M IC R O B IO L O G IC A L S P O IL A G E O F C O T T A G E C H E E S E

By
M ILFO RD DEAN BONNER

A THESIS
S u b m i t t e d t o t h e S c h o o l f o r A d v a n c e d G r a d u a t e S t u d i e s of
M i c h i g a n S t a t e U n i v e r s i t y of A g r i c u l t u r e a n d A p p l i e 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 t h e r e q u i r e m e n t s
f o r t h e d e g r e e of

DO CTO R O F PHILOSOPHY

D e p a r tm e n t of D a ir y

19 56

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ABSTRACT

T w enty-five cu ltu res w ere isolated from
a g a r ex p o su re plates.

s p o ile d c h e e s e and

The c u ltu re s w e r e id en tified , and th e type

of s p o i l a g e p r o d u c e d b y n i n e t e e n of t h e o r g a n i s m s i n d i v i d u a l l y o r
i n c o m b i n a t i o n w i t h S. l a c t i s on s t e r i l e c o t t a g e c h e e s e c u r d w a s
d eterm in ed .

T h e effect of in c u b a tio n t e m p e r a t u r e , pH, s o d iu m c h l o r ­

ide, h e a t, c h lo r in e , q u a te r n a r y , io d o p h o r, and s o r b ic a c id on the
g r o w t h of t h e s e o r g a n i s m s w a s a l s o d e t e r m i n e d .
C o tta g e c h e e s e c o n t a m in a te d w ith the s p o ila g e o r g a n i s m s w as
w a s h e d w i t h w a t e r s c o n t a i n i n g a c i d s a n d g e r m i c i d e s t o d e t e r m i n e if
d i f f e r e n t w a s h i n g p r o c e d u r e s w o u l d i n c r e a s e t h e s h e l f - l i f e of t h e
product.

V a rio u s a c id s and s t a r t e r w e re added to c h e e s e d r e s s in g s

w h i c h h a d b e e n i n o c u l a t e d w i t h t h e o r g a n i s m s to d e t e r m i n e i f t h e s e
a d d i t i v e s w o u l d i n c r e a s e t h e s h e l f - l i f e of c o t t a g e c h e e s e .
T h e i s o l a t e d o r g a n i s m s b elo n g ed to th e g e n e r a
A lcalig en es, B acillus,

A chrom obacter

B a c te r iu m , C o r y n e b a c te riu m , E s c h e r i c h i a , M i­

cro co ccu s, P seu d o m o n as, R hodotorula, T o ru lo p s is , G e o tric h u m , M ucor
and P e n ic illiu m .
W h e n i n o c u l a t e d i n t o s t e r i l e c o t t a g e c h e e s e , t h e d e g r e e of d e ­
f e c t p r o d u c e d b y s p e c i e s of c e r t a i n g e n e r a c o u l d n o t b e c o r r e l a t e d

w i t h t h e p r e s e n c e o r a b s e n c e o f S. l a c t i s .

H o w e v e r, pH w as c o r ­

r e l a t e d w i t h d e g r e e of d e f e c t , s i n c e i n n i n e of e l e v e n i n s t a n c e s w h e r e
t h e r e w e r e d i f f e r e n c e s i n b o t h t h e d e g r e e of d e f e c t a n d t h e pH, t h e
d e f e c ts w e r e m o r e p ro n o u n c e d at th e h i g h e r pH l e v e l s

r e g a r d l e s s of

w h e th e r t h e s e w e r e p r o d u c e d by the p u r e c u ltu r e s in d iv id u a lly o r
c o m b i n e d w i t h S. l a c t i s .
A f t e r s e v e n d a y s a t 3° a n d 10° C . , e i g h t a n d s i x t e e n of t h e
nineteen o rg a n ism s,

r e s p e c tiv e ly , exhibited v isib le grow th, d e m o n ­

s tr a t i n g th a t low t e m p e r a t u r e s

f a i l t o c o m p l e t e l y c o n t r o l m a n y of

the o r g a n is m s .
R e d u c e d PH l e v e l s c a u s e d r e d u c e d g r o w t h of t h e o r g a n i s m s
a s two, fo u r, and n in e

of t h e s i x t e e n t e s t e d s h o w e d l i t t l e g r o w t h a t

p H l e v e l s of 5 . 0 , 5 . 2 , a n d 5. 4 o r b e l o w , r e s p e c t i v e l y .
Seven p e rc e n t so d iu m c h lo rid e w as th e c r itic a l co n c e n tra tio n ,
s i n c e fifte e n of th e n i n e t e e n o r g a n i s m s g r e w in 5 p e r c e n t ,
o n l y f o u r of t h e n i n e t e e n g r e w i n 7 p e r c e n t s o d i u m
B acillus
f o r 30 m i n u t e s .

w hile

chloride.

f i r m u s w a s t h e o n l y c u l t u r e w h i c h s u r v i v e d 143 °
W h e n h e a t e d a t 120°

F.

F . f o r 15 m i n u t e s i n s k i m

m i l k , o n l y t w o of t h e n i n e t e e n o r g a n i s m s w e r e d e s t r o y e d .

At t h i s

s a m e t e m p e r a t u r e a n d h o l d i n g t i m e i n w h e y , o n l y t w o of t h e n i n e ­
teen o rg a n ism s survived,

iii

F i f t y p a r t s p e r m i l l i o n of c h l o r i n e w i t h 5 m i n u t e s of e x p o s u r e
d e s t r o y e d e i g h t e e n of t h e n i n e t e e n , w h i l e f i f t y p a r t s p e r m i l l i o n of
q u a t e r n a r y w i t h 10 m i n u t e s of e x p o s u r e d e s t r o y e d o n l y e l e v e n of t h e
nineteen o rg a n ism s.

F i f t y p a r t s p e r m i l l i o n of i o d o p h o r w i t h 1 m i n ­

u t e of e x p o s u r e d e s t r o y e d t h i r t e e n of t h e n i n e t e e n c u l t u r e s .
A t p H 5.2 a n d a b o v e , t h e c o n c e n t r a t i o n s of s o r b i c a c i d u s e d
w e r e i n e f f e c t i v e , w h i l e a t pH 5 . 0 a n d 4 . 8 t h e v i a b i l i t y
w as d e c r e a s e d as the so rb ic

of t h e c u l t u r e s

acid content in c r e a s e d .

T h e a d d i t i o n of a c e t i c , c i t r i c , a n d s o r b i c a c i d s

to the w a sh

w a t e r of c o t t a g e c h e e s e i n o c u l a t e d w i t h v a r i o u s s p o i l a g e o r g a n i s m s
u s u a l l y i n c r e a s e d t h e s h e l f - l i f e of t h e p r o d u c t .
S o rb ic a c id and s t a r t e r ad d ed to c h e e s e d r e s s i n g co n ta in in g
various

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

cheese.

iv

ACKNOW LEDGM ENTS

T h e a u t h o r w i s h e s to e x p r e s s h is s i n c e r e a p p r e c i a t i o n to
D r . L . G. H a r m o n f o r h i s v a l u a b l e d i r e c t i o n a n d s u g g e s t i o n s d u r i n g
th e c o u r s e of th e s tu d y h e r e i n r e p o r t e d , and fo r h is a s s i s t a n c e in
t h e p r e p a r a t i o n of t h i s m a n u s c r i p t .
S i n c e r e t h a n k s a r e e x p r e s s e d t o D r . T . I. H e d r i c k f o r h i s
a s s i s t a n c e in g r a d i n g t h e c h e e s e s a m p l e s , a n d t h e e x a m i n a t i o n of
this m a n u s c rip t.
T h e a u t h o r i s a l s o g r a t e f u l t o D r . C. K. S m i t h , of t h e D e ­
p a r t m e n t of M i c r o b i o l o g y a n d P u b l i c H e a l t h ,

f o r t h e u s e of h i s

l a b o r a t o r y a n d h i s a s s i s t a n c e i n i d e n t i f i c a t i o n of t h e c u l t u r e s
i s o l a t e d in th is study.
T h a n k s a r e a l s o e x p r e s s e d t o D r . R. N. C o s t i l o w , of t h e
D e p a r t m e n t of M i c r o b i o l o g y a n d P u b l i c H e a l t h , a n d D r .

E. S.

B e n e k e , of t h e D e p a r t m e n t of B o t a n y a n d P l a n t P a t h o l o g y , f o r
t h e i r a s s i s t a n c e i n i d e n t i f i c a t i o n of t h e y e a s t a n d m o l d c u l t u r e s
u s e d in th is in v e s tig a tio n .

v

TA BLE OF CONTENTS

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

1

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

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

3

H e a t R e s i s t a n c e of P s y c h r o p h i l e s .................................................

7

D e fe c ts in D a i r y P r o d u c t s C a u s e d by the
G r o w t h of P s y c h r o p h i l i c O r g a n i s m s ......................................

9

C o n t r o l of P s y c h r o p h i l e s b y S a n i t i z e r s .....................

1Z

C h ee se A dditives

15

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

M E T H O D S ...............................................................................................................
I s o l a t i o n a n d I d e n t i f i c a t i o n of S p o i l a g e
O r g a n i s m s in C o tta g e C h e e s e
...................................
Isolation and P u rific a tio n

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

I d e n t i f i c a t i o n of t h e I s o l a t e d C u l t u r e s

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

T y p e of S p o i l a g e P r o d u c e d b y P u r e C u l t u r e s
of C o t t a g e C h e e s e S p o i l a g e O r g a n i s m s ............................
A p p e a r a n c e of C h e e s e W h e n S p o i l a g e O r g a n i s m s
A r e in P u r e C u l t u r e a n d in C o m b in a tio n w ith
S. l a c t i s ..........................................................................................
C h a r a c t e r i s t i c s of C o t t a g e C h e e s e S p o i l a g e
O r g a n i s m s ..........................................................................................
T e m p e ra tu re L im its

of G r o w t h

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

E f f e c t of pH on G r o w t h R a t e ..........................................

vi

18

18
18
19

ZZ

ZZ

Z3
Z3
Z4

Page
Sodium C h lo rid e T o le r a n c e
Heat T olerance

24

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

R e s i s ta n c e to G e r m i c i d e s

25
25

T o l e r a n c e t o c h l o r i n e ............................

26

T o le r a n c e to q u a t e r n a r y

27

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

T o l e r a n c e t o i o d o p h o r ..............

27

R e s i s t a n c e to S o r b i c A c i d .................

27

C o n t r o l of O r g a n i s m s C a u s i n g S p o i l a g e
in C o t t a g e C h e e s e
................................................ ...
T r e a t m e n t of W a s h W a t e r
T r e a t m e n t of D r e s s i n g
RESULTS

28
28

M aterials

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

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

30
32

I d e n t i f i c a t i o n of t h e I s o l a t e d C u l t u r e s

32

T y p e s of D e f e c t s P r o d u c e d b y S p o i l a g e
O r g a n i s m s in C o tta g e C h e e s e
.....................

43

C h a r a c t e r i s t i c s of C o t t a g e C h e e s e S p o i l a g e
O r g a n i s m s ...................................................................................

47

T e m p e ra tu re L im its

of G r o w t h

E f f e c t of pH o n G r o w t h R a t e
Sodium C h lo rid e T o l e r a n c e
Heat T o le ra n c e

47
.

.

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

R e s i s t a n c e to G e r m i c i d e s

49
53
53
56

v ii

Page
T o l e r a n c e to

chlorine

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

T o le ra n c e to

quaternary

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

58

T o le r a n c e to

i o d o p h o r ...................................................

61

R e s i s t a n c e t o S o r b i c A c i d ...................................
C o n t r o l of S p o i l a g e i n C o t t a g e C h e e s e

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

56

63
68

T r e a t m e n t of W a s h W a t e r .....................

68

T r e a t m e n t of D r e s s i n g

84

M aterials

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

D I S C U S S I O N ...........................................................
I s o l a t i o n a n d I d e n t i f i c a t i o n ..............

99
99

T y p e s of D e f e c t s P r o d u c e d by S p o i l a g e
........................
O r g a n i s m s in C o t t a g e C h e e s e

100

C h a r a c t e r i s t i c s of O r g a n i s m s C a u s i n g
S p o i l a g e i n C o t t a g e C h e e s e ............................

102

T em perature

L i m i t s of G r o w t h

102

E f f e c t of pH

on G r o w t h R a t e

103

Sodium C h lo r id e T o l e r a n c e
Heat T o le ra n c e

.
.

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

104
105

R e s i s t a n c e to G e r m i c i d e s

106

T olerance

t o c h l o r i n e ..............................................

106

T olerance

to q u a t e r n a r y

108

T olerance

to io d o p h o r

R e s is ta n c e to S o rb ic A cid

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

...
...
v iii

109
Ill

Page
C o n t r o l of S p o i l a g e in C o t t a g e C h e e s e

113

T r e a t m e n t of W a s h W a t e r ..........................................

113

T r e a t m e n t of D r e s s i n g M a t e r i a l s . .

117

SU M M A RY AND CO NCLUSIONS
LIT E R A T U R E C ITED

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

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

ix

121
125

LIST O F TA BLES

TABLE
I.

II.

III.

IV.

V.

VI.

VII.

VIII.

Page
P h y sio lo g ical, M orphological, and B io ch em ical
C h a r a c t e r i s t i c s of E i g h t e e n B a c t e r i a I s o l a t e d
f ro m Spoiled C h e e s e and A g a r P l a t e s E x p o s e d
i n C h e e s e P l a n t s ........................................................................

33

P h y sio lo g ical and B iochem ical C h a r a c te r is tic s
of E i g h t e e n B a c t e r i a I s o l a t e d f r o m S p o i l e d
C h e e s e a n d A g a r P l a t e s E x p o s e d in C h e e s e
P l a n t s .............................................................................................

35

P h y s io lo g ic a l and B io c h e m ic a l C h a r a c t e r i s t i c s
of E i g h t e e n B a c t e r i a I s o l a t e d f r o m S p o i l e d
C h e e s e a n d A g a r P l a t e s E x p o s e d in C h e e s e
P l a n t s .............................................................................................

37

P h y sio lo g ical and B iochem ical C h a r a c te r is tic s
of Y e a s t s C a u s i n g S p o i l a g e in C o t t a g e C h e e s e .

39

T y p e of D e f e c t a n d p H O b t a i n e d w i t h
O r g a n i s m s C a u s in g S p o ilag e in C o tta g e C h e e s e
in P u r e C u l t u r e a n d C o m b i n e d w i t h
S. L a c t i s . . .

44

G r o w t h of C o t t a g e C h e e s e S p o i l a g e O r g a n i s m s
in T r y p t i c a s e Soy B r o th at D iffe re n t In c u b a tio n
T e m p e r a t u r e s .....................................................................................

48

G r o w t h of C o t t a g e C h e e s e S p o i l a g e O r g a n i s m s
in T r y p t i c a s e Soy B r o t h C o n ta in in g D i f f e r e n t
C o n c e n t r a t i o n s of S o d i u m C h l o r i d e ..........................

54

R e s i s t a n c e of C o t t a g e C h e e s e S p o i l a g e
O r g a n i s m s t o H e a t i n g a t 143° F . in S k i m
M i l k ..........................................................................................

55

x

TABLE
IX .

X.

XI.

XI I.

X III .

X IV .

XV.

XVI.

X V I I.

X V I II .

Page
R e s i s t a n c e of C o tta g e C h e e s e S p o ilag e
O r g a n i s m s t o H e a t i n g a t 12 0° F . f o r 15
M i n u t e s i n S k i m M i l k a n d W h e y .............................
G r o w t h of C o t t a g e C h e e s e S p o i l a g e O r g a n i s m s
a f t e r E x p o s u r e t o D i f f e r e n t C o n c e n t r a t i o n s of
C h lo rin e Solutions fo r V a rio u s T im e I n te rv a ls

5

..

G r o w t h of C o t t a g e C h e e s e S p o i l a g e O r g a n i s m s
a f t e r E x p o s u r e t o D i f f e r e n t C o n c e n t r a t i o n s of
Q u a te r n a r y Solutions fo r V a rio u s T im e I n te rv a ls
G r o w t h of C o t t a g e C h e e s e S p o i l a g e O r g a n i s m s
a f t e r E x p o s u r e t o D i f f e r e n t C o n c e n t r a t i o n s of
Io d o p h o r Solutions fo r V a rio u s T im e In te rv a ls

7

59

.

..

60

62

G r o w t h of C o t t a g e C h e e s e S p o i l a g e O r g a n i s m s
a f t e r E x p o s u r e t o D i f f e r e n t C o n c e n t r a t i o n s of
S o r b i c A c i d a t V a r i o u s p H L e v e l s .......................................

64

T h e E f f e c t of W a s h W a t e r T r e a t m e n t on
C o n tro llin g V a r io u s Spoilage O r g a n i s m s in
C ottage
C h e e s e S t o r e d a t 50° F ...................................

69

T h e E f f e c t o f W a s h W a t e r T r e a t m e n t on
C o n tro llin g V a r io u s Spoilage O r g a n is m s in
C ottage
C h e e s e S t o r e d a t 50° F ...................................

71

T h e E f f e c t of W a s h W a t e r T r e a t m e n t on
C o n tr o llin g V a r io u s Spoilage O r g a n i s m s in
C ottage
C h e e s e S t o r e d a t 50° F ...............................

73

T h e E f f e c t of W a s h W a t e r T r e a t m e n t on
C o n t r o l l i n g V a r i o u s S p o ila g e O r g a n i s m s in
C ottage
C h e e s e S t o r e d a t 5 0° F ...................................

75

T h e E f f e c t of W a s h W a t e r T r e a t m e n t on
C o n t r o l l i n g V a r i o u s S p o i l a g e O r g a n i s m s in
C ottage
C h e e s e S t o r e d a t 50° F ................................

76

xi

TABLE
X IX .

XX.

XXI .

X XII.

XXIII.

XXIV.

XXV.

XXVI.

X X V I I.

X X V I II .

Page
T h e E f f e c t of W a s h W a t e r T r e a t m e n t on
C o n tr o llin g V a r i o u s S p o ilag e O r g a n i s m s in
C ottage
C h ee se Stored
at
50°.F .............................

78

T h e E f f e c t of W a s h W a t e r T r e a t m e n t on
C o n t r o l l i n g V a rio u s S p o ila g e O r g a n i s m s in
C ottage
C h eese Stored
at
50°.F ...................................

80

T h e E f f e c t of W a s h W a t e r T r e a t m e n t on
C o n tr o llin g V a r io u s S p o ilag e O r g a n i s m s in
C ottage
C h ee se S tored
at
5 0°.F .....................

81

E f f e c t of W a s h
W a t e r T r e a t m e n t on t h e
S h e l f - L i f e of C o t t a g e C h e e s e I n o c u l a t e d
w i t h V a r i o u s S p o i l a g e O r g a n i s m s .................

83

T h e E f f e c t of D r e s s i n g T r e a t m e n t i n
C o n tro llin g V a r io u s Spoilage O r g a n is m s
i n C o t t a g e C h e e s e S t o r e d a t 50° F ................

85

T h e E f f e c t of D r e s s i n g T r e a t m e n t i n
C o n tro llin g V a rio u s Spoilage O r g a n is m s
in C o t t a g e C h e e s e S t o r e d a t 5 0 ° F .................

86

T h e E f f e c t of D r e s s i n g T r e a t m e n t i n
C o n tro llin g V a rio u s Spoilage O r g a n is m s
i n C o t t a g e C h e e s e S t o r e d a t 50° F .................

88

T h e E f f e c t of D r e s s i n g T r e a t m e n t i n
C o n tro llin g V a r io u s Spoilage O r g a n is m s
i n C o t t a g e C h e e s e S t o r e d a t 50° F .................

90

T h e E ffe c t of D r e s s i n g T r e a t m e n t in
C o n tro llin g V a rio u s Spoilage O r g a n is m s
i n C o t t a g e C h e e s e S t o r e d a t 50° F .................

91

T h e E f f e c t of D r e s s i n g T r e a t m e n t i n
C o n tro llin g V a rio u s Spoilage O r g a n is m s
i n C o t t a g e C h e e s e S t o r e d a t 50° F ....................

9^

x ii

TABLE
XXIX.

XXX.

XXXI.

X X X I I.

Page
T h e E f f e c t of D r e s s i n g T r e a t m e n t i n
C o n tro llin g V a rio u s Spoilage O r g a n is m s
i n C o t t a g e C h e e s e S t o r e d a t 50° F ...................

93

T h e E f f e c t of D r e s s i n g T r e a t m e n t in
C o n tro llin g V a r io u s Spoilage O r g a n is m s
i n C o t t a g e C h e e s e S t o r e d a t 50° F ...................................

95

T h e E f f e c t of D r e s s i n g T r e a t m e n t in
C o n tro llin g V a rio u s Spoilage O r g a n is m s
i n C o t t a g e C h e e s e S t o r e d a t 50° F ..................

96

E f f e c t of D r e s s i n g T r e a t m e n t on t h e
S h e l f - L i f e of C o t t a g e C h e e s e I n o c u l a t e d
w i t h V a r i o u s S p o i l a g e O r g a n i s m s .................

97

x iii

IN T R O D U C T IO N

C ottage c h eese is becom ing an in c re a s in g ly p o p u lar product
w ith th e c o n s u m in g public.
c re a s e d from

The p e r capita consum ption has in ­

0.9 p o u n d s i n 1935 t o 3.1 p o u n d s in 1 9 5 3 . 1

T his

p r o d u c t h a s b e e n a m e a n s of a l l e v i a t i n g m i l k s u r p l u s p r o b l e m s i n
/

certain a re a s
able ite m

d u rin g th e s u m m e r m onths and h as p ro v ed a p r o f it­

for the d a iry plant o p e ra to r.

H o w e v e r , th e c o tta g e c h e e s e i n d u s t r y is faced with a n u m b e r
of p r o b le m s of i n c r e a s i n g im p o r ta n c e .
c e n t r a l i z a t i o n of p la n ts ,

The p re s e n t tre n d is tow ard

r e s u l t i n g in l o n g e r h a u l i n g d i s t a n c e s a n d

lo n g er s to ra g e b efo re sale.

C ottage c h e e s e m a k e r s a r e producing

a s w e e t c u r d , low a c id c h e e s e w h ich is n e c e s s a r y to m e e t c o n ­
su m e r dem ands.

T h e pH of t h i s

c h e e s e i s not s u ff ic ie n tly low to

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

Inadequate r e ­

f r i g e r a t i o n in r e t a i l o u tle ts and h o u s e h o ld r e f r i g e r a t o r s is c o m m o n .
P sy c h ro p h ilic b a c te ria , y e a s ts , and m o ld s can grow and cau se u n ­
d e s i r a b l e c h a n g e s in low a c id c o tta g e c h e e s e .

The defects n o rm a lly

1 A g r i c u l t u r a l S t a t i s t i c s ( 1 9 3 7 , 1955).
U n i t e d S t a t e s D e p t , of
A g riculture.
U.S. G o v e r n m e n t P r i n t i n g O f f i c e , W a s h i n g t o n , D . C .

1

2
e n c o u n te r e d a r e m o ld m y c e lia and s u r f a c e s lim e , along w ith s ta le ,
m oldy, b itte r, y e a sty , o r fru ity fla v o rs.

M o re in fo r m a tio n about the

s p e c if ic o r g a n i s m s c a u s i n g t h e s e d e f e c ts w ould be b e n e f ic ia l to
d a ir y plant o p e r a to rs .
T h e study h e r e in r e p o r te d w as in itia te d to d e te r m in e s p e ­
cific o r g a n i s m s

re s p o n s ib le for cottage c h e e s e sp o ilag e and m eth o d s

of c o n t r o ll i n g t h e i r g ro w th .

A n u m b e r of o r g a n i s m s c a u s i n g s p o i l ­

a g e in c o tta g e c h e e s e w e r e i s o l a t e d and id e n tifie d .
pH, in c u b a tio n t e m p e r a t u r e , h e a t, sa lt,

T h e e f f e c t of

s o rb ic acid, and c h lo rin e ,

i o d o p h o r , a n d q u a t e r n a r y c o m p o u n d s o n t h e g r o w t h of t h e s e o r g a n ­
ism s

was d eterm in e d .

Cottage c h e e s e w ash w a te rs and c re a m in g

m i x t u r e s w e r e t r e a t e d with v a r i o u s c o m p o u n d s in an a t te m p t to d e ­
t e r m i n e m e t h o d s of i n c r e a s i n g t h e s h e l f - l i f e of c o t t a g e c h e e s e
in o c u la te d with th e s p o ila g e o r g a n i s m s .

It w a s f e l t t h a t i f t r e a t ­

m e n t s co uld be d i s c o v e r e d w h ic h w ould a d d a few d a y s to th e s h e lfl i f e of c o t t a g e c h e e s e t h e p r o j e c t w o u l d b e w o r t h w h i l e .

REVIEW O F L IT E R A T U R E

P s y c h r o p h ilic b a c t e r i a a r e o r g a n i s m s w hich a r e ab le to g ro w
at r e f r ig e r a to r te m p e r a tu re s .

T hese organism s p re fe r te m p e ra tu re s

I

of 60° t o 70°

F ., but m a n y w h ic h p r o d u c e u n d e s i r a b l e c h a n g e s in

d a i r y p r o d u c t s g r o w q u i t e w e l l a t 40° t o 5 0° F . o r l o w e r .

M any

i n v e s t i g a t o r s h a v e r e p o r t e d on t h e o c c u r r e n c e of t h e s e o r g a n i s m s
in d a i r y p r o d u c t s , p a r t i c u l a r l y m ilk.
C o n n (1 903) s t a t e d t h a t m i l k p r e s e r v e d a t 50°

F.

rem ains

s w e e t f o r a lo n g tim e , but th e b a c t e r i a w hich e v e n tu a lly g r o w a r e
m o r e u n d e s ir a b l e th an th o s e w hich g ro w at h i g h e r t e m p e r a t u r e s .
H e f u r t h e r s t a t e d t h a t o ld m i l k , e v e n t h o u g h p e r f e c t l y s w e e t , i s u n ­
fit f o r m a r k e t .
d eteriorated,

M o tt a n d M a z e r (1938) r e p o r t e d t h a t m i l k q u a l i t y

som etim es

q u i t e r a p i d l y , w h e n h e l d a t 4 0° F .

d e t e r i o r a t i o n w a s f o u n d t o b e c a u s e d by b a c t e r i a l g r o w t h .
and J e z e sk i

This
G reen

(1 954 ) s h o w e d t h a t a l a r g e n u m b e r of o r g a n i s m s i m ­

p o r ta n t to th e d a ir y in d u s tr y a r e ab le to grow at r e f r i g e r a t o r
tem peratures.
0° C. w a s a s

In s o m e c a s e s , t h e y found th a t co o lin g f r o m
effective as cooling fro m

keeping quality.

5° t o

30° t o 5° C. i n i n c r e a s i n g

C h a f f e e (19 52) r e p o r t e d c o n s i d e r a b l e i n c r e a s e s in

3

4
n u m b e r s of o r g a n i s m s i n m i l k h e l d i n r e f r i g e r a t e d s t o r a g e ,

resulting

i n a m a r k e d d e t e r i o r a t i o n of t h e p r o d u c t .
B u r g w a l d a n d J o s e p h s o n (1947 ) d e m o n s t r a t e d t h a t p s y c h r o p hilic b a c t e r i a w hich dev elo p in r e f r i g e r a t e d m ilk a r e p r i m a r i l y
r e s p o n s i b l e f o r t h e d e t e r i o r a t i o n of t h e p r o d u c t a n d a p p a r e n t l y a r e
r e s p o n s i b l e f o r th e d e v e lo p m e n t of a c id w hich i s p r o d u c e d in m ilk
s t o r e d a t 40°

F.

M orris

( 1 942) f o u n d t h a t c e r t a i n s a m p l e s

of r a w

m i l k h e l d o v e r n i g h t a t 4° C. d e c o l o r i z e d m e t h y l e n e b l u e i n l e s s t h a n
8 hours.

He is o la te d P s e u d o m o n a s o r g a n is m s w hich g r e w ra p id ly

i n m i l k h e l d a t 4° C.

Subsequent stu d ies show ed fa rm

w ater sup­

p l i e s t o b e a p o s s i b l e s o u r c e of t h e s e o r g a n i s m s .
T h o m a s et al.

(1947 ) i s o l a t e d a n d i d e n t i f i e d a s t o g e n e r a , a

n u m b e r of o r g a n i s m s c a p a b l e o f g r o w i n g a t r e f r i g e r a t o r t e m p e r a ­
tures.
follow ed

The m o s t c o m m o n g e n e r a a p p e a r e d to be A c h r o m o b a c t e r ,
by

F la v o b a c te riu m , P se u d o m o n a s , and A lcalig en es.

w ith n o r m a l t a s t e and o d o r c o n tain ed
of t h e a b o v e o r g a n i s m s .

M ilk

10,000,000 p e r m l. o r m o r e

O l s o n et a l . (195 3a) r e p o r t e d p s y c h r o -

p h ilic b a c t e r i a w e r e a lw a y s found in r a w m i l k s u p p l i e s , and e x ­
t e n s i v e p r o l i f e r a t i o n of t h e s e b a c t e r i a w i l l i n e v i t a b l y o c c u r i f s u c h
m i l k i s h e l d a t low t e m p e r a t u r e s .

E r d m a n and T h o rn to n (1951a,

1 9 5 1 b ) i n v e s t i g a t e d p s y c h r o p h i l i c b a c t e r i a in s i x t y - o n e s a m p l e s of
m ilk and c r e a m ,

an d found th e m to be p r e s e n t in a ll s a m p l e s

5
exam ined.

O r g a n i s m s w e r e is o la te d and id e n tifie d as belonging to

the g e n e r a A e r o b a c t e r , E s c h e r i c h i a , F la v o b a c te r iu m , L a c to b a c illu s,
P s e u d o m o n a s , and S tre p to c o c c u s.

M i k o l a j c i k a n d B u r g w a l d (1953)

s ta te d that s o m e n o n p sy ch ro p h ilic o r g a n is m s develop p sy ch ro p h ilic
te n d e n c ie s a f t e r s to r a g e at low t e m p e r a t u r e s .
show ed that the c o lifo rm

D a h l b e r g (19 46 )

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

c r e a s e c o n s i d e r a b l y d u r i n g 4 d a y s 1 s t o r a g e a t 45° t o 5 0° F .
J e z e s k i a n d M a c y (1 946) i s o l a t e d a n d c l a s s i f i e d a s t o g e n e r a
a n u m b e r of p r o t e o l y t i c a n d l i p o l y t i c c u l t u r e s f r o m

b u tte r and

w a t e r w h i c h w e r e c a p a b l e of v i g o r o u s g r o w t h a t 8° C.
isolated w ere

G enera

P se u d o m o n a s , F la v o b a c te r iu m , A lcalig en es, and

A ch ro m o b acter.

A nonlactose ferm enting y east was also iso lated

but not id e n tifie d .

F u r th e r stu d ies showed that th e se o rg a n is m s

w e r e c a p a b l e of c a u s i n g u n d e s i r a b l e o d o r s i n s t e r i l e c r e a m
b ated at r e f r i g e r a t o r t e m p e r a t u r e s .

incu­

L a w t o n a n d N e l s o n (1954) r e ­

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

c o m m e r c ia l m ilk.

E i g h t of t h e s e c u l t u r e s w e r e s e l e c t e d a s

being r e p r e s e n t a t i v e and w e re te n ta tiv e ly id entified as
dom onas ovalis,
arv illa,

(2) P s e u d o m o n a s

(4) P s e u d o m o n a s

(1) P s e u ­

f l u o r e s c e n s , (3) P s e u d o m o n a s

c r u c i v i a e , (5) P s e u d o m o n a s a q u a t i l e ,

(6) P s e u d o m o n a s f l u o r e s c e n s

( p o s s i b l y v i s c o s a ), (7) P s e u d o m o n a s

g e n i c u l a t a , a n d (8) P s e u d o m o n a s s p e c i e s .

6
B o y d e t a l . ( 1 953) r e p o r t e d t h a t p s y c h r o p h i l i c b a c t e r i a a r e
i m p o r t a n t i n t h e k e e p i n g q u a l i t y of c o m m e r c i a l l y p a s t e u r i z e d a n d
h o m o g e n iz e d m ilk.

O ls o n et al. (1953b) found t h a t p s y c h r o p h i l i c

b a c te r ia developed m o re

ra p id ly in r e c o m b in e d m ilk than in the

c o n c e n tr a te d m ilk fro m w hich it w as p r e p a re d .
M o r r i s o n a n d H a m m e r (1941) s h o w e d t h a t p s y c h r o p h i l i c
Pseudom onas

fragi is

quite w i d e s p r e a d in d a i r y p r o d u c t s and m a ­

t e r i a l s c o m i n g in c o n t a c t w i t h d a i r y p r o d u c t s .
(1952, 1953a,

1953b,

N ashif and N elson

1 9 5 3 c ) f o u n d t h a t t h e l i p a s e of P s .

c a p a b l e of c a u s i n g e x t e n s i v e b r e a k d o w n of f a t i n c r e a m
Purko

fragi was
and b u tte r.

et a l . ( 1952) a n d N e l s o n (1952 ) r e p o r t e d t h a t G e o t r i c h u m

c a n d i d u m p r o d u c e d a r a p i d a n d e x t e n s i v e h y d r o l y s i s of b u t t e r f a t i n
cream .

