T HE E F F E C T O F STORAGE UPON SHRINKAGE AND T HE
N I T R O G E N DISTRIBUTION IN I C E CRE AM

By
JA ME S B U R K E T M I CK L E

A THESIS
S u b m i t t e d to the School of G r a d u a t e S tu di es of Michigan.
State C o lle ge of A g r i c u l t u r e a nd A pp lie d S c i e n c e
i n p a r t i a l f u l f i l l m e n t of the r e q u i r e m e n t s
f o r the d e g r e e of

DOCTOR OF PHIL OSOPH Y

D e p a r t m e n t of D a i r y i n g

1953

ProQuest Number: 10008236

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ACKNOWLEDGMENTS

The a u t h o r w i s h e s to e x p r e s s h i s a p p r e c i a t i o n to the f ollowing
m em bers
assistance

of the M i c h i g a n State

College D airy D e p a r tm e n t fo r th e ir

in the e x e c u t i o n of t h i s

study:

Dr.

h i s g u i d a n c e d u r i n g the p e r i o d of the study;
D r . G. M.

T r o u t , f o r h e lp f u l s u g g e s t i o n s ;

of the d e p a r t m e n t , f o r m a k i n g

J, A. M e i s e r ,

D r.

J.

a nd D r.

Jr.,

for

R. B r u n n e r and
E a r l W eaver, head

d e p a rtm e n t facilities available.

TABLE

OF

CONTENTS

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

1

R E V IE W OF L I T E R A T U R E ...............................................

3

E f f e c t of M i x I n g r e d i e n t s on S h r i n k a g e

. .

3

E f f e c t of S t o r a g e a nd C o n t a i n e r s on S h r i n k a g e ......................

8

P ro te in Fractionation P r o c e d u r e s

9

Sum m ary

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

PL A N OF EXPERIM ENT

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

GENERAL PROCEDURE
Methods

.

.

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

of O b ta in in g and

Sampling P r o c e d u r e

13
14
15

S to r in g S a m p l e s ................
.........................................

15
16

M o j o n n i e r A n a l y s i s .............................. ..................................................

17

N itrogen D eterm ination

17

. . . .

Weight L o s s

18

Shrinkage M e a s u r e m e n t
EXPERIM ENTAL

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

18

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

19

D e v e l o p m e n t of N i t r o g e n F r a c t i o n a t i o n P r o c e d u r e

19

C o m p a r i s o n with D a t a in the L i t e r a t u r e

22

Experim ental E r r o r

.

.

. .

24

Page
RESULTS

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

26

R e l a t i o n of S h r i n k a g e , Weight L o s s , T o t a l S o lid s ,
and T o t a l N i t r o g e n
................................................................ ......................

26

C o n t a i n e r Study

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

28

C o m p a r i s o n of Top and M id dle of S a m p l e ...............................

31

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

36

C O N C L U S I O N S ......................

40

LITERATURE

CITED

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

iv

42

LI ST OF

T A BL ES

TABLE
1.

2.

3.

4.

5.

6.

7.

8.

Page
C o m p a r i s o n of n i t r o g e n v a l u e s o b t a in e d on
p a s t e u r i z e d h o m o g e n i z e d m i l k with l i t e r a t u r e .
v a l u e s ........................ , .........................................................................................

23

C o m p a r i s o n of t o t a l s o l i d s and w e ig h t l o s s of
.........................................................
ice c r e a m during sto rag e

26

C o m p a r i s o n of t o t a l s o l i d s a nd t o t a l n i t r o g e n
of i c e c r e a m d u r i n g s t o r a g e (top and m i d d l e
of p i n t s a m p l e s ) .................... . .

27

E f f e c t of t r e a t e d and u n t r e a t e d c o n t a i n e r s on
n i t r o g e n d i s t r i b u t i o n of i c e c r e a m d u r in g
s t o r a g e (top of p i n t s a m p l e s in m i l l i g r a m s p e r
100 g r a m s of i c e c r e a m )
................................................................

29

E f f e c t of t r e a t e d a nd u n t r e a t e d c o n t a i n e r s on
n i t r o g e n d i s t r i b u t i o n of i c e c r e a m d u r in g s t o r a g e
(top of p in t s a m p l e s , e x p r e s s e d a s p e r c e n t of
total nitrogen)
..............................................................................................

30

C o m p a r i s o n of n i t r o g e n d i s t r i b u t i o n of top and
m i d d l e of pint i c e c r e a m s a m p l e s
during
stor­
age (in m i l l i g r a m s p e r 100 g r a m s
of i c e c r e a m ) - .

33

C o m p a r i s o n of n i t r o g e n d i s t r i b u t i o n of top and
m i d d l e of p i n t i c e c r e a m s a m p l e s
during
storage
( e x p r e s s e d a s p e r c e n t of t o t a l n i t r o g e n ) ................................

34

V o lu m e l o s s of p in t i c e c r e a m s a m p l e s d u r in g
s t o r a g e ..............................................................................................................

35

INTRODU CTIO N

Shrinkage,
serious

d e f in e d a s a l o s s in v o l u m e , i s

p r o b l e m s i n the m a n u f a c t u r e

of i c e

one of the m o s t

cream .

It i s g e n e r a l l y

a g r e e d t h a t t h i s d e f e c t f i r s t a p p e a r e d a t the t i m e

c o n ti n u o u s f r e e z e r s

a n d p a p e r c o n t a i n e r s w e r e i n t r o d u c e d into the i c e

c re a m industry.

Shrinkage has
cause

consum ers

f ull of i c e
the

c a u s e d w i d e s p r e a d l o s s e s to the i n d u s t r y b e ­

o b j e c t to buying a c o n t a i n e r which i s

cream .

As a re su lt,

the m a n u f a c t u r e r m a y l o s e not only

c o s t of m a n u f a c t u r i n g the p r o d u c t , b ut a l s o , f u t u r e

same

only p a r t i a l l y

sales

to the

custom er.
S h r i n k a g e h a s b e e n the s u b j e c t of n u m e r o u s r e s e a r c h p u b l i ­

c a t i o n s i n the p a s t .
reported,
term ed

Although m a n y

causes

of t h i s d e f e c t h a v e b e e n

i t i s g e n e r a l l y a c c e p t e d t h a t m o s t of t h e s e f a c t o r s

can be

c o n trib u to ry r a t h e r than fundam ental.
T h i s i n v e s t i g a t i o n w a s u n d e r t a k e n in o r d e r to o bt ai n c e r t a i n

f u n d a m e n t a l d a t a c o n c e r n i n g the p r o t e i n d i s t r i b u t i o n in i c e

cream .

The o b j e c t i v e s w e r e to d e t e r m i n e the a m o u n t of n i t r o g e n which
occurs
the

in the d i f f e r e n t p r o t e i n f r a c t i o n s of i c e

cream ,

t o g e t h e r with

c h a n g e s w h ic h t h i s n i t r o g e n d i s t r i b u t i o n m i g h t u n d e r g o

during

2
storage.

It w a s h o p e d t h a t s u c h a study would c o n t r i b u t e to a g r e a t e r

understanding

of the g e n e r a l p r o b l e m of i c e

cream

shrin kage.

REVI EW OF L I T E R A T U R E

The l i t e r a t u r e

on i c e c r e a m

shrinkage

covers many phases

the p ro b le m .

H o w e v e r , f o r the p u r p o s e s of t h i s i n v e s t i g a t i o n ,

th e l i t e r a t u r e

p e r t a i n i n g to the e f f e c t of m i x i n g r e d i e n t s ,

of

only

s t o r a g e , an d

m i l k p r o t e i n s upon s h r i n k a g e will be r e v i e w e d .

E f f e c t of M ix I n g r e d i e n t s

R esearch w orkers
ingredients
w orkers

on i c e

cream

disagree

on S h r i n k a g e

c o n c e r n i n g the i n f l u e n c e of m i x

shrinkage,

to p u b l i s h a c o m p r e h e n s i v e

Erb

(1940), one of the e a r l i e r

study on s h r i n k a g e ,

state d that

t h e c o m p o s i t i o n of the m i x i n f l u e n c e d the a m o u n t of s h r i n k a g e i n the
finished ice

cream .

o pin io n t h a t

''the in g red ien ts

c o m p a r e d to the
Erb

On the o t h e r h and, L e e d e r

of the m i x w e r e of m i n o r i m p o r t a n c e

s t o r a g e of the f i n i s h e d p r o d u c t . 1'

(1940) found t h a t a ' ' h i g h ' 1 s u g a r c o n t e n t i n a n i c e

m i x w ould p r o t e c t the p r o t e i n s a n d t h e r e f o r e
of i c e

(1948) w a s of the

c r e a m m a d e f r o m t h a t m i x to s h r i n k .

decrease

cream

the t e n d e n c y

A t a b o u t the s a m e

tim e,

T r a c y , H o s k i s s o n , a n d W e i n r e i c h (1941) r e p o r t e d t h a t a high

sugar

co ncentration encouraged shrin kage.

D ru s e n d a h l, and L e e d e r

A c c o r d i n g to R a m s e y ,

(1947), s u g a r i n c r e a s e d the l i k e l i h o o d of

4
s h r i n k a g e by l o w e r i n g the f r e e z i n g p oi n t of i c e c r e a m ,
Hankinson,

D ahle ,

a n d M e i s e r (1947), u s i n g a d i f f e r e n t a p p r o a c h , found t h a t

shrin kage i n c r e a s e d as

the a m o u n t s

of m o n o s a c c h a r i d e s in the m i x

w ere increased,
D a h le a n d M e i s e r
from answ ers

(1947) c o n c l u d e d f r o m

r e c e i v e d to a q u e s t i o n n a i r e

c o n d e n s e d m i l k c o n t r i b u t e d to s h r i n k a g e .
c l u s i o n r e a c h e d by L e e d e r

t h e i r r e s e a r c h a nd

t h a t the u s e

of s w e e t e n e d

T h is was a l s o the c o n ­

(1948),

Many a u t h o r s h av e r e p o r t e d t h a t i n c r e a s i n g the b u t t e r f a t c o n ­
t e n t of the m i x will i n c r e a s e
Ramsey

shrinkage

et_ a l ., 1947; S h e u r i n g ,

1949),

(Erb,

1940;

Tracy

of the r e s u l t a n t i c e

when they i n c r e a s e d the b u t t e r f a t c o n t e n t of the m i x f r o m
Da hle a n d M e i s e r

and M e i s e r

e_t

seem s

was a d i r e c t r e l a t i o n s h i p

to be a g r e e m e n t th at high p e r c e n t a g e s
shrinkage

of t o t a l

( R a m s e y e t a l ., 1941;

1941).

The u s e
e t a l.

16

cream .

s o l i d s i n m i x e s w i ll c a u s e i n c r e a s e d
Tracy

10 to

s h r i n k a g e a n d a n i n c r e a s e in the a m o u n t of f r e e

fa tty a c i d s p r e s e n t in the i c e
There

cream

(1947), t o g e t h e r with Dahle, H a n k i n s o n ,

(1947), r e p o r t e d l a t e r t h a t t h e r e

between in c r e a s e d

1941;

H o w e v e r , H a n k i n s o n and Dahle

(1944) found l i t t l e d i f f e r e n c e in s h r i n k a g e

percent,

ejt a l . ,

of s u p e r h e a t e d c o n d e n s e d m i l k ,

a c c o r d i n g to T r a c y

(1941) a n d B e n d i x e n (1948), t e n d e d to d e c r e a s e

shrinkage;

but

5
Dahle, Hankinson,

a nd M e i s e r

(1947) s t a t e d t h a t the u s e

p r o d u c t w as n o t a r e m e d y f o r i c e

cream

of t h is

shrinkage.

