­

Heat

ple

Require­

Num­
ber

m e nt s

of

Skimmilk

Heat

A vail­

Avail­

able

able

per

f or
Fat

Gram
of F a t

(1?)

9 (C on tin ued)

Sensible

Heat

Heat

Heat

U sed

Required

R e q u ir e d
pe r

to

to Melt

Melt

Gram

1 8

1 gSolid

of

*

Solid­
ified
Fat

Fat

of F at

Fat
(cal.)

(%)

(cal.)

(cal.)

(cal.)

(cal.)

(cal.)

1

4,494.1

166.0

5.0

5.0

0.0

19.5

0.0

2

9,725.4

364.6

11.1

11.0

0.1

19.5

0.5

3

11,140.0

426.3

12.9

12.5

0.4

19.5

2.1

4

13,338.2

624.0

18.9

15.4

3.5

19.5

18.0

5

13,266.7

880.3

26.7

15.0

11.7

19.5

60.0

6

1 1,198.1

647.6

19.6

12.6

7.0

19.5

35.9

7

9,715.5

476.9

14.5

10.9

3.6

19.5

18.5

8

6,320.7

279.5

8.5

7.1

1.4

19.5

7.2

9

4,482.0

166.3

5.0

5.0

0.0

19.5

0.0

82

6

PASTEURIZED M I L K - S T O R E D
AT 4 5 * F. FOR 2 0 HR. PRIOR
TO HOMOGENIZATION

-

VISCOSITY

(CENTIPOISES)

HOMOGENIZATION
FOLLOWED PASTEURIZATION

60

80

H O M O G E N IZ A T IO N

100

120
TEMPERATURE (°F )

140

F i g u r e 7.
S h o w s the e f f e c t of the t e m p e r a t u r e of
h o m o g e n iz a t i o n on the d e v e l o p m e n t of v i s c o s i t y
w h e n b .6 p e r c e n t m i l k w a s h o m o g e n i z e d at 3 , 5 0 0
pounds p r e s su r e .

83

PASTEURIZED MILK-S TOR ED AT 4 5 • F . - 2 0 HR.
PRIOR TO HOMOGENIZATION

HOMOGENIZATION

TEMPERATURE (°F)

HOMOGENIZATION FOLLOWED PASTEURIZATION

20
30
40
PERCENTAGE OF S O L ID IF IE D FAT

F i g u r e 8.
d h o w s the p e r c e n t a g e of s o l i d i f i e d fat
o b t a i n e d at v a r i o u s h o m o g e n i z i n g t e m p e r a t u r e s
(b.b p e r c e n t fat in the m il k ) .

84

( C E N T IP O IS E S )

HOMOGENIZED AT ^ 5 0 0
POUNDS PER SQ. IN.

VISCOSITY

HOMOGENIZED AT 3^500
POUNDS PER SO. IN.

I -

_ _ _ _ _ _ _ _ _ _ _ _ I_ _ _ _ _ _ _ _ _

5

1 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ J_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

lO

15

20

PERCENTAGE OF S O L ID IF IE D FAT
F i g u r e 9.
The reLation b e t w e e n the d e g r e e of
s o l i d i f i c a t i o n of fa t and the d e v e l o p m e n t of v i s ­
c o s i t y in h i g h - f a t m i l k (b.b p e r c e n t ) h o m o g e n i z e d
f o l l o w i n g p a s t e u r i z a t i o n at t e m p e r a t u r e s r a n g in g
f r o m 140
to 60
F.

T

8

VISCOSITY

(CENTIPOISES)

7

T

HOMOGENIZED AT 2,500 POUNOS PER SQ.IN.
HOMOGENIZED AT ^ 5 0 0 POUNDS PER SO. IN.

6
5
4

2

-

±

_L

10

20

30

40

50

60

PERCENTAGE OF SOLIDIFIED FAT
Figure

10.

The r e l a t i o n b e t w e e n the d e g r e e of s o l i d i f i c a t i o n of f a t and the

d e v e l o p m e n t of v i s c o s i t y in h i g h - f a t m i l k (6. b o e r cent ) h o m o g e n i z e d at t e m o
o
p e r a t u r e s r a n g i n g f r o m 60
to 140
F . f o l l o w i n g a . 40- hour s t o r a g e p e r i o d at
4 5° F.

oo
un

DISC USSIO N

A re v i e w

of the

obtained and d i s c u s s e d
ical-state
mation.

data

reported

Whenever

conducive

45

milk

F.

sec tio n

reveal

and an i n c r e a s e

which was

various

tures.

At t hese

tem peratures,

the

g lo b u l a r

totally

solid n o r

totally liquid,

but

it e x i s t e d

solid and liquid fat.
in this

tem perature

Ap pa r en tly,
r ange

and p h y s i c a l p r o p e r t i e s
tent by the

s ta te

on fa t-g lo bu le

the

pla ye d by a

which is

adsorbed

Most

clumping

specific

on the

are

o

and

s ince

were

the
70

80

o

are

fat—
globule

at

neither

a mixture

of

state

of the fat

various

chem ical

concepts,

m aterial

surface

o

tem pera­

i dea s

ex­
and

concerned principally

clumping

F.

20 h o u rs

fat was
as

and 90

influenced to a g r e a t
of the

o

homogenizing

homogenizing

the p h y s i c a l

critical,

of milk

of the fat.

theories
r ole

is

80

stored for

and then w a r m e d to the

infor­

conditions

and between

milk which had been

and p h y s ­

in v i s c o s i t y ,

cooled to the

data

sig nific a nt

experim ental processing

following p a s t e u r i z a t i o n

for p a s te u r iz e d
o

in this

v iscosity

of h omogenization v a r i e d b etween

for p a s te u r iz e d
tem perature

h om o g e n i z a t i o n —
v iscosity

in Section I and the

to f a t - c l u m p i n g

temperatures

F.

the

general

with

a gg lu tinin -----

during

the

87
solidification p r o c e s s .
globules when it is
m aterials

are

Since

milk fat e x i s t s

in a liquid

state,

other

clumping

the f a t - c l u s t e r i n g

or

factor

coalescence

has

form

of

emulsion—
stabilizing

p o s s i b l y a d s o r b e d on the fat

that fa t-g lo bu le

in the

surface.

can be

The f ac t

induced a f t e r

b een i n a c ti v a t ed by h ea t

is

com­

mon knowledge.
Conceivably,
to explain,
recorded

partially,

in this

on the

of t h e s e

C e r ta i n l y ,

homogenization t e m p e r a t u r e ) ,
pressure;

the h ig he r

The h ig he r

tunity for f at-globule

tion were
high in fat

degrees

The

in t u r n ,

contact

abnormal

of f a t

sol id i ­

an i m p o r t a n t
9

(sa m e

a function of the

produce

the

viscosity.

a greater

degree

an i n c r e a s e d o p p o r ­

and an i n c r e a s e

S.O p e r

homogen­

solidification

the g r e a t e r

v iscosities

milk

Data in F i g u r e s

of fat

furnish

e nco un te r ed only during
(higher than

exerts

v i s c o s i t y was

the p r e s s u r e

which,

degree

of v i s c o s i t y .

homogenization p r e s s u r e s

of fat d i s p e r s i o n

structure.

in addition to the

of homogenization

identical

might be u t i li z e d

of homogenized

corresponding

development

10 show that at

concepts

high v i s c o s i t i e s

and the

the p r e s s u r e

influence
and

the

study.

ization t e m p e r a t u r e
fication,

certain

in the f a t —
cluster

obtained in this

investiga­

the homogenization of milk

cent).

88
The p r o g r e s s i v e
by Moore

and

Trout

c os it y

observed

cos it y

after

crease
third
the

t hickening

(1947)

in t h i s

is

study,

3 to 4 days

of

in v i s c o s i t y f r o m

until

a

Rishoi

state

fat

in the

the

tend to

s tiffen

into

to the

t im e

at

45°

1938a,
a firm

F.

in v i s ­

The

vis­

sli gh t in­

of h o m o g e n i z a t i o n to the

Thus,

network

sup po sition tha t

continued to

approached

1938b).

described

a maximum

e x p la i ne d on the

was

milk

increases

which a t t a i n e d

clu ster—
structure

of e q u i l i b r i u m

and S h a rp ,

sim ilar

s to rag e

o r f o u r t h day m i g h t be

g lo b u l a r

of h o m o g e n i z e d

solidify

(van Dam,

the

1923;

fat—
clusters

and g r a d u a l l y

would

increase

in

viscosity.
Data p r e s e n t e d
portion

of the f at

peratures
physical
of fat

lower
s ta te

resulted from
The

internal

probably
tion,

is

in a

than

70

of the

globules

fat

and the
the

o

8,

s o l id if i e d
F.

9 and
state

10

show t h a t a l a r g e

at homogenization t e m -

Such an o v e r —
all

co n c ei v a b ly
subsequent

change

could e xplain

cream

the

in the
coalescence

plug f o r m a t i o n

which

c h u r n i n g - e f f e c t p r o d u c e d by h om o g e n i z a t i o n .

resistance

of f a t globules

s uff ic i ent to p r e v e n t

but not g r e a t

or form

in F i g u r e s

their

clusters

of fat,

60

o

or

dispersion

enough to d e s t r o y

independent

at

their

50

as

F.

is

on h o m o g e n i z a ­

tendency

evident

o

to c o a l e s c e

a cream

plug.

89
Homogenization a t t e m p e r a t u r e s
was

in a liquid

which was

state,

above

produced

proportional

to the

100

o

a uniform

increase

F.,

when the

dispersion

in the

fat

of the f a t

h o m o ge ni z at i on

pre s s u r e .
Postulations

to

explain why p a s t e u r i z e d

been h o m o g e n i z e d within
range

(70

o

to

90

o

F.,

a rath er

depending

an u n u s u a l ly high v i s c o s i t y
are

held together

recent

theories,

is

adsorbed

solid f a t

glo bu les

m a y be

Whatever

the

the finely d i s p e r s e d
in teg ra te d c l u s t e r
increase

in the

accounted fo r

ing i n c r e a s e
globules

in

(2)

structure.

by s e m i l i q u i d

form

the

an e x t e n s i v e
structure

in cold

an a dd itional

storage,
increase

As
the

the f a t
cluster

in the

of the

layer

of the

fat,

a c on ­

probability

is

that

and highly

would c a u s e
over

of f a t d i s p e r s i o n

adsorption.

more

together.

of h o m o g e n i z e d m i lk

on the b a s i s

to the

surface

surface

stick

developed

f a t g lobules

according

the

them

Such a

the

on the

of c l u s t e r i n g ,

f a t globules

surface

solidifies

and p r o d u c e s

mode

viscosity

which,

surrounded

which would t end to m a k e

critical-tem peratu re

(1)

selectively
and

which had

heat tre atm en t)

off e r e d:

by an agglutinin,

s ol id if i ed f a t globule,

that

on the

are

partially

dition

narrow

milk

and above

and the
in the

resu lt­

individual

structure

viscosity.

an

s tiffens

SUMMARY

Fat
(70

o

to

ducive
ture

80

is

o

partially

F.,

to the

formation

and an a b n o r m a l l y

pasteurization
mogenization

stored
the

which was

18.0

F.

tem perature

to

for

milk

were

7.0 p e r

in the

sta te

probably

the p h y s i c a l

was

state

of the

sim ilar

The

to 2.0 p e r

reduced from
cent
prior

degree

p r o c e s s e d by t h e s e

but the p h y s i c a l
ules

0.5

of

in m i lk

which a r e
cluster

a mount of

80

o

struc­

solidifi­

immediately
cent

con­

after

when the
to

70

o

F.

ho—
and

which had b ee n

to h o m o ge ni z at i on when
80

o

to 90

o

F.

s o l id if i c a t io n

two m e th o d s

peripheral

the

in the

To

of the

was
fat

fat glob­

a large

a mou nt

at any given h o m o g e n i z at i o n t e m p e r a t u r e s .

There

of h e a t t r e a t m e n t ,

layers

in both c a s e s .

of the fat g o v e r n s

tem peratures

fat-globule

homo ge niz ed

increased from

a d istinct difference
of the

from

20 h o u r s

was

II

heat treatm en t)

high v i s c o s i t y .

tem perature

a t 45°

on the

of an e x t e n s i v e

increased

decreased from

SE C TIO N

s ol id if i ed a t h o m o geni z at i on

depending

c a ti on of fat in m i lk

OF

extent,

of f a t —
clustering

S E C T I O N III

PRELIMINARY

REPORT ON SOME OF

MANIFESTED IN THE NATURE OF

THE

CHANGES

THE PROTEIN-

ACEOUS MEMBRANE MATERIALS

CLOSELY

ASSOCIATED WITH THE SURFACE OF
THE FAT GLOBULE AS A RESULT
OF

HOMOGENIZATION

REVIEW OF LITERATURE

Nature

of the Normal Fat-globule

Photographic

Characteristics

Fat-globule

made

exist was

of fat globules.

me mbr a n e
is

the fat globule

As

of m a t e r i a l s

(1949),

who

isolated fr om the

shown by these photographs,

the

is not a continuous film which envelops the fat, but

a n e t - li k e

through its

surrounding

vividly d em o ns tr a t ed by Hansson

e le c tr o n p ho tomicrographs

surface

of the

Membrane

The fact that a m e m b r a n e
does

Membrane

structure

probably a t t r a c t e d to the fat surface

colloidal p r o p e r t i e s .

Trout (1950)

showed an ele c­

tron pho to microg rap h of homogenized milk in which m a t e r i a l
a s s o c i a t e d with the fat-globule
these

data,

globule

which definitely established the

membrane,

considerable

an attempt to e st a bl is h
more
or

specifically,

substances

these

can be recognized.

to c h a r a c t e r i z e

comprising

accomplished in

of the m e m br a n e,

the nature

the fat-globule

data have been obtained by d i r e c t

to

existence of a f a t -

r e s e a r c h was

the p r e s e n c e

Prior

of the

membran e.

and

substance
Some of

experimentation with

isolated fat—
membrane
the

determination

and some

we r e

of c e r t a i n p h y s i c a l

obtained i n d i r e c t l y by
and c h e m i c a l p r o p e r t i e s .

Composition of the F a t - g l o b u l e

Me mbrane

of Nonhomogenized Milk

Lacto-fibrin
years

ago,

milk w e r e
brane.
to the

and haptogenic

membrane.

Ascherson

(1840)

surrounded

and s t a b i l i z e d by a

condensation of albumin

g r e g a ti o n on the fat
observed

this

ment which has
others.

In spite

pothesis,

ishingly

been

under

haptogenic

to his

an o r d i n a r y

severely

of the

100

inform atio n was

m aterial

subsequent ag­
report,

microscope;

c r i t i c i z e d by Babcock

criticism

in

1'haptogenic*1 m e m ­

and its

According

he had
a sta te ­

(1885)

and

d i r e c t e d at A s c h e r s o n 1s hy­

the fundamental concepts

when v e r y little
solutions

surface.

m aterial

than

p o s tu la te d that the fat p a r t i c l e s

He a t t r i b u t e d the f o r m a t i o n of this
capillary

More

which he advanced at a time

available

and t h e i r p h y s i c a l p r o p e r t i e s

concerning

have p r o ve d

colloidal

to be

aston­

sound.

Babcock
s i d e r e d to be
an emulsion

(1885) pointed out that fat globules

either

with the

by a thin m e m b r a n e

(a)

"particles

serum

of the

and t h e r e f o r e

of f r e e

con­

fat in the f o r m of

milk,** o r
c e ll s

we r e

(b)

"surrou nde d

filled with f a t , "

or

94
(c)

"that

some

the

albuminous

m atter

way condensed upon t h e i r

haptogenic
namely,

m e m b r a n e . 11

ent f r o m
(1840).

state

the
In

of t r a c e s
globule

how he

haptogenic

1889,

stabilizing

c o n s i d e r e d this
membrane

membrane

could o c c u r .

plain the

natural

(1889a,

clots

and that

second condition;

(1939),

1889b)

had the

r e p o r t e d the p r e s e n c e

s am e

it had to be

some

agglutination of fat globules

the

clustering

Babcock

50 y e a r s

exerts

(1922) found that B a b c o c k ' s
hypothesis

P rotein s.

Evidence

He p o s t u ­

effect as

a t ru e

a tt e m pt e d to ex­

later,

a m ajor

theory..

showed that

influence

of n o r m a l

l a c t o - f i b r i n was

in
milk.

an a r t e f a c t ,

untenable.

was

presented

which i ndicated that the fat-globule
m a r i l y of albumin,

f a t-

r e m o v e d before

of fat and subsequent c r e a m i n g

making his

but

condition to be d i f f e r ­

agglutination of fat globules by this

and Krukovsky

called

p o s tu la te d by A s c h e r s o n

I n t e re s t in g l y ,

the

Hekma

what is

m a t e r i a l n o r m a l l y found in milk.

churning

Sharp

fo r m i n g

in milk which he b elieved to be the

lated t ha t the l a c t o - f i b r i n
fat-globule

surface,

a t t r a c t e d and in

s u r r o u n d e d by a thin m e m b r a n e ,

Babcock

of f i b r i n

milk i s

He b elieved in the

that the fat was

he did not

thus

of the

while Storch

by Bechamp

membrane

(1897)

(1896)

consisted p r i ­

b elieved it to be a

95
mucin-like protein;
and Vbltz (1909)

n e i t h e r casein n or lactalbumin.

concluded f r o m t h e i r

portions of the f a t - m e m b r a n e
of a mixture

of p ro te i n s ,

(1922) found that

and that this

material

other

contained m ore

on the bas is

membrane.

from 0.08 to 0.215 p e r

m a t e r i a l was

cent of the p ro tei n in milk.

s er u m

Hattori

that the fa t - m e m b r a n e

which he named 1’hap te i n. 11
cent nitrogen and was

undetermined composition at the
Rahn and Sharp

of 0.01

Sommer

by the gravity

to 0.028 p e r

(1928) placed considerable

separation

emphasis

of dairy products

adsorbed on the fat-globule

and Hart (1928)

cent.
on

which they believed to be

responsible for the foaming p r o p e r t i e s
probably the m a t e r i a l

Haptein contained

r e c o v e r e d fr om milk of

rate

a 11s chaumstoff11 p r e s e n t in milk,

(1909)

of its f a t - f r e e

a different p ro te in than any of the existing known

milk pro te i ns ,

Titus,

nitrogen than

They r e p o r t e d values varying

(1925) p r e s e n t e d data to demo nstrate

12 p e r

Van Dam and Sirks

difference probably r e p r e s e n t e d the nitrogen found

in the fat-globule

about

of hydrolyzed

that it probably consisted

than c a se i n.

separated c re am

was the o r e t ic a ll y possible

analysis

Abderhalden

isolated

and

surface.

” f a t - h u l l s M fr om

milk

method of Abderhalden and Vbltz

and r e p o r t e d a nitrogen value of

15.2 p e r

cent for this

96
material.

Ot h er a n a l y s es

showed that the fa t- h ul ls

have n e a r l y

identical phosphorus,

From

data,

t hese

it was

was probably c a se i n.
material
the

solubility of the

concluded that the

However,

(1930)

hull

than was

ca taphoretic

they were

studies

substance

the

aware

that the

hull

lower

than those

i n t e r fa c e ,

and Samuelsson,

fat-globule

On the b a s i s

since

their

isoelectric

In 1924, P a l m e r

1924) began a ver y extensive

chemical

in his

studies,

The

points

"m em brane"

was

was

working with emulsions

of the

obtained f r o m
introduced

with the f a t - m e m b r a n e .

and Sam uelsson (1924)
composed of a mixture

and phospholipids.
of b u t t e r

Later,

(Pa l ­

inv es ti ga ­

and physical p r o p e r t i e s

studies

Palmer

that the f a t - m e m b r a n e
like p r o t e i n s

Prie-

of n a t u r a l fat have p ro tei n

w a s h e d - c r e a m b u t t e r m i l k by an isolation p r o c e d u r e

early

of

of a r t i f i c i a l l y e mulsified fat.

membrane.

by Storch (1897)

since

was

and a r t i f i c i a l e m ul si on s ,

concluded that emulsions

tion re latin g to the

their

material

in sodium hydroxide

P h o s p h o l ip id -p r o te in complex.
mer

membrane

solubility of c ase i n.

with n o r m a l

ad s o rb ed at the f a t / l i q u i d
were

and tryptophan contents.

could have been contaminated with other p r o t e i n s

much lower

ger

sulfur

and c a s e i n

From

concluded
of globulin­

Wiese and P a l m e r

oil e mulsified in the

(1932),

various

97
known p r o t e i n f r a c t i o n s
buttermilk
ties f a r
Wiese

(1933)

to the o t h e r

d e t e r m i n e d the

cream buttermilk

sol to be

isolated free

about 0.028 p e r
The c r u d e
pholipids

concluded that n o r m a l ,

contained a s ubstance

superior

could be

of milk,

fa t-m e m b ra ne
and

some

which had emulsifying p r o p e r ­

milk f r a c t i o n s .

isoelectric

milk

dialyzed and analyzed a l i p i d - f r e e

crude

membrane
dealing

milk p r o t e i n s .

It was

and upon
at l e a s t

(1936)

results

especially

Wiese

and P a l m e r
from

the

convinced them

about

12 p e r

m aterial

cent.

that

cent of the f a t - f i l m

c omponents.