H a r m o n a n d N e ls o n (1955a) d e m o n s t r a t e d th a t th e p r e s e n c e

of S tr e p to c o c c u s l a c t i s w a s i n h ib ito r y to the p o p u la tio n d e v e lo p m e n t
o f P s . f r a g i , b u t s t i m u l a t e d t h e p o p u l a t i o n d e v e l o p m e n t of G. c a n ­
didum in c r e a m .

H o w e v e r , t h e y f o u n d t h a t t h e p r e s e n c e of S.

l a c t i s a n d t h e a c c o m p a n y i n g l o w e r i n g of pH r e d u c e d t h e l i p a s e
a c t i v i t y a n d w a t e r - i n s o l u b l e a c i d p r o d u c t i o n of G. c a n d i d u m a n d P s .
f r a g i a n d t h e p r o t e a s e a c t i v i t y of P s .

fragi.

Van d e r Zant and

N e l s o n (1 953) d e m o n s t r a t e d t h a t c e r t a i n s t r a i n s

of S. l a c t i s a r e

p r o te o ly tic by m e a s u r i n g the i n c r e a s e in so lu b le n itro g e n , try p to p h a n ,
and t y r o s i n e in m ilk in o c u la te d with th e s e s tr a i n s .

P eters

and

7
N e l s o n (1948) found th a t u n d e r c e r t a i n c o n d itio n s

M ycotorula lipolytica

p o s s e s s e d e x t r e m e l y high lip o ly tic activ ity .
I n v e s t i g a t i o n s o n t h e m i c r o f l o r a of b l u e c h e e s e s l i m e b y
H a r t l e y a n d J e z e s k i (19 54 ) r e v e a l e d t h e p r e s e n c e of s p e c i e s of
M ic r o c o c c u s along with B a c te r iu m

lin en s and B a c te riu m

erythrogenes.

M a c y a n d E r e k s o n (1 937) s t u d i e d t h e s l i m e o f s e v e r a l v a r i e t i e s of
s e m i s o f t c h e e s e s a n d found th a t B act. li n e n s w a s th e o r g a n i s m
com m only isolated.

m ost

A l f o r d a n d F r a z i e r (1950) i s o l a t e d M i c r o c o c c u s

f re u n d e n r e ic h ii, M icro co ccu s c a s e o ly tic u s , and M icro co ccu s conglom eratus

from

raw m ilk cheddar cheese.

They believed th e se o r g a n ­

i s m s w e r e i m p o r t a n t in th e r ip e n in g p r o c e s s .

H e a t R e s i s t a n c e of P s y c h r o p h i l e s

T h o m a s e t a l . (1 947) s h o w e d t h a t s p e c i e s of A c h r o m o b a c t e r ,
F lavobacterium ,

P s e u d o m o n a s , a n d A l c a l i g e n e s do n o t s u r v i v e p a s ­

t e u r i z a t i o n a t 143° F . f o r 30 m i n u t e s .

D a v i s a n d B a b e l (1954)

d e m o n s t r a t e d th a t s o m e s p e c i e s of o r g a n i s m s in th e g e n e r a P r o t e u s ,
P s e u d o m o n a s , A e r o b a c t e r , A lc a lig e n e s ^ and A c h r o m o b a c t e r a r e
heat labile.

N o n e of t h e o r g a n i s m s

stu d ied in th e s e g e n e r a

v i v e d p a s t e u r i z a t i o n a t 14 3° F . f o r 3 0 m i n u t e s .
T hornton

(1951a,

quite

sur­

E rd m a n and

1951 b) r e p o r t e d t h a t s p e c i e s of A e r o b a c t e r ,

E s c h e r i c h i a , F la v o b a c te r iu m , L a c to b a c illu s , P s e u d o m o n a s , and

8
Streptococcus r a r e ly survive pasteurization.

W atrous

(1953 ) s t a t e d

t h a t p s y c h r o p h i l i c b a c t e r i a do not w i t h s t a n d p a s t e u r i z a t i o n , but a r e
f o u n d i n c o m m e r c i a l l y p a s t e u r i z e d m i l k a s a r e s u l t of p o s t p a s t e u r ­
ization contam ination.
psychrophilic
pasteurization.

O l s o n e t a l . (195 3a) d e m o n s t r a t e d t h a t

b a c t e r i a found in r a w m i l k a r e d e s t r o y e d by p r o p e r
A t h e r o n et a l .

that bottled m ilk and c r e a m

(1953) a n d W a t r o u s

et a l . (195 2) f o u n d

n o rm a lly contained p sy c h ro p h ile s,

but

a s a p o stp a ste u riz a tio n contam inant, since la b o ra to ry p a ste u riz a tio n
a t 143°

F . f o r 30 m i n u t e s d e s t r o y e d t h e s e o r g a n i s m s .
R o g i c k a n d B u r g w a l d (195 2) f o u n d t h a t p s y c h r o p h i l e s do n o t

s u r v iv e p a s t e u r i z a t i o n by th e v a t o r the H T ST m e th o d , but p a s t e u r ­
iz e d m ilk a f te r bottling and s to r a g e in v a ria b ly co n tain s p s y c h r o ­
philes.

T h e y d e m o n s t r a t e d t h a t m o s t of t h e o r g a n i s m s a r e

tativ e r a t h e r than tru e p sy ch ro p h iles.

facul­

K e n n e d y a n d W e i s e r (1 950),

i n a s t u d y of f i f t e e n p s y c h r o p h i l i c b a c t e r i a l c u l t m e s , s h o w e d t h a t
th e m a j o r i t y w e r e quite h e a t la b ile , but s o m e w e r e not c o m p le te ly
d e s t r o y e d b y p a s t e u r i z a t i o n a t 145°

F.

f o r 30 m i n u t e s .

The optim um

g r o w t h t e m p e r a t u r e of s e v e n of t h e s e f i f t e e n o r g a n i s m s w a s c l o s e r
t o 10° t h a n t o 2 0 ° C . , a n d n o n e g r e w a t 35°

C.

S h e r m a n et a l . (194 1) s t a t e d t h a t p a s t e u r i z e d m i l k k e e p s t w o
to t h r e e t i m e s as long a s
o r b a c te r ia l content.

r a w m i l k of s u b s t a n t i a l l y t h e s a m e q u a l i t y

T h e y s u g g e s t e d th a t t h i s w a s due to the

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

R e i n o c u l a t i o n of

p a s t e u r i z e d m i l k w i t h m i n u t e a m o u n t s of r a w m i l k d e c r e a s e d i t s
k e e p i n g q u a l i t y t o a p o i n t s u b s t a n t i a l l y t h e s a m e a s t h a t of r a w
m ilk.

T h e y a l s o r e p o r t e d t h a t s p o i l a g e of m i l k h e l d j u s t a b o v e t h e

f r e e z i n g point w a s due p r i m a r i l y to g r a m - n e g a t i v e n o n s p o r e f o r m i n g
r o d s of t h e P s e u d o m o n a s g r o u p .

K a u f m a n n a n d A n d r e w s (1954)

d e m o n s t r a t e d t h a t c u l t u r e s of P s e u d o m o n a s v i s c o s a a n d P s e u d o m o n a s
m e p h i t i c a w e r e r e a d i l y d e s t r o y e d b y p a s t e u r i z a t i o n a t 143° F . f o r
3 0 m i n u t e s o r by t h e H T S T m e t h o d w h e n h e a t e d i n s k i m

m ilk.

In a d d itio n to th e a b o v e - m e n tio n e d s tu d ie s c o n c e r n in g h e a t
r e s i s t a n c e of o r g a n i s m s of d a i r y o r i g i n , R u y l e a n d S o g n e f e s t (1951)
s t u d i e d t h e r m a l r e s i s t a n c e of a f a c u l t a t i v e a e r o b i c s p o r e f o r m i n g
bacterium

in e v a p o r a t e d m ilk .

T his o rg an ism

c a u s e d th e m ilk to

t a k e on a c u s t a r d l i k e c o n s i s t e n c y a n d w a s i d e n t i f i e d a s B a c i l l u s
subtilis.

A m inim um

d e s tro y the s p o re s

of 1 6 .4 m i n u t e s a t 243 °

of t h i s o r g a n i s m .

F. w as r e q u i r e d to

M y h r a n d O l s o n (1 952)

t e s t e d t h i r t y c u l t u r e s of M i c r o c o c c i a n d f o u n d o n l y f i v e of t h e s e
s u r v i v e d h e a t i n g a t 143°

F . f o r 30 m i n u t e s .

D e f e c t s i n D a i r y P r o d u c t s C a u s e d by t h e
G r o w t h of P s y c h r o p h i l i c O r g a n i s m s

P a r k e r a n d E l l i k e r (1 952,
fragi,

1953 ) r e p o r t e d t h a t P s e u d o m o n a s

P s. v is c o s a , and A lca iig e n e s m e ta lc a lig e n e s have the ability

10
t o r e d u c e t h e b i a c e t y l c o n t e n t of c o t t a g e c h e e s e , t h e r e b y d e s t r o y i n g
t h e d e s i r a b l e f l a v o r a n d a r o m a of t h e p r o d u c t .
w orkers,

A c c o r d in g to t h e s e

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

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

B acillus g rav eo -

le n s , P s . flu o re sc e n s, Pseudom onas p u trefacien s, Ps.

fragi,

E s c h e ric h ia c o li, A e ro b a c te r a e r o g e n e s , P ro te u s v u lg a r is , A lcaiigenes
f e c a l i s , S t r e p t o c o c c u s p a r a c i t r o v o r o u s , S. l a c t i s , a n d S t r e p t o c o c c u s
c r e m o r i s w e r e t e s t e d b y E l l i k e r a n d H o r r a l l (1943) a n d E l l i k e r (19 45)
f o r t h e i r e f f e c t on t h e b i a c e t y l c o n t e n t a n d f l a v o r of b u t t e r .
la c t i s w as the only o r g a n is m
b i a c e t y l c o n t e n t of b u t t e r .
didum , P e n ic illiu m

S.

w h ic h s h o w ed little o r no e ffe c t on th e

W a l e s (19 56) d e m o n s t r a t e d t h a t G . c a n -

frequentans,

Ps.

frag i, P s . flu o rescen s, P se u ­

dom onas d e s m o ly tic u m , P se u d o m o n as t r a lu c id a , Rhodotorula fla v a ,
T o r u l o p s i s Candida, E s c h e r i c h i a f r e u n d i i , A c h r o m o b a c t e r e u r y d i c e ,
a n d A l e . m e t a l c a l i g e n e s r e d u c e d b u t d i d n ot c o m p l e t e l y d e s t r o y b i ­
a c e t y l i n c o t t a g e c h e e s e s t o r e d a t 40° a n d 50° F .
w a s m o r e p r o n o u n c e d a t 50°

F.

The reduction

He show ed f u r th e r that c h e e s e ex­

hibiting heav y s lim e fo rm a tio n still contained so m e biacetyl.
N u m e r o u s i n v e s t i g a t o r s inclu d in g T u c k e y (1951a,

1951b),

Y o u n g (1 9 5 3 ), B a k e r ( 1 9 5 3 ), K e s t e r ( 1 9 5 4 ) , a n d E l l i k e r ( 1 9 5 4 ) h a v e
r e p o r t e d on i m p r o v e d m e t h o d s of a s s u r i n g a h i g h q u a l i t y c o t t a g e
cheese.

T hey a r e in g e n e r a l a g r e e m e n t that th e r e is a need for

11
b e t t e r p lan t s a n ita tio n in m o s t d a i r i e s .

D e a n e et a l .

(1953 ) a n d

R h o d e s a n d H a r m o n (1 954) i n v e s t i g a t e d t h e q u a l i t y of c o m m e r c i a l
c o t t a g e c h e e s e and found c o n s i d e r a b l e v a r i a t i o n a m o n g s a m p l e s e x ­
am ined.
L y o n s a n d M a l l m a n n (1 954) fo u n d t h a t 64 p e r c e n t of c o t t a g e
c h e e s e s a m p l e s p a c k a g e d i n t h e p l a n t a n d 95 p e r c e n t of b u l k s a m ­
ples contained co lifo rm

bacteria.

They f u rth e r show ed that so m e

p a th o g e n ic o r g a n i s m s in o c u la te d in to c o tta g e c h e e s e e v e n tu a lly die
off, t h e d e a t h r a t e i n c r e a s i n g a s t h e pH d e c r e a s e d .

H o w ever, they

r e p o r t e d th a t d e s tr u c tio n is slow enough to p r e s e n t a p o s s ib le public
health h azard .
bacterium

G e a i r a i n a n d G e a i r a i n (1951) r e v e a l e d th a t

tu b ercu lo sis

ch eese m ade from

M yco­

r e m a i n e d v i a b l e f o r 14 d a y s i n c o t t a g e

ra w m ilk.

D a v i s a n d B a b e l (195 4) i s o l a t e d a n d c l a s s i f i e d a n u m b e r of
slim e-p ro d u c in g o rg an ism s from

cottage c h eese.

The o rg an ism s

belo n g ed to th e follow ing g e n e r a :

P ro teu s,P se u d o m o n a s, A e ro b a c te r,

A lcaiig en es, and A c h r o m o b a c te r .

C ollins

(1955a) s tu d ie d f a c t o r s

i n v o l v e d in t h e c o n t r o l of g e l a t i n o u s c u r d d e f e c t s i n c o t t a g e c h e e s e
a n d f o u n d t h a t pH a n d t e m p e r a t u r e a r e v e r y i m p o r t a n t in r e t a r d i n g
o r co n tro llin g th is defect.

L o w t e m p e r a t u r e a n d pH l e v e l s w e r e

s h o w n t o r e t a r d d e v e l o p m e n t of t h e g e l a t i n o u s c u r d d e f e c t .

These

s tu d ie s a ls o show ed that a fru ity o d o r w as the f ir s t d efect p ro d u c e d

12
by A le, m e t a l c a l i g e n e s an d P s . v i s c o s a .
that s lim e

D e a n e et a l .

(1 953) f o u n d

e v e n t u a l l y d e v e l o p e d on c o t t a g e c h e e s e h a v i n g pH l e v e l s

b e lo w 4.7 w hen r e c e i v e d .

P a r k e r e t a l . ( 1950 ,

a l . (1952) a l s o s t u d i e d o r g a n i s m s
t y p e of s p o i l a g e .
brow n slim e,

1951) a n d E l l i k e r e t

a s s o c i a t e d w ith a g e la tin o u s c u r d

"T h e y found th a t P s . v i s c o s a p r o d u c e d a y e llo w o r

w h ile Ale, m e t a l c a l i g e n e s and P s . f r a g i p r o d u c e d a

t r a n s l u c e n t , y ello w , g e la tin o u s film a r o u n d e a c h c u r d p a r t i c l e .

C o n t r o l of P s y c h r o p h i l e s by S a n i t i z e r s

T h r e e t y p e s of s a n i t i z e r s a r e c u r r e n t l y c o n s i d e r e d t o b e
u s e f u l in d e s t r o y i n g o r g a n i s m s d e t r i m e n t a l to d a i r y p r o d u c t s .
T h e s e a r e the c h lo rin e , q u a te r n a r y , and io d o p h o r c o m p o u n d s.
V a r i o u s a u t h o r s i n c l u d i n g J o h n s (19 4 7 ,

1948a,

1948b), S h e r e

( 1 9 4 8 ),

D v o r k o v i t z a n d C r o c k e r ( 1 9 5 0 ), a n d P a r k e r a n d E l l i k e r (19 51) h a v e
c o m p a re d ch lo rin e and q u a te rn a ry com pounds.
and d isa d v a n ta g e s have been shown fo r each.

Many ad v an tag es
Y ancy and F a b e r

( 1 952) s h o w e d t h a t a l k y l d i m e t h y l b e n z y l a m m o n i u m

ch lo rid e (quat­

e r n a r y ) is d e s t r u c t i v e to s o m e o r g a n i s m s a s s o c i a t e d w ith b o v in e
m astitis.

K r o g (1 942) a n d D a v i s (1947) d e m o n s t r a t e d t h a t q u a r t e r -

n a ry com pounds a re
equipm ent.

effectiv e in s a n itiz in g p r o p e r l y c le a n e d d a iry

D u B o i s a n d D i b b l e e ( 1946) f o u n d t h a t t h e s e c o m p o u n d s

a r e effective ag ainst the com m on m ilk -s o u rin g o rg a n ism s.

L u n d s t e d t ( 1 9 5 0 ) w a r n e d a g a i n s t t h e u s e of q u a t e r n a r y c o m p o u n d s
b e c a u s e they a r e effective ag ain st g r a m - p o s itiv e d e s ir a b le d a ir y
o rg a n is m s and le s s
ones.

effective ag ain st the g r a m -n e g a tiv e , u n d e s ira b le

P a r k e r e t a l . (1953 ) o b s e r v e d h y p o c h l o r i t e s t o h a v e a m o r e

ra p id g e rm ic id a l action than q u a te rn a ry com pounds ag ain st P s .
v is c o s a , P s. flu o re s c e n s , P s. p u tre fa c ie n s, Ps.
m etalcalig en es.

M any o th er au th o rs

K l a r m a n n an d W rig h t (1944,

fr a g i, and A le .

i n c l u d i n g H a r p e r et a l . (1 9 4 8 ),

1946), R a h n a n d v a n E s e l t i n e ( 1 9 4 7 ),

E l l i k e r (1950), H u c k e r a n d v a n E s e l t i n e

( 1 948), R i d e n o u r a n d A r m -

b r u s t e r ( 1 9 4 8 ), W e b e r a n d B l a c k ( 1 9 4 8 ), a n d S o i k e e t a l.

(1 952) h a v e

r e p o r t e d on m e t h o d s of t e s t i n g q u a t e r n a r y c o m p o u n d s a n d f a c t o r s
affectin g t h e i r g e r m ic id a l activity.
C ollins

( 1 9 5 5 b ) s h o w e d t h a t 3 t o 5 p a r t s p e r m i l l i o n of r e ­

s i d u a l c h l o r i n e a t p H 6 . 0 w a s e f f e c t i v e i n d e s t r o y i n g c u l t u r e s of
P s . fragi,
genes.

P s . v i s c o s a , A l e . m e t a l c a l i g e n e s , E. c o l i , a n d A. a e r o -

T h e e f f e c t i v e n e s s of c h l o r i n e w a s

c r e a s e d and te m p e r a tu r e d e c re a se d .

r e d u c e d a s pH w a s i n ­

M ost a u th o rs g e n e r a l l y a g r e e

t h a t q u a t e r n a r y c o m p o u n d s a r e m o s t e f f e c t i v e a t h i g h pH l e v e l s
a n d a g a i n s t g r a m - p o s i t i v e t y p e s of o r g a n i s m s .

These compounds

a r e n o t a s g r e a t l y a f f e c t e d by o r g a n i c m a t t e r a s t h e h y p o c h l o r i t e s .
T h e h y p o c h l o r i t e s a r e m o s t e f f e c tiv e at lo w pH l e v e l s and a g a i n s t
g r a m - n e g a t i v e t y p e s of o r g a n i s m s .

The hy p o ch lo rites p o s se s s le ss

14
organism

s p e c ific ity th an the q u a te r n a r y a m m o n iu m

c o m p o u n d s , b ut

a r e m o r e g r e a t l y affe c te d by o rg a n ic m a t t e r .
Johns

(1954) c o m p a r e d I o b a c a n d I o s a n ( i o d o p h o r s ) t o c h l o ­

r in e and q u a t e r n a r y co m p o u n d s in d e s tr o y in g

M icro co ccu s pyogenes

v a r i e t y a u r e u s , E. c o l i , and P s . a e r u g i n o s a .

The iodophors c o m ­

p a r e d v e r y f a v o ra b ly with a quick actin g h y p o c h lo rite , e s p e c i a l ly in
t h e p r e s e n c e of a d d e d s k i m
w e re m uch slow er.

m ilk.

The other compounds tested

The iodophors show ed g r e a te r capacity, d e ­

s t r o y i n g m a n y m o r e i n c r e m e n t s of t e s t o r g a n i s m s t h a n o t h e r
g e rm ic id e s tested.
a

bacteriostatic

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

effect

o n s p o r e s of B a c i l l u s s u b t i l i s , i n d i c a t i n g

ex cep tio n a lly fa v o rab le r e s u lts ag ain st this o rg a n ism .

M ueller

( 1 9 5 5 ) r e p o r t e d t h a t 25 p a r t s p e r m i l l i o n of a v a i l a b l e i o d i n e c o m ­
p a r e d f a v o r a b l y w i t h 100 p a r t s p e r m i l l i o n of a v a i l a b l e c h l o r i n e in
k i l l i n g E . c o l i , S a l m o n e l l a t y p h o s a , M. p y o g e n e s v a r i e t y a u r e u s , a n d
P s . a e r u g in o s a in the p r e s e n c e
m atter.

of h a r d w a t e r a n d a d d e d o r g a n i c

H e a l s o s t a t e d t h a t 12.5 p a r t s p e r m i l l i o n of a v a i l a b l e

i o d i n e w a s e q u i v a l e n t t o 100 p a r t s p e r m i l l i o n of a v a i l a b l e c h l o r i n e
i n d e s t r o y i n g P s . a e r u g i n o s a a n d M. p y o g e n e s v a r i e t y a u r e u s i n
d i s t i l l e d o r h a r d w a t e r , b u t n o t i n t h e p r e s e n c e of a d d e d o r g a n i c
m atter.

G e r s h e n f e l d (1 955) f o u n d t h a t i o d o p h o r s a n d i o d i n e - i o d i d e

com pounds a r e effective as

s a n it i z i n g a g e n t s in c o n c e n t r a t i o n s

from

15
25 t o 75 p a r t s p e r m i l l i o n o f f r e e i o d i n e .

H e s t a t e s t h a t 25 p a r t s

p e r m i l l i o n of f r e e i o d i n e i s e q u i v a l e n t t o 200 p a r t s p e r m i l l i o n of
av ailab le chlorine.

L azarus

( 1 9 5 4 , 195 5) l i s t s n u m e r o u s a d v a n t a g e s

i n f a v o r of i o d i n e c o m p o u n d s , w h i c h r e c o m m e n d t h e m h i g h l y f o r
dai r y p la n t u s e .

C h e e se A dditives

E lliker
parts

per

w ater

to

m illion
d estro y

dem onstrated
chlorinated
quardt

the

w ater

(1953,

starter

to

surface

slim e

of

7.5

wash

w ater
the

in
per

available

organism s

to

present

rem ove

the

cream ing

product.

m illion
the

of

wash

w ater

supply.

He

curd

with

in th e

the

He

cheese

active

m ixtures

of

2.0

M arpercent

p artially

stated

available

developm ent

the curd.

addition

also

10

cheese

of w a s h i n g

that

5 to

cottage

o rg a n ism s from

reported
cheese

t h e a d d i t i o n of

c h lo rin e to

ineffectiveness

retard ed
slim y

recom m ended

of

1954)

cottage

parts

causing

( 1 954)

that

iodine

co ntrolled

the
to

of w a t e r - b o r n e

addition

the

final

organism s

condition.

B e n e k e a n d F a b i a n (1955 ) d e m o n s t r a t e d t h a t s o r b i c a c i d i s
in h i b i t o r y to o r g a n i s m s c o m m o n ly a s s o c i a t e d with s t r a w b e r r y and
to m ato spoilage.

C o s t i l o w et a l . (1955), S h e n e m a n and C o s t i l o w

( 1 9 5 5 ) , a n d P h i l l i p s a n d M u n d t (1 9 50) w o r k e d w i t h v a r i o u s o r g a n i s m s

16
a n d p h a s e s of t h e c u c u m b e r f e r m e n t a t i o n i n d u s t r y .

T h e y found that

s o rb ic a c id w as effective in p r e s e r v in g sw eet c u c u m b e r p ick les
w hen u s e d in c o n ju n c tio n w ith a c e t i c a c id in s u c r o s e so lu tio n s an d
w a s e f f e c t i v e a t l o w p H l e v e l s a g a i n s t y e a s t s c o m m o n to c u c u m b e r
ferm entations.
S m ith and R o llin (1954a,

19 54 b) r e p o r t e d t h a t w r a p p e r s

t r e a t e d w i t h s o r b i c a c i d w e r e e f f e c t i v e i n i n h i b i t i n g m o l d s on c h e e s e .
T h e a d d i t i o n of 0. 05 p e r c e n t s o r b i c a c i d t o p r o c e s s c h e e s e i n h i b i t e d
m olds.

A c c o rd in g to th e s e w o r k e r s , th is

a c id does not affect th e ta s te ,
the c h e e se .

o d o r , c o l o r , o r e m u l s i o n s t a b i l i t y of

M e l n i c k a n d L u c k m a n n ( 1 9 5 4 a , 195 4b) s h o w e d t h a t

so rb ic acid m ig ra te s
cheese.

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

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

They p ro p o se d a s p e c tro p h o to m e tric m ethod for d e te r m in a ­

t i o n of s o r b i c a c i d i n c h e e s e a n d c h e e s e w r a p p e r s .

The m ethod,

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

sul­

fate and c a lc u la tin g the c o n c e n tra tio n fro m the a b s o rb e n c y re ad in g .
T h is m e th o d m a y be v a l u a b l e in e n f o r c in g r e g u l a t io n s

r e g a r d i n g the

a d d i t i o n of s o r b i c a c i d t o c h e e s e a n d c h e e s e w r a p p e r s .
M e ln ic k et al. (1954c,

1954d) f o u n d t h a t s o r b i c a c i d i s o x i ­

d iz e d by th e s a m e a g e n ts and at th e s a m e

rates

as the p o ly s a tu r ­

a t e d fa tty a c i d s found in v e g e ta b le o ils and b u t t e r f a t .

The

17

degradation products also a r e s im ila r.

D e u e l e t al. (1954) d e m o n ­

s t r a t e d th a t r a t s m e t a b o l i z e s o r b i c a c id , o x id izin g it c o m p l e t e l y to
c a rb o n dioxide and w a te r.

D e u e l a n d A l f i n s l a t e r (1954) r e p o r t e d th a t

t e s t s in tw o in d e p e n d e n t l a b o r a t o r i e s

show ed that s o rb ic acid is

h a r m l e s s w h e n f e d t o d o g s a t t h e r a t e of 5 p e r c e n t of t h e i r d i e t on
a d ry w eight b a s is .

T hey concluded that s o rb ic acid is c o n s id e ra b ly

l e s s to x ic th a n s o d iu m b e n z o a te w hich h a s b e e n c o m m o n ly u s e d in
c h e e s e w r a p p e r s as a fu n g istatic agent.

METHODS

I s o l a t i o n a n d I d e n t i f i c a t i o n of S p o i l a g e
O r g a n i s m s in C o tta g e C h e e s e

Isolation and P u rificatio n

C o m m e r c i a l s a m p l e s of c o t t a g e c h e e s e w e r e c o l l e c t e d f r o m
r e ta il o u tlets and m a n u fa c tu rin g p lan ts.

A p ortion from

each

s a m p l e of c h e e s e w a s t r a n s f e r r e d a s e p t i c a l l y i n t o s t e r i l e p e t r i
p l a t e s a n d i n c u b a t e d a t 10° a n d 21°

C. u n t i l s p o i l a g e o c c u r r e d .

The c h e e s e w as c o n s id e re d spoiled when slim e ,

m old grow th, o r

a d e fin ite ly u n d e s ir a b le o d o r developed.
M aterial from

s a m p l e s of c h e e s e s u s p e c t e d of b e i n g

s p o i l e d b y b a c t e r i a w a s s t r e a k e d on t r y p t o n e g l u c o s e y e a s t a g a r
plates.

T h e s a m p l e s s u s p e c t e d of b e i n g s p o i l e d by y e a s t s a n d

m o l d s w e r e s t r e a k e d on p o t a t o d e x t r o s e a g a r a c i d i f i e d t o pH of
3.5

w ith t a r t a r i c

acid.

T h e p r e d o m i n a n t c o l o n i e s a p p e a r i n g on t h e

p la te s w e r e t r a n s f e r r e d to tr y p to n e g lu c o s e y e a s t a g a r s la n ts and
acidified potato d e x tro s e a g a r sla n ts,

respectively.

The cultures

g r o w in g on th e s l a n t s w e r e th e n p u r if i e d by p la tin g , s t r e a k i n g , and
shake c u ltu re techniques.
tra n sfe rs

T h e s h a k e c u l tu r e te c h n iq u e in v o lv ed loop

f ro m a g a r s la n ts and s u b s e q u e n t s e r i a l dilu tio n s into
18

19
t h r e e t u b e s of m e l t e d t r y p t o n e g l u c o s e y e a s t a g a r , f o l l o w e d b y
p l a t i n g of t h e t u b e s of a g a r .
iso la te d and purified.

A t o t a l of t h i r t y - t w o c u l t u r e s w e r e

T h e se p urified c u ltu re s w e re u sed th ro u g h ­

out th e e n t i r e study.

I d e n t i f i c a t i o n of t h e I s o l a t e d C u l t u r e s

T h e m a j o r i t y of t h e m e d i a a n d r e a g e n t s u s e d i n t h i s s t u d y
w e r e obtained fro m

Difco L a b o r a t o r i e s , D e tr o it,

tr y p tic a s e soy b ro th w as obtained fro m
oratories,

M ichigan.

The

B a ltim o re B iological L a b ­

B a ltim o re , M aryland.

T h e c o l o n y c h a r a c t e r i s t i c s of t h e b a c t e r i a l c u l t u r e s w e r e
o b ta in e d by g ro w in g th e o r g a n i s m s on tr y p to n e g lu c o s e y e a s t a g a r
s la n ts and p la te s and p o tato d e x tr o s e a g a r p la te s .

T h e ir grow th

c h a r a c t e r i s t i c s w e r e o b s e r v e d in n u t r i e n t b r o t h a n d l i t m u s m i l k .
B u r k e ' s m o d i f i c a t i o n of t h e G r a m

s ta in and L e if s o n 's fla g e lla

s t a i n d e s c r i b e d i n T h e M a n u a l of M e t h o d s f o r P u r e C u l t u r e S t u d y
of B a c t e r i a (19 46) w e r e m a d e f r o m

2 4 - h o u r-o ld n u trie n t b ro th

c u l t u r e s of t h e o r g a n i s m s .
B i o c h e m i c a l t e s t s p e r f o r m e d in c lu d e d r e a c t i o n s in d e x t r o s e ,
m altose, lacto se,
solutions.

s u c r o s e , g a la c to s e , x y lo se , and ra ffin o se b ro th

M o t i l i t y d e t e r m i n a t i o n s w e r e p e r f o r m e d in a m e d i u m

c o n s i s t i n g of 1 0 , 0 g. of t r y p t o s e , 5 . 0 g. of s o d i u m

c h l o r i d e , 5 . 0 g.

20
of a g a r a n d 1 l i t e r o f d i s t i l l e d w a t e r .

T h e a b i l i t y of t h e o r g a n i s m s

to liq u efy g e la tin , re d u c e n i t r a t e s to n itr ite s , u tiliz e c i t r a t e s a s a
s o l e s o u r c e of c a r b o n , p r o d u c e a c i d f r o m

d e x tro s e (m ethyl r e d r e ­

action),

d e x t r o s e (V o g e s - P r o s k a u e r

form

a c e ty l-m e th y l-c a rb in o l from

re a c tio n ), h y d ro ly z e s ta r c h , and p ro d u c e u r e a s e , h y d ro g e n sulfide,
and indole

w as d e te r m in e d usin g a p p r o p r ia te m e d ia and re a g e n ts

d e s c r i b e d i n t h e D i f c o M a n u a l ( 1 9 5 3 ).
to u se a m m o n iu m
u sing a m edium

s a lts as a sole

s o u r c e of n i t r o g e n w a s d e m o n s t r a t e d

c o n s i s t i n g of 1 5 .0 g. of a g a r ,

d i-h y d ro g e n phosphate,
chlo rid e,

T h e a b i l i t y of t h e o r g a n i s m s

1 0 . 0 g. of g l u c o s e ,

0.2 g. of m a g n e s i u m

1.0 g. of a m m o n i u m

0.2 g. of p o t a s s i u m

s u l f a t e , 0.01 g. of b r o m

cresol

p u r p l e , a n d 1 l i t e r of d i s t i l l e d w a t e r .
In o c u la tio n s into th e a p p r o p r i a t e t e s t m e d ia w e r e m a d e fro m
2 4 - h o u r - o ld n u trie n t b ro th c u ltu r e s of th e o r g a n is m s

being te s te d .

T h e i n o c u l a t e d m e d i a w e r e i n c u b a t e d a t 21° C. f o r t h e r e q u i r e d
l e n g t h of t i m e a n d t h e a p p r o p r i a t e t e s t s p e r f o r m e d .
B e rg e y 's
et al.

M a n u a l of D e t e r m i n a t i v e B a c t e r i o l o g y b y B r e e d

( 194 8) a n d A g r i c u l t u r e

M o n o g r a p h No.

16, A e r o b i c S p o r e -

f o r m i n g B a c t e r i a b y S m i t h e t a l . (1952) w e r e u s e d a s g u i d e s f o r
c l a s s i f i c a t i o n of t h e i s o l a t e d c u l t u r e s .
T h e a p p e a r a n c e of t h e y e a s t c u l t u r e s w a s n o t e d o n t r y p t o n e
g l u c o s e y e a s t a g a r s l a n t s , in n u t r i e n t b r o th a n d l i t m u s m ilk .