The w o r k w h i c h h a s b e e n done with s t a b i l i z e r s i n d i c a t e s
t h e y have l i t t l e , if a ny,
by i c e

cream ,

e f f e c t on the a m o u n t of s h r i n k a g e

H a n k i n s o n a n d D a hle (1944)

s t a b i l i z e r s u s e d i n the i c e
wou ld give

somewhat le ss

c r e a m in dustry,

of f' D a r i l o i d M r e s u l t e d in s l i g h t l y m o r e

use

of o t h e r

M eiser

stabilizers,

exhibited

r e p o r t e d t h a t of the m a n y
only the u s e

of g e l a t i n

s h r i n k a g e in the f i n i s h e d p r o d u c t .

use

The

s h r i n k a g e t h a n did the

in a study r e p o r t e d by D a h l e , H a n k i n s o n , a n d

(1947).
On the o t h e r h a nd , m o s t w o r k e r s a g r e e t h a t the u s e

sifiers in creases
M eiser
cause

that

(1947)

shrin kage.

of e m u l ­

Cole a nd C h a s e (1946) a n d Dahle and

sta te d that as a group,

shrin kage, w h e r e a s ' e m u ls ifie rs

stabilizers
do.

do n o t a p p e a r to

Em ulsifiers,

as well as

egg yolk, w i ll p r o d u c e a d r i e r i c e

c r e a m a s i t c o m e s f r o m the

freezer,

and hence

s h r i n k a g e (Dahle, H a n k i n s o n , a n d

M eiser,

1947).

e t a l,
crease

r e s u l t in m o r e

T h i s i s i n a g r e e m e n t with the f i n d i n g s of R a m s e y

(1947), who r e p o r t e d t h a t the u s e of egg yolk t e n d e d to i n ­
shrinkage.
A tt e m p ts have been m a d e

in ice

cream .

Enzyme

to r e l a t e

"im provers"

s h r i n k a g e to the p r o t e i n s

which t e n d to h y d r o l y z e

the

6
proteins

will c a u s e m o r e

H a n k i n s o n a nd Da hle

shrinkage,

according

to E r b

(1940).

(1944) a n d D ahle a nd La ndo (1951)

substantiated

t h i s i n t h e i r r e p o r t t h a t the a d d i t i o n of t r y p s i n w i ll i n c r e a s e
the s p o n t a n e o u s

s h r i n k a g e of i c e c r e a m .

D e v e l o p e d a c i d w h ich d e n a t u r e s . p r o t e i n s
s h r i n k a g e a c c o r d i n g to s o m e a u t h o r s
and M e ise r,

greatly

1947).

(Erb,

may

also

cause

1940; D ahle , H a n k i n s o n ,

H o w e v e r , H a n k i n s o n a nd D ahle (1944)

sta te d that

m i x e s n e u t r a l i z e d to a n a c i d i t y of 0,015 to 0,04 p e r c e n t e x h i b i t e d
l i t t l e d i f f e r e n c e i n the

shrinkage

s u s c e p t i b i l i t y of the f i n i s h e d p r o d ­

uct,
L a n d o a n d D a hle (1949) f i r s t r e p o r t e d t h a t the whey p r o t e i n s ,
a l b u m i n a n d globulin, w e r e

of m a j o r i m p o r t a n c e in r e l a t i o n to the

shrinkage problem .

these

(1951), a s

well a s

L ater,

s a m e a u t h o r s , Dahle a nd L a n do

T a r a s s u k a n d H u tto n (1950),

stated that a d ire c t

r e l a t i o n s h i p e x i s t e d b e t w e e n the a m o u n t of d e n a t u r e d p r o t e i n a n d the
a m o u n t of s h r i n k a g e .
whey p r o t e i n s
It w as
g lo b u lin ,

These authors

c o n c l u d e d t h a t d e n a t u r a t i o n of

o c c u r r e d when s h r i n k a g e took p l a c e .
r e p o r t e d by the

s a m e two g r o u p s of w o r k e r s

when a d d e d to the m i x ,

d e c re a s e d shrinkage,

a d d i t i o n of d e n a t u r e d whey p r o t e i n s t e n d e d to i n c r e a s e
The w o r k of T h o m a s ,

Combs,

a nd C o u l t e r

that

an d t h a t the
shrinkage.

(1951), on the o t h e r hand,

i n d i c a t e d t h a t the a d d i t i o n of c o l o s t r u m m i l k , w hich w as h i g h in

7
g lo b u li n ,

t e n d e d to i n c r e a s e

noted, however,
case;

t h a t the

T h o m a s ej; al.

the a m o u n t of s h r i n k a g e .

source

of g lo b u li n w a s d i f f e r e n t i n e a c h

used c o lo stru m milk,

and C a li fo rn ia w o r k e r s

It s h ould be

w h e r e a s the P e n n s y l v a n i a

u s e d whey.

A t t e m p t s h a v e b e e n m a d e to e x p l a i n s h r i n k a g e in t e r m s of the e f ­
f e c t of h e a t on the whey p r o t e i n s .

Dahle and M e i s e r (1947) f i r s t s t a t e d t h a t

h i g h e r h e a t t r e a t m e n t s g ave l e s s s h r i n k a g e , bu t l a t e r r e p o r t e d v e r y l i t t l e
d i f f e r e n c e i n s h r i n k a g e b e t w e e n p a s t e u r i z a t i o n t e m p e r a t u r e s of f r o m 145°
F . to 170° F . e a c h f o r t h i r t y m i n u t e s (Dahle, H a n k i n s o n , a nd M e i s e r ,
1947).

T a r a s s u k and H utton (1950) c ould find l i t t l e d i f f e r e n c e i n the s h r i n k ­

a ge s u s c e p t i b i l i t y of m i x e s w ith p a s t e u r i z a t i o n t r e a t m e n t s r a n g i n g f r o m
143° F . f o r t h i r t y m i n u t e s to 190° F , f o r t h i r t y m i n u t e s .
Da hle and L a nd o (1951) found t h a t h i g h e r h e a t t r e a t m e n t s
less

shrinkage,

whereas

Thomas

t r e a t m e n t r e s u l t e d in m o r e

e t al.

shrinkage.

gave

(1951) r e p o r t e d t h a t h igh h e a t
Since W i l d a s i n and Doan (1951)

found t h a t m i l k h e a t e d to 5 0° F . and s e p a r a t e d a t t h a t t e m p e r a t u r e
had le s s
50°

F.

globulin in it a fte r

s e p a r a t i o n tha n did m i l k

and t h e n h e a t e d to 120° F . , i t i s p o s s i b l e

s e p a r a t e d at

that p r e v io u s heat

t r e a t m e n t of m i x i n g r e d i e n t s m a y h av e a c c o u n t e d f o r the l a c k of
a g r e e m e n t c o n c e r n i n g p a s t e u r i z a t i o n of the m i x .
Erb

(1940),

who i s in a g r e e m e n t with K o h l e r (1939),

reported

t h a t the s a l t b a l a n c e of the m i x a f f e c t e d s h r i n k a g e in t h a t c a l c i u m and

8
m a g n e s i u m t e n d e d to d e s t a b i l i z e the p r o t e i n s and i n c r e a s e
On the

o t h e r ha nd,

chlo rid e

Cole a nd C h a s e

(Dahle, H a n k i n s on ,

t h a t a d d e d c a l c i u m and m a g n e s i u m

E f f e c t of S t o r a g e

There is m o re

T em perature
authors.

storage

s a l t s h a d no e f f e c t on s h r i n k a g e .

and c o n t a i n e r s on s h r i n k a g e

(Erb,

Cole (1939,

changes during storage a r e
c h a n g e s will a l s o c a u s e
also

e t a l .,

the g r e a t e r

of s t o r a g e ,

shrin kage.

1947; D ah le , H a n k in s on ,

et al.

s o n and D ahle

s t a t e m e n t was

cream

1950).

(1947),
always

storing
result

s u b s t a n t i a t e d by H a n k i n ­

(1944) and l a t e r by Dahle and M e i s e r

r e p o r te d that ice

cream

and M e i s e r ,

1948; and M e i s e r ,

(1940) and R a m s e y

This

within u s u a l

shown by i c e

c r e a m i n u n w a xe d p a p e r c o n t a i n e r s will n e a r l y

in g r e a t e r

shrinkage.

s h r i n k a g e a c c o r d i n g to s e v e r a l

the s h r i n k a g e

1947; B e n d i x e n ,

A c c o r d i n g to E r b

than th e r e

stated that h e a t shock e n c o u rag e s

1940; Dahle and M e i s e r ,

1947; R a m s e y

con­

1940) s t a t e d

likely to c a u s e

t hu s the h i g h e r the t e m p e r a t u r e

tem peratures,

1947) c o n c l u d e d

a g r e e m e n t a m o n g the v a r i o u s w o r k e r s

These auth ors

shrinkage;

ice

and M e i s e r ,

c o n c e r n i n g the e f f e c t of i n g r e d i e n t s .

that p r e s s u r e

S till a n o t h e r

and C o n t a i n e r s on S h r i n k a g e

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

(1946) found t h a t a d d e d c a l c i u m

r e d u c e d the t e n d e n c y t o w a r d s h r i n k a g e .

g r o u p of w o r k e r s

shrinkage.

(1947), who

p l a c e d in c o n t a i n e r s w hic h w e r e

l in e d with

c a s e i n glue,

waxed p a p e r ,

pliofilm,

sh rinkage than unlined co n tain e rs

and a l u m i n u m f oil e x h i b i t e d l e s s

or containers

l i n e d only with

parchm ent paper.
S h r i n k a g e of i c e
to Meir ser (195 0).
lost m o re

cream is

r e l a t e d to m o i s t u r e

loss,

according

He found t h a t i c e c r e a m i n u n t r e a t e d c o n t a i n e r s

w e i g h t a nd sh o w e d g r e a t e r

p a c k a g e d in t r e a t e d

s h r i n k a g e t h a n did i c e

cream

( p a r a f f i n e d o r lined) c o n t a i n e r s .

P ro te in Fractionation P ro c e d u re s

The p r o t e i n f r a c t i o n a t i o n p r o c e d u r e
i s t h a t p u b l i s h e d by Ro w la nd (1933,
t h e s e five p u b l i c a t i o n s ,

1937a,

commonly used for m ilk
1937b,

1938a,

1938b).

In

R o w la nd d e s c r i b e d a m e t h o d f o r p r e c i p i t a t i n g

c a s e i n by a d j u s t i n g the pH of m i l k to 4.5 to 4.7 with a n a c e t i c
a c id -a c e ta te buffer.

H e a t - c o a g u l a b l e p r o t e i n s w e r e t he n p r e c i p i t a t e d

by a d j u s t i n g the pH of m i l k o r whey to 4.75 to 4.8 0 and h e a t i n g to
100°

C. f o r

filtrate

10 m i n u t e s .

N o n p r o t e i n n i t r o g e n w a s o b t a in e d i n the

f r o m m i l k when 15 p e r c e n t t r i c h l o r o a c e t i c a c i d w as u s e d to

precipitate

a l l of the p r o t e i n s .

The n i t r o g e n in the n u m e r o u s f r a c ­

ti o n s o b t a i n e d w a s d e t e r m i n e d by the s t a n d a r d K je ld a h l p r o c e d u r e .
R ow la nd d e v o t e d c a r e f u l study to the m e t h o d s d e s c r i b e d abov e,
p u b l i s h i n g c o n s i d e r a b l e d a t a to p r o v e t h e i r a c c u r a c y and r e p r o d u c i ­
bility.