The p r o t e i n a c e o u s

position f r o m

the

membrane

the haptein of H atto ri

(1925)

concluded that

c o n s i s t e d of nonnitrogenous

component

protein

Schwarz and

f r o m washed c r e a m

subsequent p u r i f i c a t i o n and a n a l y s i s

milk p ro te i n .

phos­

c h a r a c t e r i z e d by an u nac­

isolated a fat-film

30 p e r

of

cent fat.

of p r o t e i n ,

substance

it

with a milk p r o t e i n new to the f a m il y of

countably low n it ro g e n content;
Fischer

3.5 p e r

glycerides.

(1934)

they wer e

and that

They obtained yields

consisted p r im a r il y

and the

and

point of the wa s he d —

containing

h ig h-melting

m aterial

Palmer

about pH 3.9 to 4.0,

of c a lc iu m .

cent f r o m

whole

also

of Wiese

and it did not

d if fe r ed in c o m ­

and P a l m e r

resemble

(1934),

any known

98
Lundstedt (1934) postulated that lecithin r e l e a s e d f r o m
the

s urface

of the fat globule

as a r e s u l t of agitation was

sorbed on the c alcium c a s e i n a t e

s ur fa c e,

thus

tion in the c u r d tension in agitated milk.
suk (1936)

therefore,

concluded that the

c u r d tension in agitated milk was
p ro te i n m a t e r i a l .
1939;

that the

due to the

and T a r a s s u k ,

reduction in c u r d

the p a r t i a l

the

of m embrane

(Tarassuk

and P a l ­

tension which accompanied the

r e s u l t of two different phonomena;

d e s tr u c ti o n of the fat-globule

a g i ta ­

namely,

m e m b r a n e p ro te i n ,

which p re v e n t e d nor­

re nn e t clotting.
Rimpila

material
tures

release

1940) led them to conclude

and (b) the l ib e r a t i o n of n a t u r a l e s t e r a s e s
mal

and T a r a s -

reduction of the

Subsequent investigations

Palm er

tion of milk was
(a)

Palmer

a reduc­

could not lower the c u r d tension in milk by adding

Lecithin and,

mer,

causing

ad­

and P a l m e r

(1935)

analyzed the f a t - m e m b r a n e

i so la te d f r o m the washed—
c re am buttermilks

of r e - e m u l s i f i e d but te r

cluded that the
i l a r to the fat

oil and milk pro te i n.

artificially p re pa re d mem branes
m e m b r a n e found in n o r m a l

nitrogen values for
somewhat lower

the purified,

(12.35 to

milk.

cent)

mix­

They con­

were

not s i m ­

They obtained

adsorbed proteins

13.75 p e r

from

that were

than the nitrogen

99
values found to be p r e s e n t in the milk p ro tein fr a ct io n which
s erved as
this

the emulsifying

difference

on the b a s i s

the p r e p a r a t i o n s
lar g e

amounts

p re p a r a t i o n s

medium.
of t he ir

of inorganic

material.

cent of the crude

(1937b)

in milk diluted

the major

the fat m u st be protein,

isoelectric
surements,
fat was

point,
was

50 p e r

1 p a r t to 200 p a r t s

derived an i s o e l e c t r i c
They concluded that

point of the known milk pro te i ns

point of pH 2.0,

signifi­

m e a s u r e d the electrokinetic

pH 4.3 for n o rm a l fat globules.

isoelectric

and e th e r e x t r a c t -

me m br a n e.

of fat globules

of pH 4.5 to 4.6,

and

membrane

They emphasized the

a buffer and fr om these values

lower

All of the

component in that it c o m p r i s e d over

J ack and Dahle

isoelectric

because

carbo hy dra te s

contained pro tei ns , phospholipids

of the l a t t e r

bilities

analytical data,

were f r e e of chole s te rol ,

able nonphospholipid m a t e r i a l s .
cance

They could not account for

point,
was
as

was

component of the

but that

some

other

mo­
with

point of
since the

in the

range

surface l a y e r

of

m a t e r i a l with a

i . e ., phospholipid with an i s o e l e c t r i c

also p r e s e n t .

They dem o ns tr a t ed that the

determined by electrokinetic

shifted from

d i s p e r s e d in a casein

mobility m e a ­

a n orma l of pH 3.3 to 4.6 when
sol a f t e r the addition of

phospholipids,
globules
to the

but t h a t a value

(pH 4.3)

was

f a t- p h o s p h o li p i d e m u l s i o n .

probably
kinetic

e x i s t e d on the

From

surface

vations,

as

made

P a lm er's

pH 4.6 and 3.7 to
well

as

those

t h e o r y on the

3.8,

of J a c k

lished

(1945a,

reported

accounted f o r

m aterial.

taine d f r o m
of fat,

or

tein p e r

to 0.86

of fat

six t i m e s

showed the

respectively.

m illigram s
surface,

of fat,

complex.

(1935)

obser­

support
in

complex..

Jenness

and

in that p r o t e i n
cent

of p r o t e i n f o r
cream

8.9 to

of the

every

mem­

every

con­

100 g r a m s
100

square

which had been

16.3 m i l l i g r a m s

0.57 to 0.86

and

fa t-m e m b ra n e

of p r o t e i n f o r

whereas

or

T h ese

data which c o n f i r m e d the pub­

contained f r o m

100 g r a m s

on fat

of the f a t - m e m b r a n e ,

only 40 to 65 p e r

grams

it was

isoelectric

(1937b)

They found t h a t the n o r m a l

34 to 49

centim eters
w ashed

0.46

added

Electro­

(1940)

a phospholipid—
protein

data of R i m p i l a and P a l m e r

phospholipids
b ra n e

1945b)

results,

by Moyer

Phospholipid-prote in-glyceride
Palm er

sol was

f at

phospholipid/protein

and Dahle

c om p os it io n

which he b e l i e v e d it to be

these

normal

of the f a t globule.

in unwashed and washed c r e a m

to be

casein

membrane

mobility d e t e r m i n a t i o n s

globules

to t h a t f o r

obtained when the

concluded t ha t a double—
layer

points

sim ilar

m illigram s

of p r o ­

of p r o t e i n

101

per

100

square

that the
butter

ce ntim eters

m a jo r portion

after

glyceride

w ashed-cream .

(52

o

to

p r o t e i n - p h o s p h o l i p i d complex,
half of the
ing was
that

membrane

em phasized

a layer

tions

of the

globule.
ac id s

of p h o s p h a ti d e s

of t h e s e

a c id s

on the fat

the f a t - m e m b r a n e
fat globules
special

part,

to t h e i r

active

surfaces

m aterial

group

(1944)

capillary

occurring

evidently c on st it ut e
if indeed they a r e

the

of the

frac­
fat

activity.

fat

of p hosphatides

s u m m a r i z e d his

whose

normally

showed

association

work on

s ta te m e n t:

wholly o r p a r t i a l l y

outer

who

melting

The

orientation

in m a j o r

find­

identified the m a j o r

with the following
are

of this

surface

and p a l m i t i c .

of s u b s t a n c e s

greater

substances

plasm a

P alm er

about o n e -

(1950)

h ig h e r

a t the

explain the

isolated a

s t r o n g ly a tt a c h e d to the

significance

(1941)

showed

r e t a i n e d in the

r e p o r t by King

itself

oleic

in c o w s 1 m i lk

by a

C.),

The

Maddison
as

o

was

data

They a lso

p r e s u m a b l y the

o rients

ma y well

surfaces.

Their

which accounted f o r

recent

of liquid fat,

Hilditch and

53

m aterial.

in a

butterfat,

surface.

of the phospholipids

chu r ni ng the

high-melting

of f a t

“ The

surrounded

o r i g i n may be due,
The

o th er

concentration
layer

in

surfacein milk

of the fat globule

concentrated there

a t all.

4

102

The l a t t e r

are

readily

removed

when

cream

is

w a s h e d by dilu­

tion with w a t e r . "

Serum
that
as

p rotein s.

Townley

thrice—
washed c r e a m

the

original

cream ,

to about o n e —
half

reduced

to

that the

protein

has

shown

in the
ered

or

about

with i t s

minor

fat-globule

either

highly

function

oxidase

globule.

Sharp

o xidase

per

part

and Hand

100 g r a m s

sulfur

sulfur

con te n t was

nitrogen

c on te n t was

t hey

concluded

associated

with

the f a t glob­

proteins.
fat

King

in b u t t e r

probability

in mi lk

E v id e nt ly

surface-active

was

in v ol at il e

is

(1947)

rem ains
still

cov­

m aterial.

constituents

or

have

with the fat

Toyama

reported

d at a ,

f a t which in all

in c o n ne c ti on

xanthine

these

c e n t of the

surface.

Flavoprotein.

total

intimately

surface

high

a lb u m i n

Fro m

60 p e r

natural

as

sulfide—
containing

of g l o b u l a r

Various

are

m aterial

v ol at il e

that

form

with the

and the

about o n e —
ninth.

contained

nearly

although the

reduced

ule

was

and Gould (1943)

(1932)

of the
(1940)

have

most
a

been a ss o c ia te d

of t h e s e

specific

m aterials

attraction

globule.

repo rted

crude

that

membrane

a flavin-like
of the

found 70 m i l l i g r a m s

fat

of xanthine

of f a t and t h a t about o n e - h a l f of it

103
re m a i n e d attached to the fat a f t e r
that the flavoprotein was
could be

six washings.

h e a t -la b i le

dissolved copper
The

and iro n

significance

evident.

Dills

Perhaps

the

and Nelson (1942)

in some

manner.

temperature.

(1933) found that

of this finding in r e la t io n to the de­
oxidized flavor

in d airy p ro ducts

c o p p e r - p r o t e i n i so la te d f r o m
was a s s o c i a t e d with the fat

In a unique

out that all of the fat globules
a stabilizing hydrophilic

Davies

since none

r e a d i ly combined with the fat m e m ­

velopment of the lipid-type
is

176° F . ,

i so la te d f r o m fat p a s t e u r i z e d at this

Copper-containing p r o t e i n s .

b ran e .

at about

They concluded

approach, King
in milk a r e

membrane,

me mbr a n e

(1951) pointed

not

but that

milk by

sur ro u n d e d with

some

are

h y d ro -

phobic .

Agglutinin.
agglutinin-type
tified as

Sharp and Krukovsky (1939)

m a terial,

euglobulin,

which Dunkley and So m m e r

(1944)

s el ectively a d s o r b e d on the

s urface

was

solidified fat globules

showed that the

and r e l e a s e d into the p l a s m a

as

iden­
of

the fat

was liquified.

Carotenoids.
that milk carot en oi ds

Kon,
were

Mawson and

Thompson

a d s o rb e d on the

(1944)

s urface

believed

of the fat

104
globule.

This

was

obtained f r o m
the

o ri g i n a l

concluded f r o m

buttermilk

milk fat.

tained f r o m b u t t e r m i l k
of milk fat globules,
b u t t e r m i l k fat was
area

per

series

a tt a ch

of p a p e r s

phenomenon to an

the

in the

that the

fat.

average

was

mu ch l e s s

Peters

the

to the fat

m embrane.

Trout

fat globules

than the

average

ob­

size
in

adsorption

on the f at globule

and l i p a s e s .

milk p h o s p h a t a s e s
and P a l m e r

s ix t i m e s ,

we r e

and the

closely

rem ained

and that

ca n

s uc h a

str o n g ly

a dif­

l eucocyte.

(193.3)

50 p e r

in c r e a m

cent

observed

extent on the

milk could be

of

which had

a tt a c h e d to the

(1939)

were

a s s o c i a t e d with

found that

Kr u ko vs ky and H e r r i n g t o n

g lo b u la r fat

pub lish ed

resulting from

Kay and G r a h a m

(1935)

p ro b a b l y

1945b)

They a t t r i b u t e d

a ttractio n

a ctivity depended to a l a r g e
of the

(1945a,

showed how l e u c o c y t e s

in milk.

electrostatic

charge

Rimpila

been washed

sta te

of the

due to a g r e a t e r

and

Kay and Graham* s p h o s p h a t a s e

lipase

s ize

than was

c o n c e n t r a t i o n of c a r o t e n o i d s

in which they

Phosphatases
aware

in c a r o t e n o i d s

The

hence

that the fat

unit of m a s s .

themselves

ference

richer

thought to be

Leucocytes.
a

was

the o b s e r v a t i o n

fat

that

crystalline
a c t i v a t e d or

d e a c t i v a t e d by
Sharp

(1940)

a result

suitable

demonstrated

(1951)

statement:

fat globules

as

as

(1949)

a

resurfacing

In view of the

"it

is

and a

"The

of p r o t o p l a s m a

s u b st a nc e

Some

surface

of the

Changes

Changes

fold i n c r e a s e

in the

startling

cells
the

F a t Globule

Physical

m o genized

milk was

p r e s e n t e d data

total n u m b e r

globules.

appropriate.

m u s t not be
it

consists

regarded
of c o m ­

glands

Resulting

showing

115 to

a

of f at globules

He

was

1.

500— to 600as

a result

divided into

c a l c u l a t e d t ha t the

of the fat in homogenized
about

efforts

D i mensions

small

area

Som­

milk p l a s m a . "

proxim ately

surface

that the

of the l a c t i f e r o u s

and that e a c h globule

of the

repo rts,

a s s o c i a t e d with the

most

layer

of homogenization
1,200

as

Homogenization

in the

(1914)

in the

above

milk p l a s m a ;

adsorbed from

from

Wiegner

rather

single p r o t e i n , 11 s e e m s

stated:

Kr ukovsky and

the fat globules,

to identify the p r o t e i n

having been a d s o r b e d f r o m

ponents

Later,

enhanced l i p o l y s i s .

com m ents.

g e n e r a l l y have been

Mulder

that

of homogenization,

General
m e r's

heat tre a tm e n t.

Sommer

ap­
ratio

milk to nonho­
(1935)

calculated

106

that a f a t globule
globules

of n o r m a l

to

1,885

surface

milk

about

area

(a v e ra g e

377 s q u a r e

square

or

Surface

Phospholipids.
data of El

theoretically
globules

varied from

a

(1951),

of phospholipids

normal
fat
one

milk.

surface,
or

globule

to

2.58 g r a m s

of only 0.7 g r a m s

more

(1951)

as

a monolayer

10.0 m i c r o n s

1 micron
per

(1943),

Therefore,

calculated,

a mounts

the

per

major

ingredients

when the fat
He

re­

would r e q u i r e

of fat.

The

data

showed a c o n c e n t r a t i o n
100 g r a m s

p o rt i o n

c r e a t e d by homogenization,

unpub­

in d i a m e t e r .

in d i a m e t e r

however,

from

of phospholipid that

100 g r a m s

of phospholipids

of the

= 5 microns)

Increased

the

adsorbed
0.1

and H o r r a l l

1 m illiliter

of Homogenized F a t

a fat

Crane

(1947)

5-fold i n c r e a s e .

A d s o r b e d on the

p o r t e d that

of

Trout

in

of fat globule

sm aller

which on homogenization i n c r e a s e d

Sommer

Rafey

could be

of the f at globules

inches,

i nc he s ,

would yield 216

on homogenization.

diarrleter

Milk Components

lished

in d i a m e t e r

1 m i c r o n in d i a m e t e r

c a l c u l a t e d the

to be

6 microns

is

of fat

in

of the newly f o r m e d

l ef t e xp osed to a d s o r b

found in milk p l a s m a .

107
P roteins.

Wiegner

a d s o r b e d on the
milk to be

fat

lie ve d t ha t the

and,

the

e n l a r g e d f at

therefore,

reported
e nization
ticles

lost

that the

area

velop the
of the

stabilizing

adsorbed

ability.

(1936)

accompanying

in the n u m b e r

curd

adsorbed

c a s e i n was fixed

Chambers

in c u r d t e n s i o n

an i n c r e a s e

be­

s t a b i li ty of h omogenized

m atrix

Weinstein and

homog­

of fat p a r ­

and pro vi de
b eco m e

Trout

an

fixed.

(1951)

ex­

s u s c e p t i b i l i t y of h omogenized mi lk to d e­

solar—
a c t i v a t e d oxidized f l a v o r
milk

assumed

in the a mount of c a s e i n

to weaken the

increased

He

Doan (1938)

upon which the p l a s m a p r o t e i n s

oxidizable

e nizatio n

adsorbed.

that the

M ino r-p rote in f r a c tio n .
p la in e d the

amount of c a s e i n

respectively.

in the h e a t

re du c ti on

served

cent,

s ubstance

surface;
its

c a l c u l a t e d the

in nonhomogenized and homogenized

an i n c r e a s e

resulted from

which

increased

sole

decrease

resulted from

on the

surface

about 2 and 25 p e r

that c a s e i n was

milk

(1914)

components

were

on the b a s i s

that

some

r e d i s p e r s e d on homog­

and a d s o r b e d on the newly f o r m e d

surfaces.

Manifestations

of the Adsorption of Various

Components on the Surface

Lipolysis.
emulsified fat
lipase

lipolysis

Lipolysis

temperature

was

coefficient,

emulsion exhibited a negative

Moore

and T r o ut (1947)

in the

en­
while

tem pera­

believed that the

in v is co s it y of milk homogenized a t lower

due to an i n c r e a s e

re­

attacked differently by milk

a positive

in the n o r m a l

coefficient.

crease
was

was

(1940) noted that

than was the n o r m a l fat emulsion.

hanced and p o s s e s s e d

ture

of Homogenized F a t

Krukovsky and Sharp

(re su rfa c e d)

Milk

in­

temperatures

adsorption of p r o t e i n s

on the fat

globule.

Oxidation.

T r a cy ,

that homogenization
the

Ramsey

retarded

and o th e r s

have

development of the

almost

d is c o v e r e d

whereas

Hood and White

shown that homogenization enhanced the

daylight-activated oxidized flavor.

Brown and Dustman (1935)
oxidized flavor

(1933)

and inhibited the development of

c o p pe r - in du c e d oxidized flavor,

(1934)

are

and Ruehe

have

shown that the

in milk o ri gi na t e s

copper-induced

with the phospholipids

e n t i r e l y o ri e n t e d on the

Duncan and Tro u t (1951)

Thurston,

globule

surface.

which

Weinstein,

d e m o n s tr a t ed that the milk component

m o s t probably activated by daylight was

a w a t e r -s o l u b l e ,

109
surface-active
some

pro tein.

rearrangem ent

Therefore,

of the

homogenization

m aterials

on the

m ust cause

fat-globule

mem ­

b ra n e .

Electrokinetic
Dahle
for

and J a c k

(1937)

pasteurized,

and 2.65
Since

exerted

increased
from

d at a

little

the

indicate

in the
sure

also

that

tension

increased

a change

and the

Possibly

the

or

in the

was

at

2.53

respectively.

of the f a t

are

globule

assum ed
is

tha t

the

derived

available

dispersion

(1933)

which

of p r o t e i n

repo rted

t ha t hom o g ­

a c c o m p a n i e d by an i n c r e a s e

m i lk .

As

degree

increase

surf ace—
a c ti ve

data

Webb

m i lk

of the

a corresponding

adsorbed

s ize

v alues

milk

centim eter,

it c an be

Numerous

of p a s t e u r i z e d

being

mo b i li ty

and

of a dd it io n a l p r o t e i n s .

greater,

were

(1937a)

h o m o g e n i z e d fat globule

h om o g e n i z a t i o n .

surface

was

on mobi li ty ,

tension.

ind ire ctly

volt p e r

showed t h a t the

m o b i l i t y of the

accompanies

and Dahle

electrokinetic

second p e r

adsorption

eni z at io n

rep o rted

influence

Su r fa c e

Jack

n on h o m o g en iz e d and h o m o g e n i z e d

m icra per

their

mobility.

the

of f a t
in

p ro teins

homogenization p r e s ­

d ispe rsion became

surface

tension

comprising

fixed on the f a t

surface,

the

was

noted.

m i lk p l a s m a

with a c o r —

110
responding
Halloran
foaming

redu c ti on in c o n c e n tr a t io n

and Gould (1935)

presented

capacity of p a s t e u r i z e d

in the

serum.

evidence

milk was

to

Trout,

show that the

i n c r e a s e d by homog­

enization which i nd icated that the newly d i s p e r s e d fat was
ere d with m a t e r i a l s
without i n t e r f e r i n g
t heory of King

which allowed it to e n t e r
with the fo a m

(1951),

the

s tru c tu r e .

amount of f r e e

reduced by homogenization,

thus

the foam l a m e l a e
According

fat

alleviating

cov­

to the

(hydrophobic)

its

was

a nt i —
foam c h a r ­

acteristics.