The

21
a b ility of th e o r g a n i s m s to a s s i m i l a t e and f e rm e n t d e x tr o s e , m a lto s e ,
lactose, galactose,

s u c ro s e , m an n o se, and raffinose was d e m o n stra te d

a s r e c o m m e n d e d b y L o d d e r a n d K r e g e r v a n R ij ( 1 9 5 2 ).
a b ility to r e d u c e n i t r a t e s to n i t r i t e s

T h eir

was d em onstrated as d escrib ed

i n t h e D i f c o M a n u a l (1 9 53) u s i n g s u l f a n i l i c a c i d a n d a - n a p h t h y l a m i n e
re a g e n t solutions.
yeast cultures

S p o r u la tio n t e s t s w e r e p e r f o r m e d by g r o w in g th e

f o r 1 m o n t h on V - 8 v e g e t a b l e j u i c e a g a r s l a n t s a n d

then exam ining m ic ro s c o p ic a lly for sp o re s.

The y e a s t c u ltu re s

w e r e a ls o e x a m in e d fo r t h e i r a b ility to p r o d u c e s ta r c h l i k e co m p o u n d s
as

r e c o m m e n d e d b y L o d d e r a n d K r e g e r v a n R ij ( 19 52).

A T a x o n o m ic Study by t h e s e a u t h o r s

The Y e a s ts :

w as u s e d as a guide

in c l a s s i ­

f i c a t i o n of t h e i s o l a t e d y e a s t c u l t u r e s .
M orphological c h a r a c te r is tic s
grow ing th em
agar.

on C z a p e k , S a b o u ra u d ,

of t h e m o l d s w e r e o b t a i n e d b y
and tryptone glucose

yeast

T h e c u l t u r e s g r o w n on S a b o u r a u d a g a r w e r e s ta i n e d u s in g

l a c t o - p h e n o l c o t t o n - b l u e s t a i n a s o u t l i n e d by A l e x o p o u l o s a n d B e n e k e
( 1 9 5 2 ).

I d e n t i f i c a t i o n of t h e m o l d c u l t u r e s w a s m a d e u s i n g m o r ­

phological c h a r a c te r is tic s and the a p p ro p ria te identification keys
f o u n d i n G i l m a n (1 945) a n d R a p e r e t a l . (1949).
T h e th ir ty - tw o c u ltu re s w hich w e r e iso la te d and p u rifie d
w e r e c h a r a c t e r i z e d a s follow s:
three

y easts.

tw e n ty -o n e b a c te r ia , eight m o ld s , and

E ight b a c te r ia l c u ltu re s and one y e a s t w e re is o la te d

22
f r o m t r y p t o n e g l u c o s e y e a s t a g a r p l a t e s e x p o s e d in t h e c o t t a g e
c h e e s e p r o c e s s i n g r o o m s f o r 10 m i n u t e s .
catecu ltu re s
m olds,

fro m the is o la te s left eig h teen

T h e e l i m i n a t i o n of d u p l i ­
bacterial cultures,

four

and t h r e e y e a s t s w hich w e r e c a r r i e d to c o m p le te te n ta tiv e

id entification.

T y p e of S p o i l a g e P r o d u c e d b y P u r e C u l t u r e s
of C o t t a g e C h e e s e S p o i l a g e O r g a n i s m s

N in e te e n r e p r e s e n t a t i v e o r g a n i s m s fro m the g ro u p w e r e
s e l e c t e d f o r u s e in f u r t h e r s tu d ie s in v o lv in g c o tta g e c h e e s e .

The

c u l t u r e s w e r e c a r r i e d in t r y p t i c a s e soy b r o th s in c e th is m e d iu m
s u p p o r t e d t h e g r o w t h of a l l o r g a n i s m s q u i t e w e l l .
m ade from

Inoculations w e re

2 4 - h o u r - o l d b r o th c u l t u r e s into th e c h e e s e in a ll i n s t a n c e s .

A p p e a r a n c e of C h e e s e W h e n S p o i l a g e O r g a n i s m s A r e
i n P u r e C u l t u r e a n d i n C o m b i n a t i o n w i t h S. l a c t i s

C o t t a g e c h e e s e w a s p l a c e d i n l a y e r s a p p r o x i m a t e l y 1/8 i n c h
d e e p in p e t r i p l a t e s .

T he p la te s w e r e c o v e re d with s a r a n and

s t e r i l i z e d with an e le c tr o n b e a m
rep.

m a c h i n e at a d o s a g e of 5 .5 x 10

T h e s a r a n w a s r e p la c e d with s t e r i l i z e d g l a s s

covers.

The

p H of t h e s t e r i l i z e d c h e e s e w a s d e t e r m i n e d a n d t h e n t h e p l a t e s
w e r e i n o c u l a t e d w i t h 1 m l . a m o u n t s of 2 4 - h o u r - o l d b r o t h c u l t u r e s
of the o r g a n is m s .

O n e s e t of p l a t e s w a s i n o c u l a t e d w i t h p u r e

6

23
c u l t u r e s of t h e

spoilage o r g a n is m s and a seco n d set w as in o culated

i n t h e s a m e m a n n e r , b u t r e c e i v e d a l s o a n i n o c u l a t i o n of S. l a c t i s .
T h e i n o c u l a t e d p l a t e s w e r e i n c u b a t e d a t 21°

C. u n t i l s p o i l a g e o c ­

c u r r e d o r it w a s a p p a r e n t th a t no v is i b l e s p o ila g e would o c c u r .
The p la te s containing the p u re c u ltu re s and the ones containing
p u r e c u l t u r e s i n c o m b i n a t i o n w i t h S. l a c t i s w e r e c o m p a r e d a n d
photographed.

T h e e n t i r e c o n te n t? of e a c h p la te w a s th e n m ix e d

w e l l , p l a c e d i n a 50 m l . b e a k e r , a n d t h e p H d e t e r m i n e d u s i n g a
B e c k m a n M odel G pH m e t e r .

C haracteristics

of C o t t a g e C h e e s e S p o i l a g e O r g a n i s m s

T h e e f f e c t of i n c u b a t i o n t e m p e r a t u r e ,
h e a t, c h lo rin e , iodophor,

pH, s o d i u m c h l o r i d e ,

q u a t e r n a r y , a n d s o r b i c a c i d on t h e g r o w t h

of n in e te e n r e p r e s e n t a t i v e o r g a n is m s fro m th e g ro u p w as d e t e r ­
m ined.

T h e s e c h a r a c t e r i s t i c s w e r e d e t e r m i n e d in t r y p t i c a s e so y

b ro th o r m odified b ro th solutions w h e n e v e r p o ssib le .
w ere m ade from

Inoculations

2 4 - h o u r - o l d b r o th c u ltu r e s into th e a p p r o p r i a t e

m edia.

T em perature

L im its

of G r o w t h

S t e r i l e t u b e s of b r o t h i n o c u l a t e d w i t h one l o o p f u l of t h e
c u l t u r e s w e r e i n c u b a t e d at 3°, 10°, 2 0°, 35°, and 5 0

C., and

24
e x a m i n e d a f t e r 3 a n d 7 d a y s of i n c u b a t i o n .

I n c r e a s e d t u r b i d i t y of

t h e b r o t h w a s a c c e p t e d a s e v i d e n c e of g r o w t h of t h e o r g a n i s m .

E f f e c t of p H o n G r o w t h R a t e

T h e c u l t u r e s w e r e t e s t e d f o r g r o w t h i n b r o t h a d j u s t e d t o pH
l e v e l s of 4 . 0 , 4 . 4 , 4 . 6 , 4 . 8 , 5 . 0 , 5 . 2 , 5 . 4 , 6 .7 , a n d 7.4 w i t h 85 p e r ­
cent (reag en t g rad e) lactic acid.

T h e r e q u i r e d a m o u n t of a c i d w a s

a d d e d t o t h e b r o t h p r i o r t o a u t o c l a v i n g a t 15 p o u n d s p r e s s u r e f o r 15
m inutes.

T h i s a u t o c l a v i n g d i d n o t a p p r e c i a b l y c h a n g e t h e pH of

the m ed iu m .

I n o c u l a t i o n s w e r e m a d e a n d t h e t u b e s i n c u b a t e d a t 21°

C. f o r 3 d a y s a n d t h e n e x a m i n e d f o r g r o w t h .

T h e e x te n t of g ro w th

w a s d e t e r m i n e d by m e a s u r i n g th e i n c r e a s e in t u r b i d i t y w ith a K le ttS u m m e r s o n c o l o r i m e t e r e q u i p p e d w i t h a n u m b e r 42 f i l t e r .

The

c o l o r i m e t e r w a s s t a n d a r d i z e d w i t h u n i n o c u l a t e d c o n t r o l t u b e s of
b r o t h at e a c h pH le v e l.

Sodium C h lo rid e T o le r a n c e

T h e c u ltu re s w e re te s te d for s a lt to le ra n c e in b ro th solutio ns
c o n t a i n i n g 1, 3, 5, 7, a n d 10 p e r c e n t s o d i u m c h l o r i d e a d d e d t o t h e
m edium

p r i o r to s te riliz a tio n .

t u b e s i n c u b a t e d a t 21°

T h e in o c u la tio n s w e r e m a d e and

C. f o r 3 d a y s a n d t h e n e x a m i n e d f o r g r o w t h .

An i n c r e a s e in t u r b i d i t y

of t h e

broth

as

com pared

to

an

25
uninoculated

control

was

accepted

as

evidence

of g r o w t h

of t h e

o rg an ism .

Heat T o leran ce

T w e n ty -fo u r-h o u r-o ld skim

m ilk cu ltu re s

of e a c h of t h e o r ­

g a n i s m s w e r e t e s t e d f o r t o l e r a n c e to h e a t i n g a t 143°
20, a n d 3 0 m i n u t e s .
1.5

T h e c u ltu r e s w e r e h e a te d in c a p illa r y tu b e s

x 90 m m . a n d t h e n c o o l e d i m m e d i a t e l y .

i n c u b a t e d a t 21°

The cap illaries w ere

C. f o r 2 d a y s a n d t h e c o n t e n t s p l a t e d u s i n g t r y p t o n e

g lu c o s e y e a s t a g a r to d e te r m in e o r g a n is m
w e r e a l s o t e s t e d f o r t o l e r a n c e t o 120°
c o r r e s p o n d s to th e cooking t e m p e r a t u r e
four-hour-old

F . f o r 5, 10,

skim

survival.

The cu ltu res

F . f o r 15 m i n u t e s , w h i c h
of c o t t a g e c h e e s e .

Tw enty-

m ilk c u ltu re s and whey c u ltu re s p r e p a r e d from

2 4 - h o u r - o l d a g a r s l a n t s of t h e o r g a n i s m s w e r e h e a t e d f o r 15 m i n ­
u t e s at 120° F . in c a p i l l a r y tu b e s a n d th e n c o o le d i m m e d i a t e l y .
T h e c a p i l l a r i e s w e r e in c u b a te d and p la te d a s d e s c r i b e d ab o v e to
d eterm in e o rganism

survival.

R e s i s t a n c e to G e r m i c i d e s

T h e c u l t u r e s w e r e t e s t e d f o r r e s i s t a n c e t o s o l u t i o n s of 10,
25, a n d 50 p a r t s p e r m i l l i o n of c h l o r i n e , q u a t e r n a r y , a n d i o d o p h o r
f o r 1, 5, a n d 10 m i n u t e s '

exposure.

F r e s h sto c k solutions containing

26
100 p a r t s p e r m i l l i o n of c h l o r i n e , q u a t e r n a r y , a n d i o d o p h o r w e r e
p re p a re d for each determ ination.

The c h lo rin e and io d o p h o r sto ck

s o lu tio n s w e r e s t a n d a r d i z e d by s o d iu m th io s u lf a te t i t r a t i o n and the
q u a te r n a r y sto c k solu tio n by the H a r p e r - E l l i k e r m ethod d e s c rib e d
i n t h e K l e n z a d e D a i r y S a n i t a t i o n H a n d b o o k (1 954).

Stock s o lu tio n s

w e r e s t o r e d in 1 g a llo n c a p a c ity , tig h tly c lo s e d , b ro w n g l a s s b o ttle s.
O n e h u n d r e d m l . p o r t i o n s c o n t a i n i n g 10, 25, a n d 5 0 p a r t s p e r m i l ­
lio n of c h l o r i n e , q u a t e r n a r y , and io d o p h o r s o lu tio n s w e r e p r e p a r e d
f r o m t h e s t o c k s o l u t i o n s b y m i x i n g t h e a p p r o p r i a t e a m o u n t of t h e
s to c k so lu tio n w ith s t e r i l e d is tille d w a t e r ju s t p r i o r to te s tin g e a c h
culture.
ism

O n e m l . o f a 2 4 - h o u r - o l d b r o t h c u l t u r e of t h e t e s t o r g a n ­

w a s a d d e d t o e a c h 100 m l . p o r t i o n of d i s i n f e c t a n t a n d t h e

m ix tu r e w ell shaken.

At i n t e r v a l s of 1, 5, a n d 1-0 m i n u t e s , l o o p

in o c u la tio n s w e r e m a d e f ro m the o r g a n i s m - d is i n f e c t a n t m ix tu r e into
s t e r i l e t u b e s of b r o t h .
C,

for

3 days

and

then

T h e i n o c u l a t e d t u b e s w e r e i n c u b a t e d a t 21°
exam ined

for

grow th.

An

increase

in

t u r b i d i t y w a s a c c e p t e d a s e v i d e n c e of g r o w t h of t h e o r g a n i s m .

T o l e r a n c e to c h lo r in e .

T h e c h l o r i n e t o l e r a n c e of n i n e t e e n

c o tta g e c h e e s e s p o ilag e o r g a n is m s w as p e r f o r m e d as outlined above.
T h e s t o c k s o l u t i o n of c h l o r i n e w a s p r e p a r e d f r o m a s o d i u m h y p o ­
c h l o r i t e s o l u t i o n c o n t a i n i n g 8.4 p e r c e n t c h l o r i n e .

27
T o l e r a n c e to q u a t e r n a r y .

T h e a b i l i t y of n i n e t e e n c o t t a g e

c h e e s e sp o ilag e o r g a n is m s to to le r a te q u a te r n a ry com pounds was
d e m o n s tr a te d a s outlined above.

T h e s t o c k s o l u t i o n of q u a t e r n a r y

w a s p r e p a r e d f r o m a 12.8 p e r c e n t a c t i v e a lk y l d im e t h y l b e n z y l a m ­
m onium

c h lo rid e solu tio n obtained fro m the K len zade P ro d u c ts C o m ­

pany, Beloit, W isconsin.

T o l e r a n c e to i o d o p h o r .

T h e a b i l i t y of n i n e t e e n c o t t a g e c h e e s e

s p o ila g e o r g a n i s m s to t o l e r a t e io d o p h o r co m pounds w as
a s outlined above.

dem onstrated

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

f r o m a 4.77 p e r c e n t a c tiv e Iobac so lu tio n o b tain ed f ro m

L azarus

L a b o r a t o r i e s , Inc., Buffalo, N ew Y o rk .

R e s is ta n c e to S orbic A cid

T h e c u l t u r e s w e r e t e s t e d f o r r e s i s t a n c e t o c o n c e n t r a t i o n s of
0 . 0 5 , 0 . 1 0 , a n d 0.2 5 p e r c e n t s o r b i c a c i d a t p H l e v e l s of 4 . 8 , 5 . 0 ,
a n d 5.2 i n t r y p t i c a s e s o y b r o t h .

The b ro th solutions w e re m a d e

co n tain in g th e d e s i r e d s o r b i c a c id c o n c e n tr a tio n s and p r i o r to s t e r i l ­
i z a tio n th e pH w a s a d ju s te d to the d e s i r e d le v e l with c o n c e n t r a t e d
(re a g e n t g ra d e ) la c tic acid.
lev els

T h e c u l t u r e s w e r e a l s o t e s t e d a t pH

of 7 . 0 , 6 . 8 , a n d 6 . 0 w i t h s o r b i c a c i d c o n c e n t r a t i o n s of 0 .0 5 ,

0 . 1 0 , a n d 0 .2 5 p e r c e n t ,

respectively.

T h e s e pH l e v e l s r e s u l t e d w h e n

28
th e d e s i r e d s o r b i c a c id c o n c e n t r a t i o n s w e r e ad d ed to the b ro th w ith
n o a t t e m p t t o c o n t r o l pH .
pressure

S t e r i l i z a t i o n by a u t o c l a v i n g a t 15 p o u n d s

f o r 15 m i n u t e s c a u s e d n o s i g n i f i c a n t c h a n g e i n pH.

The

t u b e s of b r o t h c o n t a i n i n g s o r b i c a c i d w e r e i n o c u l a t e d w i t h o n e l o o p ­
ful of a 2 4 - h o u r - o l d b r o t h c u l t u r e of t h e o r g a n i s m .
w e r e i n c u b a t e d a t 2 1°

The tubes

C. f o r 48 h o u r s a n d t h e i n c r e a s e in t u r b i d i t y

m e a s u r e d with a K l e t t - S u m m e r s o n c o l o r i m e t e r equipped with a
n u m b e r 42 f i l t e r .

The c o lo r im e te r w as ad ju sted using uninoculated

c o n t r o l b r o t h t u b e s at e a c h pH l e v e l and s o r b i c a c id c o n c e n t r a t i o n .
In t u b e s w h i c h s h o w e d n o i n c r e a s e i n t u r b i d i t y u p o n v i s u a l i n s p e c ­
t i o n , t h e v i a b i l i t y of o r g a n i s m s w a s d e t e r m i n e d b y p l a t i n g w i t h
tryptone glucose y east agar.
w as accepted as

An i n c r e a s e i n t u r b i d i t y of t h e b r o t h

e v i d e n c e of g r o w t h of t h e o r g a n i s m , w h i l e no i n ­

c r e a s e i n t u r b i d i t y b u t g r o w t h on t h e p l a t e s w a s a c c e p t e d a s e v i d e n c e
of v i a b i l i t y b u t n o g r o w t h .

C o n t r o l of O r g a n i s m s C a u s i n g S p o i l a g e
in C o tta g e C h e e s e

T r e a t m e n t of W a s h W a t e r

T h e e f f e c t i v e n e s s of w a s h i n g c o t t a g e c h e e s e c u r d w i t h w a t e r s
containing a c etic,

c itric , la ctic, p h o sp h o ric, and s o rb ic acids,

and

c h l o r in e , io d o p h o r an d q u a t e r n a r y c o m p o u n d s in c o n tro llin g o r g a n i s m s

29
w hich c a u s e s p o ila g e in c o ttag e c h e e s e w as d e te r m in e d .

Tw enty

pounds of f r e s h d ry co ttag e c h e e s e c u rd w as obtained fro m the
M ichigan State U n iv e r s ity D a iry P la n t o r a lo cal d a iry .

One and

o n e - h a l f p o u n d s of t h e c h e e s e , w h i c h s e r v e d a s a n u n i n o c u l a t e d
c o n t r o l , w a s r e m o v e d and w a s h e d w ith 1 l i t e r of cold ta p w a te r .
T h e r e m a i n d e r of t h e c h e e s e w a s t h o r o u g h l y w a s h e d w i t h 2 l i t e r s
of w a t e r i n o c u l a t e d w i t h 2 m l . of a 2 4 - h o u r - o l d b r o t h c u l t u r e of t h e
spoilage o rg a n ism .

W ash w a te r s w e re p r e p a r e d containing sufficient

a c e t i c , c i t r i c , p h o s p h o r i c , a n d l a c t i c a c i d s to r e d u c e t h e pH o f t h e
w a s h w a t e r s t o 5 .0 .

W ash w a te r w as p r e p a r e d a lso w hich contained

0.05 p e r c e n t s o r b i c a c i d ; h i g h e r c o n c e n t r a t i o n s i m p a r t e d a n o b j e c ­
tio n a b le fla v o r to the c h e e s e .

W a t e r s c o n t a i n i n g 10 p a r t s p e r

m i l l i o n of c h l o r i n e a n d q u a t e r n a r y a n d 7.5 p a r t s p e r m i l l i o n of
iodophor w e re p r e p a r e d fro m

s t o c k s o l u t i o n s c o n t a i n i n g 100 p a r t s

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

One and o n e -h a lf-p o u n d p o rtio n s

of t h e c o n t a m i n a t e d c h e e s e w e r e w e i g h e d
of t h e p r e p a r e d w a s h w a t e r s .

into

1 liter

po rtio n s

O n e l o t of 1 - 1 / 2 p o u n d s of i n o c u l a t e d

c h e e s e w a s a l s o w e i g h e d i n t o 1 l i t e r of p l a i n c o l d t a p w a t e r ,
w as the inoculated control.
the c u rd

after

30 m inutes

c r e a m e d w ith s t e r i l e c r e a m
and 4 p e rc e n t sodium

this

The w ash w a te rs w ere drained from
of

exposure

and

the

dry

curd

was

w h i c h c o n t a i n e d 14 p e r c e n t b u t t e r f a t

chloride.

The salt was added a fte r auto­

c l a v i n g f o r 15 m i n u t e s a t 15 p o u n d s p r e s s u r e .

The cre a m

and

30
c h e e s e w e r e m i x e d in p r o p o r t i o n s w hich g a v e a p r o d u c t c o n tain in g 4
p e r c e n t b u t t e r f a t a n d 1. 15 p e r c e n t s a l t .

T he c re a m in g m ix tu re was

a llo w e d to s ta n d on th e c h e e s e f o r a p p r o x i m a t e l y 1 h o u r b e f o r e
packaging

E a c h lot of c h e e s e w as p a c k a g e d in t h r e e 1 2 -o u n c e

c o t t a g e c h e e s e c a r t o n s a n d s t o r e d a t 50° F .
am ined

The cheese w as ex­

f o r a p p e a r a n c e of v i s i b l e s p o i l a g e , g i v e n a f l a v o r s c o r e ,

and the pH d e te r m in e d in itia lly and at 2 -d a y in te r v a ls t h e r e a f t e r
until s p o ila g e o c c u r r e d .

T r e a t m e n t of D r e s s i n g M a t e r i a l s

T h e e f f e c t i v e n e s s of t r e a t i n g c o t t a g e c h e e s e d r e s s i n g w i t h
c i t r i c , l a c t i c , a n d s o r b i c a c i d s an d s t a r t e r in c o n tr o llin g o r g a n i s m s
w hich c a u s e s p o ila g e in co ttag e c h e e s e w as d e te r m in e d .

Fifteen

p o u n d s of f r e s h d r y c o t t a g e c h e e s e c u r d w a s o b t a i n e d f r o m t h e
M ichigan S tate U n iv e rs ity D a ir y P lan t o r a lo c a l d a iry .
1 -1/2

Six l o t s of

p o u n d s of t h e c h e e s e w e r e p l a c e d in s e p a r a t e c o n t a i n e r s .

F i v e p o u n d s of c r e a m

c o n t a i n i n g 14 p e r c e n t b u t t e r f a t w a s s t e r i l i z e d

b y a u t o c l a v i n g f o r 15 m i n u t e s a t 15 p o u n d s p r e s s u r e ,
percen t salt added.
of 1 - 1 / 2

A p o r t i o n of t h i s c r e a m

cooled, and 4

w a s a d d e d to one lot

p o u n d s of c h e e s e c u r d , y i e l d i n g 4 p e r c e n t b u t t e r f a t a n d

1 ^5 p e rc e n t

s a lt in th e fin is h e d p ro d u c t.

s e r v e d a s the uninoculated control.

T h i s l o t of c h e e s e

T h e r e m a i n d e r of t h e c r e a m

31
was

c o n t a m i n a t e d w i t h 1 m l . of a 2 4 - h o u r - o l d b r o t h c u l t u r e of t h e

spoilage o rg a n ism .

A p o r t i o n of t h i s c o n t a m i n a t e d c r e a m

was added

t o o n e l o t of 1 - 1 / 2 p o u n d s of c h e e s e , y i e l d i n g a s t a n d a r d i z e d p r o d ­
uct as before.

T h is lot s e r v e d as th e in o c u la te d c o n tro l.

Fifteen

h u n d r e d t h s p e r c e n t c i t r i c a n d l a c t i c a c i d s , 0.10 p e r c e n t s o r b i c a cid ,
a n d 2 . 0 p e r c e n t s t a r t e r w e r e a d d e d , r e s p e c t i v e l y , t o f o u r p o r t i o n s of
the co n ta m in a te d c r e a m .

T h e s e in o c u la te d and t r e a t e d d r e s s i n g s

w e r e th e n a d d e d to the c h e e s e and a llo w e d to s ta n d fo r a p p r o x im a te ly
1 h o u r b e fo re packaging.

E a c h l o t of c h e e s e w a s p a c k a g e d in t h r e e

1 2 - o u n c e c o t t a g e c h e e s e c a r t o n s a n d s t o r e d a t 50° F .

The ch eese

w a s e x a m i n e d f o r a p p e a r a n c e of v i s i b l e s p o i l a g e , g i v e n a f l a v o r
s c o r e , and the pH d e t e r m i n e d in itia lly and at 2 - day i n t e r v a l s t h e r e ­
a fte r until sp o ilag e o c c u r re d .

RESULTS

I d e n t i f i c a t i o n of t h e I s o l a t e d C u l t u r e s

T a b l e s I, II, III, a n d IV s h o w t h e v a r i o u s t e s t s w h i c h w e r e
p e r f o r m e d in identifying th e b a c te r ia l and y e a s t c u ltu re s .

M or­

p h o lo g ic a l c h a r a c t e r i s t i c s u s e d in id en tify in g th e m old c u l t u r e s a r e
described later.
T h e b a c te r ia l c u ltu re s w e re te n tativ ely identified as
A c h ro m o b a c te r butyri, A c h ro m o b a c te r eurydice, A lcaligenes
m e ta lc a lig e n e s, B acillus firm u s, B ac te riu m
bacterium

e ry th ro g e n e s, Coryne-

f il a m e n t o s u m , E s c h e r i c h i a coli, E s c h e r ic h ia freundii,

E sch erich ia interm edium ,

M ic ro c o c c u s a u r a n tia c u s , M icro co ccu s

candidus, M ic ro c o c c u s c o n g lo m e r a tu s , M icro co ccu s ep id erm id is,
M ic ro c o c c u s flavus, P s e u d o m o n a s d e s m o ly tic u m , P se u d o m o n a s
fluorescens, P seudom onas

fragi, and P seudom onas tra lu c id a .

The

y e a s t c u ltu re s w e re te n ta tiv e ly identified as R hodotorula fla v a ,
T orulopsis

Candida, a n d T o r u l o p s i s v e r s a t i l i s , and th e m o ld c u l t u r e s

as G e o tric h u m c a n d id u m , M ucor plum beus,
P enicillium

M ucor r a c e m o s u s , and

frequentans.

A l e , m e t a l c a l i g e n e s , C. f i l a m e n t o s u m , E. f r e u n d i i , M.
a u r a n t i a c u s , M.

c o n g l o m e r a t u s , M. e p i d e r m i d i s , M. f l a v u s , a n d
32

33
TABLE I
PH YSIOLOGICA L, M O R PH O L O G IC A L, AND B IO C H EM IC A L
C H A R A C T E R IS T IC S O F E I G H T E E N B A C T E R IA ISO­
LA TED FR O M SPO ILED C H EESE AND AGAR
P L A T E S E X P O S E D IN C H E E S E P L A N T S
Staining and
O rganism
G ram

F lagella,
M otility

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

-

-

sm all short

e u r y d i c e .........................

-

-

sm a ll sh o rt rods

-

-

s m a ll m edium rods

+

-

la r g e m ed iu m rods

-

sm a ll sh o rt rods

Ach. b u ty ri
Ach.

A le. m e t a l c a l i g e n e s . . . .
B. f i r m u s
B act.

M orphology

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

erythrogenes

a

Size and Shape

rods

. . . .

-+

C. f i l a m e n t o s u m ..................

+

-

la r g e m ed iu m rods

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

-

+

sm a ll sh o rt rods

-

sm all sh o rt

rods

-

-

sm all short

rods

M. a u r a n t i a c u s .....................

+

-

m edium

M. c a n d i d u s ............................

+

-

sm all cocci

M. c o n g l o m e r a t u s

+

-

la rg e cocci

M. e p i d e r m i d i s .....................

+

-

m edium

M. f l a v u s ...................................

+

-

larg e

+

m ed iu m sh o rt rods

+

m e d iu m long ro d s

P s . f r a g i ...................................

+

m e d iu m long ro d s

P s . t r a l u c i d a .........................

+

m e d iu m long r o d s

E. co li
E.

f r e u n d i i ................................

E. i n t e r m e d i u m

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

. . . .

P s . d e s m o l y t i c u m ..............

.

Ps.

.

flu o rescen s

Legend:

. . . . . .

,

In c a r b o h y d r a t e r e a c t i o n s , - = n o r e a c t i o n ,
d u c e d , ++ = a c i d a n d g a s p r o d u c e d .

cocci

cocci

cocci

+ = acid p r o ­

34

T A B L E I (Continued)

C arbohydrate
Dex­
trose

M al­
tose

Lac­
tose

+

-

-

+

-

+

R eactions
G alac­
tose

Xy­
lose

Raffinose

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

+

+

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

-

++

++

++

++

++

+

++

++

++

++

++

++

4"+

++

++

++

++

++

++

++

++

+

-

+

+

-

-

-

+

-

-

+

+

+

+

-

-

-

+

+

-

-

+

-

-

++

++

+

+

++

++

-

+

-

-

-

-

-

-

+

-

-

-

+

+

-

++

++

++

++

'

Su­
crose

b

+

b

+

b

b

-Lb

___

a V ariable g ra m

reaction.

b W eak c a rb o h y d ra te reactio n .

35

T A B L E II

PH Y SIO LO G IC A L A N D B IO C H E M IC A L C H A R A C T E R IST IC S O F
E IG H T E E N B A C T E R IA IS O L A T E D F R O M S P O IL E D
C H EESE AND AGAR P L A T E S E X PO SE D
IN C H E E S E P L A N T S
A p p e a r a n c e o f G ro w th
in D iffe r e n t M ed ia
___________________________________

O r g a n is m

L itm u s M ilk

N u tr ie n t B ro th

no re a c tio n

tu rb id , sed im en t

alkaline

tu rb id , sed im en t

Ale . m e t a l c a l i g e n e s . .

slight a lk alin e

tu rb id , sed im en t

B. f i r m u s

acid digestion

tu rb id , sedim ent

alkaline coagulation

tu rb id , sed im en t

no re a c tio n

tu rb id , sed im en t

acid coagulation

tu rb id , sed im en t

E . f r e u n d i i .........................

acid

tu rb id , sed im en t

E. i n t e r m e d i u m

acid

tu rb id , sed im en t

M. a u r a n t i a c u s ..............

slig h t a lk a lin e

tu rbid, sed im en t

M. c a n d i d u s .....................

slig h t a cid

tu rb id , sed im en t

M. c o n g l o m e r a t u s

no re a c tio n

tu rb id , sed im en t

M. e p i d e r m i d i s . . . .

acid

tu rb id , sed im en t

M. f l a v u s ............................

slig h t a cid

tu rb id , sedim ent

no re a c tio n

tu rb id , sed im en t

alkaline p ro te o ly s is

turbid, sed im en t

P s . f r a g i .........................

acid d ig estio n

tu rb id , sed im en t

P s. tr a lu c id a

acid

turbid, sed im en t

Ach. butyri
Ach.

B act,

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

e u r y d i c e ..................

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

erythrogenes

C. f i l a m e n t o s u m
E. coli

. .

. . . .

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

P s. d e s m o ly tic u m
P s. flu o re s c e n s

. . .

. .

. .
. . .

. . . . .

. . . .

36
T A B L E II ( C o n t i n u e d )

A p p e a r a n c e of G ro w th in D iffe re n t M edia
T ry p to n e G lucose Y east A g ar

P otato D ex tro se A g ar

sm o o th , brow n, m ucoid

sm ooth, brown

sm ooth, g ray , m ucoid

s m o o th , brown

sm ooth, brow n, m ucoid

s m o o th , dull

r o u g h , dull, d r y

rough, dull, d ry

rough, d ark , m ucoid

rough, d a rk

rough, yellow

no g ro w th

s m o o t h , w hite, m ucoid

sm ooth, brown

s m o o t h , dull, m u c o id

sm ooth, brown

sm ooth, g ra y , m ucoid

sm o o th , w hite

sm ooth, brow n, m ucoid

s m o o th , brown

s m o o t h , w hite,

sm ooth, brown

scant

s m o o th , w hite, m u co id

sm ooth, brown

sm o o th , w hite,

no grow th

sm ooth, orange,

scant
m ucoid

s m o o th , brown

s m o o th , brow n, m ucoid

sm ooth, brown

rough, g reen

rough, brow n

sm ooth, brow n, m ucoid

sm ooth, brown

sm ooth, brow n

sm ooth, brown

37
T A B L E III
PH YSIOLOGICA L AND B IO C H EM IC A L C H A R A C TE R IST IC S O F
EIG H TEEN B A CTERIA ISO LA TED FR O M SPO ILED
C H E E SE AND AGAR P L A T E S EX PO SED
IN C H E E S E P L A N T S
P h y sio lo g ical and
B io ch em ical R eactions
O rganism

L ique
fa c tio n
^ „
G elatin

A c h . b u t y r i ........................................... . . . .
A c h . e u r y d i c e .......................................
A l e . m e t a l c a l i g e n e s .....................
B. f i r m u s ..........................................
B a c t . e r y t h r o g e n e s .....................
C. f i l a m e n t o s u m ............................

..
. . .
. . .
. . .