H o w e v e r , he a l s o p r o p o s e d a m e t h o d f o r obta ining globulin

10
w ith m a g n e s i u m
little

sulfate

(Rowland,

1938a), f o r w hich he p r e s e n t e d

substantiating data.
T he p r o c e d u r e

of Ro wla nd (1938a) i s

s u m m a riz e d briefly b e ­

low:
I.

Total-protein:
T r a n s f e r m i l k d i r e c t l y to a K j e l d a h l f l a s k and d e ­
t e r m i n e n i t r o g e n c o n t e nt .

II.

Noncasein nitrogen:
A d j u s t pH of m i l k to 4.6 with a c e t i c a c i d - a c e t a t e
buffer.

F ilter;

t r a n s f e r f i l t r a t e to a K j e ld a hl f l a s k

and d e t e r m i n e n i t r o g e n p r e s e n t .
III.

Nonprotein:
Precipitate

a l l of the p r o t e i n s f r o m m i l k with 15

percent trichloroacetic
to a K j e ld a h l f l a s k ,
IV.

a c id .

Filter;

tra n s fe r filtrate

and d e t e r m i n e n i t r o g e n .

H eat- coagulable:
A d j u s t pH of c a s e i n - f r e e
4.80.

filtrate

( f r o m II) to 4.75 to

H e a t to 100° F . f o r 10 m i n u t e s .

Filter;

t r a n s f e r f i l t r a t e to K je ld ah l f l a s k and d e t e r m i n e
nitrogen.

11
V.

G lo bu li n:
A d j u s t t h e pH of t h e c a s e i n - f r e e f i l t r a t e
6.8 to 7.2.

S a t u r a t e w i th m a g n e s i u m

sulfate and

a l l o w to s t a n d a t r o o m t e m p e r a t u r e f o r
hours.

( f r o m II) to

several

F i l t e r ; t r a n s f e r p r e c i p i t a t e and f i l t e r p a p e r

to a K j e l d a h l f l a s k a n d d e t e r m i n e n i t r o g e n .
The a m o u n t s

of n i t r o g e n , a f t e r c a l c u l a t i o n , w e r e :

T otal-protein = I
Casein = 1 - 1 1
H e a t - c o a g u l a b l e = II - IV
Globulin = V
A l b u m i n = 11 - (IV + V)
N o n p r o t e i n = III
Row land's
O v e r m a n (1940).

m e t h o d (1938a) w a s m o d i f i e d by M e n e f e e and
However,

th e ir m odificatio ns w e re

concerned

m a i n l y w ith the d e t e r m i n a t i o n of t o t a l n i t r o g e n .
T he g l o b u l i n d e t e r m i n a t i o n m e t h o d a s p r o p o s e d by R o w l a n d
m a y b e o p e n to c r i t i c i s m .

B l o c k (1933) s t a t e d , b e f o r e

Rowland's

p r o c e d u r e w a s p u b l i s h e d , t h a t the t e m p e r a t u r e m u s t be c o n t r o l l e d
a t 25 ± 2° C. b e f o r e a c o n s t a n t y i e l d of g lo b u l i n c ould be o b t a i n e d
by m a g n e s iu m
O verm an,

sulfate p recipitation.

and T r a c y

According

to

Menefee,

(1941) a nd A s h w o r t h and Van O r d e n (1943), the

g l o b u l i n d e t e r m i n a t i o n a s o u t l i n e d by R o w l a n d (1938a) i s n o t

12
sufficiently
are

a c c u ra te for

such sm a ll quantities

of g l o b u l in n i t r o g e n a s

obtained f r o m milk.
M ore

recently, P ille m e r

and H u t c h i n s o n (1945) h a v e d e v e l o p e d

a m e t h o d of p r e c i p i t a t i n g g lo bu lin f r o m h u m a n b lo od s e r u m u s i n g a
40 p e r c e n t c o n c e n t r a t i o n

of m e t h a n o l .

m e th a n o l stand fo r thirty m in u tes
off th e p r e c i p i t a t e d globulin.
w ith m i l k by K e m p (1947).

T h e y l e t the

serum

p lu s

a t 0° to 1° C. an d t h e n f i l t e r e d

T h i s m e t h o d w as l a t e r m o d i f i e d f o r u s e
He r e d u c e d the c o n c e n t r a t i o n of m e t h a n o l

to 25.9 p e r c e n t a nd l e t the p r e c i p i t a t e f o r m f o r f o r t y m i n u t e s
to 5°

a t 0°

C. b e f o r e f i l t e r i n g .
Aschaffenburg

(1946) a nd W e i n s t e i n ,

Duncan,

and T r o u t (1951)

published m ethods f o r isola ting a ''m in o r p ro te in '' f ra c tio n fro m
m i l k , b e l i e v e d to be c o m p o s e d of m i l k p r o t e i n s
T h i s f r a c t i o n w a s p r e c i p i t a t e d by f i r s t r e m o v i n g

and ' ' p r o t e o s e . ' '
c a s e i n and the

h e a t - c o a g u l a b l e p r o t e i n s f r o m the m i l k and t h e n s a t u r a t i n g the r e ­
sulting

s e r u m with a m m o n i u m

sulfate.

T h e s e a u t h o r s found t h a t

l

this n itro g en fra c tio n constituted f ro m

0.1 to 3.0 p e r c e n t of the

total m ilk p ro tein s.
M an y o t h e r a u t h o r s h av e p u b l i s h e d m e t h o d s f o r f r a c t i o n a t i n g
the p r o t e i n s in m i l k ;
Jones

a nd L i t t l e

A s h w o r t h (1945,

Howe

(1921); M o i r (1931a,

(1933); P a l m e r

1931b,

1931c);

(1934); L e v i t o n (1938); H a r l a n d and

1947); B a i n a nd D e u t s c h (1948); K e m p (1950);

K em p ,

13
Johnson,

and S w a n s o n (1950);

and Macy
to i c e

(1941).

Beach,

B e r n s t e i n , Hoffman,

Teague,

H o w e v e r , t h e s e m e t h o d s w e r e n o t found a p p l i c a b l e

c r e a m in t h i s

stu d y .

Sum m ary

From
little

a r e v i e w of the l i t e r a t u r e , i t i s

ag reem en t among re s e a rc h w orkers

e n t m i x i n g r e d i e n t s upon s h r i n k a g e .
jority

of a u t h o r s ,

an i n c r e a s e

a s to the e f f e c t of d i f f e r ­

However,

in t o t a l

evident that th e re is

a c c o r d i n g to a m a ­

s o l i d s o r an e x c e s s i v e i n c r e a s e

of any one c o n s t i t u e n t a p p e a r s to b e r e l a t e d to i n c r e a s e d
M ore

r e c e n t work in d icates

t w e e n the m i x p r o t e i n s
It i s g e n e r a l l y
crease

shrin kage

w ill s h rin k m o r e

shrinkage,

that th e r e m a y be a r e la tio n s h ip b e ­

and i c e

cream

shrinkage.

accepted that higher

a nd t h a t i c e

cream

storage

tem peratures

in u n tr e a te d p a p e r

in­

containers

t h a n if the p r o d u c t w e r e in m e t a l o r i n t r e a t e d

paper containers.
A lth ou gh R o w l a n d ' s p r o c e d u r e f o r n i t r o g e n f r a c t i o n a t i o n and
d e t e r m i n a t i o n i s u s e d quite w id ely in a n a l y z i n g m i l k ,
to be r e a s o n a b l e

doubt a s

t e r m i n i n g globulin.

to the a c c u r a c y

there

seem s

of h i s p r o c e d u r e f o r

de­

P L A N OF E X P E R I M E N T

T h e c h a n g e s o c c u r r i n g i n the
ice

cream

structure

a n d c o m p o s i t i o n of

w h ic h c a u s e i t to s h r i n k o r l o s e v o l u m e h a v e n ot b e e n

d e t e r m i n e d a s y e t.

The l i t e r a t u r e

does not contain c o m p le te

r e l a t i v e to the n i t r o g e n d i s t r i b u t i o n of i c e
individual valu es fo r casein ,

albumin,

cream ,

data

although some

globulin, a nd n o n p r o t e i n n i t r o ­

gen have been published.
T he o b j e c t i v e

of t h i s r e s e a r c h w a s to o b t a i n a c o m p l e t e

of d a t a c o n c e r n i n g the n i t r o g e n d i s t r i b u t i o n i n i c e
th o u g h t t h a t t h e s e

cream .

d a t a would b e of v a l u e in solving the

set

It w a s

shrinkage

p r o b l e m , p a r t i c u l a r l y if the i n f l u e n c e of the t i m e of s t o r a g e a nd the
type of c o n t a i n e r c ou ld a l s o be d e t e r m i n e d .

Accordingly, it was

p l a n n e d to m a k e

the n i t r o g e n d i s t r i b u t i o n d e t e r m i n a t i o n s a t r e g u l a r

in te r v a ls during

storage periods

cial storage.
ice

cream

to b e

F urther,

c o m p a r a b l e in l e ng th to c o m m e r ­

the n i t r o g e n d a t a w e r e to be o b t a i n e d f r o m

s t o r e d i n d i f f e r e n t t y p e s of c o n t a i n e r s .

c o m p a r e d to c h a n g e s i n we ight,

of the i c e

cream .

total solids,

T hese data w ere
and shrin kage

GENERAL PROCEDURE

M e t h o d s of O b ta in in g a nd S t o r i n g S a m p l e s

T he i c e

cream

f ollo w in g c o m p o s i t i o n :
solids,

u s e d in this

s tu dy w a s c a l c u l a t e d to be of the

12 p e r c e n t b u t t e r f a t ,

10.5 p e r c e n t s u c r o s e ,

3.4 p e r c e n t

dextrose,

a n d 0.3 p e r c e n t g e l a t i n .

th e b a s i s

of 15 p e r c e n t s u c r o s e

11 p e r c e n t s e r u m

"S w eetose,"

T he s u g a r s w e r e

of the above c o m p o s i t i o n , w e r e

frozen cream ,

s k i m m i l k p o w d e r , whole m i l k ,

of e a c h m i x w a s

compounded fro m
sucrose,

c h e c k e d by M o j o n n i e r a n a l y s i s .

A lth ou g h t h e r e
a nd f i n a l e x p e r i m e n t s ,

a l l s a m p l e s u s e d i n any one e x p e r i m e n t w e r e f r o m
sam e

dextrose,

T he c o m p o s i t i o n , fa t, an d t o t a l s o l i d s

w e r e m i n o r v a r i a t i o n s b e t w e e n the p r e l i m i n a r y

a n d of the

c a l c u l a t e d on

sweetening equivalent.

M ixes,

' ' S w e e t o s e , 1' a n d g e l a t i n .

2.7 p e r c e n t

the s a m e m i x

com position.

T he v a n i l l a m i x w a s f r o z e n i n a Vogt c o n t i n u o u s f r e e z e r .
The

sam ples w ere

t a k e n at an o v e r r u n of a bo u t 100 p e r c e n t and

p a c k a g e d i nto p i n t n e s t y l e

containers.

The t o p s of the p i n t s w e r e

l e v e l e d w ith a s p a t u l a b e f o r e pu ttin g on the l id s .
ing a t -5°

to - 10 °

Following h a r d e n ­

F , f o r s i x t e e n to t w e n t y - f o u r h o u r s ,

w e r e p l a c e d in a n e l e c t r i c

cabinet at a te m p e r a t u re

the

sam ples

of 4° to 6° F .