Protein
effects

globule s.*'
fat globule

surfaces

appears

In addition to the
is

milk to heat
alcohol

The

1932)
loss

more

are

’resurfaced.*

d irec t

reduces
1938;

and v a r i o u s

in the

m aterials

homogenized fat globules.

d ifferent f r o m

coagulation (Doan,

’*from the

a film of p r o t e i n

the

The

that on n o r m a l fat

indications

r e s u r f a c e d by homogenization,

(Halloran,

1942).

concluded,

of the phy sica l p r o p e r t i e s

of the

to be

show that homogenization

lam,

some

the newly c r e a t e d fat globules

adsorbed lay er

to

(1950)

it may be p r e s u m e d that

a d s o r b e d to the

Thus,

Trout

of homogenization on

of milk,
is

stability.

there

is

that the
evidence

s ta bility of homogenized

Doan and Mins te r,
casein precipitants

stability of the p r o t e i n was

1933),
(Sulthought

Ill
to be due to an i n c r e a s e
the p la s m a ,
Minster,

as

1933;

well as
Doan,

in the

c a lc iu m —
ion concentration in

to fat-clumping

1931).

the adsorption of one or

(Doan,

In all c a s e s ,

1929b;

Doan and

the p os sibility of

m ore p ro te i n components on the

sur­

face of homogenized fat has been dis cu s se d.
Considerable

evidence

lating to the p r o c e s s i n g
globules a r e
literature

is

of ice

available

in the l i t e r a t u r e

re­

c r e a m which shows that the fat

r e s u r f a c e d by homogenization.

in this field is beyond the

scope

A review of the
of this

study,

but

it suffices

to say that efficient, p e r m a n e n t homogenization of

ice

mixes

cream

emulsifiers
face,

made f r o m but te r oil r e q u i r e

which o r i e n t t h e m se l ve s

along with the

serum

solids

the addition of

at the f a t / p l a s m a

inter­

of the mix to stabilize

the

fat emulsion.

Methods

Used to Study the P r o t e i n Components of

Nonhomogenized and Homogenized Milk and
Their

Respective

Fat—
globule Membrane

Proteins

Nitrogen Distribution

Titus,
h ull"

protein

Sommer

and Ha rt

(1928)

characterized their

according to Van Slyke's

system of nitrogen

"fat-

112
distribution.
distribu tion

W i e se

in t h e i r f a t —
globule

and S a n d s t r o m ' s
They a l s o
(1925)

compiled

W akem an's

(1918)

a lc o h o l —
sol ub le

the

(1935)

"haptein ,"

protein.

and P a l m e r

d istrib u tio n

of

casein,

various

ifi c a t i o n
zation"
man

and

Tracy

1940)

casein,

albumin,

globulin,

m ilk

in m i lk .

the

(1941)

M o re

determ ined

the

H etrick
to

distribution

and

for

"m em brane" —

sim ilar

data for

their

own

tec h niqu e

Shahani

determ ining

the

effect

(1947)

study the

system

of

a

mod­

"m allo ri—
O ver­

of n i t r o g e n

determ ining

on the

and

and O v erm a n,
nitrogen

nitrogen

and S o m m e r

distribution

employed

M e n ef e e ,

(Menefee
for

the

of h e a t on

effect

in m i l k .

of h o m o g e n i z a t i o n

protein

values

p roteose—
p ep to n e

fol lo we d R o w l a n d ' s

recently,

H atto ri's

with t h e i r

method fo r

studied

procedure

em ployed

effect

and

fractions.

nitrogen

Van Slyke.

re—
em ulsified butterfat.
a

in

by M o r r o w

a nd O s b o r n e

(1929)

reported

reported

sem im icro-K ieldahl

study

of

(1935)

for

globulin

(1938)

of R o w l a n d ' s
on the

values

com parison

and P a l m e r

nitrogen

d istrib u tio n but

to

lactalbumin,

for

the n i t r o g e n

m e t h o d of

a nd L i n d e r s t r o m - L a n g ' s

nonprotein n itro g e n
the

of the

Van Slyk e —
nitrogen

1' m e m b r a n e 1' —
proteins
Rowland

determ ined

*' m e m b r a n e * * p r o t e i n

m odification

proteins

Rimpila

(1934)

(1951a,

distribution
1951b)

in h o m o g e n i z e d m i l k

by

using a fractionation p ro c e d u re
nique of Rowland (1938).

bas e d p ri ncipally on the tech­

Their p ro c e d u re

ulin nitrogen differed f r o m Rowland's

for determining

(1938)

method in that

methanol was added to the noncasein f i l t r a t e
globulin.

They also

made

glob­

to p re c i pi tate

the

a detailed study of the influence of

p a s te u r iz a ti o n and homogenization on the nonprotein nitrogen
f ractions.
o nstrate

None of the above

inv es ti ga t ors

was able to dem­

any significant change in the nitrogen distribution in

p a s t e u r i z e d milk, but Shahani and Sommer
decrease

(1951b)

in globulin nitrogen and an i n c r e a s e

nitrogen in milk p a s t e u r i z e d

at

155

o

F. for

showed a

in alpha amino

30 minutes

and

homogenized at 2,000 pounds p r e s s u r e .

E l e m e n t a r y Analysis

In gen e ral ,

r e s e a r c h workers

c h a r a c t e r i z e pro te i ns
sition of nitrogen,
cium,

termining
(1933)

the

hydrogen,

These

the perc e ntage

phosphorus,

data provide

relationship between p ro t e i n s .

and Wiese

ture for

have analyzed for

carbon,

ash and oxygen.

who have attempted to

and P a l m e r

many of the p ro te i n s

compo­

sulfur,

valuable keys
Palmer

cal­
in de­

and Wiese

(1934) p r e s e n t e d data of this na­
reputedly a s s o c i a t e d with the f a t-

114
globule

membrane

Duncan and

d e r i v e d f r o m n o r m a l whole

T r o u t (1951)

presented

p r o t e i n f r a c t i o n which was
face

of the f a t

data f r o m

the

thought to be

literature

The l i t e r a t u r e
m ajor

e xt ens iv e .
niques

have

for

other

stein,

a minor-

a d s o r b e d on the

sur­

b een

known p r o t e i n s

to the

to d e t e r m i n e

have

From

quite

of the

tech­

respective

b ee n c o m p il e d by Wein­
data

of this

type

it is

molecular

weight f o r

a pro­

tein o r p r o t e i n

co m p l e x and d r a w c on c lu si on s

con c er n in g

the

characteristics

of the p r o t e i n .

have n e v e r

been

minimum

milk is

and c h e m i c a l

advantage

data

(1951).

the

a c id comp os itio n

isolated fro m

employed to the

Trout

amino

chromatographic

Some of t h e s e

of milk.

Acids

p roteins

M ic r o b i o l o g ic a l ,

Duncan and

possible

relating

and m i n o r

investigators.

data f o r

Weinstein,

in h omogenized mi lk and c o m p il e d c o r r e s p o n d i n g

Amino

of the

sim ilar

milk.

c h a r a c t e r i z e d by this

Electrophoretic

Several
acteristics

Fat-globule

investigators

of fat globules

membrane

proteins

method.

C haracteristics

have

whose

studied the

cataphoretic

electrokinetic

mobility

is

char­

115
largely
cia t ed

d e t e r m i n e d by the
with the f a t

globule.

term ined

the

fer

about pH 4.3.

to be

in the

isoelectric

iso electric

enization,

to pH 4.44.

m easurem ents,
to be

globule
cated a

per

volt p e r

milk f a t

Jack

2.53 f o r

layer

From

of the

these

membrane

phospholipid

the

data,

on the

and p r o t e i n .

iso electric
sol

or

homog­

isoelectric
stream ing

1937b)

Th eir

point

potential

globules

and

Dahle

d a t a in d i ­

mobility for

and 2.65

h o m o g e n i z e d fat.

m icra

per

homog­
seco nd

They found t h a t

sol had an i s o e l e c t r i c

point of p h o s p h o l i p i d s ----shi f te d the

isoelectric

point of n o r m a l f a t glob­

they p o s t u l a t e d
surface

change

any

point of n o r m a l f a t

electrokinetic

isoelectric

to d e t e c t

p oi nt of fat

(1937a,

de­
buf­

the

isoelectric

casein

(1930)

asso­

in an a c e t a t e

using

in a pho sp ho li pi d

a ddition of a

point t o w a r d t h a t
ules.

(1935),

n o r m a l fat

centim eter for

re-em ulsified

the

raised

isoelectric

the

closely

of p a s t e u r i z a t i o n

and Dahle

in the

point of about pH 2.0
whereas

result

not able

ZOO dilution to be pH 4.3.

increase

eniz ed m i lk f a t

and B r o c k m a n

of c a s e i n

determ ined

1 to

slight

a

d e t e r m i n e d the

(1937)

in a

as

and S o m m e r

about pH 4.3.

and J a c k

Mohr

m aterial

p oint of f a t glo bu le s

addition

North

of the

They w e r e

point

but the

nature

the p r e s e n c e

of the f a t globule,

of a d ou bl e­

consisting

of

Moyer

(1940)

r e p o r t e d the i s o e l e c t r i c

ules f r o m washed c r e a m
respectively.
brane

This

and n o r m a l milk to be pH 3.8 and 4.6,

observation indicated that

some

of the m e m ­

m a t e r i a l had been l o s t in the washing p r o c e s s .

and Sommer

(1944)

fat globules

to be pH 4.3 to 4.5.

able to show the

specific

studies

proteins

have been made

of milk,

with mobilities

on the various p l a s m a

Vleeschauwer

are

no data

and s e r u m

(1951) published e l e c ­

f o r total milk pro te i ns which showed eight

two were

of 7.5 x 10

-5

identified as
and 3.6 x 10

globulin with a mobility of 1.9 x 10
the p r e s e n c e

there

c h a r a c t e r i z a t i o n of isolated

when a sodium veronal buffer

Of these,

avail­

skimmilk and whey.

t rophoretic p a t t e r n s
components

is

and only a limited number of e le c tr o p h o r ­

Heyndrickx and De

pH 8.0.

Furthermore,

showing the electrokinetic

membrane-proteins

evidence

effect of homogenization on the e l e c t r o ­

kinetic mobility of fat globules.
available

Dunkley

det e rm in ed the i s o e l e c t r i c point of normal

No ca refu lly controlled experimental

etic

points of fat glob­

of six components

-5

.

system was

used at

casein components
-5

and another

Deutsch (1947)

as

r e po r ted

in whey and that the p at te rn s

showed m a r k e d a lt e r a t i o n s following p a r t u r i t i o n

in the cow.

11 7
Smith (1946a,

1946b)

mune globulins

made

in bovine

an e le c trophoretic

study of the i m ­

col os tr u m and whey and found that

their concentration was highest in colostrum;
idly following p a r t u r i t i o n .
ents

He also

mostly P a l m e r ' s

p r i s e d about 60 p e r

six whey compon­

however,

Li

(1946)

acetate buffers
were

beta-lactoglobulin was homogeneous,

studied the m a t e r i a l

e l e c tr o ph or e t ic a ll y in

distinct components p r e s e n t .

point of the m a jo r

in whey and identified three

descending

able
side

recorded

1951) found six com­

of them as

pseudoglobulin and beta-lactoglobulin.
(1950) were

He

component as pH 5.1.

Stanley, Andrew and Whitnah (1950,
ponents

Pedersen

ranging f r o m pH 5.3 to 5.6 and concluded that

t hr e e

the i s o e l e c t r i c

beta-lactoglobulin which com­

cent of the total whey protein.

(1936) believed that P a l m e r ' s

6.6.

rap­

and believed that the component commonly r e f e r r e d to as

lactalbumin was

there

reported

diminishing

Slatter

euglobulin,

and Van Winkle

to identify four distinct components

on the

of an electrophoretic p a t t e r n obtained at pH

They noted that i o n ic - s t r e n g t h values lower than 0.5 were

conducive to b e t t e r

resolution.

Kemp,

Johnson and Swanson

(1950) p r e p a r e d protein fractions f r o m whey by chemical p r o ­
c e du r es

and studied t h e ir purity by electrophoretic

analysis.

118
Weinstein,

Lillevik,

Duncan and Trout (1951) c h a r a c t e r i z e d a

m i n o r - p r o t e i n f ra c t io n e l e c tr o ph ore t ica ll y which had been iso­
lated fr om a whey prote o se - p ep to ne
play a role

in the

s o l a r - a c t i v a t i o n of homogenized milk.

The c a se i n of milk has been
by numerous
Groves,

workers

Cu ste r

ages

22 p e r

(Mellander,

and McMeekin,

that ca se in is made
alpha,

up of thr e e

may be a l t e r e d by enzyme

1951).

Krejci

(Warner

75 p e r

components;

Hipp,

who r e po rte d

about 75 p e r

cent gamma.

activity,

1944;

heat,

cent

These p e r c e n t
iodination and

1945; Kamal and T u r n e r ,

Nature

c h a r a c t e r i z e d ele c tro ph or e t ic a ll y

15 p e r

Summary of the

cent beta and

has

casein,

cent gamma

Membrane

c la s s i fie d the f a t - m e m b r a n e

’’haptogenic11 m a t e r i a l ,

mucin—
like

10 p e r

Review of L i t e r a t u r e

of the Fat-globule

The e a r l y l i t e r a t u r e

protein,

Warner,

(1942) obtained an alcohol-acid-soluble fraction

cent alpha,

as lac t o - f ib r in ,

1939;

and Po li s,

from milk ca sein which was
as

studied e l e c tro ph or e t ic a ll y

1950; and others)

cent beta and 3 p e r

other t r e a t m e n t s

fraction that was found to

albumin,

other than casein, f o a m - m a t e r i a l ,

" h a p t e i n , 11 s p e c ia l -

a mixture

of p roteins

phospholipid-protein complex

which was

closely

a s s o c i a t e d with a h ig h- m e lt in g

glutinin and a galaxy of m i n o r
thine oxidase,

p h o s p h a ta s e ,

a c o p p e r - c o n ta i n i n g
lieved to be

carotenoids,

m inor protein.

high d e g r e e

c o n st it u t e s
4 to

These

were

of c a p i l l a r i t y .

the f a t - m e m b r a n e ,

12 m i l l i m i c r o n s

0.3 p e r

or

cent of the

in th i c k n e s s

total

surface

ag­

xan­

and possibly

m aterials

were

be­

of the fat as

oriented there

This

has

which include

cholesterol

s p e c if i c a l ly a d s o r b e d on the

a p a r t of the f a t - m e m b r a n e
their

con stitue n ts

gly ce r i de ,

b ec a u s e

adsorbed lay er,

of

which

been e s t i m a t e d to r a ng e f r o m
and c o m p r i s e d f r o m 0.0 8 to

milk p r o t e i n s .

Effect of Homogenization on Some of the
C haracteristics

Homogenization of milk
fold i n c r e a s e
ponding
fat.

5-

in the

Certain c h a r a c te r is t ic s

decrease

in its

in a p p r o x im a t e l y a

of f at globules

in the

total

s u r fa c e

of homogenized milk,

milk p l a s m a - p r o t e i n s

are

to postulate

that one

or

100-

and a c o r r e s ­
a r e a of the
such as

s ta bility to h e a t and r e d u c e d c u r d tension,

enco ur a ge d i n v e s t i g a t o r s

surfaces

results

total n u m b e r

to 8—
fold i n c r e a s e

of Milk

more

a
have

of the

a d s o r b e d on the newly f o r m e d fat

of homogenized fat.

Changes

in the

s us ce p tibility of

homogenized milk to c o p p e r - i n d u c e d and s o l a r - a c t i v a t e d types

120
of oxidation a ls o f u r n i s h e d additional evidence
a l t e r a t i o n of the

surface

Methods

Available

ture

m ajority

of the

of the f a t - m e m b r a n e

for the Analysis

was

of the

Membrane

d i r e c t evidence

r e la t in g

obtained f r o m

and Van Slyke n it r o g e n values

obtained f r o m f a t —
membrane

which had been i so la te d f r o m n o r m a l

C o ns id e ra b le

i n fo r m a t io n concerning the n a t u r e

was

obtained by o bs erving

of the fat globules

dispersed

to the n a ­

elem entary analyses

preparations

brane

the

of homogenized glo bu la r fat.

Fat—
globule

The

regarding

the

of the fat m e m ­

electrokinetic

in n o r m a l ,

milk fat.

properties

washed and r e m a d e

substrate.
In view of the paucity of inf or m at io n in the l i t e r a t u r e
concerning

the

c om position of the f a t —
globule

homogenized milk and m o r e
experiments

we r e

specifically,

conducted to i so la te

m embrane

in homogenized milk,

the

membrane

in both homogenized and nonhomogenized milk,
of the

amino a cids

trophorized proteins

and to o b s e r v e
in v a r i o u s

also

buffer

in non­

determine

the p a t t e r n s
solutions.

proteins

of the

some
elec—

EXPERIMENTAL PROCEDURE

The
had been

milk u se d in this

r e c e i v e d and p r o c e s s e d

C r e a m e r y during
tion was

3.80 p e r

the

summer

milk was

sto pp ere d tubes
Nitrogen was
i l a r to that

duplicate

cent total

College

composi­
solids.

in Homogenized Milk

s q u ar e

after processing

were

and s t o r e d

at 45

until the n it ro ge n d e t e r m i n a t i o n s

d e t e r m i n e d by a

r e p o r t e d in the

determinations

that

rang­

inch i m m e d i a t e l y

The n it ro ge n f r a c t i o n s

and O v e r m a n

data r e p r e s e n t s

separated
o

F.

in

could be made..

semi—
m i c r o Kjeldahl

r e p o r t e d by Menefee

nitrogen value

The a v e r a g e

12.30 p e r

1,000 to 4,000 pounds p e r

soon as p o s si b l e

Michigan State

homogenized at v a r i o u s p r e s s u r e s

following p a s t e u r i z a t i o n .
as

in the

and D e t e r m in a t io n of Nitrogen

Fractions

The

pooled h e r d milk which

months.

cent f at and

Preparation

ing f r o m

study was

method s i m ­

(1940).
the

E a ch

average

of

did not v a r y beyond e x p e r i m e n t a l

error.
Four nitrogen fractions
noncasein n itrogen,

were

d e t e r m in e d :

nonheat-coagulable

n it ro g e n

total n itrogen,
and nonprotein

122
nitrogen.

Casein nitrogen was obtained by subtracting the non­

casein nitrogen f r o m

the total nitrogen,

the heat-coagulable

nitrogen was obtained by subtracting the nonheat-coagulable
nitrogen f r o m the noncasein nitrogen and the pro teo se peptone
nitrogen was obtained by subtracting nonprotein nitrogen from
the nonheat-coagulable nitrogen.

The various

nitrogen f r a c ­

tions were p r e p a r e d as follows:
(1)
to 20° C.,

Total nitrogen.
into a

Pipette

5 milliliters

1 00 -m illilite r volumetric

flask,

ume with d is tilled w ater and mix thoroughly.
aliquot,

equivalent to 0.5 m i l l i l i t e r

of milk,

of milk,

brought

dilute to vol­

A 10- m il li l it er

was

used for the

nitrogen determination.
(2) Noncasein nitrogen.
into a

100—
milliliter

Pipette

volumetric flask.

20 m i l l i l i t e r s

of milk

Add 55 to 60 m i l l i l i t e r s

of d istilled water,

3 milliliters

of

allow to stand for

15 minutes.

Adjust the pH to 4.67 ± 0.05

with 1 N sodium hydroxide,

1 N acetic

acid,

mix and

allow to stand f o r 45 minutes,

and f i l t e r

through a dry Whatman No. 42 f i l t e r paper.

milliliter

aliquot,

for

equivalent to 2 m i l l i l i t e r s

the nitrogen determination.

of milk,

mix

A 10was used

123
(3) Non-heat-coagulable
of the c a s e i n - f r e e
me tri c flask,

fil tr a t e

nitrogen.

from

adjust the pH to 4.67 ± 0.05 and place the flask

transfer

milk,

A 10—
milliliter
was used for

aliquot,

equivalent to 2 m i l l i l i t e r s of

the nitrogen determination.
Pipette

into a 50—
m i l l i l i t e r volumetric flask,
p e r cent t ri c h l o r o a c e t i c

acid,

until the p re c i p i t a t e d pro te i ns
and f i l t e r

20-milliliter
used for

volumetric flask,

and f i l t e r through a dry Whatman No. 42 f i l t e r

(4) Nonprotein nitrogen.

utes)

Cool to room t e m p e r ­

the contents to a 2 5 - m i l l i l i t e r

make to volume
paper.

25 m i l l i l i t e r s

(2) into a 5 0 - m i l l i l i t e r volu­

in a boiling water bath f o r 45 minutes.
ature,

Pipette

10 m i l l i l i t e r s

make

to volume with 15

mix thoroughly,
have

settled

of milk

allow to stand

(ca

15 to 20 min­

through a dry Whatman No. 42 f i l t e r pap e r.

aliquot,

equivalent to 4 m i l l i l i t e r s

of milk,

A

was

the nitrogen determination.

Preparation

and Determination of Milk Solids.

Nitrogen and Minerals

in Skimmilk and

C r e a m f r o m Nonhomogenized and
Homogenized Milk

Pasteurized

milk was

and skimmilk by means
arator.

sep a ra t e d at

120

o

of a s e m i c o m m e r c i a l ,

P a r t of the milk was homogenized at

F.

into c r e a m

mechanic al
130

F.

sep­

at 2,500

124
pounds p r e s s u r e

(USPHS Index l e s s

the aid of a flo w- r e d uc in g

The c r e a m

f r o m both milks

we r e

total

cedures.

solids

and s k i m m i l k

and fat.

Ash was

was

and F l e m in g
were

samples

d e t e r m i n e d by Shohl1s

determined

d e t e r m i n e d as

P reparation

to the

obtained

according

The

(1922) m o d i f i c a ­

Phosphorus

and Subbarow method (1925).