E. c o l i .................................................
E. f r e u n d i i ............................ ...
............................
E. i n t e r m e d i u m

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

M.
M.
M.
M.
M.
P
P
P
P

s.
s.
s.
s.

a u r a n t i a c u s ................................
c a n d i d u s .......................................
c o n g l o m e r a t u s .........................
e p i d e r m i d i s ................................
f l a v u s ..............................................
desm olyticum
.....................
flu o rescen s
............................
f r a g i ..............................................
t r a l u c i d a .............. ....................

.
.
.
.

Reduct i o n ot
N itrates

_

+

+
+b
+
+

-

+

+
-

-

+
+
+

_

. . . .

+b

-

+
-

+
+
_

_

. . . .

U tilizat i o n of
C itrates

+
+
+

-

-

-

-

-

+
. . . .

W eak H^S p ro d u c tio n .
^Slow liq u e fa c tio n of g e la tin .

+

-

+

+

-

38
T A B L E III ( C o n t i n u e d )

P h y sio lo g ic a l and B io ch em ical R eactions

M ethyl
Red

VogesP roskauer

Produc­
t i o n of
Indole

-

-

-

—

_

Product i o n of
H ZS

+a

+

U tilization
Produc­
o f n h 4h z p o 4
t i o n of
a s a Sole
U rease
S o u r c e of N
+

-

+

—

-

-

+
+
+

-

+

-

+

+

+
+

Hydroly s i s of
S tarch

-

-

-

+

+

+

+
+

-

-

-

-

-

_

_

_

+

-

-

-

+
+
+
+

+
-

~

_

+

+
+

39
T A B L E IV

PHYSIOLOGICAL AND BIOCHEM ICAL CHARACTERISTICS O F
Y E A ST S CAUSING SPO ILAG E IN COTTAGE CH EESE
T e s t P e r fo r m e d

T. Candida T . v e r s a t i l i s

D extrose
A s s i m i l a t i o n ......................................
F e r m e n t a t i o n ...................................

R. flaya

+
+

+
+

+

M altose
A s s i m i l a t i o n ......................................
F e r m e n t a t i o n ...................................

+

+
+

+

L actose
A s s i m i l a t i o n .............. .......................
F e r m e n t a t i o n ...................................

+

+

+

G alactose
A s s i m i l a t i o n ......................................
F e r m e n t a t i o n ...................................

+

+

+

Sucrose
A s s i m i l a t i o n ......................................
F e r m e n t a t i o n ............................... .

+

+
+

+

M annose
A s s i m i l a t i o n ......................................
F e r m e n t a t i o n ...................................

+

+

+

Raffinose
A s s i m i l a t i o n ......................................
F e r m e n t a t i o n ...................................

+

+

+

P e llic le fo rm a tio n in b ro th

+

. . .

+

R e d u c t i o n of n i t r a t e s .................
F o r m a t i o n of s p o r e s .........................
R e a c t i o n i n l i t m u s m i l k .................
P r o d u c t i o n of s t a r c h l i k e
c o m p o u n d s ..........................................

alk.
prot.

40
R. f l a v a w e r e i s o l a t e d f r o m t r y p t o n e g l u c o s e y e a s t a g a r p l a t e s e x ­
p o s e d in c o tta g e c h e e s e p r o c e s s i n g r o o m s .
T h e c h a r a c t e r i s t i c s of A c h . e u r y d i c e , M. e p i d e r m i d i s , P s .
d e sm o ly tic u m , and P s.

f l u o r e s c e ns a g r e e d w ithout d i s c r e p a n c y with

t h o s e l i s t e d b y B r e e d et a l . (1 948).
Ps. desm olyticum

T h e s e a u t h o r s do n o t d e s c r i b e

in any g r e a t detail.

P s. flu o rescen s was so m e ­

w h a t d i f f i c u l t t o i d e n t i f y , b e c a u s e it d i d n o t p r o d u c e t h e g r e e n
f l u o r e s c e n t , w a t e r - s o l u b l e p i g m e n t t y p i c a l of t h i s o r g a n i s m u n t i l
a f t e r n u m e r o u s t r a n s f e r s on a r t i f i c i a l m e d ia .
A c h . b u t y r i g a v e d a r k m u c o i d g r o w t h on a n a g a r s l a n t
r a t h e r than w hite g ro w th

a s r e p o r t e d by

ch aracteristics

by

exhibited

Ale.

B r e e d et a l . (1948).

The

m e ta lc a lig e n e s also differed from

t h o s e l i s t e d by t h e s e a u t h o r s a s follow s:

acid w as produced from

g lu c o s e and a p e ll i c l e w a s n ot f o r m e d in b ro th .
T h e o r g a n i s m t e n t a t i v e l y i d e n t i f i e d a s B. f i r m u s e x h i b i t e d
r o u g h s u r f a c e g r o w t h on

an

( 1 9 4 8 ) , B. f i r m u s

produce

should

a g a r s l a n t . A c c o r d i n g to B r e e d e t a l .
s m o o t h g r o w t h on a n a g a r s l a n t .

T h e above a u th o r s s ta te d that B act. e ry th r o g e n e s tu r n s litm u s m ilk
a b l o o d r e d c o l o r a n d e x h i b i t s o p t i m u m g r o w t h a t 28

t o 35

C.

T h e o r g a n i s m te n ta tiv e ly id en tified a s B act. e r y th r o g e n e s g r e w b est
a t 21° t o 25°

C, a n d f a i l e d t o t u r n l i t m u s m i l k a b l o o d r e d c o l o r .

B reed

et a l . (1948) s t a t e d t h a t C. f i l a m e n t o s u m

should c a u s e

a n a l k a l i n e r e a c t i o n i n c a r b o h y d r a t e s a n d l i t m u s m i l k , g r o w a t 3 7°
C., an d liq u efy g e la tin slow ly.

The o rg a n ism ten tativ ely identified

a s C. f i l a m e n t o s u m l i q u e f i e d g e l a t i n r a p i d l y a n d f a i l e d t o g r o w a t
37°

C. o r p r o d u c e a n a l k a l i n e r e a c t i o n in l i t m u s m i l k a n d c a r b o ­

hydrates.

T h e s e d i s c r e p a n c i e s m ight be sufficient to c a u s e so m e

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

H o w e v e r , it c o i n c i d e d

w i t h t h e c h a r a c t e r i s t i c s l i s t e d f o r C. f i l a m e n t o s u m m o r e c l o s e l y
than th o se lis te d for any o th e r o rg a n ism .
T h e o r g a n i s m s te n ta tiv e ly id en tified as E. coli, E. f r e u n d ii,
and E. in te rm e d iu m

show ed c h a r a c t e r is t i c s that v a rie d som ew hat

f r o m t h o s e d e s c r i b e d b y B r e e d e t a l . ( 1 948).
a tin and fa ile d to p r o d u c e in d o le.

E. coli liq u e fie d g e l ­

E. f re u n d ii fa ile d to p r o d u c e

h y d r o g e n s u l f i d e w h e n g r o w n on l e a d a c e t a t e a g a r , w h i l e E. i n t e r m edium

p r o d u c e d h y d r o g e n s u l f i d e on t h i s m e d i u m .

p ro d u c e in d o le, but not liq u efy gelatin .

E. c o l i s h o u l d

E. f r e u n d i i s h o u l d p r o d u c e

h y d r o g e n s u lfid e on p r o t e o s e , p e p to n e , f e r r i c c i t r a t e a g a r , w hile
E. i n t e r m e d i u m

s h o u l d n o t p r o d u c e h y d r o g e n s u l f i d e on t h i s m e d i u m .

T h e d i s c r e p a n c i e s in h y d r o g e n su lfid e p ro d u c tio n m ight h a v e been
due to th e d iff e r e n c e in m e d iu m

em ployed.

M. a u r a n t i a c u s f a i l e d t o r e d u c e n i t r a t e s o r p r o d u c e a c i d
from

c a r b o h y d r a te s and litm u s m ilk.

B r e e d e t a l . (1948) s t a t e d t h a t

42
this o rg a n ism

r e d u c e s n i t r a t e s w eakly and p ro d u c e s slight acid from

c a r b o h y d ra te s and litm u s m ilk.

M a n y of t h e r e a c t i o n s n o t e d i n t h e

t e n t a t i v e i d e n t i f i c a t i o n of M. c a n d i d u s w e r e e x t r e m e l y w e a k a l s o .
B r e e d e t a l . ( 1 9 4 8 ) r e p o r t e d t h a t M. c o n g l o m e r a t u s s h o u l d p r o d u c e
acid from

l a c t o s e b u t n o t h y d r o l y z e s t a r c h a n d M. f l a v u s a l s o

s h o u ld p r o d u c e a c id f ro m l a c t o s e and liq u e fy g e la tin .

N e i t h e r of

t h e s e o r g a n i s m s p r o d u c e d a c i d f r o m l a c t o s e , w h i l e M. c o n g l o m e r a t u s
h y d r o l y z e d s t a r c h a n d M. f l a v u s f a i l e d t o l i q u e f y g e l a t i n .
Ps.

f r a g i l i q u e f i e d g e l a t i n m o r e r a p i d l y but w a s l e s s p r o t e o ­

l y t i c i n l i t m u s m i l k t h a n r e p o r t e d b y B r e e d et a l.

(1948).

Ps.

t r a l u c i d a v a r i e d f r o m the ta b u la te d c h a r a c t e r i s t i c s in th at g ro w th
on an a g a r s la n t w a s good r a t h e r than s c a n t, s u c r o s e w as not f e r ­
m e n te d , and c e llu lo s e w as not u tilized .
T h e y e a s t c u l t u r e s t e n t a t i v e l y i d e n t i f i e d a s K. f l a v a , T. Can­
dida, and T. v e r s a t i l i s

( T a b l e IV) e x h i b i t e d c h a r a c t e r i s t i c s t h a t

a g r e e d w i t h t h o s e d e s c r i b e d b y L o d d e r a n d K r e g e r v a n Rij (1952)
for these o rg an ism s.
M ucor p lu m b e u s, M ucor ra c e m o s u s , Pen,

f r e q u e n t a n s , and

G. c a n d i d u m w e r e t e n t a t i v e l y i d e n t i f i e d u s i n g c h a r a c t e r i s t i c s l i s t e d
i n A M a n u a l of S o i l F u n g i b y G i l m a n (1945 ).

A M a n u a l of t h e P e n -

i c i l l i a b y R a p e r et a l . (1949) a l s o w a s u s e d i n i d e n t i f y i n g P e n ,
freq u en tan s.

43
T y p e s of D e f e c t s P r o d u c e d b y S p o i l a g e
O r g a n i s m s in C o t t a g e C h e e s e

T h e t y p e s of d e f e c t s p r o d u c e d by n i n e t e e n o r g a n i s m s c a u s i n g
s p o i l a g e i n c o t t a g e c h e e s e a n d t h e i r e f f e c t on t h e p H of s t e r i l e c o t ­
t a g e c h e e s e c u r d w h e n i n p u r e c u l t u r e a n d c o m b i n e d w i t h S. l a c t i s
a r e s h o w n i n T a b l e V.
M. c a n d i d u s a n d M. c o n g l o m e r a t u s w e r e t h e o n l y p u r e c u l ­
t u r e s th a t fa ile d to p r o d u c e a v is ib le d e fe c t, ex cep t f r e e w hey r e ­
sulting fro m

r e d u c e d pH .

T h e above two c u l t u r e s and B act.

e r y t h r o g e n e s fa ile d to p r o d u c e a v is i b l e d efe c t w hen c o m b in e d with
S. l a c t i s , e x c e p t t h e a p p e a r a n c e of f r e e w h e y a s a b o v e .
E. freundii,

Ps.

f r a g i , R. f l a v a , M u c o r p l u m b e u s , a n d P e n .

f r e q u e n t a n s p r o d u c e d a p p r o x i m a t e l y t h e s a m e d e g r e e a n d t y p e of
s p o i l a g e i n p u r e c u l t u r e a s w h e n c o m b i n e d w i t h S. l a c t i s .

Ach.

b u t y r i , B. f i r m u s , B a c t . e r y t h r o g e n e s , E . c o l i , M. f l a v u s , a n d P s .
f l u o r e s c e n s p r o d u c e d c h a r a c t e r i s t i c t y p e s of s p o i l a g e m o r e r a p i d l y
in p u r e c u l t u r e , w h e r e a s Ach. e u r y d i c e , Ale, m e t a l c a l i g e n e s , P s .
d e s m o l y t i c u m , P s . t r a l u c i d a , T. C a n d i d a , a n d G. c a n d i d u m p r o ­
duced c h a ra c te ris tic

s p o i l a g e m o r e r a p i d l y w h e n c o m b i n e d w i t h S.

lactis.
P u r e c u l t u r e s of A c h . b u t y r i , A c h . e u r y d i c e , A l e , m e t a l c a l i g e n e s , B act.

e r y t h r o g e n e s , E . f r e u n d i i , M. f l a v u s , P s .

44
TABLE V
T Y P E O F D E F E C T AND pH O B T A IN E D W ITH O R G A N ISM S
CA USING S P O I L A G E IN C O T T A G E C H E E S E IN P U R E
C U L T U R E A N D C O M B I N E D W I T H S. L A C T I S

O rganism

Initial
pH

B acteria
...............................................................................................................
Ach. b u ty ri
A c h . e u r y d i c e ...........................................................................................................

5.10
5.10

A l e . m e t a l c a l i g e n e s .............................................................................................
B. f i r m u s
..................................................................................................................
B a c t . e r y t h r o g e n e s .................................................

5.10
5.10
5.10

E. c o l i .........................................................................................................................
E. f r e u n d i i ..................................................................................................................

5.10
5.10

M.
M.
M.

c a n d i d u s .............................................................................................................
c o n g l o m e r a t u s ...............................................................................................
f l a v u s .....................................................................................................................

5.10
5.10
5.10

Ps.
Ps.
Ps.
Ps.

d e s m o l y t i c u m ................................................................................................
flu o rescen s
..............................................................................
f r a g i ......................................................................................................................
t r a l u c i d a ...........................................................................................................

5.10
5.10
5.10
5.10

Y easts
R. f l a v a .................................................................................................................. ,
T . C a n d id a
............................................................

5.10
5.10

M olds
G. c a n d i d u m ..........................................
M u c o r p l u m b e u s ....................................................................................................
P e n . f r e q u e n t a n s ....................................................................................................

5.10
5.10
5,10

45
T A B L E V (Continued)

D e f e c t a n d pH O b ta in e d
with P u r e C u ltu r e
Defect

D efect and pH O b tain ed with P u r e
C u l t u r e s C o m b i n e d w i t h S. l a c t i s
pH

Defect

pH

tapioca slim e
slight ta p io c a s lim e

5.00
5.00

slight tap io ca s lim e
tapioca slim e

5 .20
5.25

slight ta p io c a s lim e
brown slim e, digested
brow n slim e , liquefied

5.25
6.35
5.00

tapioca slim e
b ro w n s lim e , slight d ig e stio n
no v is ib le defect

5 .40
4. 75
4. 6 0

brow n slim e , digested
brown slim e

6.3 5
5.2 5

brow n s lim e , slight dig estio n
brown slim e

6.25
5.50

no v isib le defect
no v is ib le d efect
y e llo w buttons

4.60
4.60
5 .20

no v isib le defect
no v isib le defect
slight yellow buttons

4.4 5
4.5 5
5.10

slight tap io ca s lim e
green slim e
light b ro w n s li m e
slight bro w n s lim e

5.40
5.10
5.10
5.10

tapioca slim e
slight g r e e n s lim e
light brow n s lim e
brow n slim e

5.40
4.60
5.15
5.40

pink s lim e
y ellow s lim e , liquefied

5 .40
5 .70

pink s lim e
yellow s lim e , liquefied

4. 75
5.60

slight g r a y m old
brow n m old
g re e n m old

5.15
5 .60
5.40

g ra y m old
bro w n m old
g r e e n m old

5 .25
5.30
R RD

46
f l u o r e s c e n s , P s . f r a g i , P s . t r a l u c i d a , a n d G. c a n d i d u m a l t e r e d t h e
p H of t h e c o t t a g e c h e e s e c u r d 0 .0 5 t o 0.15 u n i t s .

T h e pH i n c r e a s e d

0 . 3 0 t o 1. 25 u n i t s i n c h e e s e i n o c u l a t e d w i t h p u r e c u l t u r e s of B.
f ir m u s , E. c o li, P s.

d e s m o l y t i c u m , R. f l a y a , T. C a n d i d a , M u c o r

p l u m b e u s , a n d P e n , f r e q u e n t a n s , w h e r e a s t h e pH d e c r e a s e d a p p r o x i ­
m a t e l y 0 . 5 0 u n i t s w h e n p u r e c u l t u r e s of M. c a n d i d u s a n d M. corig l o m e r a t u s w e r e in o c u la te d into th e curd.
Ach. b u t y r i , Ach.

e u r y d i c e , M. f l a v u s , P s . f r a g i , G. c a n d i ­

d u m , a n d M u c o r p l u m b e u s a l t e r e d t h e p H of t h e c o t t a g e c h e e s e c u r d
0. 05 t o 0 . 2 0 u n i t s w h e n c o m b i n e d w i t h S. l a c t i s .

W h e n S. l a c t i s

w a s c o m b i n e d w i t h A l e , m e t a l c a l i g e n e s , E . c o l i , E. f r e u n d i i , P s .
desm olyticum ,

P s . t r a l u c i d a , T . c a n d id a , and P en, f re q u e n ta n s , the

p H i n c r e a s e d 0 . 3 0 t o 1.15 u n i t s .

T h e pH d e c r e a s e d f r o m

0.35 to

0 . 7 5 u n i t s i n s a m p l e s i n o c u l a t e d w i t h S. l a c t i s c o m b i n e d w i t h e a c h
of t h e f o l l o w i n g :

B. f i r m u s , B a c t . e r y t h r o g e n e s , M. c a n d i d u s , M.

conglom eratus, P s.

f l u o r e s c e n s , a n d R. f l a y a .

In n i n e of e l e v e n c a s e s w h e r e t h e r e w e r e d i f f e r e n c e s i n b o t h
t h e d e g r e e of d e f e c t a n d t h e pH, t h e d e f e c t s e x h i b i t e d w e r e m o r e
p r o n o u n c e d a t t h e h i g h e r p H v a l u e s r e g a r d l e s s of w h e t h e r t h e s e
w e r e p r o d u c e d by t h e p u r e c u l t u r e s i n d i v i d u a l l y o r w h e n c o m b i n e d
w i t h S. l a c t i s .

47
C h a r a c t e r i s t i c s of C o t t a g e C h e e s e S p o i l a g e O r g a n i s m s

T e m p e r a t u r e L i m i t s of G r o w t h

T a b l e VI s h o w s t h e e f f e c t of t e m p e r a t u r e on t h e g r o w t h of
n in e te e n c o tta g e c h e e s e s p o ila g e o r g a n i s m s when g ro w n in t r y p t i c a s e
s oy b r o t h .
N o n e of t h e o r g a n i s m s t e s t e d e x h i b i t e d v i s i b l e g r o w t h i n 3
d a y s w h e n h e l d a t 3° C.

H o w e v e r , Ach. b u t y r i , Ach. e u r y d i c e , A l e .

m e t a l c a l i g e n e s , E . c o l i , M. f l a v u s , P s . f r a g i , P s . f l u o r e s c e n s , a n d
M u c o r p l u m b e u s e x h i b i t e d s l i g h t g r o w t h a f t e r 7 d a y s at t h i s t e m p e r ­
ature.
A f t e r 3 d a y s a t 10° C. A c h . b u t y r i , E . c o l i , E. f r e u n d i i , P s .
d e s m o l y t i c u m , a n d P s . t r a l u c i d a e x h i b i t e d a m o d e r a t e a m o u n t of
g r o w t h , w h e r e a s A c h . e u r y d i c e , A l e , m e t a l c a l i g e n e s , M. c a n d i d u s ,
P s. fragi,

P s . f l u o r e s c e n s , G. c a n d i d u m , and M u c o r p lu m b e u s

s h o w e d o n l y a s l i g h t a m o u n t of g r o w t h .

B a c t . e r y t h r o g e n e s , M.

c o n g l o m e r a t u s , and P e n . f r e q u e n t a n s w e r e the only o r g a n i s m s th a t
f a i l e d t o g r o w a f t e r 7 d a y s a t 10°

C.

A t 2 0 ° C. a l l c u l t u r e s t e s t e d g r e w , b u t e x h i b i t e d v a r y i n g
a m o u n t s of g r o w t h .
Ach.

b u ty r i, Ach.

e u r y d i c e , Ale,

m e ta lc a lig e n e s, Ps.

f l u o r e s c e n s , R. f l a v a , T . C a n d i d a , M u c o r p l u m b e u s , a n d P e n .

48
T A B L E VI
G R O W T H O F C O T T A G E C H E E S E S P O I L A G E O R G A N IS M S IN
T R Y P T I C A S E SOY B R O T H A T D I F F E R E N T I N C U B A T I O N
T E M P E R A T U R E S ( T H R E E TRIALS)
Incubation T e m p e r a tu r e s
a n d D a y s of I n c u b a t i o n
O rganism

3° C.

10° C.

20° C.

35° C.

50°

C.

3

3

3

3

3

7

+
+

-

-

++ ++ ++
+
+ ++ + +++ ++ + + + +
+ ++
+ ++

-

-

+ + +++ +++ +++ +++ + + +
++ + ++ + + + + ++ + ++ + ++

-

-

+ ++
++ ++ ++
+ ++
+ ++
+ + + ++ + ++ +++ + + +

-

-

+ ++ + ++ + ++
+ ++
+++
+
+++
+++ +++ +++

-

-

-

-

7

B acteria
A c h . b u t y r i .................
A c h . e u r y d i c e ..............

-

+
+

A le. m e t a l c a l i g e n e s .
B. f i r m u s .....................
B act. e r y th r o g e n e s .

-

+
-

E . c o l i ............................
E. f r e u n d i i .....................

-

+
-

M. c a n d i d u s .................
M. c o n g l o m e r a t u s . .
M. f l a v u s ........................

-

+

Ps.
Ps.
Ps.
Ps.

-

+
+
-

desm olyticum . .
f r a g i ........................
flu o rescen s . . .
tralu cid a . . . . .

Y easts
R. f l a v a ............................
T . C a n d i d a .....................
M olds
G. c a n d i d u m ..................
M ucor plum beus . . .
Pen. frequentans . . ■
Legend:

-

-

-

7

7

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

+
-

4-+ + + + ++ +
+ ++ + + ++
+ ++ + + +
++ +++ + ++
-

+ ++
+
++ + + + + ++

-

-

7

-

—

—

'

-

++

+
+

++
++

++
++
+

++
++
++

-f
~

++
+

'

- = n o g r o w t h , + = s l i g h t g r o w t h , ++ = m o d e r a t e

g r o w t h , +++ = p r o f u s e g r o w t h .

49
f r e q u e n t a n s f a i l e d t o s h o w g r o w t h i n 3 d a y s a t 35° C . , b u t o n l y R.
f l a y a , T. C a n d id a , a n d P e n , f r e q u e n t a n s f a ile d to g r o w a f t e r 7 d a y s
at this te m p e r a tu re .
N one of th e o r g a n i s m s s tu d ie d e x h ib ite d g r o w th a f t e r 3 o r 7
d a y s w h e n h e l d a t 5 0° C.

E f f e c t of pH on G r o w t h R a t e

T h e e f f e c t of p H on t h e g r o w t h r a t e of s i x t e e n o r g a n i s m s
c a u s in g s p o ila g e in c o tta g e c h e e s e is show n in F i g u r e s
T h e d a t a s h o w n a r e t h e r e s u l t s of t h r e e t r i a l s .

1 t h r o u g h 16.

T h e pH v a l u e s

u s e d c o v e r e d th e r a n g e n o r m a l l y e n c o u n t e r e d in c o tta g e c h e e s e .
T h e r a n g e w a s l o w e r e d to pH 4.0 to e x te n d below th e m i n i m u m
l i m i t p r o d u c e d b y S. l a c t i s .

T h e l e v e l s of 6.7 a n d 7.4 w e r e u s e d

b e c a u s e t h e y c o r r e s p o n d t o t h e a p p r o x i m a t e p H of f r e s h m i l k a n d
n o rm a l try p tic a s e soy broth,

respectively.

T h e a m o u n t of g r o w t h w a s d e t e r m i n e d by m e a s u r i n g t h e i n ­
c r e a s e i n t u r b i d i t y of t h e b r o t h w i t h a K l e t t - S u m m e r s o n c o l o r i m e t e r .
K l e t t - S u m m e r s o n r e a d in g s w e r e not u s e d with th e m old c u ltu r e s
b e c a u s e m o ld s tend to fo rm

a p e llic le r a t h e r than a tu rb id ity , and

the r e s u ltin g r e a d in g s a r e not r e p re s e n ta tiv e .

50

Turbidity

Turbidi t y

E f f e c t of pH o n t h e g r o w t h of o r g a n i s m s
c a u s i n g s p o i l a g e in c o t t a g e c h e e s e
150

150.

100

Zz I00|

■o
3

50

4.0 4.4 4.6 4.8 5.0 5 2 5 4 6.7 7.4

4.0 4.4 4.6 4.8 5.0 5.2 5.4 6.7 7.4

PH

PH

Fig. I. E. Coli

Fig. 2. E. f r e u n d i i

200

200

150

150

100

100

50

4.0 4.4 4.6 4.8 5 0 5.2 5.4 6.7 7.4

0

PH

PH

Fig. 3. Ps. d e s m o l y t i c u m
250

4.0 4.4 4.6 4.8 5 0 5.2 5.4 6.7 7.4

Fig. 4. Ps. f l u o r e s c e n s
200

Turbidity

200

= 100

150

100

50

4.0 4.4 4.6 4.8 5.0 5.2 54 6.7 7.4

PH

Fig. 6. Ps. t r a l u c i d a

4.0 4.4 4.6 4.8 5 0 5.2 5.4 6.7 7.4

pH

Turbidity

Fig. 5. Ps. f r a g i

J

■I 50

50r

0

100

4.0 4.4 4.6 4.8 5.0 5.2 5.4 6.7 7.4

PH

Fig. 7. Bact. e r y t h r o g e n e s

4.0 4.4 4.6 4.8 5.0 5.2 5.4 6.7 7.4

pH

Fig. 8. B. f i r m u s

51

Turbidi ty

E f f e c t of pH o n t h e g r o w t h o f o r g a n i s m s
c a u s i n g s p o i l a g e in c o t t a g e c h e e s e
200

200

150

150

100

!5 ioo

4.0 4.4 4.6 4.8 5.0 5.2 5.4 6,7 74

PH

Fig. 9. Ach. bu tyri

Fig. 10. Ach. e u r y d i c e

Turbidity

ioo

lOOr

50

4.0 4.4 4.6 4.8 5.0 5.2 5.4 6.7 7.4

Turbidity

4.0 4.4 4.6 4.8 5.0 5.2 5.4 6.7 7.4

PH

4.0 4.4 4.6 4.8 5.0 5.2 5.4 6.7 7.4

PH

PH

Fig. II.M . f l a v u s

Fig. 12. M. c a n d i d u s

50

lOOr

4.0 4.4 4.6 4.8 5.0 5.2 5.4 6.7 7.4

PH

Turbidity

Fig. 13. M. c o n g l o m e r a t u s

PH

50r

Fig. 14.T. C a n d i d a

4.0 4.4 4.6 4.8 5.0 5.2 5.4 6.7 7.4

PH

Fig. 15. Ale. m e t a l c a l i g e n e s
Turbidity

4.0 4.4 4.6 4.8 5.0 5.2 5.4 6.7 7.4

50r

4.0 4.4 4.6 4.8 5.0 5.2 5.4 6.7 7.4

PH

Fig. 16. R. f l a v a

52
E - CQbi

E . f r e u n d i i e x h i b i t e d l i t t l e g r o w t h a t pH 5.2 a n d

below , a s show n in F i g u r e s

1 a n d 2.

Both c u l t u r e s g r e w b e t t e r at

7.4 t h a n a n y o t h e r p H u s e d .
P s. desm olyticum

a n d P s . t r a l u c i d a ( F i g u r e s 3 a n d 6) e x ­

h i b i t e d l i t t l e g r o w t h a t pH 5.2 a n d b e l o w , w h i l e P s . f r a g i a n d P s
flu o rescen s

( F i g u r e s 4 a n d 5) s h o w e d l i t t l e g r o w t h a t pH 5.4 a n d

below.

desm olyticum

Ps.

s e e m e d t o e x h i b i t m o r e g r o w t h a t pH

6 .7 t o 7 . 4 , w i t h t h e o p t i m u m p r o b a b l y b e i n g a t a p p r o x i m a t e l y 7.0
Ps. frag i, Ps.

f l u o r e s c e n s , and P s . tr a lu c id a exhibited m o r e grow th

a t 7.4 t h a n a n y o t h e r pH e m p l o y e d .
F igures

7 a n d 8 s h o w t h a t B. f i r m u s a n d B a c t . e r y t h r o g e n e s

a l s o e x h i b i t e d l i t t l e g r o w t h a t p H 5.4 a n d b e l o w , a n d b o t h o r g a n i s m s
s e e m e d t o h a v e a n o p t i m u m pH of 7.4 o r a b o v e .
A ch. b u ty r i, Ach.

e u r y d ic e , and Ale. m e t a l c a l i g e n e s ( F ig u r e s

9, 10, a n d 15) e x h i b i t e d l i t t l e g r o w t h a t pH 5.4 a n d b e l o w .
optim um

s e e m s t o be a p p r o x i m a t e l y pH 6.7 t o 7.0.

genes exhibited le s s
F igures

11,

T h eir

Ale, m e t a l c a l i -

g ro w th th a n Ach. b u ty ri o r Ach. e u r y d i c e .
12, a n d 13 s h o w t h a t M. f l a v u s a n d M. c a n d i d u s

e x h i b i t e d l i t t l e g r o w t h a t p H 5 . 0 a n d b e l o w , w h i l e M. c o n g l o m e r a t u s
s h o w e d l i t t l e g r o w t h a t p H 5.4 a n d b e l o w .

T h e o p t i m i m pH f o r

M. c a n d i d u s a n d M. c o n g l o m e r a t u s a p p e a r e d t o be a p p r o x i m a t e l y 6.7
t o 7 . 0 , w h i l e M. f l a v u s g r e w b e t t e r a t 7.4 t h a n a n y o t h e r pH u s e d .

R. f l a v a ( F i g u r e 16) e x h i b i t e d l i t t l e g r o w t h a t a n y p H u s e d .
T h e g r o w t h of T . C a n d i d a ( F i g u r e 17) f l u c t u a t e d s l i g h t l y , b u t g r e w
w ell th ro u g h o u t th e pH r a n g e stu d ie d .

This o rg an ism

exhibited the

g r e a t e s t a m o u n t of g r o w t h a t p H 6.7 .

Sodium C h lo rid e T o le r a n c e

T h e e f f e c t of v a r i o u s c o n c e n t r a t i o n s of s o d i u m c h l o r i d e in
t r y p t i c a s e s o y b r o th , on t h e g r o w t h of n i n e t e e n o r g a n i s m s c a u s i n g
s p o i l a g e i n c o t t a g e c h e e s e i s s h o w n i n T a b l e VII.
B act. e ry th ro g e n e s
chloride.
R.

M.

flav a , and

sodium

candidus
Fen,

chloride.

B. f i r m u s ,

failed to t o l e r a te 1 p e r c e n t sodium

to lerated

frequentans

Ach.

1 but

to lerated

not

3 percent,

3 but

not

w hile

5 percent

b u t y r i , A ch, e u r y d i c e , Ale, m e t a l c a l i g e n e s ,

E. f r e u n d i i , P s . d e s m o l y t i c u m , P s . f r a g i , P s .

flu o res-

c e n s , P s . t r a l u c i d a , G. c a n d i d u m , a n d M u c o r p l u m b e u s t o l e r a t e d 5
but not 7 p e r c e n t s o d iu m c h l o r i d e .

E. coli w as th e only o r g a n i s m

t h a t t o l e r a t e d 7 b u t n o t 10 p e r c e n t s o d i u m c h l o r i d e .

M. c o n g l o m e r -

a t u s , M. f l a v u s , a n d T . C a n d i d a t o l e r a t e d 10 p e r c e n t s o d i u m c h l o r i d e .

Heat T o leran ce

T a b l e V I II s h o w s t h e r e s i s t a n c e of n i n e t e e n o r g a n i s m s c a u s i n g
s p o i l a g e i n c o t t a g e c h e e s e t o h e a t i n g a t 143

F. in s k im m ilk.

54
T A B L E V II
G R O W T H O F C O T T A G E C H E E S E S P O I L A G E O R G A N IS M S IN
T R Y P T I C A S E SOY B R O T H CONTAINING D I F F E R E N T
C O N C E N T R A T IO N S O F SODIUM C H L O R ID E
( T H R E E TRIALS)

O rganism

P e r c e n t N aC l (w/v)
-------------------------------------------------------0
1
3
5
7
10

B acteria
A c h . b u t y r i ............................... . . .
A c h . e u r y d i c e ............................ . . .

+
+

+

A l e . m e t a l c a l i g e n e s .............. . . .
B. f i r m u s ................................... . . .
B a c t . e r y t h r o g e n e s .............. . . .

+
+

-

+

+
+

“

+
+
+

+
+
-

+
+
—

+
+

-

-

E . c o l i .......................................... . . .
E. f r e u n d i i ................................... . . .