16
T he

sam ples w ere

so a r r a n g e d in the c a b i n e t t h a t a l l c o n t a i n e r s

w e r e in a s i n g l e l a y e r a g a i n s t an o u t s i d e wall.
tem perature

elim inated

d i f f e r e n c e s w i t hi n the c a b i n e t a s a v a r i a b l e .

The i c e
analysis.

This

cream

was held in this

Sam ples w ere

a f t e r r e f e r r e d to a s

cabinet until r e m o v e d for

a n a l y z e d f i r s t at t w e n t y - f o u r h o u r s

z ero weeks).

In the p r e l i m i n a r y

the s a m p l e s w e r e t h e n a n a l y z e d a t f o u r , eight,
In l a t e r e x p e r i m e n t s ,

sam ples were

(here­

experim ents

and t w e l ve w e e k s .

analyzed at biweekly in te rv a ls

o v e r a tw elv e,-w ee k p e r i o d .

Sampling P r o c e d u r e

Triplicate
periods
cream

already

pints

of i c e

described.

cream

were

a n a l y z e d i n e a c h of the

The c a r t o n s w e r e

and t h r e e - s i x t e e n t h s

s t r i p p e d f r o m the i c e

of an i n c h of the p r o d u c t w a s

cut f r o m

t he top of the p i n t u s i n g a s t r a i g h t ed ge r a z o r .

Slices w ere

from three

sam ple ja r.

different pints

three portions

and p l a c e d in a g l a s s

f r o m the top of the i c e

hereafter referred

to a s the

"top,"

cream

c o n s t i t u t e d the

cut
These
sam ple,

whic h w as u s e d f o r M o j o n n i e r

a nd n i t r o g e n a n a l y s i s .
A f t e r r e m o v i n g the top, a cube
o n e - h a l f i n c h on edge w a s

of i c e c r e a m

S-pproximately

r e m o v e d f r o m the c e n t e r of the pint.

C u b e s w e r e t a k e n f r o m the t h r e e

d i f f e r e n t p i n t s of i c e

cream

and

17
pla c e d in a g la s s

sam ple ja r.

to a s th e ' ' m i d d l e "

These th ree

cubes, h e r e a f t e r r e f e r r e d

c o n s t i t u t e d the s a m p l e w h i c h w a s u s e d f o r the

M ojonnier and n itro g e n a n a ly sis.
Th e c l o s e d s a m p l e b o t t l e s w e r e h e l d a t 40° F . u n t i l m e l t e d
(a b o u t t w e n t y - f o u r h o u r s ) a n d w e r e

kept at this t e m p e r a t u r e

except

when being u se d f o r a n a ly sis.

M ojonnier A naly sis

T o t a l s o l i d s a n d f a t w e r e d e t e r m i n e d by M o j o n n i e r a n a l y s i s
a c c o r d i n g to t h e d i r e c t i o n s

as

o u t l in e d i n t h e

" In s tru c tio n Manual

f o r S e tt i n g Up a nd’' O p e r a t i n g the M o j o n n i e r M i lk T e s t e r "
The values ap p e arin g in this

s tud y a r e

(1925).

a v e r a g e s of d u p l i c a t e d e t e r ­

m inations.

N itrogen D eterm ination
*
N i t r o g e n c o n t e n t , b u t f o r the e x c e p t i o n s n o t e d b elo w , w a s
d e t e r m i n e d a c c o r d i n g to the p r o c e d u r e p u b l i s h e d by M e n e f e e and
O v e r m a n (1940) u s i n g m e r c u r i c
sm all

sam p le used,

it was n e c e s s a ry

oxide a s the c a t a l y s t .

e s p e c i a l l y the

to u s e

s a m p l e f r o m the top of the p i n t,

1 0 0 -m illilite r Kjeldahl flask s

re d u c e the re a g e n t quantities accordingly.
w a te r dilutions w e re n e c e s s a r y

Due to the

and t h e n

O t h e r m i n o r c h a n g e s in

to a d a p t the m e t h o d f o r i c e

cream .

18
P otassium

sulfate a s

r e c o m m e n d e d by R o w la nd (1938a) w a s u s e d i n ­

s t e a d of s o d i u m s u l f a t e .
T riplicate nitrogen determ inations w ere m ade
The v alu e s app ea rin g l a t e r in this

study a r e the a v e r a g e

d e te rm in a tio n s in c lo s e s t a g re e m e n t,
erages

of t h r e e

on a l l s a m p l e s .

or,

of th e two

as in m o s t c a s e s ,

the a v ­

determ inations.

Weight L o s s

Twelve

one-pint sam ples

of i c e

c r e a m w e r e w e i g h e d on a

t r i p l e - b e a m b a l a n c e a c c u r a t e to 0.1 g r a m .

The a v e r a g e of t h e s e

twelve w eights was u s e d f o r the table which a p p e a r s

l a t e r i n the

thesis.

Shrinkage M e a s u re m e n t
/

In the p r e l i m i n a r y t r i a l s ,

K

s h r i n k a g e w a s d e t e r m i n e d by v i s u a l

o b s e r v a t i o n and by m e a s u r i n g t he a m o u n t of i c e w a t e r r e q u i r e d to
f i l l the p i n t c o n t a i n e r .
Thomas,

Combs,

In l a t e r w o r k , the d i s p l a c e m e n t m e t h o d of

a nd C o u l t e r (1951) w a s fo und to b e m o r e

cible and was th e r e f o r e used.
th e

reprodu­

T h i s m e t h o d w a s m o d i f i e d following

s u g g e s t i o n of N i c k e r s o n (1952) so t h a t the d i s p l a c e m e n t of

kerosine,
values

r a t h e r than w ater, was m e a s u r e d .

a r e the a v e r a g e

of t r i p l i c a t e

All r e c o r d e d

determ inations.

shrin kage

19
EXPERIM ENTAL

D e v e l o p m e n t of N i t r o g e n F r a c t i o n a t i o n P r o c e d u r e

The f r a c t i o n a t i o n p r o c e d u r e
adapted fo r ice

of R o w la nd (1938a),

cream

as alre ad y

described,

was

w ith m o d i f i c a t i o n s in d i l u ­

t io n only.

H i s m e t h o d s f o r n o n c a s e i n , n o n —h e a t - c o a g u l a b l e , and

n o n p r o t e i n n i t r o g e n w e r e found to be r e p r o d u c i b l e .
m e t h o d of p r e c i p i t a t i n g
c u l t to r e p r o d u c e .
Kemp

g l o b u l i n w ith m a g n e s i u m

Methanol precipitation,

(1947) w a s t h e n t r i e d .

m e t h a n o l on m e l t e d i c e

sulfate was diffi­

a s r e c o m m e n d e d by

This p ro c e d u re,

cream ,

u sin g

25.9 p e r c e n t

r e s u l t e d in a s u s p e n s i o n of a l m o s t

c o l l o i d a l d i m e n s i o n s w h i c h w a s d i f f ic u l t to f i l t e r .
Kjeldahl a n a ly sis

However, his

of t h i s p r e c i p i t a t e

gave e r r a t i c

A l s o , the
results.

In v i e w of t h e s e f in d i n g s , i t w a s th ou g h t b e s t to go b a c k to
t he 40 p e r c e n t m e t h a n o l c o n c e n t r a t i o n w h ic h P i l l e m e r
(1945) h a d o r i g i n a l l y p r o p o s e d .

a nd H u t c h i n s o n

T h u s the p r o c e d u r e of K emp (1947)

w a s found to be r e p r o d u c i b l e w hen the m e t h a n o l c o n c e n t r a t i o n was
changed fro m

25.9 to 40 p e r c e n t .

Prelim inary
precipitate

work indicated that tr ic h lo ro a c e tic

to f o r m i n the f i l t r a t e w h ic h w a s f r e e

heat-coagulable proteins.
cipitates

only l a r g e ,

Sin ce t r i c h l o r o a c e t i c

protein-like m olecules

acid caused a

of c a s e i n and

acid supposedly p r e ­

and s i n c e t h i s f i l t r a t e

20
was free

of the m a j o r m i l k p r o t e i n s , i t w a s t h o ug h t t h a t t h i s p r e ­

c i p i t a t e w a s the m i n o r p r o t e i n o r p r o t e o s e f r a c t i o n t h a t As chaff e n b u r g
(1946) and W e i n s t e i n e t a l.

(1951) h a d i s o l a t e d .

t h a t 40 p e r c e n t m e t h a n o l a l s o
which in dic ated that p a r t or

L a t e r i t w a s found

c a u s e d a p r e c i p i t a t e i n t h i s whey,

a l l of the m i n o r p r o t e i n s

or proteose

f r a c t i o n h a d b e e n p r e c i p i t a t e d w ith the g lo b u lin f r a c t i o n .
procedure,
cipitating
be

which was
some

considered

supposedly

s p e c i f i c f o r globulin, w a s a l s o p r e ­

of the m i n o r p r o t e i n s ,

the g lo bu lin v alu e could n ot

accurate.

A ccordingly,

a n o t h e r s t e p w a s a d d e d to the p r o c e d u r e ,

of d e t e r m i n i n g the m i n o r p r o t e i n o r p r o t e o s e f r a c t i o n .
d one , u s i n g the

Sinc e the

that

T h i s was

s a m e m e t h o d a s t h a t u s e d to p r e c i p i t a t e g l o b u li n (40

p e r c e n t m e t h a n o l a t 0° to 5° C.).

S ince the f r a c t i o n c a l l e d globulin

w a s o b t a i n e d f r o m whey w h i c h w a s f r e e

of c a s e i n only, the f r a c t i o n ,

w h i c h w i ll h e r e a f t e r be c a l l e d m i n o r p r o t e i n , w as o b t a i n e d f r o m the
filtrate,

w h ic h w a s f r e e

of c a s e i n a nd h e a t - c o a g u l a b l e p r o t e i n s .

a d d i t i o n to b e i n g u s e d a s
p r o t e i n p r e s e n t i n the i c e
globulin figure.

The

an i n d i c a t i o n of the a m o u n t s of m i n o r
cream ,

casein-free

p r e c i p i t a t e d f r o m the f ilt r a t e f r e e
teins ,

t h i s v alu e w as u s e d to c o r r e c t the

c o r r e c t e d glo b u lin va lu e , then,

nitrogen precipitated from

In

whey, m i n u s

e q u a l e d the
the n i t r o g e n

of c a s e i n and h e a t - c o a g u l a b l e

pro­

21
Cone a nd A s h w o r t h (1947) d e v e l o p e d a m e t h o d f o r d e t e r m i n i n g
the

s o l u b i l i t y of m i l k p o w d e r s .

T h i s p r o c e d u r e w a s m o d i f i e d a nd

u s e d i n t h i s w o r k to d e t e r m i n e the w a t e r - s o l u b l e n i t r o g e n of i c e
cream .

I t w a s h o p e d t h a t s u b t r a c t i o n of the w a t e r - s o l u b l e n i t r o g e n

f r o m the t o t a l n i t r o g e n would p r o v i d e a n i n d i c a t i o n a s to the a m o u n t
of c a s e i n w h i c h h a d b e e n d e n a t u r e d .
T h e m e t h o d c o n s i s t e d of w eig h in g Z g r a m s

of m e l t e d i c e

cream

i n t o a 50 m i l l i l i t e r v o l u m e t r i c f l a s k a n d m a k i n g up to v o l u m e with
distilled w ater.

A f t e r t h o r o u g h m i x i n g , t r a n s f e r the w a t e r - i c e

. m i x t u r e to a 50 m i l l i l i t e r

cream

c e n t r i f u g e tube a nd s p i n i n a B a b c o c k

centrifuge fo r fifteen m in u tes.