(1932).

intake

d e t e r m in e d by s t a n d a r d p r o ­

tion of the K r a m e r —
T i s d a l l method.

phorus

s e p a r a t e d with

t e s t e d by s t a n d a r d Mojonnier p r o c e d u r e s

Calcium was

by the F i s k e

10) and

device pla ced in the

s e p a r a t o r bowl.

for

than

to the

was

determined

Ph ospholipid p hos­

method of Wiese,

nitro ge n f r a c t i o n s

for

Nair

e a ch sample

outlined above.

and D et e r m in at io n of Milk Solids

Nitrogen in Washed C r e a m

and

and W a s h e d - c r e a m

Se r um f r o m Nonhomogenized and
Homogenized Milk

The c r e a m

samples

homogenized milk were
cream-washing
mer

and Wiese

diluted with t hre e
for

30 seconds

peated

diluted f r e e

technique
(1933)

obtained f r o m nonhomogenized and

of Storch

and o t h e r s .

volumes

of milk p l a s m a by the
(1897),
The

in o r d e r

to r emove

modified by P a l ­

separated

of d i s ti ll e d w a t e r ,

and then r e s e p a r a t e d .

six t i m e s

as

cream

was

agitated gently

This p r o c e d u r e

was

re­

all of the p l a s m a p r o t e i n s ,

125
as

indicated by a faintly positive

wash w a t e r .

Samples

saved f o r the

d e t e r m i n a t i o n of fat,

fractions

of c r e a m

o r negative

s e l e c t e d washings

total

s olids,

the

in the
were

nitrogen

and lipoid p h o s p h o ru s .

The washed c r e a m s
and then c hu rned.
maintained at 45
serum

from

biuret test

was

o

we r e

The b u t t e r
C.

to f r e e

stored

was

at

17

o

C. f o r

m e l t e d in a w a t e r bath

the fat f r o m

the

serum.

then combined with the b u t t e r m i l k —
like

make up the

w ashed-cream

and the n it r o g e n f r a c t i o n s

serum

were

20 h o u rs

sam p le .

Fat,

The

serum

total

to

solids

d e t e r m in e d on the washed

cream.

Preparation

of the F a t - g l o b u l e

Electrophoretic,
General

Fat-globule

Membrane

Characterization

fat-membrane
similar

to provide

proteins.

The

1924;

Palm er

11.

Forty

accord­

gallons

of

of homogenized milk were

an adequate

working

isolation p r o c e d u r e

to that u se d by P a l m e r

Samuelsson,

were p r e p a r e d

shown in F i g u r e

nonhomogenized milk and 70 gallons
s e p a r a t e d in o r d e r

for

Mi crobiological and

m embrane proteins

ing to the flow d i a g r a m

Proteins

and his

and Wiese,

was

c olleagues

1933;

supply of
somewhat

(Palm er

and

Ri mpila and P a l m e r ,

1935;

Jenness

and P a l m e r ,

supercentrifuge
a mounts

of f a t .

treating

the

cessive
ethyl

to f r e e
The

ether.

membrane

the

substituted for

this

trea tm ent

on the

extraction

ethanol

extraction

(40

o

C.)

characteristics

technique

with

to

to

sim ­

separate

the

of the f a t —
treatm en t

study the

of the p r o t e i n .

u s e d in this

were

technique

(1910)

suc­

and p u r i f i e d

e th a n o l —
ether

cold e x t r a c t i o n

gross

c o m p l e t e d by

In two p r e p a r a t i o n s

a warm
the

from

lipid m a t e r i a l s

and G a r d i n e r

blood p r o t e i n s .

was

nol—
ether

study,

cold e th a n o l —
ether

proteins,

serum

of the fat was

hot a b s o l u t e

In the p r e s e n t

from

used a Sharpies

dialyzed m e m b r a n e —
proteins

to t h a t u s e d by H a r d y

lipids

P alm er

w ashed-cream

of a c et o n e ,

e x t r a c t e d with a
ilar

the

extraction

isoelectric,

portions

1945a).

e ffec t of
The

investigation

etha­

was

as

follows;
(1)
were

Three

added to the

proteins.

T h is

of a m e c h a n i c a l
Whatman No.
(2)
to

3°

volumes

C.)

mixture
stirrer

2 filter

The

ethyl

residue.

(0

o

to

was

o

o
5
C.)

to

o
3
C.)

absolute

ethanol

d ia ly z ed f a t - m e m b r a n e

a g i t a t e d for

and then f i l t e r e d

10 m i n u t e s

by m e a n s

through a pleated

paper.

residue

purified

precipitated

cold

of cold (0

was

wa s h e d t h r e e

ether

to

remove

tim es
the

with cold

alcohol f r o m

(0

o

the

127
(3)

Three

v olumes

of ethyl e t h e r ,

ume of dialyzed m e m b r a n e - p r o t e i n s ,
ature

of m i x t u r e

minutes.

The

was

a d j u s te d to 40

mixture

was

to allow the p r e c i p i t a t e
off and e x t r a c t e d

to

by f i l t r a t i o n
(4)

The p r o t e i n

t im e s

with e t h e r ,

water

and lyophilized.
The

proteins

Elmer,

38,

was

small

was

(1948).

of the lyophilized

method.

aid of a P e r k i n s -

apparatus

The p ri nc i pl e

(1942)

scanning

A Tiselius—
type

u sed to contain the p r o t e i n

ponents

are

moving b o u n d a r i e s

formed.

of the

as

de­

of its

op­

modification

squ ar e

and in which the

several

amount of d is ti ll ed

studied with the

e lectro ph oresis

washed

and a c r o s s - s e c t i o n a l

was

drawn

s e p a r a t i o n of p r e ­

capacity of 2 m i l l i l i t e r s
centim eters

15

s e p a r a t o r y funnel

on the p a p e r

characteristics

and White

Toepler-Schlieren

temper—

and e t h e r was a c c o m p l i s h e d

e r a t i o n is b a s e d on Longsworth*s
of the

vol­

2 Whatman p a p e r .

were

Tiselius

The

C. and agitated f o r

The final

r e d i s p e r s e d with a

fat-membrane

s c r i b e d by Moore

o

added.

The p r e c i p i t a t e

times.

residue

electrophoretic

Model

settle.

proteins

through a No.

were

t r a n s f e r r e d to a

two m o r e

cipitated f a t - m e m b r a n e

b a s e d on o ri g i n a l

cell with a

area

of 0.3
solution

v ar i ou s p r o t e i n

c om­

128
a'

E le ctrop ho re tic
were

p r e p a r e d by adding

sample
liter

to

10 m i l l i l i t e r s

c e n t r if u g e

allowed to

tube.

sta nd f o r

centrifuged at
The

solutions

2,000

supernatant

600 m i l l i l i t e r s
continuous
on both

s id e s

exa c tl y 0.1
of the

The

of the

was

at

1.2°

C.

The

of the lyophilized
in a

of the tube
24 h o u r s

per

minute

we re

at
for

15—
m illi­

18°

mixed,
C.

dia ly z ed in a cellophane

maintained at

5°

cellophane

C. f o r

membrane.

p roteins

was

and then

one—
half hour.
sac

6 hours

until c o n s t a n t conductivity was

equilibrated f a t- m e m b r a n e
s is

con te n ts

r e vo lu ti on s

of buf f er ,

gram

d e s i r e d buffer

approximately

aqu a so l

a gitation,

of the f a t - m e m b r a n e p r o t e i n s

against
with

obtained

A solution of the

used for

electrophore­

c o n c e n t r a t i o n was b a s e d on the

m icro—

Kjeldahl d e t e r m i n a t i o n f o r n i t r o g e n .
The

membrane

phoretically

were

in the following buffer

chloric

acid,

citrate,

pH 8.0;

e thylamine,

samples

pH

1.5;

acetate,

characterized

systems:

pH 10.8.

glycinv-hydro-

pH 3.0; p ho sphate,

amm onia-hydrochloric
The b uff e r

acid,

solutions

electro—

pH 6.5;

pH 9.0;
were

veronal-

and v e r o n a l —

prepared

as

follows:
(1)
10.05 m o l e s

Gl y ci ne —
hydrochloric
of glycine

in

a c id buffer

500 m i l l i l i t e r s

substrate.

of d i s t i l l e d w a t e r ,

Dissolve

129
adjust the pH to

1.5 with hydrochloric acid and dilute to one

liter.
(2) Acetate buffer
dium acetate

in 500 m i l l i l i t e r s

pH to 3.0 with acetic
(3) Phosphate
monohydrated

buffer

substrate.

Veronal—
citrate

buffer

and 0.011

0.02 mole of

mole of dibasic

substrate.

of distilled water,

so­

Dissolve

0.1 mole

of sodium c i t r a t e

adjust to pH 8.0 with

acid and dilute to one l i t e r .

mo la r hydrochloric

hydroxide
(6)

acid buffer

solution t e s ts

Veronal-ethylamine buffer

of ethylamine

Add

and 0.1

pH 9.

substrate.

Dissolve

mole of diethylbarbituric

0.2

acid in

of distilled water and dilute to one l i t e r .

The buffers
strength,

substrate.

acid solution to 0.2 m o l a r ammonium

solution until the

500 m i l l i l i t e r s

ionic

Dissolve

and 2.25 g r a m s

(5) Ammonia-hydrochloric

mole

adjust the

in d istilled w a t e r and dilute to one l i t e r .

in 500 m i l l i l i t e r s

0.1

0.1 mole of so­

acid and dilute to one l i t e r .

of sodium diethyl b a r b i t u r a t e

citric

Dissolve

of distilled water,

sodium phosphate

dium phosphate
(4)

substrate.

were

calculated to be approximately 0.1

except the v e r o n a l - c i t r a t e ,

which was

0.09.

At any given pH,
the

and

salt

c o n c e n tr a t io n ,

m i g r a t i o n of a given p r o t e i n boundary p e r

(t = sec.)
tial

temperature

depends

gradient

where

is

upon the p ot en ti a l

calculated

gradient

as

follows:

F

= i/ak

F

= the p ot ential

i

= current

unit of time
(F).

The poten­

gradient,

in a m p e r e s ,

a = the

cross-sectional

k = the

specific

area

conductivity

of the

U-cell,

and

of the b uffe r p r o t e i n

solution.
The
(u),

is

s p e e d of m i g r a t i o n ,

defined as

second u n d e r
a

specific

the

distance

a pot en ti a l

buffer

system

or

the

moved

electrophoretic
in

square

centim eters

g r a d i e n t of one volt p e r
and may be

mobility

centim eter

per
in

e x p r e s s e d by the follow­

ing equation:
u(cm.
where

2

/volt,

u = mobility in

sec.)

square

= dak/it
centim eters

per

volt p e r

second,
d = d is ta n c e

moved by the p r o t e i n boundary,

a = cross-sectional
k = specific
(k = c e ll

area

of the

U—
cell,

conductivity of p r o t e i n —
b uffe r
constant/resistan ce

in ohms),

solution

i = current
t = time
Amino
techniques
c a lis

acid d e t e r m i n a t i o n s

by using L a c t o b a c i l l u s

those

various

used f o r

a c co rding

Lyman e_t al.

to the

(1946),

alanine
Stokes

and valine

were

P-60.

et al.

(1945).

e s s e n t i a l l y the

dispersed

autoclaved f o r

at

DL—
Configurations
phenylalanine
for

and valine

the amino

the p r e p a r a t i o n

run a f t e r

g ram

in 25 m i l l i l i t e r s
8 h o u rs

of a

the p r o p e r

The

as

with the

according

for

methionine,
to the

and
the

phenyl­

method of

of the f a t - m e m b r a n e
of 6 N h y d ro c h l o r i c

ex­

which were

h y d ro ly z a te s

l ysin e,

proteins

acid and

15 pounds p r e s s u r e .
of i so leucine,

were

acids,

(1946)

same

and methionine,

leucine,

prepared

One

The m e d i a used

method of Kuiken et a l . (1943)

respectively.

were

by m i c ro bi ol og ic a l

a r a b i n o s i s . S t r e p to c o c c u s f a e -

isoleucine

d e t e r m i n a t i o n of isole uc i ne ,

f or

made

d e s c r i b e d by S a u be rli c h and Baumann

prepared

ards

were

mesenteroides

determinations

ception of those

was

and

in seconds.

and Leuconostoc

in the

in a m p e r e s ,

methionine,

u s e d in the p r e p a r a t i o n

whereas

of

stand­

the L - c o n f i g u r a t i o n was

s t a n d a r d for

dilutions

leucine,

l ys in e.

had been made.

All a s s a y s

used

were

132
Certain characteristic
of nitrogen,
p ea rance

information

solubility in different buffer

in the

dry and hydrated f o r m s ,

and n it r o p r u s s i d e
also d etermined.

re a ct io ns

such as
systems,
the

the p e r

physical ap­

Molisch,

of the f a t - m e m b r a n e

cent

b iu re t

proteins

were

PASTEURIZED NONHOMOGENIZED AND HOMOGENIZED MILK

I

( S e p a ra ted , SO*C.)

I

Skimmiik

CREAM
I

(Diluted 3 volumes H O and reseparated 6 times)
I---------

Washings

WASHED CREAM
I
( C ooled,stored,churned)
____________I_______________

1

B utter

SERUM
(S era combined and
concentrated 8 !I)

I
( M elted, s e p a ra te d )
.
I

Oil

SERUM
I

CONCENTRATE
(Dialyzed 72 hours)

NONDlALYZABLE MATERIAL
I
(Treated with ethanol and ethyl ether.
R esidue d isp ersed in distilled water;
lyophilized.)

FAT'G LOBULE
MEMBRANE PRO TEINS
F i g u r e 11.
preparation

F l o w s h e e t sh o w in g the p r o c e d u r e s
o f f a t —g l o b u l e m e m b r a n e p r o t e i n s .

follow ed

in

the

RESULTS

N it r o g e n D is t r ib u t io n in H o m o g e n iz e d M ilk

The influence of homogenization on the d istribution of
nitrogen in v ar i ou s
in Table
gen p e r

10.

The

milk p ro te i n s
resu lts

100 m i l l i l i t e r s

to the p erc e n t a g e
if d e s i r a b l e .

milk,

are

obtained f r o m
pressure,

values

can be converted
6.38,

in the amount of ca se in

nitrogen,

obtained by Menefee,
(1951b).

of the total nitrogen.

a pp a ren t in the homogenized

nitrogen accompanied by a d e c r e a s e
and heat-coagulable

v a r i a ti o n f r o m

obtained for p a s t e u r i z e d milk when

that were

an i n c r e a s e

and So mmer

of n i t r o ­

milk homogenized at

show little

e x p r e s s e d as p er c e nt a ge

slight v a r i a t i o n s
i . e .,

shown

The values f or the amount of n it ro g e n in the va­

the correspo nd in g

The

milligrams

of p r o t e i n by multiplying by the fac to r

and 2,500 pounds

the values

e x p r e s s e d as

of milk, but the values

rious nitro ge n f r a c t io n s
1,000

are

in p a s t e u r i z e d milk is

are

and nonprotein

in the quantity of noncasein

in a g r e e m e n t with the

Ov er ma n and T r a c y

(1941)

results

and Shahani

135
Milk which had been homogenized at 4,000 pounds p r e s ­
sure,

however,

showed i n c r e a s e s

of 6.57 p e r

n it ro ge n

and 0.88 p e r

3.96 p e r

cent in non ca se in n itrogen,

ulable

n it ro g e n

and

cent in c a s e i n nitrogen

7.15 p e r

of the

4,000 pounds p r e s s u r e
Whether

the

increase

tion in n it r o g e n
and S o m m e r
fractions
minu te s.

5.26 p e r

was

at

143° F.

145°,

149° and

in t e m p e r a t u r e
is

difference

Rowland (1933-34)

tion of s k i m m ii k at
cent d e c r e a s e

62.5

o

C. f o r

30 m i n u te s.

1,000,

2,500

The

and

respectively.

con tribu te d to the

not known.

show little

for

153° F . ,

altera­

data of Shahani

between the n it ro g e n

of r aw milk and milk p a s t e u r i z e d
Yet,

of

cent in h e a t —
c oag-

milk homogenized at

d is tr i b u t i o n

(1951b)

and d e c r e a s e s

cent in p r o t e o s e —
peptone nitro ge n

in c o m p a r i s o n to milk p a s t e u r i z e d
The t e m p e r a t u r e

cent in nonprotein

at

155° F . f o r

30

showed that the p a s t e u r i z a 30 minutes

caused a

10 p e r

in the a lb um i n —
globulin n it ro gen f r a c t i o n .

D i s tri bu ti on of Milk Solids,

Nitrogen and M i n e r a l s

in

Skimmiik and C r e a m f r o m Nonhomogenized
and Homogenized Milk

Data

showing

the p e r c e n t a g e

s o l i d s - n o t - f a t in c r e a m
from p asteu rized

and

of total m i l k - s o l i d s ,

s kim miik which were

milk before

fat and

separated

and following homogenization at

2,500 pounds p r e s s u r e

are

of fat and total

in skimmiik and c r e a m

solids

nonhomogenized milk a r e
aration,

wh ere as

miik and c r e a m

r e c o r d e d in Table

typical and indicate

the amounts of fat and total

11.

The contents

separated from
an efficient sep­
solids

in the

s e p a r a t e d f r o m the homogenized milk

s kim­

show a

different p a t te r n .
In previous
ventional
means

studies,

T rout et al.

of r e covering

the fat in the c r e a m .
was placed in the

ahead of the bowl to i n c r e a s e
of the

separator.

a skimmiik testing

separator

Such a p ro c e d u re

1.91 p e r

In this

study,

a

ass e mbly

the efficiency of the centrifugal

a r ation of a rela t iv el y h ig h - te s t c r e a m

a 50 p e r

showed that con­

separ at io n of homogenized milk was not an efficient

flow—
reduction device

force

(1935)

cent fat.

r e s u lt e d in the

(46.60 p e r
This

sep­

cent fat)

represents,

and

roughly,

cent r e c o v e r y of the total available fat in the homog­

enized milk.

From

these

data the the o re t ic a l percentage

solid s- n ot—
fat was d et e r m in ed for each of the two c r e a m

of
sam­

ples by the expression:
[100 -

percentage

perc e nta ge

of fat in c re a m ] / 1 0 0

of s o l i d s - n o t - f a t in skimmiik.

Nitrogen distribution determinations
and c r e a m

samples

x

r e p o r t e d in Table

for the

11 are

skimmiik

tabulated in Table

137
1Z.

The determined nitrogen values,

also e x p r e s s e d as

’’p l a s m a - c o r r e c t e d ' 1 and ‘' f a t - f r e e "

The p l a s m a - c o r r e c t e d
centrations
major

in m i ll ig ra m p e r cent,

values,

which e x p r e s s

in c r e a m on a p l a s m a - f r e e

difference
cream

nitrogen.

Similarly,

the nitrogen con­

b asis,

showed that a

samples,

which is

the f a t - f r e e

gen in f a t - f r e e pla sm a

as

nitrogen in skimmiik which was
milk as

compared to the normal
The data in Table

casein

nitrogen values, which e x p re ss

(skimmiik),

in the casein nitrogen,

of the

manifested largely as

the nitrogen concentration in skimmiik on the basis

crease

nitrogen.

exists between the total nitrogen values

respective

a re

of the n itro­

showed a considerable
well as

de­

in the noncasein

s e p a r a t e d f r o m homogenized
skimmiik.

13 emphasize f u r t h e r the difference

between the distribution of milk components in nonhomogenized
and homogenized milk and show that c r e a m which was
from homogenized milk contained higher concentrations

sep ar at e d
of ash,

copper and nonphospholipid phosphorus than the amounts found
in c r e a m

sep a r a t e d from nonhomogenized milk.

pensating t re n d was noted in the
ready observed in the case

skimmiik,

A definite com­

s i m i l a r to that al­

of the nitrogen distribution data.

138
D i s tri bu ti on of Milk Solids
and W a s h e d - c r e a m

and Nitrogen in Washed C r e a m

Serum from

Nonhomogenized

and Homogenized Milk

Up to the p r e s e n t t im e ,
the

milk components

the fat globules

supposedly

have been

i n d i r e c t c o n c lu si o n s.
n at u r e

water,
from

A m ore

By washing

it was p o s s i b l e

12 shows

the

direct

cream

plasm a

washed c r e a m .

obtained f r o m

homogenized milk

six washings,

whereas

ings;
or

the

three

greatest

a p p r o a c h to d e t e r m i n e
was

made

six t i m e s

in this

the

in­

with d is ti ll ed

components

dilutions

removed.

on the fat

The f at content of washed c r e a m
remained fairly

the fat content of c r e a m
at a g r e a t e r

increase

were

rate

occurred

uni fo r m a f te r
from

nonhomog­

with s u c c e s s i v e

subsequent

wash­

to the f i r s t

two

washings.

Data
washings

of

data which p e r m i t only

effect of s u c c e s s i v e

increased

surf a c e

of

to obtain a c o n c e n tr a t io n of fat globules

content of the

enized milk

and n a t u r e

a s s o c i a t e d with the

substances

the

which the u n a s s o c i a t e

Figure

co n c en tr a t io n

derived from

of the f a t - m e m b r a n e

vestigation,

the

in F i g u r e

on the

tive

cream

per

100 g r a m s

13 i l l u s t r a t e

concentrations

samples.
of fat,

The

the

effect of

of total nitrogen

successive
in the

c o n c e n t r a t i o n of n itrogen,

dropped

sharply

respec­

in g r a m s

with the f i r s t washing.
:s,'

139
There

was

a gradual

decrease

in n i t r o g e n

content,

in the c a s e

of nonhomogenized c r e a m ,

up to the f o u r t h o r fifth washing,

where

r e d u c ti o n in the

it l e v e l e d off.