+
+

+
+

+
+

+
+

+

-

M. c a n d i d u s ............................... . . .
M. c o n g l o m e r a t u s ................. . . .
M. f l a v u s ...................................... . . .

+
+
+

+
+
+

+
+

+
+

+
+

+
+

d e s m o l y t i c u m ................. . . .
f r a g i ......................................
f l u o r e s c e n s ................. ... . . .
t r a l u c i d a ............................

+
+
+
+

+
+
+
+

+
+
+
+

+
+
+
+

-

-

asts
R, f l a v a .......................................... . . .
T . C a n d i d a ...................................

+
+

+
-t

+
+

+

+

3lds
G. c a n d i d u m ...............................
M u c o r p l u m b e u s .....................
P e n . f r e q u e n t a n s .....................

+
+

+
+
+

+
+
+

Ps.
Ps.
Ps.
Ps.

+
+

55
T A B L E V III
R E S I S T A N C E O F C O T T A G E C H E E S E S P O I L A G E O R G A N IS M S T O
H E A T I N G A T 143° F . I N S K I M M I L K ( F I V E T R I A L S )
M i n u t e s H e a t e d a t 143° F .
O rganism
0
B acteria
A c h . b u t y r i ......................................
A c h . e u r y d i c e ...................................

5

10

20

+
+

-

-

30

A l e . m e t a l c a l i g e n e s ..................... ..............
B. f i r m u s .......................................... ................
B a c t . e r y t h r o g e n e s .....................

+
+

+
+
-

_a

-

+
-

+
-

E. c o l i ................................................ ..............
E. f r e u n d i i .......................................... ..............

+
+

-

-

-

M. c a n d i d u s ...................................... ..............
M. c o n g l o m e r a t u s ........................
M. f l a v u s ............................................. ...............

+

+b
+b

-

-

-

+b
+

_a
+b

-

—

-

“

-

-

-

Ps.
Ps.
Ps.
Ps.

d e s m o l y t i c u m ........................ ................
f r a g i .............................................
flu o rescen s
............................ ...............
t r a l u c i d a ................................... ...............

+
+
+
+

Y easts
R. f l a v a ................................................. ................
T. C a n d i d a ..........................................

+

M olds
G. c a n d i d u m ...................................... ..............
M u c o r p l u m b e u s ............................ ...............
.
.
P e n . f r e q u e n t a n s ............................

+
+
+

a G r o w t h i n o n e of f iv e t r i a l s .
^ G r o w t h i n f o u r of f iv e t r i a l s .

+

‘

—

—

56
B a c t . e r y t h r o g e n e s , E . c o l i , E . f r e u n d i i , M. c o n g l o m e r a t u s ,
Ps. desm olyticum , P s.

f l u o r e s c e n s , R. H a v a , T . C a n d i d a , G. c a n -

d i d u m , M u c o r p l u m b e u s , and P en , f re q u e n ta n s fa ile d to s u r v iv e
143°

F. for 5 m inutes.

A c h . b u t y r i , Ach.

e u r y d i c e , Ale, m e t a l c a l i ­

g e n e s , M. c a n d i d u s , M. f l a v u s , a n d P s . f r a g i s u r v i v e d 10 but n o t 2 0
m inutes at this te m p e ra tu re .

B. f i r m u s w a s t h e o n l y o r g a n i s m t h a t

s u r v i v e d f o r 30 m i n u t e s a t 143° F .

Subsequent heat studies showed

B. f i r m u s w a s s t i l l v i a b l e a f t e r 120 m i n u t e s a t t h i s t e m p e r a t u r e .
F u r t h e r s t u d i e s w e r e m a d e by h e a tin g th e n in e te e n c u l t u r e s
in s k im

m i l k a n d w h e y a t 12 0° F . f o r 15 m i n u t e s .

This te m p e r a tu re

and t i m e c o r r e s p o n d s a p p r o x i m a t e l y to the cooking t e m p e r a t u r e and
holding t i m e u s e d in m a n u f a c tu r in g co tta g e c h e e s e .

T a b l e IX s h o w s

t h a t B a c t . e r y t h r o g e n e s a n d M. c o n g l o m e r a t u s w e r e t h e o n l y o r g a n ­
ism s

d e s t r o y e d b y h e a t i n g a t 120°

F . f o r 15 m i n u t e s in s k i m m i l k

a t p H 6.7, w h i l e B. f i r m u s a n d G. c a n d i d u m w e r e t h e o n l y c u l t u r e s
w h i c h s u r v i v e d t h i s t e m p e r a t u r e a n d t i m e in w h e y a t p H 4 .5 5 .

R e s is ta n c e to G e r m ic id e s

T o l e r a n c e to c h l o r i n e .

T h e g r o w t h of n i n e t e e n s p o i l a g e o r ­

g a n i s m s a f t e r e x p o s u r e t o d i s t i l l e d w a t e r s o l u t i o n s of 10, 25, a n d 50

57
T A B L E IX
R E S I S T A N C E O F C O T T A G E C H E E S E S P O I L A G E O R G A N IS M S
T O H E A T I N G A T 12 0° F . F O R 15 M I N U T E S IN SKIM
M IL K AND W HEY (T H R E E TRIALS)
S ubstrate
O rganism

B acteria
A c h . b u t y r i ..............................................................
A c h . e u r y d i c e ...................................................................................

Skim
M il k

+
+

A l e . m e t a l c a l i g e n e s . ..............................................................
B. f i r m u s ...........................
B act. e r y t h r o g e n e s

+
+
-a

E . c o l i .................................................................................................
E. f r e u n d i i
...............................................................................

+
+

M. c a n d i d u s ......................................................................................
M. c o n g l o m e r a t u s ........................................................................
M. f l a v u s .............................................................................................

+

Ps.
Ps.
Ps.
Ps.

desm olyticum
f r a g i .................
fluorescens
tralu cid a . . .

Y easts
R. f l a v a , .
T . Candida
M olds
G. c a n d i d u m . . .
M ucor plu m b eu s
Pen. frequentans
a G ro w i:h i n o n e of t h r e e t r i a l s .
^ G r o w t h i n tw o of t h r e e t r i a l s .

+

+

58
p a r t s p e r m i l l i o n of c h l o r i n e a t p H 7.5 a n d 25° C. f o r 1, 5, a n d 10
m i n u t e s i s s h o w n i n T a b l e X.
R . f la v a w a s th e m o s t s u s c e p t i b l e o r g a n i s m to c h lo r in e , a p ­
p a r e n t l y b e i n g d e s t r o y e d i n 1 m i n u t e i n 10 p a r t s p e r m i l l i o n .

Bact.

e r y t h r o g e n e s a n d M. c a n d i d u s s u r v i v e d 1 b u t n o t 5 m i n u t e s , w h i l e
Ach.

e u r y d i c e s u r v i v e d 5 b u t n o t 10 m i n u t e s in t h e a b o v e c o n c e n ­

tration.
B act.

e r y t h r o g e n e s , M. c a n d i d u s , a n d R. f l a v a w e r e a p p a r e n t l y

d e s t r o y e d i n 1 m i n u t e i n 25 p a r t s p e r m i l l i o n of c h l o r i n e , w h i l e
Ale, m e t a l c a l i g e n e s s u r v i v e d
tion.

1 b ut n o t 5 m i n u t e s i n t h i s c o n c e n t r a ­

Ach. e u r y d i c e , E. f r e u n d ii, P s . d e s m o l y t i c u m ,

P s. fragi,

Ps.

fluorescens,

P s . t r a l u c i d a , a n d G. c a n d i d u m s u r v i v e d 5 b ut n o t 10

m i n u t e s i n t h i s c o n c e n t r a t i o n of c h l o r i n e .
B . f i r m u s , M. f l a v u s , T . C a n d i d a , a n d M u c o r p l u m b e u s w e r e
th e only o r g a n i s m s th at s u rv iv e d

1 m in u te in 50 p a r t s p e r m illio n

of c h l o r i n e , a n d B. f i r m u s w a s t h e o n l y o r g a n i s m t h a t s u r v i v e d 5
a n d 10 m i n u t e s i n t h i s c o n c e n t r a t i o n .

T o l e r a n c e to q u a t e r n a r y .
organism s

T h e g r o w t h of n i n e t e e n s p o i l a g e

a f t e r e x p o s u r e t o d i s t i l l e d w a t e r s o l u t i o n s of 10, 25, a n d

50 p a r t s p e r m i l l i o n of q u a t e r n a r y a t p H 6.5 a n d 25
a n d 10 m i n u t e s i s s h o w n i n T a b l e XI.

C. for

1, 5,

59
TABLE X
G R O W T H O F C O T T A G E C H E E S E S P O I L A G E O R G A N IS M S A F T E R
E X P O S U R E T O D I F F E R E N T CO N C E N TR A TIO N S O F CH LORINE
S O L U TIO N S F O R VARIOUS T IM E IN T E R V A L S
( T H R E E TRIALS)
P a r t s p e r M i l l i o n of C h l o r i n e
a n d M i n u t e s of E x p o s u r e
O rganism

10 ppm

2 5 ppm

50 ppm

1

5

10

1

5

10

1

B acteria
A c h . b u t y r i .....................
A c h . e u r y d i c e .................

+
+

+
+

+
-

+
+

+
+

+
-

_a
-

Ale. m e ta lc a lig e n e s . .
B. f i r m u s ........................
B act. e r y t h r o g e n e s . .

+
+
+

+
+

+
+

+
+

_a
+

+

_
+

E. c o l i ...............................
E. f r e u n d i i ........................

+
+

+
+

+
+

+
+

+
+

+
_a

-

M. c a n d i d u s .....................
M. c o n g l o m e r a t u s . . .
M. f l a v u s ............................

+
+
+

_a
+
+

+
+

+
+

+
+

+
+

r

Ps.
Ps.
Ps.
Ps.

desm olyticum . . .
flu o rescen s
. . . .
f r a g i ............................
t r a l u c i d a .................

+
+
+
+

+
+
+
+

+

+
+
+
+

_a

_

+
+

+
+
+
+

_

-

_

Y easts
R. f l a v a ...............................
T . C a n d i d a ........................

+

+

+

+

+

+

+b

M olds
G. c a n d i d u m .....................
M ucor plum beus . . . .
Pen. frequentans . . . .

+
+
+

+
+
+

+
+
-f

+
+
+

+
+
+

+
+

+b

5

10

+

+

-

~

a

a G r o w t h i n o n e of t h r e e t r i a l s .
^ G r o w t h in t w o of t h r e e t r i a l s .

-

-

-----------------------------

60
T A B L E XI
G R O W T H O F C O T T A G E C H E E S E S P O I L A G E O R G A N IS M S A F T E R
E X P O S U R E TO D I F F E R E N T CONCENTRATIONS OF Q U A T ER ­
N A R Y S O L U T I O N S F O R V A R IO U S T I M E I N T E R V A L S
(T H R E E TRIALS)
P a r t s p e r M i l l i o n of Q u a t e r n a r y
a n d M i n u t e s of E x p o s u r e
O rganism

10 ppm

25 p p m

50 p p m

1

5

10

1

5

10

1

5

10

+
4~

+
+

+
+

+
+

+
+

+
+

+
+

+
+

+
+

Ale. m e t a l c a l i g e n e s . .
B. f i r m u s ............................
B act. e r y t h r o g e n e s . .

+
+

+
+

+
+

+
+

+
+

+
+

+
+

+

+
+

E . c o l i ...............................
E . f r e u n d i i ........................

+
+

+
+

+
+

+
+

+
+

+
+

+
+

+
+

-a
-

M. c a n d i d u s .....................
M. c o n g l o m e r a t u s . . .
M. f l a v u s ............................

+

+

+

-

-

-

-

-

-

+b

-

-

-

-

-

-

-

-

Ps.
Ps.
Ps.
Ps.

+
+
+
+

+
+
+
+

+
+
+
+

+
+
+
+

+
+
+
+

+
+
+
+

+
+
+
+

+
+
+
+

+
+
+
+

_a

+

+

+

-

-

-

-

+a

-

-

+
+
+

+
+
+

+
+
+

+
+
+

B acteria
A c h . b u t y r i .....................
A c h . e u r y d i c e .................

desm olyticum . . .
flu o rescen s . . . .
f r a g i ............................
t r a l u c i d a .................

Y easts
R. f l a v a ...............................
T. C a n d i d a .....................

+

_a
+

M olds
G. c a n d i d u m .....................
M ucor plu m b eu s . . . .
Pen. frequentans . . . .

+
+b
+

+
+
+

a G r o w t h i n o n e of t h r e e t r i a l s .
^ G r o w th in tw o of t h r e e t r i a l s .

+b
+

+

-

61
B act.

e r y t h r o g e n e s , M. c o n g l o m e r a t u s , a n d R. f l a v a a p p e a r e d

to b e t h e m o s t s u s c e p t i b l e o r g a n i s m s to q u a t e r n a r y , b eing d e s tr o y e d
i n 1 m i n u t e i n 10 p a r t s p e r m i l l i o n of t h i s c o m p o u n d .

M. f l a v u s

s u r v i v e d 1 b u t n o t 5 m i n u t e s i n 10 p a r t s p e r m i l l i o n of q u a t e r n a r y .
M. c a n d i d u s a n d M. f l a v u s w e r e d e s t r o y e d in 1 m i n u t e i n 25
p a r t s p e r m i l l i o n of q u a t e r n a r y .
T . C a n d id a , G. c a n d i d u m , a n d P e n . f r e q u e n t a n s s u r v i v e d 1 but
n o t 5 m i n u t e s i n 5 0 p a r t s p e r m i l l i o n of q u a t e r n a r y , w h i l e E. c o l i
a n d E . f r e u n d i i s u r v i v e d 5 b u t n o t 10 m i n u t e s i n t h i s c o n c e n t r a t i o n .
Ach. b u ty ri, Ach.

e u r y d i c e , A l e . m e t a l c a l i g e n e s , B. f i r m u s ,

d esm o ly tic u m , P s. flu o re s c e n s , Ps.

Ps.

f r a g i , P s . t r a lu c id a , and M ucor

p l u m b e u s s u r v i v e d 10 m i n u t e s in 50 p a r t s p e r m i l l i o n of q u a t e r n a r y .

T o l e r a n c e to io d o p h o r.

T h e g r o w t h of n i n e t e e n s p o i l a g e o r ­

g a n i s m s a f t e r e x p o s u r e t o d i s t i l l e d w a t e r s o l u t i o n s c o n t a i n i n g 10,
25, a n d 5 0 p a r t s p e r m i l l i o n of i o d o p h o r a t p H 3.5 a n d 25° C. f o r
1, 5, a n d 10 m i n u t e s i s s h o w n in T a b l e XII.
A m o n g th e o r g a n i s m s te s te d , B act. e r y th r o g e n e s w as the
m o s t s u s c e p t i b l e t o t h e i o d o p h o r a n d w a s a p p a r e n t l y d e s t r o y e d in
1 m i n u t e i n 10 p a r t s p e r m i l l i o n of t h i s c o m p o u n d .
only o r g a n is m
of i o d o p h o r .

A l s o it w a s t h e

d e s t r o y e d in 5 a n d 10 m i n u t e s i n 10 p a r t s p e r m i l l i o n

62
T A B L E X II
G R O W T H O F C O T T A G E C H E E S E S P O I L A G E O R G A N IS M S A F T E R
E X P O S U R E TO D IF F E R E N T CONCENTRATIONS OF
IO D O P H O R S O L U T IO N S F O R VARIOUS T IM E
IN T E R V A L S (T H R E E TRIALS)
P a r t s p e r M i l l i o n of I o d o p h o r
a n d M i n u t e s of E x p o s u r e
O rganism

10 p p m

50 p p m

25 ppm

1

5

10

1

5

10

1

5

10

B acteria
A c h . b u t y r i .....................
A c h . e u r y d i c e .................

+
+

+
+

+
+

+
+

+
+

+
+

+

+a

+

Ale. m e t a l c a l i g e n e s . .
B. f i r m u s
........................
B act. e r y th ro g e n e s , .

+
+
-

+
+
-

+
-

+
+
-

+
+
-

+
+
-

+

+

-

+
—

E . c o l i ...............................
E . f r e u n d i i ........................

+
+

+
+

+
+

+
+

+
+

+
+a

-

-

-

M. c a n d i d u s .....................
M. c o n g l o m e r a t u s . . .
M. f l a v u s ............................

+
+

+

+
+
+

+
+
+

+
+
+

+
_ I-.
D
—

-

-

+

+
+
+

Ps.
Ps.
Ps.
Ps.

+
+

+
+
+
+

+
+
+
+

+
+
+

+

+
+
+
+

Y easts
R . f l a v a ...............................
T . C a n d i d a ........................

+
+

+
+

+
+

M olds
G. c a n d i d u m .....................
M ucor plum beus . . . .
Pen. frequentans . . . .

+
+
+

+
+
+

+
+
+

desm olyticum . . .
flu o rescen s . . . ■
f r a g i ............................
t r a l u c i d a .................

a G row th

in

tw o

of t h r e e

trials.

^ G r o w t h i n o n e of t h r e e t r i a l s .

-b

-

_

U
u

+
+
+

+

+a

—

~

+
+
+

+
+
+

-

-b

+

+

+

+
+
+

+
+
+

+
+
+

■"
—

+

+
+
+

63
R . f l a v a w a s d e s t r o y e d i n 1 m i n u t e in 25 p a r t s p e r m i l l i o n
and w a s th e only o r g a n is m

in ad d itio n to B act. e r y th r o g e n e s w hich

w a s d e s t r o y e d i n 5 a n d 10 m i n u t e s i n t h i s c o n c e n t r a t i o n of i o d o p h o r .
A c h . b u t y r i , A l e , m e t a l c a l i g e n e s , E . c o l i , E . f r e u n d i i , M.
c o n g l o m e r a t u s , M. f l a v u s , P s . d e s m o l y t i c u m , P s . f l u o r e s c e n s , P s .
f r a g i , a n d T. C a n d i d a w e r e d e s t r o y e d in 1 m i n u t e i n 5 0 p a r t s p e r
m i l l i o n of i o d o p h o r , w h i l e M. c a n d i d u s s u r v i v e d 1 but n o t 5 m i n u t e s
in t h i s c o n c e n t r a t i o n .

A c h . e u r y d i c e , B. f i r m u s , P s . t r a l u c i d a , G.

c a n d id u m , M ucor p lu m b e u s , and Pen,

f r e q u e n t a n s s u r v i v e d 10 m i n ­

u t e s i n 5 0 p a r t s p e r m i l l i o n of i o d o p h o r .

R e s i s t a n c e to S orbic Acid

T h e e f f e c t of v a r i o u s C o n c e n t r a t i o n s of s o r b i c a c i d a t d i f f e r ­
e n t p H l e v e l s o n t h e v i a b i l i t y of o r g a n i s m s c a u s i n g s p o i l a g e i n
c o t t a g e c h e e s e i s s h o w n i n T a b l e XIII .

The d a ta shown a r e the

r e s u l t s of d u p l i c a t e t r i a l s w h e n t h e o r g a n i s m s w e r e g r o w n i n t r y p t i c a s e soy broth.
B a c t . e r y t h r o g e n e s f a i l e d t o f u r v i v e at pH 5.7 w i t h 0.25
percent sorbic

a c i d , w h i l e R. f l a v a s h o w e d v a r i a b l e r e s u l t s a t

t h i s p H a n d s o r b i c a c i d c o n c e n t r a t i o n , w i t h o n e of t w o t r i a l s
show ing s u rv iv a l.

A l l o t h e r o r g a n i s m s s u r v i v e d a t pH 5.7 a n d

a b o v e w i t h s o r b i c a c i d c o n c e n t r a t i o n s of 0 . 0 5 , 0 . 1 0 , a n d 0.25 p e r c e n t .

64
T A B L E X I II
G R O W T H O F C O T T A G E C H E E S E S P O I L A G E O R G A N IS M S A F T E R
E X P O S U R E T O D I F F E R E N T C O N C E N T R A T IO N S O F S O R B IC
A C I D A T V A R IO U S p H L E V E L S ( T W O T R I A L S )
pH

of

M edium i and

pH

pH

pH

pH

7.3

6.7

6.4

5.7

0.00

0.05

0.10

0.Z5

. . . . .

4 44

444

+++

+ ++

+++

+4+

O rg an ism

B acteria
...............................................................

Ach.

b utyri

Ach.

e u r y d i c e ..........................................................

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

444

444

A le.

m e t a l c a l i g e n e s .........................................

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

444

444

+++

+ 4+

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

444

444

444

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

444

444

+++
+++

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

444

444

+++

444

f r e u n d i i ...................................................................

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

444

444

++ +

444

c a n d i d u s ...............................................................

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

444

444

B.

firm us

B act.

E.
E.

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

ery th ro g en es

coli

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

-

M.
M.

+++

+++

c o n g l o m e r a t u s .............................................

+++

++ +

4

M.

f l a v u s ........................................................................

+++

+++

444

+ ++
+++
+ ++
++ +

+++
+++
+++
+++

444

+++
++ +

+
+ ++

*

+ ++
+++
+++

+++
+++

444

+ ++

444

P s . d e s m o l y t i c u m .............................................
P s . flu o rescen s

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

444

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

444

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

P s . f r a g i ........................................................................
P s . t r a l u c i d a ...........................................................

444
44 4
4 44

Y easts

R.
T.

f l a v a .................................... ........................................
C a n d i d a ....................................................................

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

444

p l u m b e u s ..................................................

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

444

f r e q u e n t a n s ..................................................

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

4 44

444

M olds

G.

c a n d i d u m ...............................................................

M ucor
Pen.

Legend:
grow th,
g row th

444
on

=

-

= no

profuse

d uplicate

grow th,
grow th,

trials.

+
*

=

=

slight

one

g ro w th ,

p o sitiv e

and

44

=

one

444

m o d erate
n eg ative

65

T A B L E X III ( C o n tin u e d )

P e r c e n t S o rb ic A cid w /v
pH
5.2

pH
5.0

0.00

0.05

0 .1 0 ' 0.25

0.00

+ ++

444

444

44

4

0. 05

444

4

PH
4.8

0.10

4

0.2 5

0.00

0.05

0.10

0.25

-

-

-

+

-

-

-

-

-

-

-

++

-

-

+++

444

444

4

+

4

*

4

4

4

4

-

4

44

44

4

4

44

44

+

+

+

++

++

+

-

-

-

-

-

-

4

-

++ +

+

4

-

4

-

++

+

4

-

-

444

444

444

-

*

-

-

444

44

444

444

4 44

444

4 44

44 +

+

-

+++

+

444

444

444

4 44

4 44

444

+ ++

+

+++

+ ++

+

4

4

4

44

4

4

4

-

r

+

-

-

+

+

4

-

-

-

-

44

44

44

4

44

4

+

+

+ + +

444

444

444

444

444

4+4

+

-

+++

++

44

4

4

4

4

4

4

-

+

-

+ ++

444

444

444

444

4+

+ ++

+ ++

_

4

4

-

-

4H
—h

44 +

+ + +

++

+

+ + +

+ + +

444

++

+ + +

+ +

+

++ +

+ ++

4

+ ++

+++

4
444

444

444

444

4

444

444

4

++

-

+

-

444

444

444

4

444

+

4

+4 +

444

444

4

444

++

+

-

*

+

4
+

-

66
B act. e r y th ro g e n e s and P s .

flu o re sc e n s showed v a ria b le r e ­

s u l t s a t p H 5 . 2 even, i n t h e a b s e n c e of s o r b i c a c i d ;
s h o w e d s u r v i v a l i n o n e of t w o t r i a l s .

both c u l t u r e s

The above-m entioned organ—

i s m s a n d R » f l a v a f a i l e d t o s u r v i v e a t p H 5.2 w i t h 0.05 p e r c e n t
s o rb ic acid.

A le, m e ta lc a lig e n e s

e x h i b i t e d v a r i a b l e r e s u l t s a t pH

5.2 w i t h 0 . 1 0 p e r c e n t s o r b i c a c i d , s u r v i v i n g i n one of t w o t r i a l s .
Ach. e u r y d i c e , Ale, m e t a l c a l i g e n e s , and E. coli show ed v a r i a b l e r e ­
s u l t s a t p H 5 .2 w i t h 0. 25 p e r c e n t s o r b i c a c i d , w i t h o n e of t w o t r i a l s
show ing s u rv iv a l.
B a c t. e r y th r o g e n e s and P s.

f l u o r e s c e n s f a i l e d to s u r v i v e at

pH 5 . 0 e v e n i n t h e a b s e n c e of s o r b i c a c i d , w h i l e A l e , m e t a l c a l i g e n e s
gave v a ria b le

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

one of tw o t r i a l s

show ing s u rv iv a l.

5 . 0 w i t h 0.05 p e r c e n t s o r b i c a c i d .

R . f l a v a f a i l e d t o s u r v i v e a t pH
A ch. e u r y d i c e , Ale, m e t a l c a l i -

g e n e s , a n d P s . f r a g i e x h i b i t e d v a r i a b l e r e s u l t s a t p H 5.0 w ith 0.05
p e r c e n t s o r b i c a c i d , w i t h s u r v i v a l in o n e of t w o t r i a l s .

Ach. e u r y -

d i c e f a i l e d t o s u r v i v e a t p H of 5 . 0 w i t h 0. 10 p e r c e n t s o r b i c a c i d ,
w h i l e A c h . b u t y r i , A l e , m e t a l c a l i g e n e s , E. c o l i , M. c o n g l o m e r a t u s ,
Ps.

fragi,

P s. tra lu c id a , and M ucor plum beus

showed v aria b le r e ­

s u l t s a t p H 5 . 0 w i t h 0 . 1 0 p e r c e n t s o r b i c a c i d , s u r v i v i n g in o n e of
two t r i a l s .
M. c a n d i d u s ,

A c h . b u t y r i , A l e , m e t a l c a l i g e n e s , E. c o l i , E. f r e u n d i i ,
Ps.

desm olyticum , Ps.

f r a g i , and Ps

t r a l u c i j a failed

67

t o s u r v i v e a t p H 5 . 0 w i t h 0 .2 5 p e r c e n t s o r b i c a c i d ; w h e r e a s , T.
C andida, G. c a n d i d u m , M u c o r p lu m b e u s , and Hen. f r e q u e n ta n s sh ow ed
v a r i a b l e r e s u l t s at th i s pH and s o r b i c a c id c o n c e n tr a tio n , with s u r ­
v i v a l i n o n e of t w o t r i a l s .
A t pH 4.8 w ith n o s o r b i c a c i d a d d e d , B act. e r y t h r o g e n e s and
P s . f l u o r e s c e n s f a i l e d t o s u r v i v e , w h i l e A l e , i m e t a l c a l i g e n e s a n d R.
flaya g av e v a r i a b l e

r e s u l t s , w i t h s u r v i v a l in o n e of t w o t r i a l s .

Ach.

b u t y r i , A c h . e u r y d i c e , A l e . m e t a l c a l i g e n e s , P s . f r a g i , a n d R. f l a v a
f a i l e d t o s u r v i v e a t p H 4 . 8 w i t h 0.0 5 p e r c e n t s o r b i c a c i d , w h i l e
M. c o n g l o m e r a t u s a n d M u c o r p l u m b e u s e x h i b i t e d v a r i a b l e r e s u l t s at
t h i s p H a n d s o r b i c a c i d c o n c e n t r a t i o n , w i t h o n e of t w o t r i a l s s h o w ­
in g s u r v i v a l .

M. c o n g l o m e r a t u s f a i l e d to s u r v i v e a t pH 4.8 w i t h

0.10 p e r c e n t s o r b i c a c id , w h ile E. c o l i , P s . d e s m o l y t i c u m , P s .
t r a l u c i d a , G. c a n d i d u m , a n d M u c o r p l u m b e u s g a v e v a r i a b l e
at th is pH and

sorbic

acid

concentration.

results

B. f i r m u s , M. c a n d i d u s ,

a n d M. f l a v u s w e r e t h e o n l y o r g a n i s m s t e s t e d t h a t s u r v i v e d a t pH
4.8 w i t h 0 .2 5 p e r c e n t s o r b i c a c i d .
T h e e x t e n t o f g r o w t h w a s d e t e r m i n e d by m e a s u r i n g t u r b i d i t y
w i t h a K l e t t - S u m m e r s on c o l o r i m e t e r , but t h e r e s u l t s
te r m in a tio n s a r e not shown.

of t h e s e d e ­

C o n s id e ra b le difficulty w as en co u n tered

in o b t a i n i n g r e l i a b l e r e a d i n g s , p a r t i c u l a r l y a t t h e l o w e r pH l e v e l s .
T h i s m i g h t h a v e b e e n d u e t o s o m e p r e c i p i t a t i o n of t h e p r o t e i n

68
c o n s titu e n ts in th e m e d iu m

c a u s e d b y t h e a d d i t i o n of t h e s o r b i c a n d

lactic acid s, sin ce c o lo rim e tric

r e a d i n g s ab ove and below z e r o w e r e

o b ta in e d in t r i a l s w h ic h e x h ib ite d v ia b ility and n o n v ia b ility upon
plating.

C o n t r o l of S p o i l a g e i n C o t t a g e C h e e s e

T r e a t m e n t of W a s h W a t e r

T h e e f f e c t of t r e a t i n g c o t t a g e c h e e s e w a s h w a t e r w i t h v a r i o u s
a c i d s a n d g e r m i c i d e s t o c o n t r o l s p o i l a g e c a u s e d by A c h . b u t y r i , A ch .
e u r y d i c e , A l e , m e t a l c a l i g e n e s , B. f i r m u s , E . c o l i , E. f r e u n d i i , M.
c a n d i d u s , M. c o n g l o m e r a t u s , P s . d e s m o l y t i c u m , P s . f l u o r e s c e n s ,
P s. fragi,

P s . tralu cid a,

R. f l a v a , T . C a n d i d a , P e n , f r e q u e n t a n s , a n d

G. c a n d i d u m i s s h o w n i n T a b l e s X I V t h r o u g h XX I.

S o m e of t h e

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

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

i n c r e a s e d o r d e c r e a s e d in s o m e c a s e s w ithout r e g a r d a s to the
t y p e of o r g a n i s m

in o c u la te d into the ch e e se .

P ro b a b ly th is was

due to th e h ig h ly v a r i a b l e m i c r o f l o r a o r c o n ta m in a tio n w hich th e
c h e e s e n o r m a lly contains.
T h e s a m p l e of c h e e s e i n o c u l a t e d w i t h A c h . b u t y r i ( T a b l e
XIV) a n d w a s h e d w i t h w a t e r c o n t a i n i n g a c e t i c a c i d s p o i l e d in 14

69
T A B L E X IV
T H E E F F E C T O F W A SH W A T E R T R E A T M E N T ON C O N T R O L L IN G
V A R IO U S S P O I L A G E O R G A N IS M S IN C O T T A G E C H E E S E
S T O R E D A T 5 0° F .

T reatm ent

De­
scrip ­
tion

Ini­
tial
pH

Initial
F lavor
Score

Days
Until
Spoil­
age

Type
of
Spoilage

F i­
nal
pH

S p o ilag e by Ach. b u ty ri
C ontrols
U ninoculated
Inoculated
A cids
A cetic
C itric
L actic
P hosphoric
Sorbic
G erm icides
C hlorine
Iodophor
Q uaternary

pH
pH
pH
pH
pH

5.0
5.0
5.0
5.0
5.0

10 ppm
10 ppm
10 ppm

4.98
5.10

3 9 .0
3 9 .0

14
6

m old
tapioca

4.62
5.2 7

5.00
5.13
5.13
5.15
5 .0 5

39-0
39-0
3 9 .0
39.0
38.0

14
6
6
6
6a

pink s lim e
tapioca
tapioca
tapioca
c h e m i c a l 3-

4.81
5 .2 0
5.20
5. 16
5.10

5.17
5. 25
5.13

39.0
39.0
39.0

6
6
6

tapioca
tapioca
tapioca

5.18
5. 28
5 .30

S p o ila g e by Ach. e u r y d i c e
C ontrols
U ninoculated
Inoculated
A cids
A cetic
Cit r ic
L actic
P hosphoric
Sorbic
G erm icides
C hlorine
Iodophor
Q uaternary

5. 02
4 .9 5

39.5
39.5

12
6

w h e y e d off
tapioca

4. 30
4.51

pH 5.0
pH 5.0
pH 5.0
pH 5.0
0.05%

5.01
4.90
5.05
5.05
5.10

39.5
39.5
39.5
39-5
38.5

12
6
6
6
6

w h e y e d off
tapioca
tapioca
tapioca
tapioca

4. 30
4.61
4.50
4. 49
4 .72

10 ppm
10 ppm
10 ppm

5.00
4.98
4.98

39.5
3 5 . 0b
39.5

tapioca
tapioca
tapioca

4 .80
4.65
a c.
r\
4.
5U

6
6
6

a D i s c a r d e d a t s i x d a y s w i t h a c h e m i c a l f l a v o r , but a p p e a r ­
a n c e of t h e c h e e s e w a s g o o d .
^H alogen flavor.

70
days.

H ow ev er, spoilage w as not c h a ra c te ris tic

p r o d u c e d by A ch. b u t y r i .

of t h a t n o r m a l l y

AVithin 6 d a y s a t a p i o c a s l i m e c h a r a c t e r ­

i s t i c of A c h . b u t y r i f o r m e d o n a l l t h e r e m a i n i n g s a m p l e s e x c e p t t h e
one w a s h e d w ith w a t e r c o n ta in in g su ffic ie n t s o r b i c a c id to lo w e r the
p H of t h e w a t e r t o 5 . 0 .