T he n, t r a n s f e r

5 m illiliters

of the

s u p e r n a t a n t l iq u i d to a 100 m i l l i l i t e r K j e l d a h l f l a s k and d e t e r m i n e
- t h e a m o u n t of n i t r o g e n i n the s a m e m a n n e r a s f o r t o t a l n i t r o g e n (I).
With t h e s e m o d i f i c a t i o n s , the n i t r o g e n f r a c t i o n s
in this

determ ined

s tu d y w e r e : ’
I.
II.
III.
IV.
V.
VI.
VII.

Total nitrogen
N oncasein n itrogen
N onprotein nitrogen
N o n —h e a t - c o a g u l a b l e n i t r o g e n
G l o b ul i n p lu s m i n o r - p r o t e i n n i t r o g e n
M in o r -p ro te in nitrogen
W a te r-so lu b le nitrogen

C a l c u l a t i o n of the v a r i o u s n i t r o g e n f r a c t i o n s t h e n b e c o m e s :
Total n itrogen = I
W a t e r - i n s o l u b l e n i t r o g e n = I - VII
C asein = 1 - 1 1

22
H e a t - c o a g u l a b l e = II - IV
G l o b u l i n = V - VI
A l b u m i n = (II - IV) - (V - VI)
M i n o r - p r o t e i n = VI
N o n p r o t e i n = III
The t e r m s
are

u s e d to d e s c r i b e

the v a r i o u s n i t r o g e n f r a c t i o n s

n ot m e a n t to be a b s o l u t e n o m e n c l a t u r e .

fra c tio n labeled

cream .

It i s

m ig h t contain som e nitrogen,

are

the

' ' g l o b u l i n " i s n o t n e c e s s a r i l y a l l of the g lo b ul i n s

p r e s e n t in the ic e

These te rm s

F o r example,

also possible that this fraction

which would be d e f i n e d a s a lb u m i n .

a r e , f o r the m o s t p a r t ,

u s e d h e r e f o r the

conventional designations,

and

s a k e of c o n v e n i e n c e .

C o m p a r i s o n w ith D a t a i n the L i t e r a t u r e

A s p r e v i o u s l y p o i n t e d out, the l i t e r a t u r e
com plete n itro g en distribution data f o r ice

d o e s n o t c o n ta in

cream .

Therefore,

o r d e r to c h e c k the p r o c e d u r e i t w a s a p p l i e d to m i l k ,
sults

c o m p a r e d to t h o s e

Menefee, O v erm an ,
are

in

and the r e ­

of S h a ha ni and S o m m e r (1951) and of

and T r a c y

(1941).

In T a b le

1, t h o s e v a l u e s

s ho w n f o r w h ic h c o m p a r a b l e v a l u e s a p p e a r e d in the l i t e r a t u r e .
Total,

c a s e i n , h e a t - c o a g u l a b l e , and n o n p r o t e i n n i t r o g e n v a l u e s

o b t a i n e d by the p r o c e d u r e f o r i c e
c o r d e d by Sh ah a ni and S o m m e r

cream

a re higher than those

re­

(1951), b u t l o w e r t ha n the v a l u e s

of

23
Table

1.

C o m p a r i s o n of n i t r o g e n v a l u e s o b t a i n e d on p a s t e u r i z e d
h o m o g e n i z e d m i l k , w i th l i t e r a t u r e v a l u e s (in m g . p e r 100
m l . of m i l k ) .

N itrogen
/F raction

Ice C r e a m
Procedure

S h a ha n i and
S o m m e r (1951)*

Total

521

464

536

C asein

418

379

427

H eat-coagulable

56

41

66

Albumin

19

29

49

Globulin

37

12

17

N onprotein

27

22

29

Average

of t h r e e

M e n e f e e e t al.
(1941)2

sam ples.

H o m o g e n i z e d a t 2,500 l b s . p r e s s u r e .

M e ^ e f e e e t a l.

(1941).

f a l l w i t h in t h e r a n g e

I t would s e e m , t h e r e f o r e ,

that these values

of n o r m a l v a r i a t i o n i n m i l k .

T h e v a l u e f o r the m i n o r p r o t e i n f r a c t i o n i n t h i s
on m i l k w a s

13 m i l l i g r a m s p e r c e n t .

When c a l c u l a t e d on the b a s i s

of 10 p e r c e n t n i t r o g e n , a s found by W e i n s t e i n e t al.
equals

0.13 g r a m s

of p r o t e i n i n 100 g r a m s

c l o s e a g r e e m e n t w ith the
(1951).

same tria l

(1951), t h i s

of m i l k , w h ic h i s in

0.10 p e r c e n t o b t a i n e d by W e i n s t e i n e t al.

W hen c a l c u l a t e d on the b a s i s

of 13.95 p e r c e n t n i t r o g e n a s

r e p o r t e d b y A s c h a f f e n b u r g (1946), i t e q u a l s
w hich is

0.093 p e r c e n t p r o t e i n ,

a l s o v e r y c l o s e to t h e y i e l d of W e i n s t e i n e t a l .

T h e v a l u e o b t a i n e d f o r g l o b ul i n i s h i g h e r t h a n t h o s e v a l u e s
r e p o r t e d by M e n e f e e

ejt al.

the v a l u e f o r a l b u m i n i s

(1941) an d S h ah a n i a nd S o m m e r (1951);

also co rrespondingly lower.

Evidently,

40 p e r c e n t m e t h a n o l p r e c i p i t a t e s m o r e p r o t e i n t h a n d o e s
with m a g n e s iu m

s u l f a t e a s u s e d by M e n e f e e e t al.

saturation

(1941), o r 25.9

p e r c e n t m e t h a n o l u s e d by S h ah a ni and S o m m e r (1951).

However,

a s m e n t i o n e d p r e v i o u s l y , n e i t h e r of t h e s e l a t t e r two p r o c e d u r e s
w o u l d g ive a r e p r o d u c i b l e v a l u e w h en a p p l i e d to m e l t e d i c e

cream .

Experim ental E r r o r

In the c o u r s e

of c o l l e c t i n g d a t a , t h e r e w e r e v a r i a t i o n s b e ­

t w e e n r e p l i c a t e d e t e r m i n a t i o n s on the s a m e s a m p l e .

The m a x i m u m

v ar^ -tio n s which o c c u r r e d fo r each nitrogen d eterm in atio n a r e
co rd ed below in t e r m s

of m i l l i g r a m s p e r

a n d i n p e r c e n t of t o t a l n i t r o g e n .

re­

100 g r a m s of i c e c r e a m

25
N itrogen F ra c tio n
I.
II.
III.
IV.
V.
VI.
VII.

% Total

M g .%

T o ta l
N oncasein
N onprotein
N on —h e a t - c o a g u l a b l e
G l o b u l i n a nd m i n o r - p r o t e i n
M inor-protein
W a te r- soluble

2.4
0.5
2.3
0.5
1.0
0.6
1.1

16.0
3.0
15.0
3.0
6.0
4.0
7.0

* C a l c u l a t e d on the b a s i s of the a v e r a g e a m o u n t of t o t a l
n i t r o g e n p r e s e n t d u r i n g the tw elv e w ee k s t o r a g e p e r i o d .

The e r r o r ,
determ inations
largest e r r o r

w hic h m i g h t be due to v a r i a t i o n s b e t w e e n r e p l i c a t e

on e a c h c a l c u l a t e d n i t r o g e n f r a c t i o n ,
which e n t e r e d into the c a l c u l a t i o n .

n itro g e n fra c tio n s in this
N itrogen F ra c tio n
Total
W ate r - i n s o l u b l e
C asein
H eat- coagulable
G l o b ulin
Albumin
M inor-protein
N onprotein
Unaccounted

the n b e c o m e s the

The f i g u r e s f o r the

study a r e :
Mg.fo
16.0
16.0
16.0
3.0
6.0
6.0
4.0
15.0
16.0

% Total
2.4
2.4
2.4
0.5
1.0
1.0
0.6
2.3
2.4

26
RE S U L T S

R e l a t i o n of S h r i n k a g e , W e i g h t L o s s ,
and T o t a l N i t r o g e n

Th e d a t a g a t h e r e d in t h i s
latio nship

of the i c e

t h a t b oth t o t a l s o l i d s
storage increased,
ship.

Since t h e s e

his m o re

s tu dy i n d i c a t e d t h a t a d i r e c t r e ­

e x i s t e d b e t w e e n the t o t a l s o l i d s

p i n t a nd w e i g h t l o s s

T o t a l S o li d s ,

cream .

c o n t e n t of the top of the

It c a n be

se e n in Table

2

and w e i g h t l o s s i n c r e a s e d a s the l e n g t h of
S e i f e r t (1951) a l s o d e m o n s t r a t e d t h i s r e l a t i o n ­

d a t a a r e i n a g r e e m e n t with S e i f e r t ' s ,

d e ta il e d findings w e r e

th o u g h t u n n e c e s s a r y

and s i n c e

a v a i l a b l e f o r r e f e r e n c e , i t w as

to o b t a i n m o r e i n f o r m a t i o n of t hi s type in th is

study.

Table

2.

C o m p a r i s o n of t o t a l
d u r i n g s to r a g e .

s o l i d s a nd w ei g h t l o s s of i c e

cream

W ee ks of S t o r a g e
D eterm ination

Total solids

(% )

W e ig h t l o s s
(gm. p e r pint)

0

4

8

38.44

38.97

39.63

42.23

2.6

5.1

7.5

0

12

27
F u r t h e r r e s e a r c h re v e a le d that a s i m i l a r rela tio n sh ip existed
b e t w e e n t o t a l s o l i d s a nd t o t a l n i t r o g e n general,

3 in d ic a te s that, in

a n i n c r e a s e i n t o t a l s o l i d s w a s a c c o m p a n i e d by a n i n c r e a s e

in total nitrogensolids

Table

Values in this table also indicated that both total

and total n itro g e n i n c r e a s e d m o r e

c a rto n than at the m id d le.

r a p i d l y a t t h e top of the

This difference in total solids between

the top a n d t h e m i d d l e of t h e p i n t s a m p l e i s a l s o i n a g r e e m e n t with
the f i n d i n g s of S e i f e r t (1951).

Table

3.

C o m p a r i s o n of t o t a l s o l i d s a n d t o t a l n i t r o g e n of i c e
d u r i n g s t o r a g e (top a nd m i d d l e of p i n t s a m p l e s ) .

Top
W e e k s of
Storage

cream

M id d le

Total
S o l i ds (%)

Total
N . (M g.% )

Total
S o lid s (%)

Total
N.(Mg.ft)

0

37.41

586

37.11

587

4

4 0.6 4

626

37.95

565

8

39.59

680

36.46

618

12

41.59

697

38.54

633

/

As was m en tio n ed e a r l i e r ,

the m e t h o d of m e a s u r i n g

shrin kage

by f i l l i n g the v o l u m e l o s t i n the p i n t c a r t o n with d i s t i l l e d w a t e r i s
s u b j e c t to c r i t i c i s m .

T h i s m e t h o d of s h r i n k a g e m e a s u r e m e n t w a s

28
u s e d i n c o n j u n c t i o n w ith the
2 a n d 3.

Values obtained fo r duplicate

average figures w ere
trials
the

s t u d i e s f o r w h ich d a t a a p p e a r in T a b l e s

erratic.

However,

i n d i c a t e d t h a t the v o l u m e l o s s

storage period,

ge n.