The

n it ro g e n in homo ge niz ed c r e a m
first

washing

and

was

remained fairly

c o n c en tr a t io n of

largely

arrested

u n i f o r m up to the

after

the

sixth w a s h ­

ing.
In c r e a m
milk,
per

the

concentration

100 g r a m s

washing
(Fig.

which had b een

of fat)

and then

14).

separated from

of phospholipid p h o s p h o ru s
decreased

slightly following

remained fairly

Further

washings

pholipid p h o s p h o r u s .

The

washed,

constant

accelerated

in the

trast.

Subsequent to the f o u r t h washing,

cream
The

cream s
tention

grams

was

washings

decrease

in p h o s ­

h ig h e r

made
the

a unique

con­

c o n c e n t r a t i o n of

than tha t found in the o r i g ­

sample.
concentration

of fat and

and w a s h e d - c r e a m
should be

centration

the f i r s t

a f t e r four

the

homogenized c r e a m

phospholipid p h o s p h o r u s

(m illigram s

c o n c e n t r a t i o n of phospholipid p h o s ­

phorus

inal

nonhomogenized

d irected

sera

The

recorded

in Table

to the f o u r t h column where

of s o l i d s - n o t - f a t a r e

of f a t.

are

solids-not—
f a t in the washed

washed,

expressed

as

grams

homogenized c r e a m

15.

At­

the con­

per

contained

100

141
homogenized
serum from

Some

serum.

This

nonhomogenized milk was

C h aracteristics
from

Some

p ro t e i n s

Isolated

characteristics

of

i s o l a t e d f r o m nonhomogenized and
in Table

on a l i p i d - f r e e

17.

The n i t r o g e n con­

basis,

averaged

13.50

cent.

Electrophoretic

C h aracteristics

Fat—
membrane

Electrophoretic
ethanol-ether
and buffer

me dia

migrating

in Table

18.

patterns

are

protein

components,

The

were

p ro t e i n s

15 to 21,

in Table

19.

were

Where

r e s o l u t i o n of the p r o t e i n components

sometimes

three

p r o m i n e n t and d is ti n c t peaks

pH

inclusive.

r e p r e s e n t e d by peaks

m obi li ti es

cold

in v a r i o u s

m e a s u r e d and the

electrophoretic

each peak and r e c o r d e d

phoretic

of unit magnification f o r

i l l u s t r a t e d in F i g u r e

patterns,

of the

Proteins

extracted fat-membrane

electrophoretic

f or

P ro te in s

and c h e m i c a l

tabulated

m aterials,

Some

The

heated.

of F a t - m e m b r a n e

of the phy sica l

homogenized milk a r e
tent of t h e se

when

Nonhomogenized and Homogenized Milk

the f a t —
m embrane

per

condition was not o b s e r v e d

in the

data tabulated
c alc ul ate d
good e l e c t r o ­

occurred,
were

two and

observed

in

142
the

e le ctro p h o re tic

patterns

of the

pared from

non ho mog en iz e d milk.

resen tative

of the n o r m a l

o bt ained f r o m
o r four

the

In m o s t

distinct

difference

phoretic

p attern s

These

fat-m em brane

data,

then,

h ow e v e r ,

in the b a s i c

there

p ro teins

pre­
rep­

The p a t t e r n s
show t h r e e

r e s o l u t i o n was

appeared

characteristics

of f a t - m e m b r a n e

are

p ro teins

when good e l e c t r o p h o r e t i c

instances,

proteins

proteins.

h om o g e n i z ed f a t - m e m b r a n e

distinct peaks

obtained.

fat-m em brane

of the

to be

a

electro­

p rep ared from

non­

h om o g e n i z ed and h o m o g e n i z ed m ilk.
The
traction
brane

e ffec t of w a r m

on the

electrophoretic

proteins

in pho sp hate

M easurements
18 and the
in

Table

phoretic
had an
This

of the

C ertain

patterns
effect

The p r o t e i n s
than t h o se

was

t h a t the

also

of the

are

recorded

differences

tem perature
resulting

by cold e x t r a c t i o n .

in F i g u r e

m obilities

extraction

and c old

ex­

of the f a t —
mem­

illustrated

s u b s t a n t i a t e d by

p r e p a r e d by w a r m

prepared

is

electrophoretic

on the n a t u r e

difference

b uf f e r

characteristic

indicate

treatm ent

characteristics

c om ponent p e a k s

correspo nd in g

20.

eth ano l—
ether

in
are

in the

22.

Table
recorded
electro ­

of t r e a t m e n t

p ro tein

solubility
were

m aterial.
studies.

less

soluble

143
The
membrane
patterns
23.

e ff ec t s

of v a r i a t i o n in the

proteins

on the

obtained in

The p e a k s

sured

and the

l at e d.

These

the

trial

corresponding
data a r e

centrations
the

differed

respective

differed

the

membrane

slightly,

the

assay

m aterial

is

for

results

six e s s e n t i a l

amino

a c id s

mobilities

of

cent p r o t e i n

con­

concentration

of

component.

of the

Proteins

obtained f r o m

the

microbiological

extracted fat-m em brane

are

par­

to c o n s i d e r when de­

C haracteristics

cold e thanol—
ether

Although

u s e d in this

electrophoretic

that the

mea­

calcu­

18 and 21.

buffers

a factor

were

mobilities

mobility of a p r o t e i n

M icr o b i o l o g ic a l

a n a l y t ic a l

of the

Tables

enough to indicate

electrophoretic
shown in F i g u r e

in 0.84 and 0.43 p e r

F at-m em brane

The

are

of f a t -

c omponents

e lectrophoretic

of the phosphate

electrophoretic

Some

of the

systems

t ab ul a te d in

components

electrophorized

termining

buffer

various

the p o t e n ti a l g r a d i e n t s
ticular

characteristics

sim ilar

of the

concentration

given in Table

22.

The

amino

a c id c o m p o s it io n of the

m in o r-p ro te in fraction,

min,

pseudoglobulin and euglobulin a r e

in­

purposes.

pro­

beta—
lactoglobulin,

cluded f o r
t eins

comparative

contained a p p r o x i m a t e l y

the

The
same

casein,

proteins

lactalbu-

two f a t - m e m b r a n e
concentrations

of

methionine,
none

valine,

l eu c in e,

v a r i e d by m o r e

cent d if f e r e n c e
The

than

in the

j e c t to f u r t h e r
additional

lys in e

The

significance

acids.

that the f a t - m e m b r a n e

other

characterized

of anhydrous

values

are

mately

same

proteins
(1925)

proteins

expressed

a mount of lysine

cent,

the

the non­
is

determination

data indicate,

differ

as

sub­
of

how­

markedly fro m

in its
grams

and the
and

amino

other

Titus

respectively.

as

less

amino
per

the

acid

100 g r a m s

the

Th e se

and a p p r o x i ­

m inor-protein f ra c ­
(1951).

The l ac k

acid content of the f a t - m e m ­

recognized

et a l.

methionine,

valine

Duncan and T r o u t

(1928)

n i t r o g e n in n o r m a l f a t - m e m b r a n e
per

samples.

difference

contain m o r e

and phenylalanine;

of s i m i l a r i t y between the

H a t to r i

of this

well as

proteins

tion r e p o r t e d by Weinstein,

b ra n e

two

a 22 p e r

protein.

i so le uc i ne
the

was

and

the homogenized milk

milk p r o t e i n f r a c t i o n s

The f a t - m e m b r a n e
leu c in e,

in the

The p r e l i m i n a r y

ever,

content when all

T h e re

than that obtained f r o m

inv e s ti g a t io n as

amino

cent.

obtained f r o m

to contain m o r e

homogenized milk.

10 p e r

and phenylalanine

amount of l ys in e

m em brane-proteins

appear

iso le uc ine

milk p r o t e i n s

r e p o r t e d v alues

m aterials

values

are

as

6.11

is

evident.

f o r lysine

and 6.69

in good a g r e e m e n t

with the value
and P a l m e r

f o r l y s in e

(1934) found the

" m e m b r a n e 11 p r o t e i n
The
membrane

to be

minimum
p roteins

was

(M min.)

here

as

11.01 p e r

weight (M min.)

= (Ra x Ma x

Ra = is

whereas

minimum
the

100)

in

of the f a t -

equation:
/

(%)*

molecular

integer

of specific

Wiese

cent.

c a l c u l a t e d by the

= the

5.92,

l ysine n i t r o g e n c o n c e n t r a t i o n

molecular

(M min.)
wh e re

reported

weight,

represen ting

amino

a cid

the n u m b e r

residues

in the

m o lecule,
Ma = is

the

acid,
(%)

= is

the

sm allest

the p e r

integers.

The

p r e s e n t e d in

are

Table

27,500

amino

was

the

100

protein.

amino

u se d to make
the

acid in

acid p r e s e n t
the

(M min.)

in

a d j u s t m e n t to

c a lc ul a ti on s

are

23.
t he se

fraction,

not c o m p a r a b l e .

fat-m em brane

of anhydrous

data u s e d to make

In c o m p a r i n g
m inor-protein

cent of amino

which r e p r e s e n t s

concentration,

weight of the

and

gram s
Methionine,

molecular

proteins

in c o m p a r i s o n

data with those

it is

The
was

r e p o r t e d f o r the

evident that the

minimum

molecular

c a l c u l a t e d to be

to 70,300 f o r

two p r e p a r a t i o n s

the

weight of the

approximately

m in o r-p ro te in fraction,

146
12,800 f o r

casein

and 42,020 f o r beta-lactoglobulin,.

f e r e n c e between the minimum m o l e c u l a r
p ro tei n s

smal l to
two.

proteins.

was

a pp roximately

suggest that t h e r e

F u rth er

and the

weight of the

obtained f r o m nonhomogenized (28,926)

milk (26,798)

work is

is

6 per

contemplated,

i n t e r e s t and i m p o rt a n c e .

dif­

membrane

and homogenized

a difference

difference

however,

investigation of the p r o p e r t i e s
Information on this

cent;

an actual

The

too

between the

on the isolation

of the f a t - m e m b r a n e

type of p r o t e i n

is

of fundamental

TABLE 10
The effect of homogenization at various p r e s s u r e s on the nitrogen distribution in m ilk p aste u r­
ized at 143° F . for 30 m inutes

N onhomoge­
nized m ilk
(Control)

Homogenization P r e s s u r e ( l b . / s q . in.)
1,000

N i- ■
troPer
gen
cent
of
(m g./
Total
100
m l.)

Per
cent
V ari­
ation
from
Con­
trol

N i­
tro­
gen
(m g./
100
m l.)

Per
cent
of
Total

Per
cent
V a r i­
ation
from
Con­
trol

0.2

450.1
88.0

100.0
19.6

0.0
- 0 .8

8.8
4.7

0.0
0.1

39.1
22.0

8.7
4.9

-0.1
0.3

365.0
51.2

80.0
11.2

0.2
-0 .2

362.1
48.9

80.5
10.8

0.7
- 0 .6

18.8

4.1

-0.1

17.6

3.9

- 0 .3

N i­
tro­
gen

N i­
tro­
gen
(m g./
100
m l.)

Per
cent
of
Total

445.8
90.1

100.0
20.2

449.0
91.8

100.0
20.4

0.0
0.2

456.4
91.4

100.0
20.0

39.0
20.5

8.8
4.6

38.5
21.5

8.6
4.7

- 0 .2
0.1

40.2
21.4

355.7
Casein N
Heat-coagulable N 51.1
Proteose18.5
peptone N

79.8
11.4

357.2
53.3

79.6
11.9

- 0 .2
0.4

4.2

17.3

3.9

- 0 .3

Nitrogen
F raction

4,000

2,500

(mg./
100

Per
cent
of
Total

m l.)

Per
cent
V ari­
ation
from
Con­
trol

Determined
Total N
N oncasein N
N on h eat-coagulable N
Nonprotein N

0.0

Calculated

148
TABLE
D i s tri b u ti o n of fat and

11

s o l i d s - n o t - f a t in c r e a m

and

s k i m m ii k

f r o m nonhomogenized and homogenized m i lk

Difference

Mojonnier

Theoretical^

Values

tual

Obtained

IV?

Fat

(% )

(% )

Percentage

Cream
Solids-

Solids

and A c ­
of

So li d s —
not—
fat in the

for

Product

between the

not-fat

Samples

Theoretical

Difference

(% )

(% )

(%)

Pasteurized
12.25

3.76

8.49

•

t

«

•

•

•

8.85

0.10

8.75

•

•

•

•

■

•

35.91

29.60

6.31

6 .1 6

0.15

skimmiik

10.63

1.91

8.72

•

•

cream

52.02

46.60

5.42

4.66

milk
Nonhomogenized
skimmiik
cream
Homogenized

Calculated on b a s i s

•

•

percentage

of

•

0.76

of f o r m u la :

P e r c e n t a g e of s o l i d s - n o t - f a t in c r e a m =
[100 - p e r c e n t a g e of fat in c r e a m ] / l 0 0

•

x

s o l i d s - n o t - f a t in s k i m m ii k .

4

149
TABLE

12

D i s t r i b u t i o n o f the n i t r o g e n f r a c t i o n s in c r e a m
f r o m n o n h o m o g e n iz e d and h o m o g e n iz e d m ilk

and

sk im m iik

Skimmiik
Nitrogen

Non­

Fraction

homogenized

Homogenized

(0.12% fat;
8.85% t.s.)
TOTAL N
( m g . / 100 ml.)

(1.91% fat;
10.63% t.s.)

Difference
Due

to Ho­

mo ge niz ation

470

442

•

470

451

-19

•

•

Fat-free
( m g . / 100 ml.)
P lasm a-corrected
(mg./lOO

g. fat)

•

•

•

(mg./lOO

g.

•

•

•

cream)

•

•

•

•

•

t

•

106

100

•

•

«

106

101

-

•

•

•

•

NONCASEIN N
( m g . / 100 ml.)
Fat—
free
(m g . / 10 0 m l .)

5

Plasm a—
cor rected
( m g . / 100 g. fat)

•

•

•

•

•

•

•

m

m

m

NONHEAT-COAGULABLE N
(mg./lOO ml.)

47

49

47

50

Fat—
free
(mg./lOO

ml.)

3

P l a s m a - c o r re cted
(mg./lOO

g. fat)

•

NONPROTEIN N
( m g . /100 ml.)

•

•

•

•

30

26

•

•

•

30

27

-

•

•

•

•

Fat-free
(mg./lOO

ml.)

3

Plasm a-corrected
( m g . / 100 g. fat)

F a t-fr e e N determined
of p la s m a ) ] x 100.
to e .
h .

•

•

as

•

•

follows:

•

•

[(N d e t e r m in ed )

•

•

/

•

(Vol.

150

TABLE

12 ( C o n t i n u e d )

C ream
Pasteurized
Nonhomogenized

Homogenized

Difference

(29.60% fat;

(46.60% fat;

Due to Ho­

35.91% t.s.)

52.02% t.s.)

mogenization

336

•

•

•

Milk

(3.76% fat;
12.25% t.s.)

295

.

.

.

456

•

•

•

•

•

•

•

•

•

54

150

96

•

•

•

16

67

51

•

•

•

75

63

•

•

•

•

•

10

I3

34

29

•

•

•

•

♦

7

9

22

15

•

•

•

7

•

of fat)

/

98

•

•

♦

•

•

•

•

•

•

3

•

•

•

40

•

•

•

•

•

a

•

•

•

2

•

•

•

28

•

•

•

•

•

•

•

•

♦

•

2

-

5

•

•

•

Plasm a—
c o r r e c t e d N d e t e r m in e d as
age

Whole

follows:

(100 x 1.0 34)] x skimmiik value.

[(100 —p e r c e n t ­

15 1
TABLE

13

D i s t r i b u t i o n of a s h , c a l c i u m and p h o s p h o r u s in c r e a m
s k im m iik f r o m n o n h o m o g e n iz e d and h o m o g e n iz e d m ilk

and

Skimmiik
Component

Non­
homogenized

Homogenized
(1.91% fat;
10.63% t.s.)

(0.12% fat;
8.85% t.s.)
ASH
(mg./lOO

Difference
Due

to Ho­

mogenization

ml.)

720

690

•

ml.)

720

710

-10

•

•

•

•

•

118

1 14

•

•

• •

118

116

-

• • •

• •

•

•

•

ml.)

101

100

•

•

•

ml.)

101

102

•

•

Fat—
free
(mg./lOO

Plasm a—
c o r r e cted
( m g . /100 g. fat)

•

TOTAL C O P P E R
(mg./lOO ml.)

•

•

•

F at—
free
(mg./lOO

ml.)

2

P lasm a-corrected
(mg./lOO

g. fat)

•

.

TOTAL PHOSPHORUS
(mg./lOO
Fat—
free
(mg./lOO

1

P lasm a-corrected
(mg./lOO

g.

fat)

•

•

•

•

•

•

•

•

•

•

•

•

•

•

»

•

•

•

PHOSPHOLIPID
PHOSPHORUS
( m g , / 100 g.

Fat—
free

values

of p l a s m a ) ]
Plasm a
sion:
value.

fat)

x

determined

follows:

[(total value)

/

(val.

100.

corrected
[(100 -

as

values

percentage

d e t e r m i n e d f r o m following
of fat)

/

(100 x

1.034)]

expres­

x skimmiik

152

TABLE

13 ( C o n t i n u e d )

Cream
Pasteurized
Nonhomogenized

Homogenized

Difference

(29.60% fat;

(46.60% fat;

Due to Ho­

35.91% t.s.)

52.02% t.s.)

mo genization

490

•

•

•

•

•

710

•

•

•

•

«

•

•

77

•

•

•

•

•

81

72

•

•

•

•

•

•

112

•

•

•

•

•

•

45

•

•

•

45

72

•

•

12.25% t.s.)

•

-1.4

•

(3.76% fat;

•

77

•

Milk

392

0

•

Whole

67

•

•

•

10

21

11

12

98

•

•

•

•

•

•

•

•

«

11

•

•

•

•

•

•

•

•

»

T A B L E 14

The effect of s u c c e s s i v e dilutions and re se parations on the concentration of fat, nitrogen and
lipoid phosphorus in c r e a m fro m nonhomogenized and hom ogenized milk

Sample
No.

Number of Washings
0

1

2

3

4

5

6

7

8

Fat (%)

Nonhomogenized

Homogenized

i1

29.0

48.5

2

27.4

3

. . .

52.5

■

.

54.5

54.5

. . .

• • •

48.9

52.3

• • .

54.1

55.0

. . .

• i •

33.0

48.6

52.9

• • .

54.8

55.3

. . .

• k »

i1

52.5

52.5

53.0

• • .

53.5

54.5

. . .

• • •

2

47.2

50.1

49.2

• • .

52.6

54.5

. . .

• • •

3

54.2

54.6

55.2

• • .

55.8

56.4

. . ,

• • •

0.08

. . .

0.05

0.04

.........................

0.10

. . .

0.05

. . .

0.05

0.08

. . .

0.04

. . .

0.04

r

Nitrogen (g. per 100 g. of fat)
1

1.16

2

1.22

3

1.10

0.19
0.25
0.20

. . .
. . .
. . .

0.06
0.05

153

Nonhomogenized

2

TABLE

14 (Continued)

Numbe r of Washings

Sample
No.

0

1

2

4

3

5

6

7

8

Nitrogen (g. per 100 g. of fat) [Continued]

Homogenized

I2

0.64

0.19

. . .

0.18

. . .

0.17

0.17

•

2

0.70

0.20

. . .

0.18

•

• •

0.15

0.16

. . .

0.16

3

0.63

0.20

. .. .

0.17

0.16

0.17

. . .

0.16

17.6

17.0

•

•

•

•

Lipoid phosphorus (mg. per 100 g. of fat)

Nonhomogenized

Homogenized

I3

20.8

19.0

. . .

19.0

18.5

•

2

18.4

17.0

. . .

17.0

16.5

15.8

. . .

15.0

3

19.4

17.2

. . .

17.0

16.9

16.2

. . .

15.1

i3

21.1

20.8

. . .

20.7

20.5

• • •

21.2

21.8

2

19.2

18.8

. . .

18.6

18.4

18.8

. . .

19.4

3

19.6

19.4

. . .

19.4

19.5

19.9

. . .

20.3

Data used in F igu re 12.

2

Data u sed in Figure 13.

•

•

•

3

•

•

Data u sed in Figure 14.

•

155
TABLE

15

D i s t r i b u t i o n o f f a t a n d s o l i d s —n o t —f a t i n w a s h e d c r e a m a n d
w a s h e d —c r e a m s e r u m o f n o n h o m o g e n i z e d a n d h o m o g e n i z e d
m ilk

M o jo nn ie r

Value s
Solids-no t-

Obtained f o r
Product

fat p e r
Total
Solids

Fat

Solids-

g.