T h is s a m p le exhibited a definite c h e m ic a l

flav o r and w as d isc a rd e d .
W h e y i n g - o f f a t a pH of 4.3 w a s a p p a r e n t a f t e r 12 d a y s i n
t h e u n i n o c u l a t e d c o n t r o l a n d t h e s a m p l e of c h e e s e i n o c u l a t e d w i t h
A c h . e u r y d i c e ( T a b l e XIV) a n d w a s h e d w i t h w a t e r c o n t a i n i n g a c e t i c
acid.

I n 6 d a y s t h e r e m a i n d e r of t h e s a m p l e s w e r e s p o i l e d b y a

t a p i o c a s l i m e t y p i c a l of A c h . e u r y d i c e .

A halogen flavor w as d e ­

t e c t a b l e i n c h e e s e w a s h e d w i t h w a t e r c o n t a i n i n g 10 p a r t s p e r m i l ­
lion io d ophor.

It s h o u l d b e n o t e d t h a t t h e t a p i o c a s l i m e d e v e l o p e d

o n c h e e s e e x h i b i t i n g t h e h a l o g e n f l a v o r a s w e l l a s c h e e s e w i t h pH
ranging fro m
An

4.5 t o 4 .8 .

atypical

spoilage

d e v e lo p e d in 6 d a y s on th e u n in o c u la te d

c o n t r o l a n d on th e s a m p l e i n o c u la te d w ith Ale, m e t a l c a l i g e n e s (T able
XV) a n d w a s h e d w i t h w a t e r c o n t a i n i n g a c e t i c a c i d .

The sam ple

w a s h e d w ith w a t e r c o n ta in in g s o r b ic a c id and all r e m a in in g s a m p le s
d e v e l o p e d a t a p i o c a s l i m e c h a r a c t e r i s t i c of A l e , m e t a l c a l i g e n e s
a fte r 6 and 4 days,

respectively.

71
T A B L E XV
T H E E F F E C T O F W A SH W A T E R T R E A T M E N T O N C O N T R O L L IN G
V A R IO U S S P O I L A G E O R G A N IS M S IN C O T T A G E C H E E S E
S T O R E D A T 50° F .

T reatm ent

De­
scrip ­
tion

Ini­
tial
pH

Initial
F lavor
Score

Days
Unt il
Spoil­
age

Type
of
Spoilage

F i­
nal
PH

Spoilag e by Ale. m e ta lc a lig e n e s
C ontrols
U ninoculated
Inoculated
A cids
A cetic
C itric
L actic
Phosphoric
S orbic
G ejrm icides
C hlorine
Iodophor
Q uaternary

4 .7 5
4.88

39 . 0
3 9 .0

6
4

pink s li m e
tapioca

4.8 0
5.00

pH 5.0
pH 5.0
pH 5.0
pH 5.0
0.05%

4 .85
4 .8 3
4.8 3
4 .8 2
4. 85

39-0
39.0
39 .0
39.0
39.0

6
4
4
4
6

pink s lim e
tapioca
tapioca
tapioca
tapioca

4.9 0
4.91
5.00
5.0 3
4.95

10 ppm
7.5 p p m
10 ppm

4.90
4.87
4.88

39.0
39-0
39.0

4
4
4

tapioca
tapioca
tapioca

5.05
5 .06
5.08

S p o i l a g e b y B. f i r m u s
C ontrols
U ninoculated
Inoculated
A cids
A cetic
C itric
L actic
P hosphoric
Sorbic
G erm icides
C hlorine
Iodophor
Q uaternary

5 .00
4.97

40.0
40.0

10
10

brown slim e
brown slim e

4.9 8
4.85

pH 5.0
pH 5.0
pH 5.0
pH 5.0
0. 05%

4.90
5.15
5.07
5.10
5.17

40.0
40 . 0
40 . 0
40 . 0
40 . 0

16
16
16
16
10

w h e y e d off
w h e y e d off
brown slim e
brown slim e
brown s lim e

4.3 0
4.5 0
4.65
4.40
4.95

10 ppm
10 ppm
10 ppm

5.00
5.17
5.17

40.0
3 8 .0a
40.0

10
10
10

brown slim e
brow n slim e
brown slim e

4.55
4.80
4 .80

a Slight h a lo g e n fla v o r.

72
W h e y i n g - o f f o c c u r r e d a f t e r 16 d a y s in t h e s a m p l e s i n o c u l a t e d
-B* f i r m u s

( T a b l e XV) a n d w a s h e d w i t h w a t e r s c o n t a i n i n g a c e t i c

and c itric acids.
with w a t e r s

A b r o w n s l i m e d e v e l o p e d on t h e c h e e s e w a s h e d

c o n t a i n i n g l a c t i c a n d p h o s p h o r i c a c i d s a f t e r 16 d a y s .

T h e r e m a i n d e r of t h e s a m p l e s , b o t h u n i n o c u l a t e d a n d i n o c u l a t e d ,
s h o w e d t h e b r o w n s l i m e i n 10 d a y s .
brow n slim e, this o rg a n ism

A l t h o u g h B. . f i r m u s c a u s e s a

m i g h t n o t h a v e b e e n t h e c a u s e of s p o i l ­

ag e in t h e s e s a m p l e s , s in c e th e u n in o c u la te d c o n tro l dev elo p ed the
brown slim e also.
A f t e r 12 d a y s a b r o w n s l i m e c h a r a c t e r i s t i c of E. c o l i a p ­
p e a r e d o n t h e u n i n o c u l a t e d c o n t r o l a n d on s a m p l e s i n o c u l a t e d w i t h
this o rg a n ism

( T a b l e X V I) a n d w a s h e d w i t h w a t e r s c o n t a i n i n g

phosphoric and so rb ic acids.

The in o cu lated c o n tro l and th e s a m p le s

w a sh e d w ith w a t e r s containing c itr ic and la c tic acid s and ch lo rin e
a n d q u a t e r n a r y d e v e l o p e d t h i s b r o w n s l i m e i n 10 d a y s .

The s a m p le s

w a s h e d w i t h w a t e r s c o n t a i n i n g a c e t i c a c i d a n d i o d o p h o r s p o i l e d i n 10
d a y s , b u t s p o i l a g e c h a r a c t e r i s t i c s w e r e n o t t y p i c a l of E . c o l i .
An a t y p i c a l f r u i t y f la v o r d e v e lo p e d in th e s a m p l e s in o c u la te d
w i t h E . f r e u n d i i ( T a b l e XVI ) a n d washed* w i t h w a t e r s c o n t a i n i n g
c h l o r i n e a n d s o r b i c a c i d ill 12 a n d 14 d a y s , r e s p e c t i v e l y .

A f t e r 12

days the s a m p l e s w a s h e d with w a t e r s co ntaining a c e tic and phos
p h o r i c a c i d s a n d t h e i o d o p h o r d e v e l o p e d d e f e c t s n o t c h a r a c t e r i s t i c of

73
T A B L E XVI
T H E E F F E C T O F W ASH W A T E R T R E A T M E N T ON C O N T R O L L IN G
V A R IO U S S P O I L A G E O R G A N IS M S IN C O T T A G E C H E E S E
S T O R E D A T 50° F .

T reatm ent

De­
scrip ­
tion

Ini­
tial
pH

Initial
FI avo r
Score

Days
U n ti l
Spoil­
age

Type
of
Spoilage

F i­
nal
PH

S p o i l a g e by E . c o l i
C ontrols
U ninoculated
Inoculated
A cids
A cetic
C itric
L actic
P hosphoric
S orbic
G erm icides
C hlorine
Iodophor
Q uaternary

4 .8 2
4.90

38 .5
38.5

12
10

brown slim e
brown slim e

4.9 6
4.8 7

pH 5.0
pH 5.0
pH 5.0
pH 5.0
0.0 5%

4.80
4.7 9
4 .76
4.81
4.77

38.5
38.5
38.5
38.5
38.5

10
10
10
12
12

m old
brown
brown
brown
brown

slim e
slim e
slim e
slim e

4.82
4.8 0
4. 72
4.85
4.85

10 ppm
7.5 p p m
10 ppm

4.81
4.8 2
4 .6 2

38 .5
38.5
38.5

10
10
10

brow n slim e
pink s lim e
brown slim e

4.88
4.9 0
4.85

S p o i l a g e b y E.
C ontrols
U ninoculated
Inoculated
A cids
A cetic
C itric
L actic
P hosphoric
S orbic
G erm icides
C hlorine
Iodophor
Q uaternary

freundii

4 .9 5
4.90

3 9 .0
3 9 .0

10
10

brown slim e
brown slim e

4.80
4 .78

pH 5.0
pH 5.0
pH 5.0
pH 5.0
0.05%

4.90
5.00
5 .0 5
4.82
4.91

39 .0
39-0
39-0
39.0
39 .0

12
12
12
12
14

m old
brown slim e
pink s l i m e
m old
fruity

4.75
4. 90
4.85
4.85
4 .85

10 ppm
7.5 p p m
10 ppm

4.93
4 .9 3
4 .8 9

39-0
39 .0
39 .0

12
12
10

fruity
m old
brown slim e

4 .80
4 .8 0
4 .83

74
E. f r e u n d i i .

T h e s a m p l e w a s h e d with w a t e r co n tain in g c i t r i c acid

w a s s p o i l e d w i t h a b r o w n s l i m e i n 12 d a y s , w h i l e t h e t w o c o n t r o l s
and th e s a m p l e w a s h e d w ith w a t e r co n tain in g q u a te r n a r y developed
b r o w n s l i m e c h a r a c t e r i s t i c of E . f r e u n d i i in 10 d a y s .
T h e s a m p l e i n o c u l a t e d w i t h M. c a n d i d u s

( T a b l e XVII) a n d

the u n in o cu lated c o n tro l show ed fre e whey a f te r 6 days.
defect w as ap p aren t.

C h e m ic a l and h a lo g en fla v o rs

No o t h e r

w e r e n o t e d in

t h e s a m p l e s w a s h e d w i t h w a t e r s c o n t a i n i n g 0.05 p e r c e n t s o r b i c
a c i d a n d 10 p a r t s p e r m i l l i o n of i o d o p h o r , r e s p e c t i v e l y .
S p o i l a g e o c c u r r e d i n a l l t h e s a m p l e s i n o c u l a t e d w i t h M.
conglom eratus
14 d a y s .

( T a b l e X V II) a n d t h e u n i n o c u l a t e d c o n t r o l a f t e r 8 t o

T h i s s p o i l a g e w a s d u e t o o r g a n i s m s o t h e r t h a n M. c o n -

glo m eratu s,

since th is o rg a n ism

c a u s e s no v i s i b l e d e f e c t o t h e r t h a n

fre e whey r e s u ltin g fro m acid production.

S orbic acid s e e m e d the

m o s t effective com pound a g a in s t the dom inant spoilage o rg a n is m ,
a s 14 d a y s w e r e r e q u i r e d f o r s p o i l a g e t o o c c u r i n t h e s a m p l e
w ash ed w ith w a t e r c o n tain in g th is com pound.
A m o n g th e s a m p l e s in o c u la te d with P s . d e s m o ly tic u m

(Table

X V I II ) , t h e c o n t r o l a n d t h e s a m p l e w a s h e d w i t h w a t e r c o n t a i n i n g
l a c t i c a c i d w e r e f r u i t y i n 6 d a y s , w h i l e t h e s a m p l e w a s h e d w ith
w a t e r c o n t a i n i n g c i t r i c a c i d w a s b i t t e r in 12 d a y s .

A f t e r 24 d a y s

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

75
T A B L E X V II
T H E E F F E C T O F W A SH W A T E R T R E A T M E N T ON C O N T R O L L IN G
V A R IO U S S P O I L A G E O R G A N IS M S IN C O T T A G E C H E E S E
S T O R E D A T 5 0° F .

T reatm ent

De­
scrip ­
tion

Ini­
tial
pH

Initial
F lavor
Score

Days
U n ti l
Spoil­
age

Type
of
Spoilage

F i­
nal
pH

S p o i l a g e b y M. c a n d i d u s
C ontrols
U ninoculated
Inoculated
A cids
A cetic
C itric
L actic
P hosphoric
Sorbic
G erm icides
C hlorine
Iodophor
Q uaternary

5.20
5.10

39.0
39-0

6
6

w h e y e d off
w h e y e d off

4. 70
4.7 0

p H 5.0
pH 5.0
pH 5.0
pH 5.0
0.05%

5.05
5 .1 2
5. 12
5.09
5.10

39-0
39-0
39 .0
39-0
3 7 .0a

6
6
6
6
6

wheyed
wheyed
wheyed
wheyed
wheyed

off
off
off
off
off

4. 70
4.85
4.70
4. 80
4. 70

10 ppm
10 ppm
10 ppm

5.10
5.10
5.1 2

39.0
3 8 . 0b
39.0

6
6
6

w h e y e d off
w h e y e d off
w h e y e d off

4.7 0
4.8 0
4.8 0

S p o i l a g e by M. c o n g l o m e r a t u s
C ontrols
U ninoculated
Inoculated
A cids
A cetic
C itric
L actic
Phosphoric
Sorbic
G erm icides
C hlorine
Iodophor
Q uaternary

Q

4.85
4 .8 5

39-0
3 9 .0

8
10

pink s lim e
pink s lim e

4.8 0
4.9 0

pH 5.0
pH 5.0
pH 5.0
pH 5.0
0.05%

4.83
4.8 5
4.81
4.8 2
4.8 2

39-0
39.0
3 9 .0
39-0
39-0

10
10
10
10
14

m old
pink
pink
pink
pink

slim e
slim e
slim e
slim e

4 .8 8
4. 80
4.71
4.85
4.8 7

10 ppm
7.5 p p m
10 ppm

4.88
4.8 5
4.88

39.0
39.0
39.0

10
10
10

pink s lim e
pink s lim e
pink s lim e

4.83
4 .89
4 .94

C h em ical flavor
kSlight h a lo g e n fla v o r.

76
T A B L E X V III
T H E E F F E C T O F W A SH W A T E R T R E A T M E N T ON C O N T R O L L IN G
V A R IO U S S P O I L A G E O R G A N IS M S IN C O T T A G E C H E E S E
S T O R E D A T 50° F .
De­
scrip ­
tion

T reatm ent

Ini­
tial
pH

Initial
F lavor
Score

Days
U n ti l
Spoil­
age

Type
of
Spoilage

F i­
nal
pH

S p o ila g e by P s . d e s m o ly tic u m
C ontrols
U ninoculated
Inoculated
A cids
A cetic
C itric
L actic
P hosphoric
Sorbic
G erm icides
C hlorine
Iodophor
Q uaternary

pH
pH
pH
pH
pH

5.0
5.0
5.0
5.0
6 .0

10 ppm
10 ppm
10 ppm

4.70
4.88

4 0 .0
4 0 .0

20
6

w h e y e d off
fruity

4. 40
5.00

4.80
4 .7 5
4.85
4. 85
4. 85

40.0
40.0
40.0
40.0
3 9 ■0a

20
12
6
20
24b

w h e y e d off
bitter
fruity
w h e y e d off
(b)

4. 50
4. 60
5. 00
4 .75
4. 50

4 .9 3
4.92
4.92

40.0
40.0
40 .0

20
20
20

w h e y e d off
w h e y e d off
w h e y e d off

4.81
4 .50
4.55

S p o ilag e by P s .
C ontrols
U ninoculated
Inoculated
A cids
A cetic
C itric
L actic
P hosphoric
Sorbic
G erm icides
C hlorine
Iodophor
Q uaternary

pH
pH
pH
pH
pH

5.0
5.0
5.0
5.0
5.0

10 ppm
10 ppm
10 ppm

fluorescens

4.9 5
5.15

38.5
39-5

14
8

bitter
g re e n slim e

4.6 0
5 .02

5 .00
5.15
5.1 2
5.1 5
5.10

40.0
40.0
40.0
39.5
3 6 .0C

8
14
6
8
14

green slim e
bitter
g reen slim e
green slim e
chem ical0

5.05
4.4 0
4. 40
4.9 0
4.9 0

5.17
5.20
5.21

40 .0
38.5d
4 0 .0

6
6
6

g reen slim e
green slim e
green slim e

4.65
4.41
4.35

a Slight c h e m i c a l fla v o r.
^ S till

m ark etab le

after

tw en ty -fo u r

days.

° D i s c a r d e d due to c h e m ic a l flavor.
d H a l o g e n f l a v o r d e t e c t e d in f r e s h c h e e s e only, d i s a p p e a r e d
a f t e r tw o d ay s.

77
l o w e r t h e p H of t h e w a t e r t o 6.0 w a s s t i l l m a r k e t a b l e .

The r e ­

m a i n d e r of t h e s a m p l e s i n c l u d i n g t h e u n i n o c u l a t e d c o n t r o l w e r e
s o u r a n d w h e y e d - o f f a f t e r Z0 d a y s .
T h e d e v e l o p m e n t of a g r e e n s l i m e w a s a p p a r e n t in 6 d a y s
on t h e s a m p l e s i n o c u l a t e d w i t h P s . f l u o r e s c e n s

( T a b l e XVIII) a n d

w a sh e d w ith w a t e r s co n tain in g la c tic acid, and ch lo rin e , iodophor,
and q u a t e r n a r y c o m p o u n d s.

T h i s g r e e n s l i m e a p p e a r e d in 8 d a y s

on t h e i n o c u l a t e d c o n t r o l a n d t h e s a m p l e s w a s h e d w i th w a t e r s c o n ­
taining a c e tic and p h o sp h o ric acids.

A f t e r 14 d a y s t h e u n i n o c u l a t e d

c o n tro l an d th e s a m p l e w a s h e d with w a t e r containing c itr ic acid
w ere b itter.

T h e s a m p l e w a s h e d with w a t e r c o n tain in g sufficient

s o r b i c a c i d t o l o w e r t h e pH of t h e w a t e r t o 5 . 0 w a s b e l a t e d l y d i s ­
c a r d e d a f t e r 14 d a y s b e c a u s e of a d e f i n i t e c h e m i c a l f l a v o r .

A

h a l o g e n f l a v o r w a s n o t e d in t h e s a m p l e w a s h e d w i t h w a t e r c o n t a i n ­
i n g 10 p a r t s p e r m i l l i o n of i o d o p h o r w h e n t h e c h e e s e w a s f r e s h ,
b ut t h e f l a v o r d i s a p p e a r e d a f t e r Z d a y s of s t o r a g e .
A m o n g t h e s a m p l e s i n o c u l a t e d w i t h P s . f r a g i ( T a b l e XIX),
the c o n tr o l and th e s a m p l e s w a s h e d with w a t e r s containing a c e tic ,
c i tr ic , la c tic , and p h o s p h o ric a c id s , iodophor, and q u a te r n a ry de­
v e l o p e d a b i t t e r f l a v o r n o t c h a r a c t e r i s t i c of P s . f r a g i in 6 d a y s .
W ithin 8 d a y s th e s a m p l e s w a s h e d with w a t e r s co n tain in g s o rb ic
a c id and c h lo r in e and the u n in o c u la te d c o n tro l a ls o developed this
b itte r flavor.

78
T A B L E X IX
T H E E F F E C T O F W ASH W A T E R T R E A T M E N T ON C O N T R O L L IN G
V A R IO U S S P O I L A G E O R G A N IS M S IN C O T T A G E C H E E S E
S T O R E D A T 50° F .

T reatm ent

De­
scrip ­
tion

I ni
tial
pH

Initial
F lavor
Score

Days
U n t il
Spoil­
age

Type
of
Spoilage

F i­
nal
pH

S p o i l a g e by P s . f r a g i
C ontrols
U ninoculated
Inoculated
A cids
A cetic
Cit r ic
L actic
P hosphoric
Sorbic
G erm icides
C hlorine
Iodophor
Quate r n a r y

4.98
4.99

39.0
39-0

8
6

bitter
bitter

4.8 0
4.7 5

pH 5.0
pH 5.0
pH 5.0
pH 5.0
0.05%

4.93
5 .0 2
5.05
5 .00
5 .0 3

39.0
39.0
39.0
39-0
39.0

6
6
6
6
8

bitter
bitter
bitter
bitter
b itter

4.82
4 .7 0
4.75
4. 73
4 .7 0

10 ppm
7.5 p p m
10 p p m

5.04
5.00
5.03

39.0
39.0
39 .0

8
6
6

bitter
bitter
bitter

4 .70
4.75
4.68

S p o ila g e by P s . t r a l u c i d a
C ontrols
U ninoculated
Inoculated
A cids
A cetic
C itric
L actic
P hosphoric
Sorbic
G erm icides
C hlorine
Iodophor
Q uaternary

5.00
4.90

40.0
40.0

16
16

bitter
bitter

4.45
4.55

pH 5.0
pH 5.0
pH 5.0
pH 5.0
0.05%

4.90
4.92
4.90
4.90
4 .9 5

40.0
40.0
4 0 .0
40.0
4 0 .0

16
16
16
16
16

bitter
bitter
bitter
bitter
bitter

4.38
4 .3 0
4.40
4.40
4.50

10 ppm
10 ppm
10 ppm

4.90
4.80
4.95

4 0 .0
40.0
40.0

16
16
16

bitter
bitter
bitter

4.45
4. 43
4. 60

79
A f t e r 16 d a y s t h e c o m p l e t e s e t of s a m p l e s i n o c u l a t e d w i t h
P s . t r a l u c i d a ( T a b l e XIX) a n d t h e u n i n o c u l a t e d c o n t r o l w e r e d i s ­
c a r d e d w i t h a b i t t e r f l a v o r n o t c h a r a c t e r i s t i c of P s . t r a l u c i d a .
T a b l e X X s h o w s t h a t t h e s a m p l e s i n o c u l a t e d w i t h R. f l a v a
and w a s h e d w ith w a t e r s co n tain in g a c e tic acid, ch lo rin e , iodophor,
and q u a t e r n a r y a s w e ll a s th e c o n tr o l, d ev elo p ed pink s li m e c h a r ­
a c t e r i s t i c of R. f l a v a i n 4 d a y s , w h i l e t h e s a m p l e s w a s h e d w it h
w a t e r s c o n ta in in g c i t r i c , l a c t i c , and p h o s p h o r ic a c id s sh o w ed pink
s lim e in 6 d ay s.

A f t e r 18 d a y s t h e s a m p l e w a s h e d w i t h w a t e r c o n ­

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

but h a d

not

developed th e pink s lim e defect.
W h e n i n o c u l a t e d i n t o t h e c h e e s e , T . C a n d id a ( T a b l e XX)
c a u s e d th e c o n t r o l a n d th e s a m p l e w a s h e d with w a t e r c o n tain in g
i o d o p h o r to d e v e lo p a y e a s t y f la v o r in s ix d ay s.

Within s ix d ay s

th e s a m p l e s w a s h e d w ith w a t e r s c o n tain in g a c e tic , la c tic , and
p h o sp h o ric a c id s , and q u a te r n a r y developed a yellow s lim e c h a r ­
a c t e r i s t i c of T . C a n d i d a , w h i l e t h e s a m p l e s w a s h e d w i t h w a t e r s c o n ­
tain in g c i tr ic and s o rb ic ac id s and c h lo rin e r e q u ir e d 8 days to d e ­
velop th is slim e.
T h e s a m p l e in o c u la te d w ith

P e n , f r e q u e n t a n s ( T a b l e XXI)

w a sh e d with w a t e r co n tain in g s o rb ic a c id developed

and

typical b lu e -g re e n

80
T A B L E XX
T H E E F F E C T O F W ASH W A T E R T R E A T M E N T ON C O N T R O L L IN G
V A R IO U S S P O I L A G E O R G A N IS M S IN C O T T A G E C H E E S E
S T O R E D A T 50° F .

T reatm ent

D e­
scrip ­
tion

Ini­
tial
pH

Initial
F lavor
Score

Days
Until
Spoil­
age

Type
of
Spoilage

F i­
nal
PH

m old
pink s lim e

4.80
4.90

pink
pink
pink
pink
stale

slim e
slim e
slim e
slim e

4.85
4.9 0
4.80
4.85
4.5 5

pink s lim e
pink s li m e
pink s lim e

4.9 2
4.92
4.92

S p o i l a g e b y R. f l a v a
C ontrols
U ninoculated
Inoculated
A cids
A cetic
C itric
L actic
P hosphoric
Sorbic
G erm icides
C hlorine
Iodophor
Q uaternary

4.90
4.94

40.0
40.0

6
4

pH 5.0
pH 5.0
pH 5 . 0
pH 5.0
0. 05%

4 .87
4.81
4.89
4. 9 0
4.90

40.0
40 .0
4 0 .0
4 0 .0
40.0

4
6
6
6
18

10 ppm
7.5 p p m
10 ppm

4 .9 2
4.9 3
4.9 3

40.0
40.0
40.0

4
4
4

S p o i l a g e b y T. C a n d i d a
C ontrols
U ninoculated
Inoculated
A cids
A cetic
C itric
L actic
Phosphoric
S orbic
G erm icides
C hlorine
Iodophor
Q uaternary

4.9 5
4.97

3 9 .0
39.0

8
6

pink s li m e
yeasty

4. 82
4 .7 0

pH 5.0
pH 5.0
pH 5.0
pH 5.0
0.05%

4.98
4.9 5
4.95
5.00
5.00

39-0
39.0
39-0
3 9 .0
39-0

6
8
6
6
8

yellow
yellow
yellow
yellow
yellow

slim e
slim e
slim e
slim e
slim e

4.85
4.72
4.65
4.85
4.85

10 ppm
7.5 p p m
10 p p m

4.95
4.95
4.90

3 9 .0
3 8 .0a
39.0

8
6
6

yellow s lim e
yeasty
yellow s lim e

4 .81
4 .70
4 .83

a Slight h a lo g e n fla v o r .

81
T A B L E XXI
T H E E F F E C T O F W A SH W A T E R T R E A T M E N T ON C O N T R O L L IN G
V A R IO U S S P O I L A G E O R G A N IS M S IN C O T T A G E C H E E S E
S T O R E D A T 50° F .

T reatm ent

De­
scrip ­
tion

Ini­
tial
pH

Initial
F lavor
Score

Days
U n til
Spoil­
age

Type
of
Spoilage

F i­
nal
PH

S p o ila g e by P en. f r e q u e n ta n s
C ontrols
U n inoculat ed
Inoculated
A cids
A cetic
C itric
L actic
P hosphoric
S orbic
G erm icides
C hlorine
Iodophor
Q uaternary

4.9 2
4.90

39-0
39.0

10
10

m old
m old

5 .00
4.83

p H 5.0
pH 5.0
pH 5.0
pH 5.0
0 . 05%

4. 9 5
4.98
5.00
5 .01
4.97

39.0
39 .0
39-0
39 .0
3 9 .0

10
10
10
10
14

m old
m old
m old
m old
m old

5.0 0
5. 00
4.95
5.15
4.92

10 ppm
7.5 p p m
10 ppm

4 .9 5
4.90
4.93

39-0
39-0
39. 0

10
10
10

m old
m old
m old

5 .08
5. 02
4.98

S p o i l a g e by G. c a n d i d u m
C ontrols
U ninoculated
Inoculated
A cids
A cetic
C itric
L actic
P hosphoric
S orbic
G erm icides
C hlorine
Iodophor
Q uaternary

4.92
4. 90

39. 0
3 8 .0

8
6

yellow s lim e
m old

4.92
4.98

pH 5.0
pH 5.0
pH 5.0
pH 5.0
0.05 %

4.90
4.86
4.89
4.90
4.87

38. 0
38.5
39-0
39.0
39. 0

6
6
6
6
8

m old
m old
m old
m old
m old

5.05
4.99
5 .05
4. 98
4 .9 6

10 ppm
7.5 p p m
10 ppm

4.93
4.91
4.90

39.0
39-0
39.0

6
6
6

m old
m old
m old

5 .04
4.84
5.04

A

r

/

A

82
m o l d i n 14 d a y s , w h i l e t h e r e m a i n d e r of t h e s a m p l e s d e v e l o p e d t h i s
d e f e c t i n 10 d a y s .
A f t e r 8 d a y s m o l d g r o w t h c h a r a c t e r i s t i c of G. c a n d i d u m
d e v e lo p e d on t h e s a m p l e i n o c u la te d with th is o r g a n i s m

(T a b le XXI)

and w a s h e d w ith w a t e r con tain in g s o rb ic acid, w hile the r e m a in in g
s a m p l e s d e v e lo p e d th is m o ld in 6 days.
T a b l e X X I I s h o w s t h e n u m b e r of d a y s of i n c r e a s e i n s h e l f life p r o d u c e d by v a r io u s w ash w a t e r t r e a t m e n t s when cottage c h e e s e
was in o c u la te d w ith d iffe re n t spoilage o rg a n is m s .
T h e s h e l f - l i f e w a s i n c r e a s e d i n s i x of s i x t e e n t r i a l s w h e n
a c e tic and c i t r i c a c id s w e r e added to th e w ash w a te r.

Lactic and

p h o s p h o r i c a c i d s i n c r e a s e d t h e s h e l f - l i f e i n t h r e e a n d f iv e of s i x t e e n
t r i a l s , r e s p e c t i v e l y , w h i l e s o r b i c a c i d i n c r e a s e d t h e s h e l f - l i f e in
e l e v e n of s i x t e e n t r i a l s .

T h e a d d i t i o n of q u a t e r n a r y , i o d o p h o r , a n d

c h l o r i n e t o t h e w a s h w a t e r i n c r e a s e d t h e s h e l f - l i f e in o n e , t w o , a n d
f o u r of s i x t e e n i n s t a n c e s , r e s p e c t i v e l y .
W hen s p o il a g e w a s p ro d u c e d by P s. f l u o r e s c e n s , the d e v e lo p ­
m e n t o f g r e e n s l i m e w a s h a s t e n e d a p p r o x i m a t e l y 2 d a y s by t h e a d ­
d i t i o n of l a c t i c a c i d , c h l o r i n e , i o d o p h o r , a n d q u a t e r n a r y to t h e w a s h
w ater.

83
T A B L E X X II
E F F E C T O F W A S H W A T E R T R E A T M E N T ON T H E S H E L F - L I F E
O F C O T T A G E C H E E S E I N O C U L A T E D W IT H VAR IO US
S P O I L A G E O R G A N IS M S
T r e a t m e n t of W a s h W a t e r a n d N u m b e r
of D a y s A d d e d t o S h e l f - L i f e w h e n
C o m p a r e d to an In o cu lated C o n tro l
O rganism
Acetic
A cid

A c h . b u t y r i ..................
A c h . e u r y d i c e ..............

8

C it- L a c n c tic
A cid A cid

Phos_
,
Sor- .
Io - Q u a phor- , . C hlor- ,
.
bic
.
doteric
ine
. . . Acid
phor nary
Acid

6

0
0

0
0

0
0

0
0

0
0

0
0

0
0

Ale. m e t a l c a l i g e n e s .
B. f i r m u s .....................

Z
6

0
6

0
6

0
6

z

0
0

0
0

0
0

E. c o l i ............................
E . f r e u n d i i .....................

0
Z

0

z
z

z

z

0
Z

4

0
2

0
2

0
0

M. c a n d i d u s .................
M. c o n g l o m e r a t u s . .

0
0

0
0

0
0

0
0

0
4

0
0

0
0

0
0

desm olyticum . .
flu o rescen s
. . .
f r a g i ........................
t r a l u c i d a ..............

14
0
0
0

6
6
0
0

0

18
6
2
0

14
-Z

0
0

14
0
0
0

0

14
-2
0
0

14
-Z
0
0

R. f l a v a ................. ...
T. C a n d i d a .....................

0
0

Z
Z

z

z

0

0

14
Z

0
z

0
0

0
0

Pen. frequentans . . .
G. c a n d i d u m ..................

0
0

0
0

0
0

0
0

4
Z

0
0

0
0

0
0

Ps.
Ps.
Ps.
Ps.

-z

0

z

84

T r e a tm e n t of D r e s s i n g M a te r ia ls

T h e e f f e c t of t r e a t i n g c o t t a g e c h e e s e d r e s s i n g m a t e r i a l w i th
v a r i o u s a c i d s a n d s t a r t e r in c o n t r o l l i n g s p o i l a g e o r g a n i s m s in c o t ­
t a g e c h e e s e i s s h o w n i n T a b l e s X X I II t h r o u g h XXXI.
W h e n s a m p l e s w e r e i n o c u l a t e d w i t h A c h . b u t y r i ( T a b l e XXIII),
a t y p i c a l t a p i o c a s l i m e d e v e l o p e d i n 4 d a y s on t h e c o n t r o l a n d t h e
s a m p l e s c o n ta in in g l a c t i c a c id and s t a r t e r , w hile the s a m p l e s with
c itr ic an d s o r b i c a c i d s d ev elo p ed th is ta p io c a s lim e in 6 days.
A m o n g th e s a m p l e s in o c u la te d with Ach. e u ry d ic e (T able
XX III ), t h e c o n t r o l a n d t h e s a m p l e c o n t a i n i n g c i t r i c a c i d , a s w e l l a s
t h e u n i n o c u l a t e d c o n t r o l , d e v e l o p e d a c h a r a c t e r i s t i c t a p i o c a s l i m e in
6 days.

S p o i l a g e n o t r e p r e s e n t a t i v e of A c h . e u r y d i c e o c c u r r e d in

t h e s a m p l e s c o n t a i n i n g l a c t i c a c i d a n d s t a r t e r in 6 a n d 8 d a y s ,
respectively.