These

as

are

who p u b l i s h e d a n e x h a u s t i v e

and

v i s u a l o b s e r v a t i o n f o r both

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

did w e i gh t l o s s ,

observations

sam ples varied greatly,

total solids,

a nd t o t a l n i t r o ­

s i m i l a r to t h o s e of M e i s e r

(1950),

study c o n c e r n i n g the r e l a t i o n s h i p b e ­

t w e e n w e i g h t an d v o l u m e l o s s e s in i c e

cream .

C o n t a i n e r Study

This

c o m p a r i s o n c o n c e r n e d the d i f f e r e n c e s whic h o c c u r r e d

i n the n i t r o g e n d i s t r i b u t i o n due to the type of c a r t o n .
cream

w a s d i v i d e d into two l o t s ;

The i c e

one l o t w as p a c k a g e d i n u n t r e a t e d

p a p e r c o n t a i n e r s , w h e r e a s the o t h e r lo t w as p a c k a g e d in p a p e r c o n ­
tainers
tops

w h i c h h a d b e e n t r e a t e d i n s i d e a nd o u t with p a r a f f i n .

of t h e s e

s a m p l e s w e r e a n a l y z e d f o r n i t r o g e n d i s t r i b u t i o n at

four-w eek intervals.
4 records
gram s

The d a t a a r e

the d a t a i n t e r m s

of i c e

cream .

th e n i t r o g e n v a l u e s

are

shown i n T a b l e s

of m i l l i g r a m s

4 and 5.

of n i t r o g e n p e r

Table

100

T a b l e 5 c o n t a i n s the s a m e data; h o w e v e r ,
e x p r e s s e d a s p e r c e n t of t o t a l n i t r o g e n .

A lth ou gh the r e s u l t s
facts w ere

The

evident f r o m this

were

somewhat variable,

study.

The p e r c e n t a g e

a few g e n e r a l
of t o t a l n i t r o g e n

29
Table

4.

E f f e c t of t r e a t e d a n d u n t r e a t e d c o n t a i n e r s on n i t r o g e n
d i s t r i b u t i o n of i c e c r e a m d u r i n g s t o r a g e (top of p in t
s a m p l e s in m g . p e r 100 g m. of i c e c r e a m ) .

W e e k s of Sto rag'e
N itrogen F ractio n

U ntreated C onta iners

T r e a ted C o n t a i n e r s

0

4

8

12

0

4

8 ’

12

Total

633

646

663

753

586

626

68 0

697

Casein

497

498

504

593

452

481

518

544

33

31

35

35

27

24

42

22

Albumin
G l o b u li n

4
29

15
16

17
18

22
13

15
12

4
20

24
18

Nonprotein

47

49

63

73

55

64

62

77

M inor-protein

32

48

49

46

42

35

39

32

Unaccounted

24

20

12

6

10

22

19

22

98

94

100

17

69

49

66

H e a t- coagulable

Wa t e r - i n s o l u b l e

—

❖

Value no t o bta in e d.

— —

— —

30
Table

5.

E f f e c t of t r e a t e d and u n t r e a t e d c o n t a i n e r s on n i t r o g e n
d i s t r i b u t i o n of i c e c r e a m d u r i n g s t o r a g e (top of p in t
s a m p l e s , e x p r e s s e d a s °]o of t o t a l n i t r o g e n ) .

W e e k s of S t o r a g e
N itrogen
F raction

Untreated Containers

T re a te d C ontain ers

0

4

8

12

0

4

8

12

78.5

77.1

76.0

78.7

77.1

77.0

76.2

78.1

H eatcoagulable

5.2

4.8

5.3

4.6

4.6

3.8

6.2

3.2

Albumin
Globulin

0.6
4.6

2.3
2.5

2.6
2.7

2.9
1.7

2.6
2.0

0.6
3.2

3.5
2.7

---*

N onprotein

7.4

7.6

9.5

9.7

9.4

10.2

9.1

11.1

M inorprotein

5.1

7.4

7.4

6.1

7.2

5.6

5.7

4.6

Unaccounted

3,8

3.1

1.8

0.9

1.7

3.4

2.8

3.0

--*

15.2

14.2

13.3

2.9

11.0

7.2

9.5

C asein

W aterinsoluble

*

Value n o t o b t a in e d .

31
increased m ore

w ith l e n g t h of s t o r a g e i n the u n t r e a t e d c a r t o n s

i t did i n the t r e a t e d

cartons.

t w e e n t r e a t e d a nd u n t r e a t e d
consistent.

This was

A lth ou g h the a m o u n t of d i f f e r e n c e b e ­
carto n s was

sm all,

the t r e n d s

r e f l e c t e d in g r e a t e r sh rin k ag e

i n th e u n t r e a t e d c o n t a i n e r s .

than

of i c e

were
cream

Sh rin kage o b s e r v a tio n s w e r e again

visual.
The a m o u n t of n i t r o g e n i n the v a r i o u s f r a c t i o n s
during

storage.

However,

Table

f r a c t i o n s i n c r e a s e d no m o r e

5 indicates

th at, in g e n e r a l , t h e s e

t han did t o t a l n i t r o g e n .

th e p e r c e n t w h ic h t h e v a r i o u s f r a c t i o n s

also i n c r e a s e d

In o t h e r w o r d s ,

c o n s t i t u t e d of the t o t a l n i t r o ­

g e n did n o t v a r y m a t e r i a l l y .
T h e r e w e r e i n d i c a t i o n s t h a t the h e a t - c o a g u l a b l e

and globulin

nitrogen m ight decrease

with t i m e ,

r e f l e c t e d i n an i n c r e a s e

in the a m o u n t s of a l b u m i n and n o n p r o t e i n

nitrogen.

V ariations,

experim ental e rro r;

and t h a t this d e c r e a s e m i g h t be

f o r the m o s t p a r t ,

w e r e w ithin the l i m i t s of

t h u s , i t w as t h o u g h t t h a t t h e s e p o s s i b l e

trends

w a r r a n te d f u r th e r investigation.

C o m p a r i s o n of Top and Middle of S a m p l e

D i f f e r e n c e s in n i t r o g e n d i s t r i b u t i o n b e t w e e n the top and
m iddle
The ice

of p in t s a m p l e s w e r e
cream

was

c o m p a r e d in t h i s p o r t i o n of the study.

s t o r e d in u n t r e a t e d p a p e r c o n t a i n e r s in o r d e r

32
to o b t a i n a s m u c h s h r i n k a g e

as possible.

t r i a l would r e v e a l w h e t h e r s h r i n k a g e w a s
enon o r w heth er

It w a s h op e d t h a t t h i s
entirely

a surface phenom­

c h a n g e s , if any, took p l a c e in the c e n t e r of the c o n ­

tainers.
These

sam ples were

twelve week sto rag e
trials

an aly zed at biweekly i n t e r v a l s

period.

N i t r o g e n d i s t r i b u t i o n d a t a in p r e v i o u s

h a d sh ow n v e r y i n c o n s i s t e n t r e s u l t s .

creasing

It w as t ho ught t h a t i n ­

the n u m b e r of o b s e r v a t i o n s o v e r the s a m e tw e lv e w e ek

period m ight rem ove
dem onstrate m o re

some

of the u n a v o i d a b l e v a r i a t i o n s

of s t o r a g e .

T h e n i t r o g e n d a t a a r e p r e s e n t e d in T a b l e s

gram s

6 is

e x p r e s s e d in t e r m s

of i c e

cream ;

Table

p e r c e n t of t o t a l n i t r o g e n .
sa m e ice

cream

a ge f i g u r e s

were

and help

c l e a r l y the t r e n d s which o c c u r r e d in the d a ta

w ith i n c r e a s e d t i m e

Table

over a

of m i l l i g r a m s

6, 7, and 8.

of n i t r o g e n p e r

100

7 p r e s e n t s the s a m e d a t a in t e r m s

of

T a b l e 8 c o n t a i n s s h r i n k a g e d a t a f o r the

o v e r the s a m e

observatio n period.

(These

shrink­

o b t a i n e d by the d i s p l a c e m e n t m e t h o d of m e a s u r e ­

m ent. )
Data in these

tables

d e m o n s t r a t e d , a s did T a b l e

t o t a l n i t r o g e n of the top of the
storage.
These

F urtherm ore,

shrin kage

3, t h a t the

s a m p l e s i n c r e a s e d with le n g th of

as to ta l solids i n c r e a s e d ,

so did s h r i n k a g e .

d a t a c o n f i r m the v i s u a l o b s e r v a t i o n s which w e r e

M4
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35
Table

8.

V o lu m e l o s s

of p i n t i c e

cream

sam ples

during

storage.

W e e k s of S t o r a g e
Vo l u m e

As m l.

lost

0

2

0

10

4

20

8

24

28

34

_
0

m a d e in e a r l i e r

The n i t r o g e n i n the v a r i o u s f r a c t i o n s

4.2

_
5.1

10

A s °Io of t o t a l v o l u m e
lost

work.

_
2.1

6

5.9

12

38

7,2

8.1

a ls o

i n c r e a s e d , b u t the p e r c e n t w h i c h they c o n s t i t u t e d of the t o t a l n i t r o ­
g en did n o t v a r y m a t e r i a l l y .
fr o m four
rem ove

(in T a b l e s

som e

I n c r e a s i n g the n u m b e r

2, 3, 4, and 5) to s e v e n i n t h i s t r i a l , h e l p e d

of the v a r i a b l e

At f i r s t glance, these

results

figures may

w hich w e r e

tween r e p lic a t e s , it is

o b ta in ed p r e v i o u s l y .

s t i l l s e e m quite i n c o n s i s t e n t , but

w h e n c o n s i d e r e d i n the l i g h t of the v a r i a t i o n s

range

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

whic h o c c u r r e d b e ­

s e e n t h a t the d a t a v a r y l i t t l e o u t s i d e of the

of e x p e r i m e n t a l e r r o r .
T he n i t r o g e n d a t a f o r the m i d d l e of the p in t did not v a r y

m aterially

d u r i n g the tw elve w e ek p e r i o d ; n e i t h e r t o t a l n i t r o g e n n o r

any of the o t h e r f r a c t i o n s
of e x p e r i m e n t a l e r r o r .

v a r i e d c o n s i s t e n t l y o u t s i d e of the l i m i t s

36
T he t r e n d s

a s to c h a n g e s i n a l b u m i n and g l o b u l i n v a l u e s ,

w h i c h w e r e i n d i c a t e d i n p r e v i o u s w o r k a n d whic h w e r e
the l i t e r a t u r e

(Dahle a n d L a n d o ,

f a i l e d to m a t e r i a l i z e i n t h e s e

r e p o r t e d in

195 0; T a r a s s u k a nd H utton ,

data.

Perhaps

i c a n t f a c t r e v e a l e d by t h e s e d a t a i s

195 0),

then, the m o s t s i g n i f ­

the a b s e n c e

of any s u c h t r e n d s .

T o t a l n i t r o g e n i n c r e a s e d , b u t the n i t r o g e n f r a c t i o n s w hich c o n s t i ­
tuted this

t o t a l did n o t v a r y i n t h e i r

r e l a t i o n s h i p to e a c h o t h e r o r

to the t o ta l.

DISCUSSION

T h e d a t a c o l l e c t e d u n d e r the c o n d i t io n s of t h is
cated a relatio n sh ip betw een total solids,
a nd s h r i n k a g e .
in the i c e
cream

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

cream increased,

decreased.

study i n d i ­

total n itr o g e n , weight lo ss,

of t o t a l s o l i d s and to ta l n i t r o g e n

the w e ig h t and v o l u m e of t h a t i c e

T h e s e f in d i n g s w e r e in a g r e e m e n t w ith the r e ­

p o r t s in the l i t e r a t u r e

(M eiser,

1950; S e i f e r t ,

1951).