100

of F a t

not-fat

<%)

(%)

(%)

No nh omogenized

54.30

54.10

0.18

0.33

H o m ogenized

55.03

54.40

0.63

1.16

Washed

cream

0.83

D i f f e r en c e
W ashed-cream

serum

Nonhomogenized
H o m o ge ni zed

2.25

1.59

0.66

12.14

10.81

1.33

•

•

•

TABLE

16

Distribution of the nitrogen fractions in the washed cream and washed-cream serum from
nonhomogenized and homogenized milk

W a sh e d -c r e a m Serum

Washed C ream
Non­
homog­
enized
(0.18%
SNF)

Nitrogen
F raction

Homogenized
(0.63%
SNF)

D iffe rence Due
to Homogenization

Non­
homog­
enized
(0.18%
SNF)

Ho­
m og­
enized
(0.63%
SNF)

97

187

99

210

D iffer­
ence Due
to Ho­
m oge­
nization

TOTAL N
22

(mg./lOO ml.)

93

•

•

•

F at-free^
(mg./lOO ml.)
S e r u m -c o r r e c t e d

•

•

•

i

t

*

■

•

•

111

2

( m g . / 100 g. fat)

41

171

7

7

130

•

•

•

•

•

•

•

•

•

•

•

•

NONCASEIN N
(mg./lOO ml.)

1

23

1

25

Fat-free

It

•

i t

•

•

•

»

•

•

24

156

(mg./lOO ml.)

T A B L E 16 (Continued)

W a sh ed -cream Serum

Washed C ream

Nitrogen
F raction

Non­
homog­
enized

Ho­
mog­
enized

(0.18%

(0.63%

SNF)

SNF)

Diff e r ence Due
to Ho­
m oge­
nization

Non­
homog­
enized

Ho­
m og­
enized

(0.18%

(0.63%

SNF)

SNF)

Differ­
ence Due
to Ho­
m oge­
nization

S e r u m -c o r r e c t e d
(mg./lOO g. fat)

13

13

0

0

•

•

•

1

6

•

•

•

*

1

7

0

•

•

•

•

•

•

NONHEAT-COAGULABLE N
(mg./lOO ml.)

•

•

•

Fat-free
(mg./lOO ml.)

•

•

•

Fat-free N determined as follows:

•

•

[(N determined)

Plasma-corrected N determined as follows:
skimmilk value.

/ (Vol. of plasma)] x 100.

[(100 - percentage of fat)

/ (100 x 1.034)] x

6

158
TABLE

17

S o m e c h a r a c t e r i s t i c s o f f a t —m e m b r a n e p r o t e i n s
n o n h o m o g e n iz e d and h o m o g e n iz e d m ilk

Fat-m em brane

Proteins

iso la ted fro m

Isolated from

Nonhomogenized

Homogenized

Milk

Milk

Property
Warm

Cold

Warm

Cold

Ethanol

Ethanol

Ethanol

Ethanol

T reat­

T reat­

Treat­

Treat­

m e nt

me nt

m e nt

ment

<%)

(%)

(%)

(%)

12.20

7.00

13.00

2.66

12.50

12.20

11.80

13.30

14.26

13.11

13.57

13.65

Mo li sc h

+

+

+

+

Biuret

+

+

+

+

-

-

—

-

—

-

+

+

Lipoid

m aterial

Nitrogen
Nitrogen

(fat—
free)

N itroprusside
Before
After

heating

heating

crystal—
Appearance

fine,

fine,

dull

dull

<
crystal­

line,

line,

bright

bright

159
TABLE
Distances

m i g r a t e d by the f a t —
membrane

in v a r i o u s

buffers

and the

eff ec ts

t r e a t m e n t with w a r m

ethanol

m em brane-proteins.

(All

the

original

_ ,r
Buffer

Acetate

1.5

3.0

Veronalc itra te

6.5

8.0

Nonhomogenized

Homogenized

Milk

Milk

Ascend-

8.0

Descending

(d^)

Ascending (dj)

Desc e nd ­
ing

(d^

(cm.)

(cm.)

1.16

1.45

1.80

2

1.19
0.77

0.67

1.16

1.58

3

0.48

•

0.88

1.23

1

1.69

1.59

3.65

3.60

2

•

•

•

»

3.00

•

•

•

•

1.32

1.50

•

•

•

0.41

0.48

•

•

4.18

3.53

•

•

3
•

•

•

•

•

•

•

1

3.46

•

2

3.30

3.20

3.00

2.46

3

2.90

2.85

2.73

2.23

4

0.82

0.95

0.38

0.56

1

2.70

2.68

3.28

2.93

2

2.42

2.67

2.20

3

2.39
0.66

0.86

1.37

1.20

4

•

1
A m m o n ia —

from

(cm.)

4

Ph o s p h a te

made

(cm.)

1
Glycine-HCl

were

of

negative.)

Peak
No.

components

c o n c en t r a t i o n

m easurem ents

electrophoretic

pH

p ro tein

p r o d u c e d on m i g r a t i o n by

and by the

ing ( d x)

HC1

18

•

•

•

•

•

0.26

0.53

•

•

•

3.14

2.70

2.57

2.03

2

2.91
2.45

2.31

3

2.26

•

4

0.70

•

•

•

•

2.23

•

•

0.57

0.57

•

•

160
TABLE

Buf fe r

pH

18 (C o n tin u e d )

Nonhomogenized

Homogenized

M ilk

M ilk

Peak
No.

Ascending

D e scend­

in g

(d 2)

ing (d2)

ing (dx)

(cm.)

(cm.)

(cm.)

(cm.)

1

3.25

3.02

3.58

2.82

2

3.00

2.64

3

2.89
1.53

1.68

2.13

1.90

4

0.60

0.65

1.36

1.38

5

•

0.62

0.84

Phosphate

1

3.36

(Warm

2

2.84

•

ethanol

3

2.64

2.62

treatment)

4

0.56

•

•

Phosphate

1

•

•.

•

•

2

•

•

•

3

•

*

4

•

•

Veronale th y l -

8.0

amine

(Effect of
0.43% con­
centratio n)

L. C
0 . 0

6 5

(d^

D e scend— A s c e n d -

•

•

•

•

•

•

•

•

•

•

•

2.60

2.22

2.07

1.67

•

0.27

0.50

•

•

3.23

3.05

•

•

•

2.47

2.37

•

•

•

•

2.12

2.01

•

•

*

•

0.70

0.85

•

•

•

•

•

•

•

•

TABLE 19
Mobility of peaks in the electrophoretic pattern of the fat-m em b ran e protein components as
shown in F ig u res 15 to 20. (Mobility [U] = cm.^, volt- *, s e c . - * x 10 )

Buffer System
Peak
No.

GlycineHC1
pH 1.5
(Fig. 1)

Acetate
pH 3.0
(Fig. 2)

Phosphate
pH 6.5
(Fig. 3)

V eronalcitrate
pH 8.0
(Fig. 4)

A m m on iaHC1
pH 8.0
(Fig. 5)

V eronalethylamine
pH 10.8
(Fig. 6)

(+)

(+)

(-)

(-)

(-)

(-)

6.70

6.77?

5.65
5.61
5.63A

6.70A

Nonhomogenized milk
1 a
avg.

4.58
4.47
4.53A

2 a
d
avg.

2.96
2.58
2.77B

6.46
6.26
6.36A

5.00
5.06
5.03B

5.64
5.31
5.48B

3 a
d
avg.

1.90

5.78
5.58
5.68B

1.38
1.80
1.59C

5.20

d

6.77
•

•

•

1.60
1.86
1.73C

•

•

•

•

•

•

5.20?
1.61
•

•

•

1.61C

6.50
6.04
6.27A
5.78
•

•

•

5.78B
3.06
3.36
3.21?
1.20
1.30
1.25C

161

4 a
d
avg.

1.90C

3.12
2.94
3.03A+B

TABLE 19 (Continued)
Buffer System
Peak
No.

GlycineHC1
pH 1.5
(Fig. 1)

Acetate
pH 3.0
(Fig. 2)

Phosphate
pH 6.5
(Fig. 3)

Veronalcitrate
pH 8.0
(Fig. 4)

A m m on ia HC1
pH 8.0
(Fig. 5)

V eronalethylamine
pH 10.8
(Fig. 6)

(+)

(+)

(-)

(-)

(-)

(-)

Homogenized milk
1 a
d
avg.

4.87
6.05
5.46A

10.28
10.13
10.21A

8.18
6.90
7.54A

8.10
7.24
7.67A

7.15
6.15
6.60A

8.66
6.82
7.74A

2 a
d
avg.

3.90
5.3!
4.61B

8.47
8.47B

5.87
4.82
5.35B

6.60
5.44
6.02B

5.86
4.62
5.24B

7.26
6.38
7.32?

3 a
d
avg.

2.95
4.27
3.61C

3.72
4.25
3.99C

5.34
4.36
4.85C

3.39
2.96
3.18C

5.08
5.08C

5.16
4.60
4.88B

1.15
1.35
1.25D

0.74
1.04
0.89D

0.64
1.31
0.88D

1.30
1.30
1.30D

3.29
3.34
3.32C

4 a
d
avg.

...

...

5 a
d
avg.
a - Denotes asc^endijig p^tte^n. d - Denotes descending pattern.
A , B, C, and A , B , C , D
designate main components.
? - Doubtful component.

1.50
2.02
1.76D

163
TABLE
The

effect of t e m p e r a t u r e

phoretic
phosphate

20

of ethanol

treatm ent

mobility of the f a t —
membrane
b uffer

(pH 6 . 5 ) .

on the

electro­

p r o t e i n components

(Mobility [ u ]

= cm.^,

volt- *,

in

s e c . - *,

x 10- 5 .)

Milk

Nonhomogenized

Peak
No.

(hot)

(cold)

1 a
d

6.77

4.67

•

•

•

•

•

•

Homogenized Milk

(diff.)

(cold)

2.10

8.18

•

•

•

•

•

•

6.90

•

•

•

•

•

•

•

•

«

•

•

•

«

•

(hot)

(diff.)

6.77

4.67

2.10

7.54A1

•

2 a

6.46

3.95

2.51

5.87

7.51

-1 . 6 4

d

6.26

•

4.82

6.42

-1.60

6.36A

3.95A

2.41

5 . 35B 1

6.9 7B1 - 1.62

3 a

5.78

3.67

2.1 1

5.34

5.98

-0.64

d

5.58

3.65

1.93

4.36

4.83

- 0.47

5.68B

3.66B

2.02

4.85C1

5.41C

- 0.56

4 a

1.60

0.78

0.82

0.74

0.78

-0.04

d

1.86

•

•

•

•

-

-

1.04

1.45

-0.41

1.73C

•

•

•

•

.•

•

0.89D1

1.12D1 - 0 . 2 3

avg.

avg.

avg.

avg.

•

•

•

••

a -

Denotes

asc e n ding p a t t e r n ,

d -

Denotes

descending

A,

B,

C,

and A*,

B*,

•

pattern.

C* and D*

designate

main

components.

164
TABLE
The

21

e f f ec t of c o n c e n t r a t i o n of the f a t —
membrane

ponents

in h o m o g e n i z ed

in p h o sp ha te
s ec. -

x

buffer

milk

on the

(pH 6.5).

p ro tein

e le ctro p h o re tic

(Mobility [U ] = c m . ^ ,

com­

mobi li ty
volt- ^,

10” ^.)

Concentration

Peak
No.

(0.84%)

(0.43%)

(diff.)

1 a

8.18

10.04

1.86

d

6.90

9.47

2.57

7 .5 4A 1

9.76A1

2 .2 2 A 1

2 a

5.87

7.67

1.80

d

4.82

7.36

2.54

5.35B1

7.52B1

2.17B1

3 a

5.34

6.58

1.24

d

4.36

6.24

1.88

4.85C1

6.41C 1

1. 5 6 C 1

4 a

0.74

2.17

1.43

d

1.04

2.64

1.60

0.89D1

2.41 D 1

1.52D1

avg.

avg.

avg.

avg.

a -

Denotes

ascending p atte rn ,

d -

Denotes

descending

A*,

B*,

C 1 and D^

pattern.

designate

main

components.

TABLE 22
A com parison of som e amino acid values obtained for the fa t-m em b ran e protein s with the
m inor-p rotein fraction, casein, lactalbumin, lactoglobulin, pseudoglobulin and euglobulin^
(All values e x p r e s s e d as g ra m s per 100 g r a m s of anhydrous protein)

F at-m em b r an e
P rotein from^
Constituent

Non­
homog­
enized
Milk

Ho­
m oge­
nized
Milk

Minorprotein
Frac­
tion

Casein

Lac­
talbu­
min

Betalactoglobulin

Pseudoglob ulin

Euglobulin

8.40

3.1

3*1

Isoleucine

5.66

6.00

3.66

6.1

•

Leucine

8.71

9.22

5.71

9.2

15.0

15.60

9.1

10.4

Lysine

5.92

7.54

5,74

8.2

9.0

11.40

7.2

6.3

Methionine

2.08

2.20

1.34

2.8

2.8

3.22

1.08

0.98

Phenylalanine

4.97

4.51

2.35

5.0

5.6

3.50

3.8

3.6

Valine

5.65

5.50

9.74

7.2

4.0

5.80

9.4

10.4

Total nitrogen (%)

15.67

15.67

15.67

Nitrogen (%)^

12.20

13.30

9.99

•

•

•

15.63

•

.•

•

•

15.60

•

i

i

i

•

•

•

•

•

•

•

•

•

•

•

«

•

•

•

i

•

•

•

•

•

Literature values reported by Weinstein, Duncan and Trout (1951).
Samples prepared by cold ethanol-ether extraction.
Actual nitrogen content of the anhydrous fat-m em b ran e protein s.

•

•

•

T A B L E 23

The number of amino acid r e sid u e s in the fat-m em b ran e protein s prepared by cold ethanol
treatment

Fat- membrane P r o t e in s Obtained from
Homogenized Milk

Nonhomogenized Milk

Constituent
Yield

Moles
per
105 g.
P rotein

(%)

Molar
Ratio
when
Methi­
onine
= 4

Yield

Moles
per
105 g.
P rotein

Molar
Ratio
when
Methi­
onine
= 4

(%)

Isoleucine

5.67

43.3

12

6.00

45.8

12

Leucine

8.71

66.4

19

9.22

70.3

19

Lysine

5.92

40.5

12

7.54

51.6

14

Methionine

2.08

14.0

4

2.20

14.8

4

Phenylalanine

4.97

30.1

9

4.51

27.3

7

Valine

5.65

48.3

14

5.50

47.0

13

(M min.)

28,926

26,798

CREAM FROM
NON H O MOG E N I Z E D MILK

—

CREAM FROM
HOMOGENIZED MILK

201______L.
O
I

■ J_________I_________I_______ I

2

NUMBER

3

4

5

O F W A S H IN G S

F i g u r e 12.
The effect of s u c c e s s i v e
w a s h i n g s on the f a t c o n t e n t of c r e a m
fr o m n o n h o m o g en ized and h o m o g e n iz e d
m ilk.

6

168

1.2
CREAM ( 2 9 . 0 0 % FAT) FROM
NON - H O M O G E N I Z E D MI L K

NITROGEN (g./IOOg. f o t )

1.0

C R E A M ( 5 2 . 5 0 % FAT) FROM
HOMOGENIZED MILK

0.8

0.6

0.4

0.2

O

2

3

N U M B E R O F W A S H IN G S

F i g u r e 1 3.
T ne e f f e c t of s u c c e s s i v e
w a s h i n g s on the t o t a l n i t r o g e n c o n t e n t of
c r e a m f r o m n o n n o m o y e n i z e d and h o m o g ­
enized m ilk.

I

169

CREAM ( 2 9 . 0 0 % FAT) FROM
NON-HOMOGENIZED MILK
CREAM ( 52.50% FAT) FROM
HOMOGENIZED MILK

20

LIPOID

PHOSPHORUS

(m g./IO O g.fot)

30

O

2

3

4

5

6

7

N U M B E R OF W A S H IN G S

F i g u r e 14.
T h e e f f e c t of s u c c e s s i v e w a s h i n g s on the
lip oid p h o s p h o r u s con ten t of c r e a m f r o m n o n h o m o g ­
e n i z e d and h o m o g e n i z e d m ilk .

170

A S C E N D IN G

D E S C E N D IN G

72 2 5 sec.; 3.6 volts cm*1; concentration 0.22%

1 2

8 0 0 0 sec.; 3.7 volts cm.'1; concentration 0.97 %

F i g u r e 15.
E l e c t r o p h o r e t i c p a t t e r n s of f a t - m e m b r a n e
p r o t e i n s i s o l a t e d f r o m n o n h o m o g e n i z e d m il k (top) ana
h o m o g e n i z e d m ilk (b ottom ) and d i s p e r s e d in g l y c i n e h y d r o c h l o r i c a c i d b u f f e r at pH 1.5 a n d i o n i c s t r e n g t h
of 0.1.

171

A S C E N D IN G

D E S C E N D IN G

i

2307sec.; 2 3.4 volts cm.1; concentration 0.69%

i

1535 sec., 23.3 volts cm.

concentration 0.97%

F ig u r e lb.
E le c t r o p h o r e t ic p attern s of fa tiriem brane p ro tein s iso la te d fr o m n o n h o m o g en ized
m i l k (top) and h o m o g e n i z e d m i l k ( b o t t o m ) and
d i s p e r s e d in a c e t a t e b u ffer at pH 3.b and io n i c
s t r e n g t h oi J .1 .

1 72

A S C E N D IN G

D E S C E N D IN G

>

<

6 0 0 0 sec.; 8.0 volts cm*1; concentration 0.45%

5 0 0 0 sec.; 8.1 volts cm."'; concentration 0.98%

F i g u r e 17.
E ie c t r o p l i o r e ti c p a t t e r n s o f f a t - m e m b r a n e
p r o t e i n s i s o l a t e d f r o m n o n h o m o g e n i z e d m i l k (top) and
h o m o g e n i z e d m i l k ( b o t t o m ) a n d d i s p e r s e d in p h o s p h a t e
Duffer a t p H 6 . 5 a n c i o n i c s t r e n g t h o f 0 . 1 .

173

A S C E N D IN G

DESCENDING

4 ----------------------------------------------

*

5 0 0 0 sec.; 10.2 volts cm'1; concentration 0.38%

5 0 0 0 sec. 10.2 volts cm. ; concentration 0 .8 4 %

F ig u r e 18.
E l e c t r o p h o r e t i c p a t t e r n s of f a t - m e m b r a n e
p r o t e i n s i s o l a t e d f r o m n o n h o m o g e n i z e d m i l k (top) and
h o m o g e n iz e d m ilk (bottom ) and d is p e r s e d in v e r o n a lc i t r a t e buffe
at pH S . J a n d i o n i c s t r e n g t h of 0 . 0 9 .

174

A S C E N D IN G

D E S C E N D IN G

8 0 0 0 s e c .; 5.4 volts cm. ; concentration 0.21 %

8 0 0 0 sec.; 5.5 volts cm."1; concentration 0.75%

F i g u r e 19.
E l e c t r o p h o r e t i c p a tte r n s of f a t - m e m b r a n e
p r o t e i n s i s o l a t e d f r o m n o n h o m o g e n i z e d m il k (top) and
h o m o g e n i z e d m i l k ( b o t t o m ) and d i s p e r s e d in a m m o n i a h y d r o c h l o r i c a c i d b u ffe r at pH 9 .0 and i o n i c s t r e n g t h
of 0.1.

175

A SC E N D IN G

D E S C E N D IN G

4 8 0 0 s e c . ; 1 0 .4 v o l t s cm .’1; c o n c e n t r a t i o n 0 . 2 6 %

*

<

4 0 0 0 s e c . ; 1 0 . 3 v o l t s c m ? 1; c o n c e n t r a t i o n 0 . 5 8 %

F i g u r e ZQ.
E l e c t r o p h o r e t i c p a t t e r n s o f f a t —m e m b r a n e
p r o t e in s i s o l a t e d f r o m n o n h o m o g e n i z e d m il k (top) and
h o m o g e n i z e d m i l k ( o o t t o m ) a n d d i s p e r s e d in v e r o n a l e t h y i a m m e b u f f e r at pH 1 0 . b an d i o n i c s t r e n g t h of 0 .1 .

1 76
MEM B R A N E - PROTEINS FROM
H O M O G E N IZE D M IL K

MEM BR ANE-PRO TEIN S FROM
NONHOMOGENIZED MILK
ASCENDING

DESCENDING

ASCENDING

DESCENDING

pH I 5; G lyc in e-H C L Buffer

pH 3 0 ' , A c e t a t e Bu f f er

pH 6 . 5 ’, P h o s p h a t e Buf f er

pH 8 . 0 ' , Veronal - Citrate B u ff e r

pH 9 . 0 , A m m o n i a HCL

Bu f f er

pH 10.8', V e r o n a l - E t h y l a m i n e B u f f e r

F i g u r e 21.
C o m p o s i t e of e l e c t r o p h o r e t i c p a t t e r n s
m e m b r a n e p r o t e i n s in v a r i o u s o u f f e r m e d i a .

of f a t-

ASCENDING

^

DESCENDING

ASCENDING

»

DESCENDING

<

5 0 0 0 s e c . , 10.2 volts c m 1, concentration 0.3 8 %

►

SOOOsec., 10.2 volts cm*.1; concentration 0 .8 4 %

COLD EXTRACTION (0 °to 3 °C .)

«--------------------------------------------

»

4 0 0 0 s e c . , l 0 . 8 volts cm!l;c o n c e n tra tio n 0 .2 9 %

^

<

3 2 0 0 s e c ., 10.8 volts cm’1; concentration 0 .5 2 %

WARM EXTRACTION (40°to45°C .)