A f t e r 12 d a y s f r e e w h e y w a s e v i d e n t in t h e s a m p l e

c o n tain in g s o r b ic acid.
T h e c o n t r o l s a m p l e in o c u la te d with Ale, m e t a l c a l i g e n e s
( T a b l e X X IV ) d e v e l o p e d c h a r a c t e r i s t i c t a p i o c a s l i m e i n 6 d a y s ,
w h e r e a s th e d e f e c t w a s d e la y e d u n til 8 d ay s in s a m p l e s c o n tain in g
citric and lactic acids.

T h e s a m p l e with ad d ed s t a r t e r developed

a lo w pH an d ta p i o c a s l i m e in 8 d ay s.
acteristic

of A l e ,

The tapioca slim e c h a r ­

m e t a l c a l i g e n e s d e v e l o p e d a f t e r 10 d a y s m t h e

s a m p le w hich c o n tain ed s o rb ic acid.

85
T A B L E X X III
T H E E F F E C T O F D R E S S IN G T R E A T M E N T IN C O N T R O L L IN G
V A R IO U S S P O I L A G E O R G A N IS M S IN C O T T A G E
C H E E S E S T O R E D A T 50° F .

T r e a tm ent

De­
scrip
tion

Ini­
tial
pH

Initial
F lavor
Score

Days
U ntil
Spoil­
age

Type
of
Spoilage

F i­
nal
pH

S p o i l a g e by A c h . b u t y r i
C ontrols
U ninoculated
Inoculated

4.8 2
4.90

39-0
39.0

8
4

m old
tapioca

4.65
5.03

A cids
C itric
L actic
Sorbic

0.15%
0.1 5%
0.1 0%

4.85
4.81
4.86

39.0
39-0
39-0

6
4
6

tapioca
tapioca
tapioca

5 .00
5.0 8
5.25

S tarter

2.0%

4.86

39-0

4

tapioca

5.15

tapioca
tapioca

4.82
4.75

S p o i l a g e b y Ach.
C ontrols
U ninoculated
Inoculated

eurydice

4.67
4.5 9

3 8. 0a
3 8 . 0a

6
6

A cids
C itric
L actic
Sorbic

0.15%
0 . 15%
0. 10%

4.64
4.60
4.60

3 8 . 0a
3 8 . 0a
3 8 .0a

6
6
12

tapioca
pink s lim e
w h e y e d off

4.85
4. 78
4.75

S tarter

2.0%

4.59

38.0a

8

pink s lim e

4.62

a Sour.

86
T A B L E X X IV
T H E E F F E C T O F D R E S S IN G T R E A T M E N T IN C O N T R O L L IN G
V A R IO U S S P O I L A G E O R G A N IS M S IN C O T T A G E
C H E E S E S T O R E D A T 5 0° F .

T reatm ent

De­
scrip ­
tion

Ini­
tial
pH

Initial
F lavor
Score

Days
U ntil
Spoil­
age

Type
of
Spoilage

F i­
nal
PH

pink s li m e
tapioca

5.02
5.15

tapioca
tapioca
tapioca

5.05
5.24
5.0 8

tap io caa

4.5 3

S p o ila g e by Ale. m e t a l c a l i g e n e s
C ontrols
U ninoculated
Inoculated

5.20
5,20

40 .0
40 .0

8
6

A cids
C itric
L actic
S orbic

0.1 5%
0.15 %
0.10%

5.21
5.15
5.18

40.0
4 0 .0
4 0 .0

8
8
10

S tarter

2.0%

5.20

40.0

8

S p o i l a g e by B. f i r m u s
C ontrols
U ninoculated
Inoculated

4 .6 2
4.63

39.5
39.5

8
6

m old
m old

4. 62
4.69

A cids
C itric
L actic
S orbic

0.15%
0.15%
0. 10%

4.58
4.57
4.61

39-5
39.0
39-5

6
8
10

m old
m old
m old

4.72
4. 64
4 .7 0

S tarter

2.0%

4.61

39.5

6

m old

4. 70

P in k s lim e .

87
A fter 6 days

s p o il a g e a p p e a r e d in th e c o n tr o l s a m p l e i n ­

o c u l a t e d w i t h B. f i r m u s

( T a b l e XX IV ) a s w e l l a s t h o s e i n o c u l a t e d

s a m p l e s c o n t a i n i n g c i t r i c a c i d a n d s t a r t e r , but s p o i l a g e w a s not
t y p i c a l of B. f i r m u s .

T h e s a m e s p o i l a g e o c c u r r e d in t h e s a m p l e

c o n ta in in g l a c t i c a c id , th e s a m p l e c o n ta in in g s o r b i c acid, and the
u n i n o c u l a t e d c o n t r o l i n 8, 10, a n d 8 d a y s , r e s p e c t i v e l y .
A fter 6

days

c h a r a c t e r i s t i c b ro w n s l i m e o c c u r r e d in the

c o n t r o l s a m p l e i n o c u l a t e d w i t h E. c o l i ( T a b l e X X V ), w h i l e t h e
s a m p l e s c o n t a i n i n g c i t r i c a n d l a c t i c a c i d s d e v e l o p e d t h i s d e f e c t in
8 days.

The s a m p le containing s t a r t e r developed a fruity flavor

in 8 d a y s , a n d t h e s a m p l e c o n t a i n i n g s o r b i c a c i d d e v e l o p e d a b i t t e r
f l a v o r a f t e r 10 d a y s .

T h e two l a t t e r d e fe c ts a r e not c h a r a c t e r i s t i c

of th o s e p r o d u c e d by E. c o l i .
A m o n g t h e s a m p l e s i n o c u l a t e d w i t h E. f r e u n d i i ( T a b l e XXV),
a ty p ic a l s p o ila g e o c c u r r e d a f t e r 6 d ay s in th e un in o cu lated co n ­
tro l, the c o n tro l, and the s a m p le containing s t a r t e r .

The brown

s l i m e d e f e c t t y p i c a l of E . f r e u n d i i d e v e l o p e d on t h e i n o c u l a t e d c o n ­
t r o l a n d t h e s a m p l e s c o n t a i n i n g c i t r i c a n d l a c t i c a c i d s in 6 d a y s ,
w hile th e s a m p l e co n tain in g s o rb ic acid r e q u ir e d 8 days to develop
this defect.
M. c a n d i d u s p r o d u c e s n o v i s i b l e d e f e c t o t h e r t h a n f r e e w h e y
r e s u l t i n g f r o m a c id d e v e lo p m e n t, but a f t e r 6 days a pink s lim e

88
T A B L E XXV
T H E E F F E C T O F D R E S S IN G T R E A T M E N T IN C O N T R O L L IN G
V A R IO U S S P O I L A G E O R G A N IS M S IN C O T T A G E
C H E E S E S T O R E D A T 50° F .

T reatm ent

De­
scrip ­
tion

Ini­
tial
pH

Initial
F lavor
Score

Days
U n t il
Spoil­
age

Type
of
Spoilage

F i­
nal
PH

Spoilag e by E . coli
C ontrols
U ninoculated
Inoculated

4,84
4.86

3 9 .0
39.0

8
6

m old
brown slim e

4.78
5. 20

brown slim e
brown slim e
b itter

5.05
5.05
4 .8 8

fruity

4.9 7

A cids
C itric
L actic
S orbic

0.15%
0.15%
0.10%

4.86
4.90
4.90

39 .0
39-0
39-0

8
8
10

S tarter

2.0%

4 .8 2

39-0

8

S p o i l a g e b y E. f r e u n d i i
C ontrols
U ninoculated
Inoculated

5. 12
5. 12

40 .0
40.0

6
6

m old
brown s lim e a

5.18
5 .00

A cids
C itric
L actic
Sorbic

0.15%
0. 15%
0. 10%

5.08
5.10
5. 12

4 0 .0
40.0
4 0 .0

6
6
8

brown slim e
brown slim e
brown slim e

4.78
4.72
4.93

S tarter

2. 0%

5.10

4 0 .0

6

m old

4.45

a M old.

89
d e v e lo p e d in m o s t of th e s a m p l e s in t h e s e r i e s in o c u la te d with
M. c a n d i d u s { T a b l e X X V I ) .

H o w e v e r , no s p o il a g e o c c u r r e d in th e

s a m p le co n tain in g s o r b ic acid.
T h e s a m p l e s i n o c u l a t e d w i t h M. c o n g l o m e r a t u s ( T a b l e XXVI)
s p o i l e d i n 6 t o 10 d a y s w i t h d i f f e r e n t t y p e s of a t y p i c a l d e f e c t s .
M. c o n g l o m e r a t u s p r o d u c e s no v i s i b l e d e f e c t o t h e r t h a n f r e e w h e y
resulting from

acid developm ent.

A ll of th e s a m p l e s in o c u la te d with P s .

desm olyticum

(Table

X XVII) d e v e l o p e d m o l d in 8 d a y s , e x c e p t t h e s a m p l e c o n t a i n i n g
s o r b i c a c i d , w h i c h d i d n o t s h o w m o l d u n t i l t h e f o u r t e e n t h day .
T h e s a m p l e c o n ta in in g la c tic a c id and in o c u la te d with P s .
fluorescens

( T a b l e X X V II) d e v e l o p e d a g r e e n s l i m e in 6 d a y s .

The

r e m a i n d e r of t h e s a m p l e s d e v e l o p e d a t y p i c a l t y p e s of s p o i l a g e in
10 d a y s .
A l l s a m p l e s i n o c u l a t e d w i t h P s . f r a g i ( T a b l e XXVI II) , a s w e l l
a s t h e u n i n o c u l a t e d c o n t r o l , d e v e l o p e d m o l d i n 10 d a y s .
M old g r o w t h o c c u r r e d in 6 to 8 d ays in all s a m p l e s in o c u ­
l a t e d w i t h P s . t r a l u c i d a ( T a b l e X X V I II ) , e x c e p t t h e s a m p l e c o n t a i n ­
i n g s o r b i c a c i d i n w h i c h m o l d w a s d e f e r r e d u n t i l t h e s i x t e e n t h day .
The ch aracteristic

p i n k s l i m e a p p e a r e d a f t e r 6 to 8 d a y s on

a l l s a m p l e s i n o c u l a t e d w i t h R. f l a v a ( T a b l e XX IX ), e x c e p t t h e s a m p l e

90
T A B L E XXVI
T H E E F F E C T O F D R E S S IN G T R E A T M E N T IN C O N T R O L L IN G
V A R IO U S S P O I L A G E O R G A N IS M S I N C O T T A G E
C H E E S E S T O R E D A T 50° F .

T reatm ent

De­
scrip ­
tion

Ini­
tial
PH

Initial
F lavor
Score

Days
U n til
Spoil­
age

Type
of
Spoilage

F i­
nal
PH

S p o i l a g e by M. c a n d i d u s
C ontrols
U ninoculated
Inoculated

4.60
4 .6 2

38.0
38.0

6
6

pink s lim e
pink s li m e

4.72
4.59

A cids
C itric
L actic
S orbic

0.15%
0.15%
0.10%

4.57
4.58
4. 62

38.0
38 .0
39-0

6
6
12

pink s li m e
pink s lim e
w h e y e d off

4. 53
4.53
4.65

S tarter

2.0%

4.63

38.0

6

pink s lim e

4.46

S p o i l a g e b y M. c o n g l o m e r a t u s
C ontrols
U ninoculated
Inoculated

4 .8 5
4 .8 5

39.0
39-0

10
8

bitter
m old

4.5 8
4.75

A cids
C itric
L actic
Sorbic

0.1 5%
0.15%
0. 10%

4.84
4.87
4 .8 3

39 .0
39-0
39-0

10
6
10

bitter
bitter
bitter

4.77
4.95
4.84

S tarter

2.0%

4.88

39-0

10

m old

4.52

91
T A B L E X X V II
T H E E F F E C T O F D R E S S IN G T R E A T M E N T IN C O N T R O L L IN G
V A R IO U S S P O I L A G E O R G A N IS M S IN C O T T A G E
C H E E S E S T O R E D A T 5 0° F .

T reatm ent

De­
scrip ­
tion

Ini­
tial
pH

Initial
F lavor
Score

Days
Until
Spoil­
age

Type
of
Spoilage

F i­
nal
pH

S p o i l a g e by P s . d e s m o l y t i c u m
C ontrols
U ninoculated
Inoculated

4.65
4.66

39.5
39.5

8
8

mold
mold

4. 67
4.71

A cids
C itric
L actic
Sorbic

0.15%
0.15%
0.10%

4.60
4.62
4.64

39-5
39-5
39.5

8
8
14

m old
m old
m old

4.64
4 .6 6
4.72

S tarter

2.0%

4.68

39-5

8

m old

4.45

S p o i l a g e by P s . f l u o r e s c e n s
C ontrols
U ninoculated
Inoculated

4.75
4.72

3 7 . 0a
3 7 . 0a

10
10

m oldb
mold*3

4.75
4.7 8

A cids
C itric
L actic
Sorbic

0.15%
0.15%
0.10%

4.7 5
4.7 4
4.71

3 7 . 0a
3 7 .0a
3 7 .0a

10
6
10

mold*3
green slim e
m oldk

4.69
4.61
4.6 6

S tarter

2.0%

4 .7 5

3 7 .0a

10

stale

4.6 8

Sour.
b P in k s lim e .

92
T A B L E X X V IH
T H E E F F E C T O F D R E S S IN G T R E A T M E N T IN C O N T R O L L IN G
V A R IO U S S P O I L A G E O R G A N IS M S IN C O T T A G E
C H E E S E S T O R E D A T 50° F .

T reatm ent

De­
scrip
tion

Ini­
tial
pH

Initial
F lavor
Score

Days
Until
Spoil­
age

Type
of
Spoilage

F i­
nal
PH

S p o i l a g e by P s . f r a g i
C ontrols
U ninoculated
Inoculated

4.7 5
4.73

3 7 . 0a
3 7 . 0a

10
10

m old
m old

4 .6 8
4 .7 8

A cids
C itric
L actic
Sorbic

0.15%
0.15%
0. 10%

4.71
4.75
4.75

3 7 . 0a
37.0a
37.0a

10
10
10

m old
m old
m old

4.65
4.65
4.7 3

S tarter

2.0 %

4. 75

37.0a

10

m old

4.65

m old^
m old

4.72
4.95

m old
m old
w h e y e d off

4.78
4 .8 6
4.62

m old

4.47

Spoilage by P s. tr a lu c id a
C ontrols
U ninoculated
Inoculated

4 .6 2
4 .6 5

39.5
39.5

6
6

A cids
C itric
L actic
Sorbic

0.1 5%
0 .1 5 %
0. 10%

4.58
4. 62
4.58

39.5
39-5
39.5

6
6
16

S tarter

2.0%

4.60

39-5

8

a Sour.
b P in k s lim e .

93
T A B L E X X IX
T H E E F F E C T O F D R E S S IN G T R E A T M E N T IN C O N T R O L L IN G
V A R IO U S S P O I L A G E O R G A N IS M S IN C O T T A G E
C H E E S E S T O R E D A T 50° F .

T reatm ent

De­
scrip ­
tion

Ini­
tial
pH

Initial
F lavor
Score

Days
Until
Spoil­
age

Type
of
Spoilage

F i­
nal
PH

S p o i l a g e b y R. f l a v a
C ontrols
U ninoculated
Inoculated

4.90
4.90

3 9 .0
39. 0

10
6

mold
pink s li m e

4.75
4.81

Acids
C itric
L actic
S orbic

0.15%
0.15%
0.10%

4.88
4.89
4.90

39 .0
39-0
39-0

6
6
16

pink s lim
pink s lim e
w h e y e d off

4.80
4.83
4.71

S tarter

2.0 %

4 .8 9

39-0

8

pink s lim e

4 .7 0

S p o i l a g e b y T. c a n d i d a
C ontrols
U ninoculated
Inoculated

5.1 5
5.1 2

40.0
40.0

6
4

m old
yellow s lim e

5.12
5.32

Acids
C itric
L actic
Sorbic

0.1 5%
0 .1 5 %
0.10%

5.10
5.1 2
5.1 5

40.0
40.0
40.0

4
4
6

yellow s lim e
yellow s lim e
yellow s lim e

4.98
5 .02
5.12

S tarter

2.0 %

5.1 2

40.0

6

yellow s lim e

4.51

94
containing s o rb ic acid.

On the s ix te e n th day the l a t t e r sa m p le

sh o w ed f r e e w hey but no pink s lim e .
A l l s a m p l e s i n o c u l a t e d w i t h T . C a n d i d a ( T a b l e XXIX) d e v e l o p e d y e l l o w s l i m e a f t e r 4 to 6 d a y s .

T he s a m p le s containing

s o r b i c a c i d o r s t a r t e r r e q u i r e d l o n g e r f o r d e v e l o p m e n t of t h i s d e ­
fect.
M u c o r p lu m b e u s g r e w in 6 d a y s in all the s a m p l e s in o cu lated
w ith th is o r g a n is m

( T a b l e X XX), e x c e p t t h e s a m p l e c o n t a i n i n g s o r b i c

a c i d w h i c h s h o w e d g r o w t h of M u c o r a f t e r 14 d a y s .
A ll s a m p l e s i n o c u la te d with P en.

f r e q u e n t a n s ( T a b l e XXX)

s h o w e d m o l d i n 8 t o 10 d a y s , w i t h t h e e x c e p t i o n of t h e s a m p l e c o n ­
ta in in g s o r b i c a c id , w hich d elay ed m old d e v e lo p m e n t until th e f o u r ­
te e n th day.
A m o n g t h e s a m p l e s i n o c u l a t e d w i t h G. c a n d i d u m ( T a b l e XXI),
th e c o n t r o l a n d th e s a m p l e s w ith c i t r i c and l a c t i c a c id s and
s t a r t e r a d d e d d e v e lo p e d t h i s m o ld in 8 d a y s , w hile th e s a m p l e with
s o r b i c a c i d s h o w e d m o l d g r o w t h i n 12 d a y s .
T a b le XXXII sh o w s th e
p r o d u c e d by v a r i o u s

dressing

n u m b e r of d a y s i n c r e a s e in s h e l f - l i f e
t r e a tm e n ts when cottage c h e e s e was

in o c u la te d w ith s p o ila g e o r g a n is m s .
T h e a d d i t i o n of l a c t i c a n d c i t r i c a c i d s t o c o t t a g e c h e e s e
d r e s s i n g i n c r e a s e d t h e s h e l f - l i f e i n f o u r a n d f iv e of s e v e n t e e n t r i a l s ,

95
T A B L E XXX
T H E E F F E C T O F D R E S S IN G T R E A T M E N T IN C O N T R O L L I N G
V A R IO U S S P O I L A G E O R G A N IS M S IN C O T T A G E
C H E E S E S T O R E D A T 50° F .

T reatm ent

De­
scrip ­
tion

Ini­
tial
PH

Initial
F lavor
Score

Days
U n til
Spoil­
age

Type
of
Spoilage

F i­
nal
pH

S p o ila g e by M u c o r p lu m b e u s
C ontrols
U ninoculated
Inoculated

4.88
4.89

39 .0
39.0

12
6

m old
m old

4.71
4.72

A cids
C itric
L actic
Sorbic

0. 15%
0.15%
0.10%

4.87
4.88
4.87

39-0
39 . 0
3 9 .0

6
6
14

m old
m old
m old

4.78
4.80
4.65

S tarter

2.0%

4 .8 9

39.0

6

m old

4.80

S p o ila g e by Pen.
C ontrols
U ninoculated
Inoculated

frequentans

5.10
5 .1 2

40.0
40.0

12
8

brown slim e
m old

5.1 5
5 .02

A cids
Cit r ic
L actic
Sorbic

0.15%
0.15%
0.10%

5.07
5.10
5.11

40.0
40 . 0
40.0

10
10
14

m old
m old
m old

5 .00
5.05
5 .01

S tarter

2.0%

5.10

40.0

10

m old

5.08

96
T A B L E XXXI
T H E E F F E C T O F D R E S S IN G T R E A T M E N T IN C O N T R O L L I N G
V A R IO U S S P O I L A G E O R G A N IS M S I N C O T T A G E
C H E E S E S T O R E D A T 50° F .

T reatm ent

De­
scrip ­
tion

Ini­
tial
pH

Initial
F lavor
Score

Days
Until
Spoil­
age

Type
of
Spoilage

F i­
nal
PH

S p o i l a g e b y G. c a n d i d u m
C ontrols
U ninoculated
Inoculated

5.12
5 .1 3

40.0
40.0

14
8

brown s lim e
m old

5.10
4.9 8

A cids
C itric
L actic
Sorbic

0. 15%
0.15%
0.10%

5.10
5.11
5.10

40.0
40.0
40.0

8
8
12

m old
m old
m old

5.02
4.95
4.98

S tarter

2.0%

5.12

40.0

8

m old

4. 9 7

97
T A B L E X X X II
E F F E C T O F D R E S S I N G T R E A T M E N T ON T H E S H E L F - L I F E O F
C O T T A G E C H E E S E I N O C U L A T E D W I T H V A R IO U S
S P O I L A G E ORGANISM S

O rganism

T r e a t m e n t of D r e s s i n g a n d N u m b e r
of D a y s A d d e d t o S h e l f - L i f e w h e n
C o m p a r e d to an Inoculated C o n tro l
C itric
Acid

L actic
A cid

Sorbic
Acid

S tarter

A c h . b u t y r i ............................ . . .
A c h . e u r y d i c e ........................

2
0

0
0

2
6

0
2

A le. m e t a l c a l i g e n e s . . . . . . .
B. f i r m u s
...............................

2
0

2
2

4
4

2
0

E. c o l i ...................................... . . .
E . f r e u n d i i ...............................

2
0

2
0

4
2

2
0

M. c a n d i d u s ............................ . . .
M. c o n g l o m e r a t u s ..............

o
2

0
-2

6
2

0
2

Ps.
Ps.
Ps.
Ps.

d e s m o l y t i c u m .............. . . .
f l u o r e s c e n s .................. . . .
f r a g i ................................... . . .
t r a l u c i d a ........................

0
o
o
0

0
-4
0
0

6
0
0
10

0
0
0
2

R. f l a v a ....................................... . . .
T. C a n d i d a ............................ ...

o
0

0
0

10
2

2
2

M u c o r p l u m b e u s ................. . . ,
P e n . f r e q u e n t a n s .................
G . c a n d i d u m ............................

0
2
0

0
2
0

8
4
4

0
2
0

98

resp ec tiv ely .

S ta r te r and s o r b ic a c id added to the d r e s s i n g i n ­

c r e a s e d th e s h e l f - l i f e in eight and fifte e n of s e v e n t e e n t r i a l s , r e ­
sp ec tiv ely .

The s h e l f - l i f e w a s d e c r e a s e d by 2 and 4 d ays,

r e s p e c t i v e l y , w hen l a c t i c a c id w a s added to the d r e s s i n g of c h e e s e
in o c u la te d w ith M. c o n g lo m e r a tu s and P s . f l u o r e s c e n s .

DISCUSSION

I s o la tio n an d Id e n tific ation

O n l y f o u r of e i g h t e e n b a c t e r i a l c u l t u r e s i s o l a t e d s h o w e d
c h a r a c t e r i s t i c s w h ic h a g r e e d w ithout d i s c r e p a n c y with th o s e li s t e d
b y B r e e d e t a l . ( 1 948) f o r t h e s e o r g a n i s m s .
eurydice,

T h e s e f o u r w e r e Ach.

M. e p i d e r m i d i s , P s . d e s m o l y t i c u m , a n d P s . f l u o r e s c e n s ;

a n d of t h e s e ,

Ps.

the above a u th o rs .

desm olyticum

w as not d e s c r i b e d in an y d e ta il by

P s . f lu o r e s c e n s failed to p ro d u c e a g r e e n p ig ­

m ent when firs t isolated; how ever, the o rg a n ism
ch aracteristic after num erous tra n sfe rs

developed this

on a r t i f i c i a l m e d i a .

i s o l a t e d c u l t u r e m i g h t h a v e b e e n a m u t a n t s t r a i n of P s .
Species a re

The

flu o rescen s.

f r e q u e n t l y e n c o u n t e r e d w h i c h do n o t c o n f o r m t o

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

d e s c r i b e d b y B r e e d et a l . ( 1 948).

The

v a r i a t io n s a r e a ttr ib u te d to m u ta n t s t r a i n s , c h a n g e s in a r tif ic ia l
m edia, and p e rh a p s hum an e r ro r .
T h e y e a s t an d m o ld c u l t u r e s w e r e id e n tifie d w ith l e s s

diffi­

c u lty b e c a u s e t h e i r c h a r a c t e r i s t i c s c o n f o r m e d to the k e y s u s e d in
identification.

T h e c h a r a c t e r i s t i c s u s e d in i d e n t i f i c a t i o n of t h e m o l d

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

99

100
th eir ch aracteristics.

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

f o u n d i n A M a n u a l of S o i l F u n g i b y G i l m a n (1945 ).

T y p e s o f D e f e c t s P r o d u c e d by S p oilag e
O r g a n is m s in C ottag e C h e e s e

C o t t a g e c h e e s e i s b y n o m e a n s a s t e r i l e p r o d u c t , s i n c e it i s
s u b j e c t e d t o t e m p e r a t u r e s n o h i g h e r than 143°

F.

The product

n o r m a ll y c o n ta in s a h ig h ly v a r i a b l e m ic r o f lo r a , which m a k e s it d iffi­
c u l t t o r e p r o d u c e t h e t y p e of s p o i l a g e c a u s e d by a p u r e c u l t u r e of
any p a r t ic u la r o rg a n is m .

C o tta g e c h e e s e c u r d cannot be s t e r i l i z e d

by h e a tin g , s in c e th is p r o c e s s a l t e r s th e a p p e a r a n c e and p h y s ic a l
nature of th e p rod u ct.

Jin on e p o r t io n o f t h i s s tu d y , the cu rd w a s

s t e r i l i z e d b y a n e l e c t r o n b e a m w i t h a d o s a g e of 5.5 x 10

6

rep.

T w o of t h e p u r e c u l t u r e s a n d t h r e e c u l t u r e s , w h e n c o m b i n e d
w i t h S. l a c t i s , f a i l e d t o p r o d u c e a v i s i b l e d e f e c t o t h e r t h a n f r e e
w h e y on s t e r i l e c o t t a g e c h e e s e c u r d .

F i v e of t h e n i n e t e e n c u l t u r e s

p r o d u c e d a p p r o x i m a t e l y t h e s a m e d e g r e e a n d t y p e of s p o i l a g e in
p u r e c u l t u r e a s w h en c o m b in e d w ith S . l a c t i s .

Six of t h e n i n e t e e n

c u l t u r e s p r o d u c e d m o r e p r o n o u n c e d d e f e c t s in p u r e c u l t u r e , w h i l e
s ix o t h e r s p r o d u c e d m o r e p ro n o u n c e d d e f e c ts when c o m b in e d with
S. l a c t i s .

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

h ig h e r pH in c u ltu re s

s h o w i n g m o r e p r o n o u n c e d s p o i l a g e in p u r e

101

c u ltu re and to s y m b io tic

r e la tio n s h ip s in in s ta n c e s show ing m o re

p r o n o u n c e d d e f e c t s w h e n c u l t u r e s w e r e c o m b i n e d w i t h S. l a c t i s .
attem pt w as m a d e to d e te rm in e

No

sy m b io tic r e la tio n s h ip s in this

study.
T h e d e g r e e of d e f e c t p r o d u c e d b y s p e c i e s of t h e s a m e g e n ­
e r a of t h e o r g a n i s m s t e s t e d c o u l d n o t b e c o r r e l a t e d w i t h t h e p r e s ­
e n c e o r a b s e n c e of S. l a c t i s .

F o r e x a m p le , Ach. b u ty ri and P s .

f l u o r e s c e n s p r o d u c e d m o r e p ro n o u n c e d d e fe c ts in p u r e c u ltu r e , while
Ach. e u r y d i c e , P s . d e s m o l y t i c u m , and P s . t r a lu c id a p ro d u c e d m o r e
p r o n o u n c e d d e f e c t s w h e n c o m b i n e d w i t h S. l a c t i s .

E. f r e u n d i i p r o ­

d u c e d a p p r o x i m a t e l y t h e s a m e d e g r e e of s p o i l a g e i n p u r e c u l t u r e
a s w h e n c o m b i n e d w i t h S. l a c t i s , w h i l e E. c o l i p r o d u c e d m o r e p r o ­
nounced d e fe c ts w hen in p u r e c u ltu re .

H ow ever, th e re was a c o r ­

r e l a t i o n b e t w e e n p H a n d d e g r e e of d e f e c t .

I n n i n e of e l e v e n i n s t a n c e s

w h e r e t h e r e w e r e d i f f e r e n c e s i n b o t h t h e d e g r e e of d e f e c t a n d t h e
pH, t h e d e f e c t s e x h i b i t e d w e r e m o r e p r o n o u n c e d a t t h e h i g h e r pH
v a l u e s r e g a r d l e s s of w h e t h e r t h e s e w e r e p r o d u c e d by th e p u r e c u l­
t u r e s in d iv id u a lly o r w hen c o m b in e d w ith S . l a c t i s .

T h e se data in d i­

c a t e t h e i m p o r t a n c e of l o w p H i n r e t a r d i n g t h e d e v e l o p m e n t of m a n y
of th e o r g a n i s m s c a u s i n g s p o ila g e in c o tta g e c h e e s e .
s u b s t a n t i a t e d b y E l l i k e r (1 95 2) a n d C o l l i n s

T his fact is

( 1 9 5 5 a ) , w h o r e p o r t e d on

102

t h e e f f e c t i v e n e s s of l o w p H i n r e t a r d i n g t h e d e v e l o p m e n t of g e l a ­
tinous c u rd d efects.

C h a r a c t e r i s t i c s of O rg a n ism s C au sin g
S p o ila g e in C o tta g e C h e e s e

T e m p e r a t u r e L i m i t s of G r o w t h

T h e d a ta in d ic a te th a t m a n y o r g a n i s m s a r e a b le to g r o w - s o m e q uite r a p i d l y - - a t t e m p e r a t u r e s n o r m a l l y m a in ta in e d w ith c o m ­
m e r c i a l r e f r i g e r a t i o n , a n d t h a t l o w t e m p e r a t u r e s a l o n e c a n n o t be
e x p e c t e d t o p r e v e n t m i c r o b i o l o g i c a l s p o i l a g e of c o t t a g e c h e e s e .
E i g h t of t h e n i n e t e e n o r g a n i s m s t e s t e d e x h i b i t e d v i s i b l e
g r o w t h a f t e r 7 d a y s a t 3°

C. (3 7 .4 °

F.).

T h is t e m p e r a t u r e is

l o w e r t h a n n o r m a l l y f o u n d i n c o m m e r c i a l r e f r i g e r a t i o n of c o t t a g e
cheese.

H a r m o n e t a l . ( 1 9 5 5 b ), in a s t u d y of f o r t y - e i g h t s a m p l e s

of c h e e s e f r o m t w e n t y - f o u r r e t a i l o u t l e t s s h o w e d t h a t t h e t e m p e r a ­
t u r e o f c o m m e r c i a l d i s p l a y c a b i n e t s a v e r a g e d a p p r o x i m a t e l y 45° t o
5 0° F .

It w o u l d b e e x p e c t e d t h a t s o m e o r g a n i s m s w o u l d e v e n t u a l l y

g r o w in p r o p e r l y r e f r i g e r a t e d co ttag e c h e e s e .
T w e l v e of t h e n i n e t e e n o r g a n i s m s e x h i b i t e d v a r y i n g a m o u n t s
o f g r o w t h i n 3 d a y s a t 10° C. (50" F . ) .

At t h i s t e m p e r a t u r e , w h i c h

a p p r o x im a te s a v e ra g e c o m m e r c ia l conditions, s e v e ra l spoilage o r ­
g a n i s m s m u ltip ly quite r a p id ly and w ould be e x p e c te d to c a u s e

103
sp o ilag e in c h e e s e .

T h is w o r k is s u p p o r t e d by J e z e s k i and M acy

( 19 46) a n d T h o m a s

et a l . ( 1 9 4 7 ) , w h o s h o w e d t h a t s p e c i e s of P s e u ­

d o m o n a s, F l a y o b a c t e r i u m , A lc a lig e n e s , and A c h r o m o b a c te r a r e able
t o g r o w v i g o r o u s l y a t 8° C.
O n l y t h r e e o f t h e n i n e t e e n c u l t u r e s f a i l e d t o g r o w in 7 d a y s
a t 10° C .

A l l of t h e c u l t u r e s g r e w a t 2 0° C. i n 3 d a y s , a n d t h i s

t e m p e r a t u r e a p p e a r e d to be th e o p tim u m
M a n y o f t h e c u l t u r e s a l s o g r e w a t 35° C.

f o r m o s t of t h e o r g a n i s m s .
Kennedy and W e is e r

(195 0) s t a t e d t h a t t h e o p t i m u m t e m p e r a t u r e f o r s e v e n of f i f t e e n
p s y c h r o p h i l i c b a c t e r i a w a s c l o s e r t o 10° t h a n t o 20°
g re w at 35°

C. a n d n o n e

C . ; h o w e v e r , t h e y d i d n o t r e p o r t t h e i d e n t i t y of t h e

c u ltu re s studied.