A t the p r e s e n t t i m e the b a s i c knowledge of p r o t e i n s
their properties

is

and

so i n a d e q u a t e t h a t only a b s t r a c t e x p l a n a t i o n s

be o f f e r e d to e x p l a i n the n i t r o g e n d i s t r i b u t i o n d a t a .

can

To p r e s e n t a l l

the p o s s i b l e t h e o r i e s which m i g h t h e lp to e x p l a i n the d a t a r e c o r d e d
would m a k e

this d is c u s s io n volum inous;

obvious th e o rie s

will be

set forth.

so only a few of the m o r e

37
A t f i r s t g l a n c e , i t m a y be
d a t a in t h i s

s e e n t h a t the n i t r o g e n d i s t r i b u t i o n

s t u d y h a v e only a d d e d to the g e n e r a l d i s a g r e e m e n t in

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

H ow ever, this is not n e c e s s a r i l y

m a i n conclusions

m ethod.

o ft e n s m a l l e r

o b ta in e d f o r a l b u m i n and

t ha n the e x p e r i m e n t a l e r r o r of the

Menefee, O verm an,

a nd T r a c y

a n d V a n O r d e n (1943) t h a t the a c c u r a c y

(1941) a g r e e w ith A s h w o r t h
of the e x i s t i n g m e t h o d s f o r

d e t e r m i n i n g g l o b u l i n i s n o t g r e a t enough,
am ounts

One of the

w h ic h c a n b e d r a w n f r o m a study of the d a t a i s

t h a t the v a r i a t i o n s b e t w e e n a v e r a g e v a l u e s
globulin w e r e

true.

c o n s i d e r i n g the

of n i t r o g e n o b t a i n e d in t h i s d e t e r m i n a t i o n .

sm all

These auth ors

w e r e r e f e r r i n g to the m a g n e s i u m s u l f a t e m e t h o d of p r e c i p i t a t i n g
g l o b u lin ,
study.

r a t h e r t h a n the m e t h a n o l m e t h o d which w a s u s e d i n t h i s

However,

the

same

c r i t i c i s m i s a p p l i c a b l e to the m e t h a n o l

m e t h o d of d e t e r m i n i n g globulin, i n vie w of the s m a l l p e r c e n t a g e s
globulin re p o rte d .
this

relatively large

Assum ing that other w o rk ers

of

also experienced

e x p e r i m e n t a l e r r o r , m a n y of the v a r i a t i o n s

re­

p o r t e d i n th e l i t e r a t u r e m a y n o t h a ve e x c e e d e d the e x p e r i m e n t a l
error.
A nother plausible

e x p l a n a t i o n f o r the d i f f e r e n c e s b e t w e e n d a ta

r e p o r t e d in t h i s and o t h e r
ice

c re a m m ixes.

studies

Percentage

v a r y f r o m w o r k e r to w o r k e r .

c o n c e r n s the c o m p o s i t i o n of the

c o m p o s i t i o n and i n g r e d i e n t s u s e d
S k i m m i l k p o w d e r w as u s e d in the

38
m i x e s in this

st ud y , w h e r e o t h e r

T a r a s s u k and H utton,
d ensed m ilk.

1950;

authors

Thomas

Heat treatm ent,

(Dahle and L a n d o,

ejt a l . , 1951) h a v e u s e d c o n ­

such as is given s k im m ilk powder,

w i l l d e n a t u r e the whey p r o t e i n s a c c o r d i n g to H a r l a n d ,
Jenness

(1952),

a nd will i n c r e a s e

why the n i t r o g e n d i s t r i b u t i o n in i c e

suggests

cream

several reasons

s hould n o t change

(195 0) s t a t e d t h a t m a n y p r o t e i n s

n a t u r e d by r e p e a t e d f r e e z i n g a nd th awing.

He a l s o

a r e not d e ­
said that a

h i g h s o l v e n t v i s c o s i t y would i n h i b i t p r o t e i n d e n a t u r a t i o n ,
ice

c re a m is

e x tre m e ly viscous.

A further

the e f f e c t t h a t h i g h c o n c e n t r a t i o n s
of p r o t e i n s .

On t h i s

subject,

s h o w t h a t the a m i n o a c i d ,
D. g l u c o s e ,

D galactose,

C arbohydrates
from horse

and

(1940).

On the o t h e r h a n d , the l i t e r a t u r e

Haurow itz

Coulter,

the n o n p r o t e i n n i t r o g e n con te nt,

a c c o r d i n g to H o l l a n d and D a h l b e r g

rapidly .

1950;

and f r o z e n

s t a t e m e n t w a s m a d e to

of s u g a r will i n h i b i t d e n a t u r a t i o n

S c h u b e r t (1939) g i v e s e v i d e n c e to

cysteine,

will c o m b i n e with the s u g a r s ,

and l a c t o s e .

c on ta in in g a l b u m i n and g lo b u li n w e r e i s o l a t e d

s e r u m by M c M e e k i n (1940).

W e i n s t e i n e t al.

(1950)

i n d i c a t e d t h a t t h e i r m i n o r - p r o t e i n f r a c t i o n was c o m b i n e d with a
carbohydrate.

T here is,

then,

e v i d e n c e t h a t s u g a r s will c o m b i n e

w ith p r o t e i n s

and t h a t t h e s e g l u c o p r o t e i n s

a nd in m i l k .

There is

do o c c u r i n blood s e r u m

additional evidence that s u g a r s p r o te c t

39
proteins

from

d e n a t u r a t i o n ( o r c ha nge ).

protective m ech an ism is

I t m a y be p o s s i b l e

t h a t t hi s

c o n n e c t e d w it h the c o m b i n a t i o n of t h e s e two

substances.
I t s h o ul d be e x p l a i n e d t h a t a lt h o u g h the d a t a i n d i c a t e d no
c h a n g e i n the p r o t e i n s

of i c e

cream

d u r i n g tw elve w e e k s '

sto rage,

t h i s w a s n o t m e a n t to convey the though t t h a t the n i t r o g e n d i s t r i b u ­
t i o n would n e v e r
kept in c r e a s in g

c h a n ge .

If the t o t a l s o l i d s

w ith t i m e ,

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

a p o in t would be r e a c h e d e v e n tu a l l y w h e r e

t he h i g h c o n c e n t r a t i o n of s o l i d s would tend to
tein s.
this

' ' s a l t o u t 1' the p r o ­

J u s t w h e n t h i s p o i n t would be r e a c h e d i s bey on d the

s co p e of

study.
Th e r e s u l t s

of t h i s

study i n d i c a t e d t h a t the only change i n

n i t r o g e n d u r i n g a tw e lv e w e e k s t o r a g e p e r i o d wa s i t s g r a d u a l c o n ­
c e n t r a t i o n a t the top of the c o n t a i n e r .

T h is i s

shown by the i n c r e a s e

of t o t a l n i t r o g e n of the top a nd by the d a t a i n d i c a t i n g a r e l a t i v e l y
c o n s t a n t r e l a t i o n s h i p b e t w e e n the p r o t e i n f r a c t i o n s w hich m a k e up
this

t o ta l .

Since t o t a l s o l i d s and n i t r o g e n d i s t r i b u t i o n do n o t c hange

m a t e r i a l l y i n the m i d d l e

of the p int, i t follows t h a t s h r i n k a g e i s

probably a s u rfa c e phenomenon.
cates
loss

that m o is tu r e
of i c e

cream

M o s t of the e v i d e n c e to da te i n d i ­

l o s s i s r e s p o n s i b l e f o r the w ei gh t a nd v ol u m e
d u r i n g the f i r s t tw elve w e e k s of s t o r a g e .

40
A c c o r d i n g to th e l i t e r a t u r e ,
tainers

trea tin g p a p e r ice c r e a m

con­

w ith p a r a f f i n s h o u ld s lo w down the i n c r e a s e i n t o t a l s o l i d s

and sh rinkage.

The f in d i n g s of t h i s

s tud y i n d i c a t e d t h a t t h e r e

n o t too m u c h d i f f e r e n c e i n s h r i n k a g e of i c e
t r e a t e d and u n t r e a t e d

containers.

c r e a m p a c k a g e d i n the

I t m a y w ell be t h a t l o o s e fitting

l i d s on the t r e a t e d c o n t a i n e r s i n f l u e n c e d t h e s e r e s u l t s .
the l i d s w e r e t r e a t e d with p a r a f f i n ,
m oisture

A l th ough

a s . w e r e the c a r t o n s , a i r and

c o u ld Still e s c a p e a r o u n d o r f r o m u n d e r t h e s e l i d s ,

they w e re not seale d ;

was

a nd the c a r t o n s

since

w e r e , t h e r e f o r e , not c o m ­

p l e t e l y a i r tigh t.

CONCLUSIONS

T h e follow in g c o n c l u s i o n s w e r e

r e a c h e d following a study of

the d a t a o b t a i n e d u n d e r the c o n d it i o n s of t h i s i n v e s t i g a t i o n .
1.

The i n c r e a s e s i n p e r c e n t a g e s

s o l i d s of the i c e

cream

of t o t a l n i t r o g e n and t o t a l

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

d i r e c t l y to w e i g h t and v o l u m e

losses

of the i c e

cream

related
during s t o r ­

age,
Z.

T h e a m o u n t of n i t r o g e n i n the i c e

cream

at the top of

the c o n t a i n e r i n c r e a s e d d u r i n g the tw e lv e w e ek s t o r a g e p e r i o d .
ever,

the p e r c e n t w h ich the v a r i o u s n i t r o g e n f r a c t i o n s

the t o t a l n i t r o g e n did n o t v a r y m a t e r i a l l y .

How­

c o n s t i t u t e d of

41
3.
fractions

N e i t h e r t o t a l n i t r o g e n n o r any of the c o m p o n e n t n i t r o g e n
v a r i e d m a t e r i a l l y i n the m i d d l e of the p i n t of i c e

with i n c r e a s e d
4.

ice

cream
5.

s to ra g e tim e.

Shrinkage

in d icatio n s a r e

appears

that m o is tu r e

to be a s u r f a c e p h e n o m e n o n ,

and

l o s s w a s the m a i n f a c t o r g o v e r n i n g

s h r i n k a g e d u r i n g the t w e lv e w e e k s t o r a g e p e r i o d .
Less

s h r i n k a g e o c c u r r e d whe n i c e

paraffin tre a ted p ap er
paper

cream

cream

w as s t o r e d in

c o n t a i n e r s t h a n when s t o r e d i n u n t r e a t e d

containers.
6.

I m p r o v i n g the c l o s u r e s

tainers

so t h a t a t i g h t e r s e a l i s

reduce

shrinkage.

on the p a r a f f i n t r e a t e d p a p e r con­

o b t a i n e d would p r o b a b l y f u r t h e r

L I T E R A T U R E C IT E D

1.

2.

3.

4.

5.

6.

7.

8.

9.

A s c h a ff en b u rg , R .
1946
S u r fa c e A c tiv ity and P r o t e in s of M ilk .
D a ir y R e s e a r c h .
14: 3 1 6 - 3 2 9 .
A s h w o r t h , U . S ., an d V a n O r d e n , H . O.
1943
N i t r o g e n D i s t r ib u t io n in D r ie d M ilk .
T e c h n o l.
6 (5 ): 2 7 2 - 2 7 3 .
B a in , J . A ., a n d D e u t s c h , H . F .
194&
S t u d ie s o n L a c t o g l o b u l i n s .
2 2 1 -2 2 9 .

Jour.

J o u r . M ilk

A r c h . B io c h e m .