Figure

22.

E l e c t r o p h o r e t i e p a t t e r n s of f a t - m e m b r a n e

proteins isolated fro m nonhomogenized

m i l k ( l e f t ) and h o m o g e n i z e d m i l k ( r i g h t ) and s h o w i n g the e f f e c t of t r e a t m e n t w i t h bot h c o l d
and w a r m e t h a n o l .

178

A S C E N D IN G

DESCENDING

5 0 0 0 sec.; 10.2 volts cm. concentration 0 .8 4 %

2 5 0 0 sec.; 12.9 volts cm.1; concentration 0 .4 3 %

F i g u r e 23.
E l e c t r o p h o r e t i c p a t t e r n s of f a t - m e m b r a n e
p r o te in s is o la t e d f r o m h o m o g e n iz e d m ilk and show ing
t h e e f f e c t o f t, r o t e i n c o n c e n t r a t i o n o n t h e r e s u l t i n g p a t ­
t e r n s in p h o s p h a t e o u f f e r at pH 6 . 5 and i o n i c s t r e n g t h
of 0.1;

DISCUSSION

General

The

work

tain m o r e

reported

in f o r m a t io n

in this

concerning

section was
the

s pe c ifi ca l ly ,

membrane.

The

should not be
difficulties
ponent o r
milk a r e

that

obvious.

resulting

The

hand,

of nat ur e

investigator

of its

may not be

simply b e c a u s e

of a pp roach.

as

should always

entirely

should not h e s i t a t e

evidence.

a m a te rial

although

be

as

the

i n n er

of

en­

c o u n t e r p a r t;

re presen ta tiv e.

it e x i s t s

com­

aware

may not be

of the lack of an absolute

The f a t - m e m b r a n e

The

complex as

significant f o r

to invade

and

a biological

naturally occurring
data,

in n a t u r e

as final

as finally isolated,

experimental

one

from

in milk

of the f a t —
globule

exploratory

e x p e r i e n c e d in isolating

m aterial,

iso la ted ,

is

interpreted

group of components

represen tativ e

m aterials
o th er

data p r e s e n t e d

which a r e

of p r o t e i n s

effect on the n a t u r e

construed o r

the fact that the
tirely

the

to ob­

effect of homogenization

on the p h y s i c a l and c h e m i c a l p r o p e r t i e s
and m o r e

u nd ertaken

and

the
On the
secrets

certainty

in n a t u r e ,

clo se ly

asso cia te d

with f a t

globules

a t the p l a s m a / f a t

interface,

offers

such a c h a l le ng e .
The
have
more

m em brane-m aterials

been investigated fr o m
recent

However,

workers

the

c hanges

fat-m em brane
extensively.
since

on c e r t a i n

time

been P a l m e r

in the n a t u r e

been

changes

a va i la b l e

recorded prim arily
in the

chem ical

homo ge niz ation .

Section III a r e

not c o n c lu si v e ,

i n f o r m a t i o n to the

curring

nature

is

the

co l le a g u e s .

milk p r o t e i n s

isolated

and the
studied

in n a t u r e ,

observations

and p h y s i ca l p r o p e r t i e s

Although the
they

m i lk s

among

s p e c u l a ti v e

from

data p r e s e n t e d

of
in

supply additional f un da m e n ­

of the f a t - m e m b r a n e

proteins

oc­

in both nonhomogenized and homogenized milk.

D i s c u s s i o n of E x p e r i m e n t a l

Influence

The f r a c t i o n a t i n g
l i s h a definite
adopted a f t e r
procedure

Results

of Homogenization on the Ni t ro g e n
Distribution

34)

notably

and his

of the

information

milk following

tal

to t i m e ,

and r e m a d e

wrought by h omogenization have not been
The

i t has

have

of n o r m a l

series

in Milk

technique
f.

used

in this

study to

of n i t r o g e n - c o n t a i n i n g f r a c t i o n s

careful p relim ina ry
and c e r t a i n

of its

trials

was

with Rowland's

m o dific a tion s

estab—

(Hetrick,

(19331947).

181
The f o u r f r a c t i o n s
coagulable
fractions
tionable
certain

isolated

and n o n p r o t e in n i t r o g e n

of milk p r o t e i n s .
a lb um i n

characteristics

of p r o c e s s i n g

of the

entire

fractions

would be

fraction.

separated.
as

a

a ttainable

between the

ques­

attempted because

of

and in the

If both of t h e s e

single f r a c t i o n

then any

m a n i f e s t e d in the n i t r o g e n

Such data would be

suitable

for

value
compar­

studies.
Both of

nitrogen were

Rowland's
tried,

in the n i t r o g e n

was

The n i t r o g e n

n it ro g e n .

These

data

determining

d if f e ren c e

n o n c a s e in

was

method outlined in the

used because

of its

obtained f o r

milk

which

substan­

and a c o r r e ­

and p r o t e o s e - p e p t o n e

in p a r t

homogenization

experi­

showed a

and n o n p r o t e in n i t r o g e n

reflected,

observed

convenience.

at different p r e s s u r e s

in h e a t —
coagulable

f e c t of h i g h - p r e s s u r e
though the

so the

in c a s e i n -

sponding d e c r e a s e

for

d i s t r i b u t i o n v al u e s

had b e e n h omogenized
increase

procedures

but no not ic eab le

values,

mental p ro ce du re

tial

was

nonheat—

readily

separation p ro cedu res

had b e e n d e t e r m i n e d

effect

ative

No d if f e r e n t i a t i o n

in the

of the

n o n c a s e in ,

represent

and globulin f r a c t i o n s

irregularities

components

t otal n i t r o g e n ,

at l e a s t ,

(Rowland,

data of Shahani and S o m m e r

(1951)

the

h e a t ef­

1933-1934),
do not

seem

al­
to

be

so p ronounced in this

respect.

The

significant changes

the n it ro ge n d i s t r i b u t i o n have been a s s u m e d to be

due to the

a ds orp ti on of c e r t a i n

milk p r o t e i n s

faces

homogenized at high p r e s s u r e s

when milk was

on the

in

i n c r e a s e d fat

sur­

(Trout,

1950).

Influence

of Homogenization on the

Milk Components

Solids-not—
fat.
p o r ti o n of the
position

to the

By making the

separated
s kimmilk,

t r a t i o n of s o l i d s - n o t —
fat
umn 4).

When the

n o t -f a t was
Column
tained

3),

the c r e a m

in the

to r e p r e s e n t
or

cream

cream

as s u m p t i o n that the p l a s m a

(Table

it is p o s si b l e
in the

cream

the

11)

is

sim ilar

to e s t i m a t e

samples
the

(Table

concen­

11, Col­

amount of s o l i d s -

d e t e r m i n e d value

separated from

in com­

the

(Table

11,

homogenized milk con­

amount of s o l i d s - n o t —
fat p e r

unit of fat

s e p a r a t e d f r o m nonhomogenized milk.

c o n c e n tr a t io n of s o l i d s - n o t - f a t was

that p o r ti o n of the

which is

fat globule,

and Skimmilk

e s t i m a t e d value f o r

a much l a r g e r

difference

creams

subtracted from

than did the

in C r e a m

D i s tr i bu ti on of

o r p os si bl y p a r t

assum ed

solids-not-fat p re se n t

c lo s e l y a s s o c i a t e d with the

su r f a c e

of the f a t - m e m b r a n e

This

in milk
of the

proteins.

183
By an additional
value

represents

d ra w

some

a s s u m p t io n ;

only p r o t e i n - l i k e

c on c lu si on

namely,

that this

m aterials,

c o n c e r n in g the

i t is p o s s i b l e

and c o n c e n t r a t i o n of the f a t - m e m b r a n e

At l e a s t

not u n r e a s o n a b l e

tween the

determ ined

the

cream

samples

as

a direct

result

remained
in the
4-

equal.

tion of

theoretical

In this

instance

t h a t the

increase

(Tro ut,

since

there

surface

1947).

solids-not-fat p er

This

was

other
a

5-fold i n c r e a s e

area

d if fe r e n c e

in the

to ho­

concentra­

when a

was found to e x i s t between

plasm a—
free,
enized

milk

washed c r e a m s
(Table

d if f e re n c e

from

the

various

sig ni f ic a nt
the

h omogenized and nonhomog—

Similar

c on c lu si on s

c o n c e rn in g

in c o n c e n t r a t i o n of s o l i d s - n o t - f a t were

data obtained f r o m

fractions

ho­

14).

Nitrogen distribu tion .
the

from

even m o r e

from

milk

a ls o

was

with the

of the fat due

unit of fat between c r e a m s

d iff e r en c e

in

conditions

m o genized and nonhomogenized
sim ilar

be­

s o l i d s - n o t - f a t value

of s o l i d s - n o t - f a t which coincides
in the

m aterial.

homogenized milk o c c u r r e d

of homogenization,

6-fold i n c r e a s e

mo ge niz ation

to a s s u m e

obtained f r o m

concentration

to

and the

to

effect of homogenization

on the n a t u r e
it is

s pecific

of c r e a m

the
and

distribution
skimmilk

evident

of n it ro g e n

(Table

1Z).

in the

Th ese

184
data indicate
corrected

that the

increase

cream from

in total n it ro g e n

homogenized milk was

c a s e i n n i t r o g e n even though low er values
total n it ro g e n

and n on c a s e in nit ro gen .

of n i t r o g e n in the
cream s

cream

samples

c o m p a r e d to 0.426 p e r

homogenized milk

(Table

11).

r e c o r d e d for

When the

are

expressed

Similar

(1922) f o r

mogenized milk.

differences

the f a t —
free

M inerals.
p h o sp ho ru s

adequately

cent,

Since

c o n c e n tra t io n s
as p ro t e i n ,

were

the

cent
from

c a lc u l a te d

s e p a r a t e d f r o m nonho­

in the p r o t e i n
creams

we r e

content between
r e p o r t e d to be

respectively.

some of the

sk i m m il k

s ample

expressed,

t he se

c a lc iu m nonphospholipid

in milk a r e

milk p r o t e i n s ,
was

their

determined

m aterials

conceivably a s s o ­

co n c en tr at io n

c o n c en tr a t io n s

c o n c e n tr a t io n of p r o t e i n
homogenized milk.

values

cream

and f a t - f r e e

and a s h components

c iated with c e r t a i n
and

The

sk i m m il k

0.08 and 0.215 p e r

from

were

cent p r o t e i n in c r e a m s

by van Dam and S i r k s

in the

d e t e r m i n e d as

f r o m nonhomogenized milk contained 0.102 p e r

p ro t e i n ,

cream

in the p l a s m a -

(Table

in each
13).

When

pointed to an i n c r e a s e

per

unit of f at in c r e a m

185
Influence of Homogenization on the Distribution of Milk
Components

in Washed C r e a m and

W a s he d -cr e a m Serum

The data concerning the
various

fractions

distribution of nitrogen in the

of washed c r e a m s

higher concentration of nitrogen p e r

(Table

15)

show that a

unit of fat existed in c r e a m

f r o m homogenized milk than in c r e a m f r o m nonhomogenized
milk and that this
However,
samples

increase

the w a s h e d - c r e a m

other

teins

that were

were

det er m in ed as

work.

Such an observation s e e m s logical,

reta i ne d in the p ro te i n precipitate

However,

in the ca se

were produced f r o m washed c r e a m s

est

pro­

casein nitrogen by the fractionation p r o c e d ­

all of the fat was

colloidal p roteins
consequently

coagulable

Presumably,

adsorbed o r a s s o c i a t e d with the f a t - m e m b r a n e ,

employed in this

state,

heat-coagulable p roteins

or h ea t - st ab le p ro te i n s .

formed at pH 4.67.

the

casein nitrogen.

which indicated the p r e s e n c e

than casein, namely,

and some p r o t e o s e s

since

manifested as

s e r a obtained fr om the homogenized

yielded nitrogen values

of pro te i ns

ure

was

were f ree

as

of the

sera

which

a r e s u l t of churning,

to function as

in the n a t u r a l

some of the protein was m e a s u r e d as h e a t -

and some

concentration was

as proteose-peptone nitrogen.
m e a s u r e d as

c a se i n nitrogen.

The l a r g ­

186

In flu e n c e of S u c c e s s i v e W a s h in g s on the C o n c e n t r a t io n o f F a t ,
T o t a l —p r o t e i n N i t r o g e n a n d L i p o i d P h o s p h o r u s i n C r e a m
f r o m H o m o g e n iz e d and N o n h o m o g e n iz e d M ilk
The

data

dif f e ren ti ate

shown g ra p h i c a l ly

in F i g u r e

between the f a t - m e m b r a n e

nized and homogenized milk.

The

m aterial

cream

the

second washing,

dilution effect,
or

(c)

(b) the

a gra d ual

loss

of the

would low er

of fat

the

ules

since

would be

total

in total n it ro ge n

membrane

s m a l l e r fat globules.

the

su rf a c e

sm aller.

area

Similar

results

were

nounced drop

was

differ f o r

expressing

after

believed that the t r e n d was

deg r e e

of change

agree

in a g e n e r a l

unit

observed from
but a more

the f ou r th washing.

the

pro­

Since

the

n it ro ge n and phospholipid phosphorus,

it was

indicated.

Any of t hese

of the re m a in in g fat glob­

of the phospholipid phosphorus,
observed

material

con c en tra t io n of nitro ge n p e r

determination

units

of nonhomoge­

e i t h e r by (a) a continuation of the

sloughing off of the

possibilities

14 help to

s e p a r a t e d f r o m non­

homogenized milk exhibited a g r a d u a l l o s s
after

13 and

The

way with those

mo re

significant than the

data obtained f o r n o r m a l
r e p o r t e d by J a c k

cream

and Dahle

(1937b).
The
nized c r e a m

values

obtained on the washings f r o m

showed a different b eh avior.

the homoge­

The n it ro ge n values

187
per

unit of fat l e v e l e d off m o r e

which would indicate
ciated

more

with the fa t-g lo bu le

lipid p h o s p h o ru s
constant p e r

serve

rise

after

sion in homogenized

the

increased

Chemical

as

of F a t - m e m b r a n e

The
proteins

13 to

14 p e r

reported

in this

generally
centration

reported
is

and

in the

in the f a t - m e m b r a n e

cent.

Whether the

had a degrading

some

thus

the p e r c e n t a g e

should be noted,
ether

not known and can only be
however,

extraction p ro cedu re

that the
resulted

cold (0

o

the p r o ­

effect on

of n i t r o g e n

conjectured.
to

con­

methods

from

investigators

is

than that

in which the n it ro ge n

tein u se d by v a r i o u s

to be l o w e r ,

amount

C haracteristics

somewhat h ig he r

12 p e r

causing

the

of homogenization.

s e p a r a t i o n of the phospholipids

of the p r o t e i n ,

showed an

Proteins

in the l i t e r a t u r e ,

approximately

of p r e p a r a t i o n

increase

c e nt of n it r o g e n
study is

but

Nevertheless,

a result

and P h y s i c a l

remained fairly

s t a b i l i t y of the f a t e m u l ­

milk and a m a r k e d
fat

the phospho­

w a s hings,

the fifth washing.

value,

t e n a c i o u s ly a s s o ­

In g e n e r a l ,

successive

a d s o r b e d on the

Some

was

content of homogenized c r e a m

to i l l u s t r a t e

of p r o t e i n

protein

surface.

unit of f a t on

unaccountable
data

that

quickly and at a h i g h e r

o
3
C.)

It

ethanol—

in the b e s t f a t - m e m b r a n e

p re p a ra t io n,

even to the extent of being more

removal of phospholipids fr om the crude
In these p a r t i c u l a r
l ip id -f r e e

basis,

samples

was

membrane

the percentage

slightly lower

t hese

than for the ho­

(13.65 p e r

data r e p r e s e n t only one p r e p a r a t io n ,

cent).

Since

it is difficult to

relationships between the nitrogen content

of the n orma l m e m b r a n e - p r o t e i n s
enized milk.

on a

(13.11 p e r cent) for the

membrane p roteins

a s c e r t a i n any definite

material.

of nitrogen,

nonhomogenized milk, f a t - m e m b r a n e p roteins
mogenized milk,

efficient in the

The two samples

and that isolated fr om homog­

used in this

study r e p r e s e n t

what was thought to be the b e s t of eight previous p r e p a r a t io n s
isolated by s e v e r a l
one or

mo re

different techniques,

technical

r e p r e s e n t e d the mo st

reasons.

p roteins for

analyses.

In view of some

c e r t a i n other

remain to be

The final isolation procedure

electrophoretic
divergent

modifications

the f at-

and microbiological
results

in the

obtained in this

separation procedure

studied.

The positive
garding the nature
the p re s e n c e

d is ca rd ed for

s at is f ac to ry method of preparing

membrane

study,

but were

Molisch r eaction furnished
of the membrane

of a carbohydrate

m aterials

residue

some

clue

re­

and indicated

on one o r more

of the

1 89
constituent p r o t e i n s .

The negative

that the isolation p r o c e d u r e
bearing p r o te i n s ,
the

results

if they were p r e s e n t .

of p r o t e i n s

re s p e c t iv e

However,

an absence

per

unit volume

p ro te i n p r e p a r a t i o n s

(1925)

re­

membrane.
were

l ig hter

The n o r ­
in weight

cr y s t a l l i n e

structure

and

of the homogenized p r e p a r a t i o n s .

El e c tr o p h o r e ti e

Characteristics

Fat-membrane

Electrophoretic

patterns

electrophoretic patterns
tions

Hattori

of powder than those p r e p a r e d f r o m homoge­

nized milk and also lacked the c l e a r
luster

in the m e m b r a n e -

in ‘‘h a p te i n , 11 a protein

supposedly i solated f r o m the fat-globule
mal f a t - m e m b r a n e

of

sulfur in the n o r m a l f a t -

homogenized milk.
groups

the nature

suggest the absence

of such m a t e r i a l s

of reducing

sulfur-

t e s t following the

strongly

which contain h e a t - la b i le

proteins p rep ared from
p or te d

aquasols,

and the p r e s e n c e

t e s t indicated

had no effect on c e r t a i n

obtained with the n i t r o p r u s s i d e

heating of the

m e m br an e

nitroprusside

in the

citrate

buffer

resolution.

systems

Proteins

in v ariou s

obtained with the

gly cine -h yd ro c hloric

buffer m e d i a .
m em brane

acid, phosphate

showed the c l e a r e s t

In these p a r t i c u l a r

of the

patterns

The

prep ara­

and v e r o n a l -

elec tr o ph or e t ic

for normal fat-membrane
1

190
proteins,
ence

there

were

two main peaks,

of two different m e m b r a n e —
p r o te i n components of a l m o s t

equal

mobility.

Occasionally

ponent a p p e a r e d in the

a t hird and even a fourth com­

e l e c t r o p h o r e t i c p a t t e r n as

peak of low concentration.

These

usually o c c u r r e d in the ascending
and may

represent

their

cor re s po nd in g

m i g ra ti o n of p r o t e i n
takes place

and pH within the

of u nmeasurable

usually d e t e r m i n e d for
ties

mobilities

aquasol

representative

U-cell

were

changes

bility as

those

gen er ally

in the

conductivity

mobilities

are

e ach component by averaging the mobili­
and descending p a t t e r n s .

the homogenized milk, f a t - m e m b r a n e
s y s te m s

The

side of the

and a r e

during e l e c t r o p h o r e s i s ,

in both the ascending

buffer

calculated.

of the p ro te i n components.

An examination of the e l e c t r o p h o r e t i c
for

U-tube

m e a s u r e d and

in the descending

through the p r o te i n

bec a us e

T i s el iu s

of e l e c t r o p h o r e s i s ,

the diffused peaks

components

a diffused

diffused peaks

side of the

electrophoretic

c o n s i d e r e d to be mo re
However,

m i no r o r

certain abnormalities

but whenever p ossible,

cell

which indicated the p r e s ­

show two
appearing

strong peaks
in comparable

enized m e m b r a n e - p r o t e i n s ,

but they

patterns

p r o te i n s

in the

of somewhat
patterns

show m a j o r

obtained
same

similar

mo­

for nonhomog­
differences

in

191
the quality and quantity of the components.
p ri nc i pa l

components,

a ppeared,
occurs
as

In addition to these

a t h i r d peak of con side ra ble prominence

but it p o s s e s s e d a very low mobility.

so n e a r

to whether

to the initial boundary that it was

it was

initial boundary,

a component-peak o r

but it was p r e s e n t

descending p a t t e r n s

in all of the

of the homogenized milk,

A fourth peak of minor prominence

character

also

occasionally

appeared.

The

of the e l e c t r o p h o r e t i c p a t t e r n s

electrophoresis

of homogenized milk,

teins,

therefore

ads or b e d on the fat of n o r m a l

ascending

and

fat-membrane
and of diffused
and

obtained by the

f a t - m e m b r a n e p ro te i n s

obtained f o r n o r m a l

the assumption was

questionable

appearance

characteristics

the p a t t e r n s

it

a d is tortion of the

proteins.

differed fr om

In fact,

m embrane—
pro­

made that the components

milk differs

f r o m those

asso­

ciated with the fat of homogenized milk.

Mobility-pH relat io ns hi ps
Because
direct
this

of various

of the p r e l i m i n a r y nature

c o m p a r i s o n of the

study with the

misleading.