16:

B e a c h , E . F . , B e r n s t e i n , S . S ., H o ff m a n , O ., T e g u e , D . M ., an d
M a c y , I. G .
1941
D is t r ib u t io n o f N it r o g e n a n d P r o t e i n A m in o A c id s
in H u m a n a n d in C o w s ' M ilk .
J o u r. B io l. C h em .
1 3 9 : :5 7 -6 3 .
B e n d ix e n , H .
A.
1948
I c e C r e a m S h r in k a g e . I c e C r e a m
4 4 (2 ): 4 6 , 4 7 , 9 0 - 9 4 .

T rad e Jour.

B l o c k , R. J.
1933
T h e B a s i c A m in o A c id s o f S e r u m
*
B io l. C h em .
10 3 : 2 6 1 - 2 6 7 .

P r o te in s .

Jour.

C o le , W . C .
1939
F a c t o r s A f f e c t in g
3 4 (4 ): 3 2 - 3 4 .

S h r in k a g e .

Tee C r e a m F i e l d .

C o le , W . C .
1940
F a c t o r s A f f e c t in g
3 6 (4 ): 3 0 .

S h r in k a g e .

Ice C ream

F ie ld .

C o le , W . C ., a n d C h a s e , E . S .
1946
I c e C r e a m S h r in k a g e i n C o n t a in e r s . I n t e r n a t l .
A s s o c . Ic e C r e a m M fr s, 42nd A nn. C onv. P r o c .
2: 7 5 - 8 5 .

43
10.

Cone, J. F . , a nd A s h w o r t h , U. S.
1947
A New Q u a n t i t a t i v e M e t h o d f o r D e t e r m i n i n g the
S o lu bility of M i l k P o w d e r s .
J o u r . D a i r y Sci.
30: 4 6 3 - 4 7 2 .

11.

D a hl e, C. D., H a n k i n s o n , D. J . , and M e i s e r , J. A., J r .
1947
S h r i n k a g e i n I ce C r e a m .
Milk P l a n t Monthly
36(1): 3 2 -3 3 , 36-38.

12.

D a h l e , C. D., and L a n d o , J. C.
1950
R e p o r t on S h r i n k a g e .
I n t e r n a t l . A s s o c . Ic e C r e a m
M frs.
46th Ann. Conv. P r o c .
2: 71-79, 1950,

13.

D a h l e , C. D., a n d M e i s e r , J. A., J r .
1947
T he S h r i n k a g e P r o b l e m .
I n t e r n a t l . A s s o c . Ice
C r e a m M f r s . P r o c . 4 3 r d Ann. Conv.
2: 3 3-41.
E r b , J . H.
1940
C o n t r o l of S h r i n k a g e i n Ice C r e a m .
Ice C r e a m
R e v. 25(5): 33.

14.

15.

Hankinson,
1944

D, J . , and D ahle , C. D.
S h r i n k a g e D e f e c t i n Ice C r e a m .
Sou. D a i r y P r o d .
Jour.
P a r t I 36(4): 17, P a r t II 36(5) 34, 36.

16.

H a r l a n d , H. A., a nd A s h w o r t h , U. S.
1945
The P r e p a r a t i o n and E f f e c t of H e a t T r e a t m e n t on
the Whey P r o t e i n s of Milk.
J o u r . D a i r y Sci. 28:
8 7 9 -8 8 6 .

17.

H a r l a n d , H. A., and A s h w o r t h , U. S.
1947
A R a p id M e t h o d f o r E s t i m a t i o n
of Whey P r o t e i n s
a s an I n d i c a t i o n of Ba king Q u a lity of N o nf at Dry
M i l k S o l i d s.
F o o d R e s . 12: 24 7- 2 5 1 .

18.

H a r l a n d , H. A., C o u l t e r , S. T . , and J e n n e s s ,
1952
The E f f e c t of the V a r i o u s S te p s
on the E x t e n t of S e r u m P r o t e i n
Non fa t D ry Milk So lid s.
Jour.
3 68.

19.

H aurow itz,
1950

R.
i n the M a n u f a c t u r e
D e n a t u r a t i o n in
D a i r y Sci.
35: 363-

F.
C h e m i s t r y and Biology of P r o t e i n s . 374 pp. p lu s
x ii.
New Y o rk :
A c a d e m i c P r e s s Inc.
p. 131.

44
20.

H o l l a n d , R.
1940

F . , a n d D a h l b e r g , A. C.
The E f f e c t of the T i m e and T e m p e r a t u r e of
P a s t e u r i z a t i o n Upon So m e of the P r o p e r t i e s and
C o n s t i t u e n t s of M ilk.
N. Y, (Geneva) A g r . Expt.
Sta. T e c h n o l . Bui. 122, 55 pp.

21.

Howe, P .
1921

E.

22.

Jo n es, F,
1933

S., a n d L i t t l e , R. B.
P r o t e i n s of the Whey F r a c t i o n in M i l k f r o m N o r m a l
and A b n o r m a l U d d e r s .
J o u r . D a i r y Sci.
16: 101109.

23.

K e m p , A.
1947

R.

T h e Use of S o d iu m Sulfate as the G l o b u lin P r e ­
c i p i t a n t i n the D e t e r m i n a t i o n of P r o t e i n s in Blood.
J o u r . Biol. C h e m .
49: 9 3 -1 07 .

A Study of the N i t r o g e n D i s t r i b u t i o n in the M ilk of
V a r i o u s B r e e d s of D a i r y Cows.
M a s t e r 's T hesis,
Univ. of 111., U r b a n a , 111.

24.

K e m p , A. R.
1950
S e p a r a t i o n of F r a c t i o n s a nd C o m p o n e n t s of N o n C a s e i n P r o t e i n s i n Milk.
D o c t o r a t e T h e s i s , Univ.
of W i s . , M a d i s o n , Wis,

25.

K e m p, A. R., J o h n s o n , B. C., and Swanson, A. M.
1950
I s o l a t i o n of the N o n - C a s e i n P r o t e i n s of M ilk (Abst.)
J o u r . D a i r y Sci. 33: 395: M2.

26.

K o h l e r , R.
1939

27.

28.

Lando, J.
1949

F a c t o r s C a u s i n g S h r i n k a g e in I ce C r e a m .
Internatl.
A s s o c , of I ce C r e a m M f r s , 39th Ann. Conv. P r o c .
2: 2 8 - 3 5 .
C., and D a h l e , C. D.
A D i f f e r e n t A p p r o a c h to Ice C r e a m S h r i n k a g e .
C r e a m Rev. 33(3): 150, 152-155.

L e e d e r , J . G1948
P r e s e n t S t a t u s of Ice C r e a m S h r i n k a g e .
Rev. 31(8): 152.
( O r i g i n a l not s e e n . )

Ice

Ice C r e a m

45
29.

M cMeekin,
1940

30.

M e i s e r , J. A., J r .
1950
W e ig h t C h a n g e s i n P a c k a g e d Ic e C r e a m a t C a b i n e t
T em peratures.
Mich . A g r . Expt. Sta. Q u a r t . Bui,
32(4): 4 50 - 4 6 4 .

31.

M e n e f e e , S, G., a n d O v e r m a n , O. R.
1940
A S e m i m i c r o - K j e l d a h l M ethod f o r the D e t e r m i n a t i o n
of T o t a l N i t r o g e n in M ilk.
J o u r . D a i r y Sci,
23:
1 1 77 -1 1 8 5 .

32.

M e n e f e e , S. G., O v e r m a n , O. R ., and T r a c y , P . H.
1941
The E f f e c t of P r o c e s s i n g on the N i t r o g e n D i s t r i b u ­
t io n of M ilk.
J o u r . D a i r y Sci.
24: 953-968.

33.

M o i r , G. M.
1931
The D e t e r m i n a t i o n of M i l k P r o t e i n s .
III. P r o p o s e d
Method fo r Casein.
IV, The C o m b i n e d D e t e r m i n a ­
tion of A l b u m i n a n d Globulin.
V. The S e p a r a t e
D e t e r m i n a t i o n of A l b u m i n and Globulin.
A n a l y s t 5 6:
14 7- 1 4 9 , 2 2 8 - 23 5.

34.

M o j o n n i e r B r o t h e r s C o m p a ny
1925
I n s t r u c t i o n M a n u a l f o r Setting Up and O p e r a t i n g the
M o j o n n i e r Milk T e s t e r .
Bui. 101, 71 pp.
Mojonnier
B r o s . Co., C h i c a g o , 111.

35.

N ickerson,
1952

3 6.

T. L.,
P r e p a r a t i o n and P r o p e r t i e s of S e r u m and P l a s m a
Proteins,
II. C r y s t a l l i z a t i o n of a C a r b o h y d r a t e Containing Album in f r o m H o r s e S e ru m .
Jour.
A m e r . Chejna. Soc.
62: 3393-3 396.

T. A.
C o m m u n i c a t i o n to J.

R. B r u n n e r , J u n e ,

P a l m e r , A. H.
193 4
The P r e p a r a t i o n of a C r y s t a l l i n e
A l b u m i n F r a c t i o n of Cows Milk.
104: 359 -372.

1952.

G lobulin f r o m the
J o u r . B i o l. Ch e m.

46
3 7.

P illem er,
1945

38.

R a m s e y , R. J . , D r u s e n d a h l , J. G . , and L e e d e r , J. G.
1947
F a c t o r s A f fe c ti ng the S h r i n k a g e of Ice C r e a m .
I ce C r e a m Rev. 30(7): 71.

39.

R o w l a n d , S. J,
1933
T he H e a t D e n a t u r a t i o n of A lb u m in and G lo b u lin in
M ilk,
Jour. D airy R esearch .
5: 46-53.

40.

R o w la nd , S, J.
1937a
T he H e a t D e n a t u r a t i o n of A l b u m i n and G lo b u lin in
Milk.
II. D e n a t u r a t i o n a nd D e g r a d a t i o n of P r o t e i n
a t T e m p e r a t u r e s of 75-12 0° C e n t i g r a d e .
Jour.
D airy R esearch.
8: 1-5.

41.

R o w la nd , S, J.
193 7b
The Soluble P r o t e i n F r a c t i o n of Milk.
R esearch.
8: 6-14,

42.

L.,

and H u t c h i n s o n , M. C.
T he D e t e r m i n a t i o n of the A l b u m i n and G lobulin
C o n t e n t s of H u m a n S e r u m by M e t h a n o l P r e c i p i t a ­
tion.
J o u r . Biol. C h e m . 158: 29 9- 3 0 1 .

Jour,

R o w la nd , S. J.
1938a
The P r e c i p i t a t i o n of the P r o t e i n s in Milk.
D airy R e s e a r c h .
9: 30-41.

Dairy

Jour,

43.

R o w la nd , S. J.
1938b
T h e D e t e r m i n a t i o n of the N i t r o g e n D i s t r i b u t i o n i n
Milk.
J o u r . D a i r y R e s e a r c h . 9: 42-4 5.

44.

Schubert,
1939

45.

46.

M. P .
T he C o m b i n a t i o n of C y s t e i n e with S u g a r s .
B io l. C h e m . 130: &01-603.

S e i f e r t , D.
1951

Jour.

F a c t o r s A ff ec tin g I c e C r e a m P a c k a g i n g .
M aste r's
T h e s i s , M ic h. State C o l le g e , E a s t L a n s i n g , Mich,

S h a h a ni , K. M., a n d S o m m e r , H, H.
1951
The P r o t e i n and N o n - P r o t e i n F r a c t i o n s in Milk.
III. T h e E f f e c t of H e a t T r e a t m e n t s and H o m o g e n ­
ization.
J o u r . D a i r y Sci.
34; 1035-1041.

47
47.

Sheuring,
1949

J.

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