Hence,

e x p e r im e n t s,

c alculated p e a k - m o b il it ie s

e le c tr o p h o r e t ic

milk p ro te i n components

of these

m embrane-proteins.

appearing

the n ature

mobilities

a

obtained in

of the various

in the l i t e r a t u r e

would be

of the individual protein components

192
appearing

in the

electrophoretic

h o m o g en i z ed f a t - m e m b r a n e
t a i n e d until

the

homogeneous

various

form

buffer

then be

c o m p a r e d with

p ro tein

components.

characterize
Some
e nt s

c an be

ities

against

Figure
milk,
for

media

chemical

24,

comp on ents

at

sim ilar

the

information
obtained,

however,

representing

pH line

milk,

The p oints
at

generally

zero

component.

nature

the

iso electric

but in the

of the

25,

the

isoelectric

to

c o n t e m p la t e d .
of the

compon­

calculated

mobil­

obtained.

represen ting
show t his

the

area

of no

data

relation­

mobility c u r v e s

and the

mobility,

point of the p r o t e i n

d at a a r e

too l i m i t e d to

zone for

the

normal

data,

obtained f o r nonhomogenized

represents
the

the

could

known milk

required

which they were

and F i g u r e

an a p p r o x i m a t e
case

study is

to the

data

e lectrophoretic

m em brane-proteins,

to a s

T h e se

would be

of i n t e r c e p t i o n of the

Obviously,

s e p a r a t e d in a

c h a r a c t e r i z e d in

by plotting

from

values

mobility

referred

a ls o

Such a

relative

pH v a l u e s

homogenized

been

data obtained f r o m

tests

components.

the

have

In addition to t h e s e

and p h y s i c a l

and

cannot be defi ni tel y a s c e r ­

d i f f e r e n t pH v a l u e s .

m em brane-proteins

ship.

proteins

of nonhomogenized

and e l e c t r o p h o r e t i c a l l y

various

other

p attern s

components

m embrane-proteins,

establish
involved,
one

I

193
electrophoresis

(un r e po r te d)

pH 3.8 with no a p p a r e n t
after

two h o u r s

vation
sample

was

the

with the

fore,

the

approximate

ited to the

norm al

studies

limitations,

in this
it

tha t

Dahle

(1937b),

pro teins

was

the

zone of t h i s

somewhat

warm

e th a n o l —
ether

h om o ge ni z ed

This

at

iso electric
was

trial

was

zone

curves.

r a ng e

(1933)

there­
was

lim ­

More

pre­

of n o r m a l
the

same

and J a c k

homo ge nized

not

Within t hese

approximately

Wiese

obser­

p articular

m em brane-proteins,

on the

milk,

and

mem brane-

The

electrophoretic

extraction

procedure

noted in the

electrophoretic

sulted f r o m

a loss

p attern s

of a p r o t e i n

the

electrophor­

m aterials,

mem brane-proteins.

mobili­

of lipid m a t e r i a l

a ffected

of the f a t - m e m b r a n e

milk,

b uffe r

h ig h e r .

of t e m p e r a t u r e

characteristics

A sim ilar

contemplated.

and

of the

of m e m b r a n e - p r o t e i n s .

by the
etic

(ca pH 3.8)

that

f ield.

respective

are

that the

by P a l m e r

while

Influence
ties

electric

of an i s o e l e c t r i c

of the

respect

appears

rep o rted

m ilk,

l o ca ti o n

shape

m em brane-proteins
as

to the

isoelectric

homo ge niz ed

in a c e t a t e

of the p r o t e i n comp on ents

a p p r o x i m a t e l y pH 3.8.

made

cise

that

attempted

m igration

of e x p o s u r e

suggests

was

especially

Whether

shown in F i g u r e

component o r

the

changes

22 r e ­

a portion

of a

c om ponent
K rejci,

soluble

1942;

electrostatic
be

in alcohol

and o t h e r s ) ,
properties

or

from

of the

and

Wakeman,

1918;

f u n d a m e n t a l cha n ge s

p roteins

themselves

in the

could not

ascertained.

Influence

of c o n c e n t r a t i o n on the

of m e m b r a n e - p r o t e i n s .
bility of the
membrane

p rotein

electrophorized

whey p r o t e i n
ever,
vary

only

soluble

pared

that

membrane

with the

to the

norm al

(1940)

solutions,

pH of the b u f f e r .

difference

in t h e i r

found that

''haptein"

of the

respective
was

compositions.

insoluble

in w a t e r ,

f or
how­

mobilities

protein.
never

degree

t o t a l ly

of

solu­

consistently

m em brane-m aterial
m aterial

in

behavior,

were

The

of the

mobilities

that

but the

fa t-

m aterial

this

stated

concentration

fat-m em brane

mo­

reduced from

repo rted

demonstrated

h omogenized milk,

in the

resolution

solution was

p rotein p re p a ra tio n s

in any of the b uffe r

mobility

h omogenized milk,

of m e m b r a n e

Smith (1946b)

c o m p on e nt s

s olub ility of the

of the

buffer—
p ro tein

s lightly with the

varied

show an i n c r e a s e

concentration

c ent.

electrophoretic

electrophoretic

L o n g s w o r t h and Maclnnes

The

b ility

data

and b e t t e r

when the

0.84 to 0.43 p e r

The

components

proteins

com p on e nt s
the

(Osborne

als o

greater

as

com­

suggests

Hattori
dilute

a

(1925)

a c id s

and

195
bases,

but was

to w h e t h e r

soluble

the

strong

alkali.

e le ctro ph oriz ed p ro teins

s en ta t iv e

of the

portion.

The

centration

in

whole

membrane

e lectro ph oretic

hydrated portion

was

or

as

repre­

only the h y d r a t e d

obtained a t d i f f e r e n t con­

systems

representative

que stio n a r i s e s

in solution w e r e

m aterial,

patterns

and in d i f f e r e n t b uffer

The

of the

i nd icated tha t the
entire

membrane

preparations.

Amino Acid A s s a y of F a t - m e m b r a n e

The
p ro teins

differences

and o t h e r

not m a n i f e s t e d to the

p os it io n of the
concentrations
determ ined,
ations
acids.

in the

chemical
sa m e

and p hy si ca l

extent in the

as

of only

six of the

no evidence

is

essential

a vailable

amino

exception

minimum

of l ysin e,

re m a in in g

the

amino

m em brane-proteins

molecular

weights

amino

acid c o m ­
Since

a c id s

we r e

are

the

were

con c er n in g p o s s i b l e

c o n c e n t r a t i o n of the four

With the

shown by

characteristics

two m e m b r a n e - p r o t e i n p r e p a r a t i o n s .

of the nonhomogenized,
and the

e x i s t between the f a t - m e m b r a n e

of n on homogenized and homogenized milk

electrophoresis
are

that

Proteins

vari­

essential

amino

acid composition
quite

of the

sim ilar

s ame

order.

196
The
mixture
study,
nature

f a c t t h a t the

of p r o t e i n

p erm its

tion of the

p ro tein

altered

as

p la u s ib le

preparations.

m ajor

had n ot b e e n

c om p o n e n t s,

several

of t h e s e

m em brane-proteins

of homo geni z at i on w e r e

ciated
ment

proteins

in the

membrane;

fat-m em brane

such t h a t the

over-all

by chance

quite

sim ilar

to the

On the

other

t ei ns

represent

homogeneous
the

a mixture

component,

apparently

c on cen tra­

a

reasonable

sli gh t v a r i a t i o n s

position

of t h e s e

preparations

in t h e i r

s pecific

p rotein

in the
denote

same

the

of homogenized
acid

since

of p r o t e i n s

the

as
amino

tha t is n o r m a l l y

c omposition
hand,

secondly,

surfaces

and t h i r d l y ,

amino

the

m em brane-proteins

of e s s e n t i a l l y
mixture

have b e e n

brane-proteins.

the

a d s o r b e d on the fat

the p r o t e i n

with the f a t - g l o b u l e
of p r o t e i n s

possibly
in the

of this

con c er n in g

m a t e r i a l l y by homogenization;

a

as

e xplanations

components

the p l a s m a

a c id c o m p o s i t i o n

c o m p o s e d of a

shown in o t h e r p a r t s

First,

perhaps
result

are

the

milk may

original

mem­

m em brane-pro­
than a

assumption
over—
all
very

rearrange­

composition was

of the

rather

asso­

single

would be that

amino

acid

com­

significant d i f f e r e n c e s

con stitution.

W '

197

10

MOBILITY (uWcm., )voltH1 se c .’ 1, xlO5)

8

COMPONENT A
COMPONENT B
COMPONENT C

6

4
ISOELECTRIC AREA
2
O

-2
-4
-6

-0
i

5

6

8

10

II

PH

F i g u r e 24.
p H -m o h ility c u r v e s f o r the m a jo r
t h e n o n h o m o g e n i z e d —m i i k m e m b r a n e - p r o t e i n s .

com ponents

ol

12

198

12

t

1- - - - - - - - - - - 1- - - - - - - - - - - - 1- - - - - - - - - - - - 1- - - - - - - - - - - - 1- - - - - - - - - - - - 1- - - - - - - - - - - - 1- - - - - - - - - - - - 1- - - - - - - - - - - - 1- - - - - - - - - - - - r

A1
10

8

C O M P ON E N T
COMPONENT
COMPONENT

A
B
C

COMPONENT

D

6

4
2
0

-2
-4
-6
-8
-10.

J_______ I_______ I_______ L_______ 1_______ I_______ i_______ i_______ i_______ I_______ L

I

2

3

4

5

6

7

8

9

10

II

pH

F ig u r e 25.
p H —m o b i l i t y c u r v e s l o r t i i e m a j o r
the h o r n o g e n i z e d - m i l k r:.emo r a n e r o t e i n s .

com ponents

ol

SUMM ARY

Normal
effect on the
pasteurized

F O R S E C T I O N III

homogenizing p r e s s u r e s

d i s t r i b u t i o n of n it r o g e n

milk,

whereas

(2,500 pounds)

had little

in v a r i o u s f r a c t i o n s

high homogenizing p r e s s u r e s

pounds)

c a u s e d a re du c ti on

peptone

n it ro g e n

in h ea t -co a gu labl e

and an i n c r e a s e

of
(4,000

and p r o t e o s e -

in the

c a se i n

and nonprotein

solids

in c r e a m

nitrogen.
The

concentration

enized milk

showed a fivefold i n c r e a s e

content o v e r

increase.

gen p e r

a lso

for

samples

a th r e e fo ld

found in the

from

The

the homogenized

These

observa­

d i s tr i b u ti o n data.

solids,

fat and n it ro g e n

homogenized

of fat.

distribu­

obtained in total n i t r o ­

mineral

in the

homog­

showed a s i m ­

separated from

total

increase

100 g r a m s

was

c a s e i n n itrogen.

s upported by the

determinations

and n it ro g e n p e r
gen was

cream

d e t e r m i n e d as

washed c r e a m

proximately

in the

increase

from

solids-not-fat

various protein fractions

A t h r e e f o ld

were

The
the

in the

unit of fat

milk and was
tions

in the

that found in nonhomogenized milk.

tion of n it ro gen
ilar

of total

milk

in

showed ap­

con c en tra t io n of solids

The

increase

casein—
n it ro ge n f r a c t i o n .

in total n i t r o ­

The

d is tr i b u ti o n

200

of n it ro g e n

in the

n it r o g e n in the
t e r m i n e d as
in the

sera

washed-cream

serum from

sera

the nonhomogenized milk was

casein—
n it ro g e n while
from

the n i t ro ge n that was p r e s e n t

and p r o t e o s e —
peptone

The lyophilized f a t - m e m b r a n e

per

sera

cent on the

gave

positive

aquasol

both before

positive n i t r o p r u s s i d e

reaction

Although no definite
of the

of the p r o t e i n
it is

three

components

components

were

observed

in the

a f te r

heating;

can be

patterns

are

observed

individual

of the non­

a negative

nitro—

w h e re a s

the

showed a

three

made

from

concerning

in the f a t - m e m b r a n e

whereas

13.5

heating.

homogenized milk,

of the

Aquasols

m embrane-proteins

conclusions

we r e

m em brane-proteins,

identification

p r e p a r e d f r o m the

The p r e p a r a t i o n

gave

and a f t e r

characteristics

milk,

The

reactions.

electrophoretic

evident that t h e i r

two o r

basis.

m embrane-proteins

of homogenized milk,

e xamination

proteins

lipid—
free

Molish and b i u r e t

reaction,

nitrogen.

had a n it ro g e n content of app r ox im at el y

anhydrous,

homogenized milk,
prusside

de­

homogenized milk included c a s e i n —
nitrogen,

h e a t - c o a g u l a b l e n it r o g e n

washed-cream

showed that all of the

an

the n a t u r e

preparations,

different.

Generally,

in the nonhomogenized
to four

components

membrane

preparation.

components has not been

201
achieved.
the

The

tem perature

concentration

phenylalanine

sine

in the

showed a

and valine

concentration

in the

amino

d if f e r e d

rather

for

i s o le uc i ne ,

made

and

solu­

sim ilar

m aterial from

any of the

m ethi­
proteins

r e v e a l e d only

amino

a c i d c o m p o s i t i o n of both of the

markedly from

fractions.

of t h e s e

but a

leucine,

on f a t - m e m b r a n e

sig nifica nt i n c r e a s e

membrane

extraction

of the p r o t e i n components.

analyses

two m e m b r a n e - p r o t e i n s ,

of lys in e
The

e l e c t r o p h o r i z e d buffer

nonhomogenized and homogenized milk

differences
the

in the

mobilities

Microbiological

from

ethanol—
ether

of p r o t e i n

tion influenced the

onine,

of the

acids

slight

between

determination for
in the

ly­

concentration

homogenized milk.
m embrane-proteins

recognized

milk p r o t e i n

G E N E R A L SUMM ARY

Experiments
fat and

solids-not-fat

in t e m p e r a t u r e
t ie s

have been

fied f at

in globular

conducted with milks

content to

and p r e s s u r e

in homogenized

A N D CO NC LUSIO NS

milk,

study the

to d e t e r m i n e

the

development of high v i s c o s i t i e s

the

isolation,

patterns

Influence

Procedures

the

amounts

which a r e

and to r e p o r t

of solidi­

conducive
resu lts

to

on

c h a r a c t e r i z a t i o n and e l e c t r o p h o r e t i c

of the fa t- g lo bu le

The

effect of v ar i a t i o n s

on the production of high v i s c o s i ­

fat at t e m p e r a t u r e s

prelim inary

of varying

membrane

of V a r i a ti o n s

proteins.

in the Homogenization

and the Composition of Milk on the

Efficiency of Homogenization and the
Vi scosity of Milk

Milk containing five p e r
nization

tem peratures

(80° to 70° F.)

homogenization p r e s s u r e s
tions

that

c ontribute

cent o r

clustering

development of a high v i s c o s i t y
detrimental

effects

were

or

low homoge­

single-stage

higher)

are

of fat globules

in homogenized milk.

of t hese p r o c e s s i n g

c o s it y of homogenized milk

fat,

and high,

(2,500 pounds

to the

m o re

conditions

reduced

or

condi­

and to the
The

on the

completely

vis­

203
e l i m i n a t e d by double —
stage
the

tem perature
Normal

produced

homogenization

of homogenization
variations

in the

above

o r by maintaining
100° F .

solids—
not—
fat content of milk

insignificant variations

in the

viscosity

of homogenized

milk.

The

Influence

of the P h y s i c a l

State

of the

Fat

on the

Efficie ncy of Homogenization and the
V i scosity of Milk

At homo ge ni z at i on t e m p e r a t u r e s
to the

form ation

and a high v i s c o s i t y ,

The

e x t e n t of f at

the

had b een

o

F.)

conducive

cluster-like

struc­

solidifed.

s ol id ification in milk homogenized i m m e d i a t e l y

7.0 to

stored

to 90

milk fat was p a r t i a l l y

after pasteurization varied from
and f r o m

o

of an extensive fa t- g l o b u l e ,

ture

cent

(70

at

18.0 p e r

45° F .

for

a p p r o x i m a t e l y 0.5 to

cent in p a s t e u r i z e d
20 h ours

prior

2.0 p e r

milk which

to h omogeniza­

tion.
Milk t ha t
homo geniz ed was

showed e v e r y
processed

and a t t e m p e r a t u r e s

above

indication of being

when the fat was
100

o

F.

efficiently

in a liquid

state

204
Som e

C h a r a c t e r i s t i c s o f the F a t - m e m b r a n e P r o t e i n s
N o n h o m o g e n iz e d and H o m o g e n iz e d M ilk

Moderate
little

effect on the

proteins.

The
and c r e a m
as

in the

distribution

as

in the

proportion

caused

a

and p r o t e o s e —
peptone n it ro g e n

of fat and

solids-not-fat

respective

milk,

equivalent amount

observation
tribution

however,

of milk

and

and n on pr ot e in n it r o g e n .

of the

f at in homogenized

with an

(4,000 pounds),

fractions

had

in the

s k i m m il k

s e p a r a t e d f r o m nonhomogenized and homogenized

well

a greater

casein

(2,500 pounds)

content of v a r i o u s

in h e a t - c o a g u l a b l e

an i n c r e a s e

the

n it r o g e n

High p r e s s u r e s

r e d u c ti o n

milk,

homogenization p r e s s u r e s

of

was

per

unit of fat,

substantiated f u rth e r

phospholipid p h o s p h o r u s

tained f r o m

s o l i d s - n o t - f a t were

total

in the

the b u t t e r m i l k - l i k e

total

respective

than was

with

associated

cream

washed-cream

dis­

sam ples.

of washed c r e a m

milk

This

c a l c i u m and non-

in the p r o t e i n f r a c t i o n s

sera

nonhomogenized and homogenized
in the

associated

by data b a s e d on the

a sh ,

d i s t r i b u t i o n of n it ro g e n

protein fractions

showed that

of fat in nonhomogenized milk.

of p r o t e i n n it ro g e n ,

The

washed c r e a m s ,

ob­

from

showed that the m a j o r
serum

from

homogenized

205
mi lk w e r e

m ade

up ot

and piroteose—
peptone

eth ano l-eth er
was

sera

n itro ge n ,

p roteins

were

by e x t r a c t i n g

washing technique,

dispersed

h e a t - c o a g u la b l e

n it r o g e n

n it r o g e n .

Fat-m em brane
butterm ilk—
like

casein

in d i s t i l l e d w a t e r

isolated from

the lipoid

after

washed c r e a m ,

m aterials

by an

which the p r o t e i n

residue

and l yophilized to an anhydrous

p owd e r .
The
per

l yo philized m e m b r a n e - p r o t e i n s

of the

e xhibited p os itive

of the

brane—
p roteins

Molisch and b i u r e t

gave

nitroprusside

c omponents
The
b ra n e

two

Aquasols

positive

e lectrophoretic

in the

in v a r i o u s

reactions,

but were

patterns
buffer

characteristics

milk,

mem­

reactions,

showed a positive

indicating the p r e s e n c e

nega­

and heated

of homogenized

Molisch and b i u r e t

aqu aso l

tes t;

m em brane-proteins

in both the unheated

that contain l a b i l e - s u l f u r

p ro teins

ferences

test

aquasols.

h ea t ed p o r t i o n of the

to the

the

nonhomogenized milk,

to the n i t r o p r u s s i d e

portions

the

13.5

c ent n i t r o g e n .
Aquasols

tive

contained about

but

reaction

of p r o t e i n

(whey p r o t e i n s ) .
obtained f o r

systems

showed d is ti n c t

of the p r o t e i n

m em brane-protein preparations,

the f a t - m e m ­

components

dif­
of

indicating that the

206
fat—
membrane
ferent

m aterial

than the f a t —
m em brane

mogenized milk fat.
ponents

were

sibly four

nature

of the

terize

the

electrophoretic

were

m em brane-proteins.

Due

it was not p o s s i b l e

individual

No definite

in the

conclusions

lysine

which is p r e s e n t

proteins.
amino

for

amino acids

Both of the

milk.

do exist,

in a h igher

m em brane-proteins

Some

in the ho­

and c h a r a c ­

from

the

of

dif fe r en c es

in the

than in the n o r m a l

any

proteins

m i no r

concentration

any of the

resu lts

concerning

e sp e c ia ll y in the

m em brane-proteins

acid compositions

tein f r a c t i o n s .

to isolate

composition of the f a t - m e m b r a n e

acid c o n c e n tr a t io n s

enized milk,

and p o s ­

to the p r e l i m i n a r y

can be f o r m e d f r o m

nonhomogenized and homogenized
in amino

of non­

three

present

c om­

components.

microbiological analyses

differences

d istinct

patterns

whereas

components

work,

dif­

a s s o c i a t e d with the ho­

m em brane-proteins,

d is ting uish a ble

mogenized milk,

m aterial

milk fat is

Two and o cc a sionally t h r e e

a p p a r e n t in the

homogenized milk,

of the

a s s o c i a t e d with n o r m a l

case

of

homog­

m embrane-

differed in t h e i r
rec og nize d milk p r o ­

LITERATURE

(1) Abderhalden,
1909.

E.,

and Voltz,

B ertrag
der

1925.

G.,

Natur

der

Quelques

Compt.

and Sharp,
647-674.
F.

Zus am me n se tzu ng
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