E f f e c t of p H on G r o w t h H a t e

E i g h t , f o u r , a n d t w o of t h e s i x t e e n o r g a n i s m s

studied exhibited

l i t t l e g r o w t h a t p H l e v e l s of 5 . 4 , 5 . 2 , a n d 5.0 o r b e l o w , r e s p e c t i v e l y .
O nly one o r g a n i s m ,

R. f l a v a , e x h i b i t e d l i t t l e g r o w t h w i t h i n t h e p H

r a n g e u s e d , w h ile T. Candida g r e w quite w ell th ro u g h o u t th e ra n g e .
F i f t e e n of t h e s i x t e e n o r g a n i s m s t e s t e d e x h i b i t e d l i t t l e g r o w t h a t
p H v a l u e s b e l o w 5 . 0 w h e n g r o w t h w a s m e a s u r e d in t r y p t i c a s e s o y
b r o t h b y d e t e r m i n i n g t h e i n c r e a s e i n t u r b i d i t y w i t h a K l e t t - S u m m e r s on
co lo rim eter.

Sm all am ounts

of g r o w t h m i g h t h a v e b e e n u n d e t e c t e d by

104

the c o lo r im e t e r .

T e c h n iq u e s s u c h a s p latin g to d e t e r m in e gro w th

m a y be m o r e a c c u r a t e and d e s ir a b l e th an the c o lo r im e tr ic m ethod.
S i n c e l i t t l e g r o w t h o c c u r r e d a t p H of 5.0 a n d b e l o w w i t h
f i f t e e n o f t h e s i x t e e n o r g a n i s m s , t h e d a t a i n d i c a t e t h a t g r o w t h of
m a n y s p o i l a g e o r g a n i s m s s h o u ld be r e t a r d e d in c o tta g e c h e e s e w ith
pH of 5 . 0 o r b e l o w .

C o l l i n s ( 1 9 5 5 a ) , P a r k e r et a l . (1950), a n d

E l l i k e r e t a l . ( 1 9 5 1 ) r e p o r t e d t h a t l o w pH t e n d s t o r e t a r d d e v e l o p ­
m e n t of t h e g e l a t i n o u s c u r d t y p e of s p o i l a g e i n c o t t a g e c h e e s e .
e v e r , a c c o r d i n g t o D e a n e e t al.

How­

( 1 953), o r g a n i s m s c a u s i n g g e l a t i n o u s

c u r d a r e not c o m p l e t e l y in h ib ite d by low pH, and th e y sh o w ed th a t
s l i m e e v e n t u a l l y d e v e l o p e d o n c o t t a g e c h e e s e h a v i n g p H b e l o w 4. 7 .
The data h e re in

r e p o r t e d i n d i c a t e t h a t pH b e lo w 5.0 r e t a r d s th e

g r o w t h of m a n y o r g a n i s m s c a u s i n g s p o i l a g e i n c o t t a g e c h e e s e .

Sodium C h lo rid e T o le r a n c e

B a c t . e r y t h r o g e n e s a n d M. c a n d i d u s w e r e t h e o n l y o r g a n i s m s
in h ib ite d by 3 p e r c e n t s o d iu m c h lo r id e and only B act. e r y t h r o g e n e s
w a s in h ib ite d by 1 p e r c e n t .
t o 1.5 p e r c e n t s o d i u m

C o t t a g e c h e e s e n o r m a l l y c o n t a i n s 1.0

chloride.

C o n c e n t r a t i o n s a b o v e 1.5 p e r c e n t

a r e not a c c e p ta b le to th e a v e r a g e c o n s u m e r .
t r a t i o n of s o d iu m

The c ritic a l concen

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

a p p r o x i m a t e l y 7 p e r c e n t , s i n c e f i f t e e n of t h e n i n e t e e n o r g a n i s m s

105

t e s t e d g r e w i n a 5 p e r c e n t , w h i l e o n l y f o u r of t h e n i n e t e e n g r e w in
a 7 p e r c e n t solution.

S in c e 5 to 7 p e r c e n t s a l t c a n n o t be u s e d in

co ttag e c h e e s e , the d a ta show that sodium

ch lo rid e offers little p r o ­

te c tio n a g a in s t spoilage.

Heat T o leran ce

E l e v e n of t h e n i n e t e e n o r g a n i s m s t e s t e d w e r e d e s t r o y e d i n 5
m i n u t e s a t 143°

F . ( a n d s i x o t h e r s w e r e d e s t r o y e d i n 10 m i n u t e s

at this te m p e ra tu re .

One o rg a n is m

w a s d e s t r o y e d i n 20 m i n u t e s ,

a n d o n l y B. f i r m u s s u r v i v e d f o r 30 m i n u t e s a t 143°

F.

B. f i r m u s

d o e s n o t a p p e a r a s o f t e n a s s o m e of t h e o t h e r o r g a n i s m s t h a t c a u s e
s p o ila g e in c o tta g e c h e e s e .

W a t r o u s et a l.

(1952) a n d A t h e r t o n et al.

(1 9 5 3 ) r e p o r t e d t h a t p s y c h r o p h i l i c b a c t e r i a do n o t w i t h s t a n d l a b o r a ­
t o r y p a s t e u r i z a t i o n a t 143°
specify the o rg a n is m s

F.

studied.

f o r 30 m i n u t e s , b u t t h e y d i d not
The r e s u lts obtained w e re su p ­

p o r t e d by K e n n e d y a n d W e i s e r ( 1 9 5 0 ), w h o s h o w e d t h a t t h e m a ­
j o r i t y of p s y c h r o p h i l i c b a c t e r i a l c u l t u r e s w e r e q u i t e h e a t l a b i l e ,
b u t s o m e w e r e n o t c o m p l e t e l y d e s t r o y e d a t 145°
Thom as

et al.

in 30 m i n u t e s .

( 1 9 4 7 ) a n d D a v i s a n d B a b e l (1954) s h o w e d t h a t s p e c i e s

of A c h r o m o b a c t e r ,

F layobacterium , P seu d o m o n as, A lcaligenes,

P r o t e u s , a n d A e r o b a c t e r w e r e d e s t r o y e d a t 143°

F . i n 30 m i n u t e s

E r d m a n a n d T h o r n t o n ( 1 9 5 1 a , 1951b) r e p o r t e d t h a t s p e c i e s of

106
A e r o b a c te r , E s c h e r ic h ia , F la y o b a c te riu m , L a cto b acillu s, P seud o m o n a s , and S trep to co ccu s

r a r e ly su rv iv e pasteu rizatio n .

Sherm an

e t a l . ( 1 9 4 1 ) , R o g i c k a n d B u r g w a l d (1 9 5 2 ), a n d K a u f m a n n a n d
A ndrew s

(1 954) d e m o n s t r a t e d t h a t s p e c i e s of P s e u d o m o n a s an d

o t h e r p s y c h r o p h i l e s d i d n o t s u r v i v e p a s t e u r i z a t i o n a t 143° F . f o r
30 m i n u t e s .
T h e d a ta h e r e i n r e p o r t e d and the su p p o rtin g li t e r a t u r e in d i­
c a t e t h a t h e a t i n g a t 143°

F. fo r 3 0 m in u te s d e s tr o y s the m a jo r ity

b ut n o t a l l o f t h e p s y c h r o p h i l i c b a c t e r i a e n c o u n t e r e d in d a i r y p r o d ­
ucts.

G e n e ra lly , the psychro p h ilic contam ination r e p r e s e n ts p o s t­

p a s t e u r i z a t i o n c o n t a m i n a t i o n a s p o i n t e d out by W a t r o u s (195 3),
W a t r o u s et al.

(1952)

a n d A t h e r t o n e t a l . (1 953 ).

F u r t h e r h e a t s t u d i e s s h o w e d t h a t B a c t . e r y t h r o g e n e s a n d M.
c o n g l o m e r a t u s w e r e t h e o n l y o r g a n i s m s of t h e n i n e t e e n t e s t e d t h a t
w e r e d e s t r o y e d a t 120°

F . i n 15 m i n u t e s i n s k i m m i l k .

H ow ever,

B. f i r m u s a n d G. c a n d i d u m w e r e t h e o n l y c u l t u r e s w h i c h s u r v i v e d
t h i s t e m p e r a t u r e a n d h o l d i n g t i m e in w h e y .

R e s i s t a n c e to G e r m i c i d e s

T o l e r a n c e to c h lo r in e .

O n l y f o u r of t h e n i n e t e e n o r g a n i s m s

t e s t e d w e r e d e s t r o y e d b y 10 p a r t s p e r m i l l i o n c h l o r i n e a t pH 7.5
a n d 25°

C . , a n d t h i s r e q u i r e d 10 m i n u t e s of e x p o s u r e t o o b t a i n

107
p o s itiv e d e s tr u c t i o n in t h r e e t r i a l s .

T w en ty -fiv e p a r ts p e r m illion

c h l o r i n e w a s n o t e f f e c t i v e in 1 a n d 5 m i n u t e s , d e s t r o y i n g o n l y t h r e e
and fo u r s p e c ie s ,

respectively.

H o w e v e r, e le v e n of the n in e te e n

c u l t u r e s w e r e d e s t r o y e d i n 10 m i n u t e s w i t h 25 p a r t s p e r m i l l i o n
chlorine.

T h e 50 p a r t s p e r m i l l i o n c h l o r i n e w a s c o n s i d e r a b l y m o r e

effective as

only fo u r c u l t u r e s s u rv iv e d

1 m inute

and

only

one

c u l t u r e , B. f i r m u s , s u r v i v e d 5 a n d 10 m i n u t e s i n t h i s c o n c e n t r a t i o n .
T h e s e d a t a i n d i c a t e t h a t 50 p a r t s p e r m i l l i o n of c h l o r i n e
w i t h 5 m i n u t e s o f e x p o s u r e i s n e c e s s a r y t o d e s t r o y m o s t of t h e
o rg a n is m s u n d e r con sid eratio n .

H o w e v e r , i n t h i s s t u d y , 1 m l . of

a b r o t h c u l t u r e of t h e o r g a n i s m

w a s a d d e d t o 100 m l . of t h e g e r m i ­

cide.

T h i s c o n s t i t u t e s a c o n s i d e r a b l e a m o u n t of o r g a n i c m a t t e r a n d

a m uch hig h er organism

p o p u latio n th a n would e v e r be e n c o u n te re d

in a c o m m e r c i a l w a t e r supply.

No a t t e m p t w a s m a d e t o d e t e r m i n e

t h e r e s i d u a l c h l o r i n e o r t o c o n t r o l t h e pH.

T h e s e r e s u l t s show the

i n e f f e c t i v e n e s s of l o w c o n c e n t r a t i o n s of c h l o r i n e i n t h e p r e s e n c e of
o r g a n i c m a t t e r a g a i n s t o r g a n i s m s c a u s i n g s p o ila g e in c o tta g e
cheese.
trates

In v e s tig a tio n s should be m ad e using w ash ed cell co n c e n ­
a n d c o n t r o l l e d n u m b e r s of t h e s e n i n e t e e n c u l t u r e s t o d e t e r ­

m i n e t h e i r r e s i s t a n c e t o c h l o r i n e i n t h e a b s e n c e of e x c e s s o r g a n i c
m atter.

C o l l i n s ( 1 9 5 5 b ) s h o w e d t h a t 3 t o 5 p a r t s p e r m i l l i o n of

r e s i d u a l c h l o r i n e a t pH 6 . 0 w a s e f f e c t i v e in d e s t r o y i n g P s . f r a g i ,

108

P s . y i s c o s a , A l e , m e t a l c a l i g e n e s , E . c o l i , and. A. a e r o g e n e s , a n d
E l l i k e r (1 9 54) d e m o n s t r a t e d t h a t t h e a d d i t i o n o f 5 t o 10 p a r t s p e r
m i l l i o n of c h l o r i n e w a s e f f e c t i v e i n d e s t r o y i n g o r g a n i s m s i n t h e
w a sh w a t e r supply.

T o l e r a n c e to q u a t e r n a r y .
q u a t e r n a r y a t p H 6.5 a n d 25 °

T e n a n d 2 5 p a r t s p e r m i l l i o n of

C. w a s n o t e f f e c t i v e a g a i n s t t h e o r ­

g a n i s m s t e s t e d , w ith o n ly five and s ix c u l t u r e s ,
d e s t r o y e d i n 10 m i n u t e s .

O n l y e l e v e n s p e c i e s w e r e d e s t r o y e d by 50

p a r t s p e r m i l l i o n q u a t e r n a r y in 10 m i n u t e s .
am ong the firs t c u ltu re s
flavus failed to s u rv iv e

r e s p e c tiv e ly , being

The M icrococci w ere

d e s t r o y e d a s M. c o n g l o m e r a t u s a n d M.
1 and 5 m inutes,

p e r m i l l i o n of q u a t e r n a r y .

r e s p e c t i v e l y , i n 10 p a r t s

T w e n t y - f i v e p a r t s p e r m i l l i o n of q u a t ­

e r n a r y d e s t r o y e d M. c a n d i d u s i n 1 m i n u t e .
M u c o r p l u m b e u s w a s t h e o n l y m o l d t h a t s u r v i v e d 5 a n d 10
m i n u t e s i n 5 0 p a r t s p e r m i l l i o n of q u a t e r n a r y .
freundii re q u ire d

E. c o l i a n d E.

10 m i n u t e s e x p o s u r e i n t h i s c o n c e n t r a t i o n of

q u a t e r n a r y b e f o r e d e s t r u c t i o n w as c o m p le te , and t h e s e w e r e the
only g r a m - n e g a t i v e o r g a n i s m s in th is stu d y which w e r e d e s tro y e d .
T h e s p e c i e s of A c h r o m o b a c t e r a n d P s e u d o m o n a s , a l o n g w i t h
A l c a l i g e n e s m e t a l c a l i g e n e s a n d B. f i r m u s w e r e n o t d e s t r o y e d in
10 m i n u t e s i n 5 0 p a r t s p e r m i l l i o n of q u a t e r n a r y

T h e s e a r e the

t y p e s of o r g a n i s m s u s u a l l y r e s p o n s i b l e f o r t h e s l i m y c u r d o r
ta p io c a d e f e c ts c o m m o n ly e n c o u n te r e d in co ttag e c h e e s e spoilage.
It a p p e a r s t h a t q u a t e r n a r y i s i n e f f e c t i v e , e v e n i n h i g h c o n c e n t r a t i o n s
i n d e s t r o y i n g t h e s e t y p e s of o r g a n i s m s .
A c c o rd in g to th e d a ta , q u a te r n a r y is effective ag ain st the
g r a m - p o s i t i v e o r g a n i s m s , w i t h t h e e x c e p t i o n of B. f i r m u s , but i n ­
effective a g a in s t the g r a m - n e g a tiv e o r g a n is m s .

T h e se data a r e

s u p p o r t e d b y t h e w o r k of v a r i o u s a u t h o r s i n c l u d i n g D u B o i s a n d
D ib b le e (1946), J o h n s (1947,
v i t z a n d C r o c k e r (1 950),

1 9 4 8 a , 1 9 4 8 b ) , S h e r e (19 48) , D v o r k o -

L u n d s t e d t ( 1 9 5 0 ), a n d P a r k e r a n d E l l i k e r

(1951), w ho r e p o r t e d th a t q u a t e r n a r y a m m o n i u m

compounds a re

e f f e c t i v e a g a i n s t g r a m - p o s i t i v e o r g a n i s m s but l e s s e f f e c t i v e a g a i n s t
g ra m -n e g a tiv e ones.

T o l e r a n c e to iodo p h o r.
p h o r a t p H 3.5 a n d 25°
tested.

B act.

T e n a n d 25 p a r t s p e r m i l l i o n i o d o -

C. w e r e n o t e f f e c t i v e a g a i n s t t h e o r g a n i s m s

e r y t h r o g e n e s w a s t h e o n l y o r g a n i s m d e s t r o y e d in 1,

5 , a n d 10 m i n u t e s i n 10 p a r t s p e r m i l l i o n .
B act.

I n 25 p a r t s p e r m i l l i o n

e r y t h r o g e n e s a n d R. f l a v a w e r e t h e o n l y c u l t u r e s d e s t r o y e d in

1, 5 , a n d 10 m i n u t e s .

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

s i d e r a b l y m o r e effectiv e a s tw elve, t h ir te e n , and t h ir te e n of the
c u l t u r e s w e r e d e s t r o y e d i n 1, 5, a n d 10 m i n u t e s , r e s p e c t i v e l y .

The

110

i n c r e a s e d e x p o s u r e t i m e s o f 5 a n d 10 m i n u t e s d i d not a p p e a r to i n ­
c r e a s e t h e e f f e c t i v e n e s s of 5 0 p a r t s p e r m i l l i o n of t h e s o l u t i o n ,
which in d ic a te s th a t th e c o m p o u n d is

ra p id acting.

D i f f e r e n t s p e c i e s of t h e s a m e g e n e r a d id n o t r e a c t s i m i l a r l y
when exposed to iodophor.

A c h . e u r y d i c e s u r v i v e d 1, 5, a n d 10

m i n u t e s in 5 0 p a r t s p e r m i l l i o n , w h i l e A c h . b u t y r i w a s d e s t r o y e d in
1, 5, a n d 10 m i n u t e s i n t h i s c o n c e n t r a t i o n .

P s. t r a l u c i d a w as the

o n l y s p e c i e s of P s e u d o m o n a s s u r v i v i n g 1, 5, a n d 10 m i n u t e s i n 5 0
p a r t s p e r m i l l i o n of i o d o p h o r .

T h e r e a s o n s f o r d i f f e r e n t s p e c i e s of

t h e s a m e g e n e r a r e a c t i n g d i f f e r e n t l y t o t h e i o d o p h o r i s n o t k now n.
T h e i n e f f e c t i v e n e s s of i o d o p h o r a g a i n s t m o l d s s h o u l d n o t be
o v e r lo o k e d a s th e m o ld c u l t u r e s g r e w at all c o n c e n tr a tio n s and e x ­
p o su re tim e s used.
In p a r t t h e a b o v e d a t a a r e s u p p o r t e d by J o h n s (1954), w h o
r e p o r t e d t h a t c o n c e n t r a t i o n s of i o d o p h o r c o m p a r e d f a v o r a b l y w i t h t h e
s a m e c o n c e n t r a t i o n s of c h l o r i n e i n d e s t r o y i n g E. c o l i .

H ow ever, the

d a t a h e r e i n r e p o r t e d d o n o t a g r e e w i t h d a t a by M u e l l e r (19 55), w h o
f o u n d t h a t 2 5 p a r t s p e r m i l l i o n of i o d i n e c o m p a r e d f a v o r a b l y w i t h
10 0 p a r t s p e r m i l l i o n of c h l o r i n e i n k i l l i n g E. c o l i , a n d G e r s h e n f e l d
( 1 9 5 5 ), w h o s t a t e d t h a t 25 p a r t s p e r m i l l i o n of i o d o p h o r w a s e q u i v ­
a l e n t t o 200 p a r t s p e r m i l l i o n of c h l o r i n e .

J o h n s (1954) a l s o f o u n d

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

Ill

e f f e c t on s p o r e s o f B. s u b t i l i s , i n d i c a t i n g e x c e p t i o n a l l y f a v o r a b l e r e ­
s u lts a g a in s t th is o r g a n i s m , but in th is study the io d o p h o r w as not
e f f e c t i v e a g a i n s t B. f i r m u s .

T h e s e tw o o r g a n i s m s would be e x ­

p e c te d to r e a c t s i m i l a r l y to iodophor.
W h en u s e d in th e s a m e c o n c e n t r a t i o n s with th e s a m e e x p o s u r e
t i m e s , i o d o p h o r a p p e a r e d t o b e m o r e e f f e c t i v e t h a n q u a t e r n a r y but
not a s effectiv e a s c h lo rin e ag a in st the nin eteen c u ltu re s tested.

R e s i s t a n c e to S o rb ic Acid

A t p H v a l u e s of 5 . 7 , 6 . 4 , 6 .7 , a n d 7. 3, s o r b i c a c i d i n t r y p t i case

s o y b r o th w a s not e ffe c tiv e even in high c o n c e n tr a tio n s

organism s

c a u s in g s p o ila g e in co ttag e c h e e s e .

w as d estroyed,

against

Bact. e r y th r o g e n e s

M. c o n g l o m e r a t u s w a s r e t a r d e d , a n d R. f l a v a

s h o w e d v a r i a b l e r e s u l t s a t p H of 5.7 w i t h 0.2 5 p e r c e n t s o r b i c a c i d .
T h e s ix t e e n r e m a i n in g c u l t u r e s w e r e ab le to g ro w quite w ell at
t h i s pH a n d s o r b i c a c i d c o n c e n t r a t i o n .

O n ly a s m a l l n u m b e r of

t h e o r g a n i s m s t e s t e d w e r e d e s t r o y e d b y 0 .0 5 , 0 .1 0 , a n d 0.25 p e r ­
c e n t s o r b i c a c i d a t pH 5 . 2 , but a t pH 5 . 0 a n d 4 . 8 , t h e v i a b i l i t y of
the c u ltu re s w as d e c r e a s e d c o n s id e ra b ly a s the so rb ic acid content
in c re a s e d from

0.05 t o 0.25 p e r c e n t .

T h e d i f f e r e n c e in v i a b i l i t y a m o n g s p e c i e s of t h e s a m e
is

genera

a n i n t e r e s t i n g o b s e r v a tio n , but the r e a s o n s fo r t h e s e d iff e r e n c e s

112

a r e unknown.

U s u a l l y t h e v i a b i l i t y of o r g a n i s m s d e c r e a s e d a s t h e

s o r b ic a c id c o n te n t i n c r e a s e d an d the pH d e c r e a s e d .
T h e s e d a t a m a y n o t r e p r e s e n t t h e a c t u a l v a l u e of s o r b i c a c i d
a s a n i n h i b i t o r of t h e o r g a n i s m s

stu d ied , s in c e the r e s u l ts shown

a r e t h e v i a b i l i t i e s e x h i b i t e d b y t h e o r g a n i s m s w h e n p l a t e d on
tryptone glucose y e a st ag ar,

r a t h e r t h a n a m e a s u r e of i n h i b i t i o n .

S o r b i c a c i d m a y b e b a c t e r i o s t a t i c t o m a n y of t h e o r g a n i s m s b u t n o t
g e r m ic id a l, and w hen th e acid w as diluted d u rin g plating, the o r g a n ­
i s m s w e r e a b le to g ro w .

Loop in o c u la tio n s w e r e m a d e into the

b r o t h s o l u t i o n s c o n t a i n i n g s o r b i c a c i d a t t h e v a r i o u s pH l e v e l s ,
b u t t h e a c t u a l n u m b e r of c e l l s o r s p o r e s a d d e d m a y h a v e v a r i e d
considerably.
T he concentrations

of s o r b i c a c i d r e q u i r e d t o d e s t r o y t h e

o rg a n ism s under consideration

( T a b l e XIII) w e r e s u b s t a n t i a l l y

h i g h e r t h a n t h o s e r e p o r t e d b y S h e n e m a n a n d C o s t i l o w (19 55) a n d
B e n e k e a n d F a b i a n (195 5) a s n e c e s s a r y f o r i n h i b i t i o n .

However,

the above a u th o r s w e r e d e te r m in in g inhibition r a t h e r th an d e s t r u c ­
t i o n a n d w e r e w o r k i n g a t p H l e v e l s of 4 . 4 a n d b e l o w , w h i l e in t h e
s t u d y h e r e i n r e p o r t e d , 4 . 8 w a s t h e l o w e s t pH e m p l o y e d .
A l t h o u g h t h e p H of c o t t a g e c h e e s e m a y n o t b e s u f f i c i e n t l y
low to o b ta in th e m a x i m u m

b e n e f i t of s o r b i c a c i d , t h e d a t a i n d i c a t e

t h a t a t p H v a l u e s of 4 . 8 a n d 5 . 0 , t h e r e w o u l d b e s o m e i n h i b i t i o n

113
a n d d e s t r u c t i o n of b a c t e r i a , y e a s t s , a n d m o l d s c a u s i n g s p o i l a g e .
T h e a d d i t i o n of s o r b i c a c i d t o c o t t a g e c h e e s e c o u l d c o n c e i v a b l y a d d
a f e w d a y s t o t h e s h e l f - l i f e of t h e p r o d u c t .

C o n t r o l of

Spoilage in C ottage C h e e se

S e v e r a l i n s t a n c e s of s p o i l a g e r e s u l t i n g f r o m t h e d e v e l o p m e n t
of m o l d , p i n k s l i m e , b i t t e r f l a v o r s , w h e y i n g - o f f o r o t h e r a t y p i c a l
t y p e s of s p o i l a g e i n s a m p l e s i n o c u l a t e d w i t h v a r i o u s s p o i l a g e o r g a n ­
ism s

s h o w s th e d iff ic u lty e n c o u n t e r e d in c o n tr o llin g o r p r o d u c in g a

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

T r e a t m e n t of W a s h W a t e r

T h e s a m p l e w a s h e d w ith
in o c u la te d with Ach. b u ty ri w as

w a t e r co n ta in in g a c e tic a c id and
t h e o n l y o n e w i t h pH

b elo w 5.10at

th e t i m e of s p o il a g e , a n d th e lo w pH r a t h e r th an th e a c e tic acid
m ight

h a v e i n h i b i t e d t h e t a p i o c a s l i m e c h a r a c t e r i s t i c of A c h . b u t y r i .
A c e tic a c id added to the

w ash w a t e r a p p e a r e d to inhibit

t a p i o c a s l i m e f o r m a t i o n on c o t t a g e c h e e s e i n o c u l a t e d w i t h A c h .
eurydice.

T h i s s a m p l e h a d a p H of 4 . 3 , w h i c h m a y h a v e d e l a y e d

th e f o r m a t i o n of s l i m e .

H o w e v e r , s l i m e d e v e l o p e d in 6 d a y s on

t h e r e m a i n d e r of t h e s a m p l e s ,
a s 4.5.

s o m e of w h i c h h a d pH v a l u e s a s l o w

T h is in d i c a t e s th a t low pH l e v e l s fail to c o m p le te ly inhibit

114
slim e form ation.

T h i s o b s e r v a t i o n i s s u p p o r t e d b y D e a n e et al.

( 1 9 5 3 ) , w h o r e p o r t e d t h a t s l i m e e v e n t u a l l y d e v e l o p e d on c o t t a g e
c h e e s e h a v in g pH b e lo w 4.7.
B o t h s p e c i e s of A c h r o m o b a c t e r e m p l o y e d in t h i s s t u d y f a i l e d
t o d e v e l o p t a p i o c a s l i m e on s a m p l e s w a s h e d w i t h w a t e r c o n t a i n i n g
a c e tic acid.

T h e r e a s o n is unknown.

S o r b i c a c i d i n t h e w a s h w a t e r i n h i b i t e d A c h . b u t y r i but
failed to in hibit A ch.

eurydice.

H o w e v e r , t h e c o n c e n t r a t i o n s of

s o r b i c a c i d u s e d w e r e d i f f e r e n t , an d th e a m o u n t e m p lo y e d w ith Ach.
b u ty r i i m p a r t e d a n o b je c tio n a b le f la v o r to th e c h e e s e .
M a r q u a r d t ( 1 9 5 3 , 1954) r e p o r t e d t h a t t h e a d d i t i o n of 7.5 p a r t s
p e r m i l l i o n of i o d i n e t o t h e f i n a l w a s h w a t e r r e t a r d e d t h e d e v e l o p ­
m e n t of w a t e r - b o r n e o r g a n i s m s

cau sin g the s lim y condition.

How­

e v e r , in t h i s s tu d y th e o r g a n i s m s w e r e p r e s e n t on the c h e e s e c u r d
in l a r g e n u m b e r s

r a t h e r th a n in th e w a s h w a t e r in s m a l l n u m b e r s .

P r e v i o u s d a ta i l l u s t r a t e th a t th e io d o p h o r is fast actin g , and th is
c o m p o u n d m i g h t b e e f f e c t i v e a g a i n s t s m a l l n u m b e r s of o r g a n i s m s in
t h e w a t e r s u p p l y , e s p e c i a l l y i n t h e a b s e n c e of e x c e s s o r g a n i c m a t t e r .
It i s n o t e w o r t h y t h a t t h e s a m p l e i n o c u l a t e d w i t h B. f i r m u s a n d
w a s h e d w i t h w a t e r c o n t a i n i n g 10 p a r t s p e r m i l l i o n of i o d o p h o r p o s ­
s e s s e d a halogen flavor,
at a pH of 4.80.

b u t d e v e l o p e d t h e b r o w n s l i m e i n 10 d a y s

115
E . c o l i m i g h t n o t h a v e b e e n t h e c a u s e of s p o i l a g e in t h e
s a m p le s in o c u la te d w ith th is o r g a n is m , sin c e the uninoculated con­
t r o l d e v e l o p e d t h e b r o w n s l i m e t y p i c a l of E. c o l i a l s o .
V a r i o u s t y p e s of s p o i l a g e o c c u r r e d i n 10 t o 14 d a y s on a l l
s a m p l e s in o c u la te d w ith E. f r e u n d ii.
and p h o s p h o ric a c id s,

Sorbic, a c e tic , c itric , lactic,

c h lo r in e , and io d o p h o r added to the w ash

w a t e r s e e m e d t o i n c r e a s e t h e s h e l f - l i f e of c o t t a g e c h e e s e s o m e w h a t ,
with s o r b ic a c id being th e m o s t effective.

A l t h o u g h E. f r e u n d i i

c a u s e s a b r o w n s l i m e on c o t t a g e c h e e s e , i t m i g h t n o t h a v e b e e n t h e
organism

c a u s in g th e s li m e in th is in s ta n c e , s in c e the u n inoculated

c o n tro l d ev elo p ed th is defect also.
T a b l e X V I I i s of l i t t l e s i g n i f i c a n c e , s i n c e n e i t h e r M. c a n d i d u s
n o r M. c o n g l o m e r a t u s

e x h ib ite d v is ib le d e f e c ts o t h e r th a n f r e e whey

in s t e r i l e c o tta g e c h e e s e c u r d in a p r e v i o u s

experim ent.

H ow ever,

it d o e s p o in t out t h a t s o r b i c a c id and i o d o p h o r a r e s o m e t i m e s d e ­
t e c t a b l e u p o n o r g a n o l e p t i c e x a m i n a t i o n w hen c h e e s e is w a s h e d with
w a t e r c o n t a i n i n g 0 . 0 5 p e r c e n t a n d 10 p a r t s p e r m i l l i o n ,

respectively,

of t h e s e c o m p o u n d s .
T h e s a m p l e i n o c u la te d w ith P s. d e s m o ly tic u m and w a sh e d
w i t h w a t e r c o n t a i n i n g s u f f i c i e n t s o r b i c a c i d t o r e d u c e t h e p H of t h e
w a t e r t o 6 . 0 w a s s t i l l m a r k e t a b l e a f t e r 24 d a y s .

T h e pH of t h i s

l a t t e r s a m p l e h a d d e c r e a s e d t o 4 . 5 0 , a n d t h i s l o w pH m i g h t h a v e

116

i n c r e a s e d t h e s h e l f - l i f e of t h e p r o d u c t m o r e t h a n t h e a d d e d s o r b i c
acid.

Since P s .

desm olyticum

a tapioca slim e , this o rg an ism

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

s p o il a g e in an y s a m p l e s , e x c e p t t h e in o c u la te d c o n tr o l and the
s a m p l e w a s h e d w i t h w a t e r c o n t a i n i n g l a c t i c a c i d , b o t h of w h i c h d e ­
veloped fru ity fla v o rs.

T h i s s e e m s l i k e l y , s i n c e C o l l i n s (19 5 5 a) a n d

E l l i k e r e t a l . (19 52) r e p o r t e d a f r u i t y o d o r p r e c e d e s t h e d e v e l o p m e n t
of t h e g e l a t i n o u s c u r d d e f e c t .
W ash w a te rs
v e l o p m e n t of g r e e n

containing so rb ic and c itric acids

retarded de­

s l i m e i n s a m p l e s i n o c u l a t e d w ith P s .

fluorescens.

T h e s a m p l e s w a s h e d with w a t e r s containing la c tic acid, c h lo rin e ,
io d o p h o r, and q u a t e r n a r y exhib ited m o r e r a p id s lim e fo rm a tio n than
th e inoculated control.
B a b e l (1 9 5 4 ), w ho

T h i s a g r e e s w i t h t h e f i n d i n g s of D a v i s a n d

showed

that

w a s h in g c o tta g e c h e e s e c u r d with

w a t e r c o n t a i n i n g 100 p a r t s p e r m i l l i o n of c h l o r i n e f o r 10 m i n u t e s
e n h a n c e d s l i m e f o r m a t i o n c a u s e d b y s p e c i e s in t h e g e n e r a A c h r o m o b a c t e r , A e r o b a c t e r , A l c a l i g e n e s , P r o t e u s , and P s e u d o m o n a s .

The

s a m p le w a s h e d with w a te r containing io d ophor exhibited a halogen
f l a v o r w h e n f r e s h , b u t d e v e l o p e d g r e e n s l i m e in 6 d a y s , w h i c h i n d i ­
c a t e s t h e i n e f f e c t i v e n e s s of t h i s c o m p o u n d a g a i n s t P s . f l u o r e s c e n s .
Ps.

f r a g i a n d P s . t r a l u c i d a f o r m a l i g h t b r o w n s l i m e on

c o tta g e c h e e s e , although th e r e s u l t s

fail to d e m o n s t r a t e th is fact.

117
In 6 t o 16 d a y s , a l l s a m p l e s

b e c a m e b i t t e r and the pH d e c r e a s e d .

P r o b a b l y low pH r a t h e r th a n th e w a sh w a t e r s

r e t a r d e d the d e v e l­

o p m e n t of t h e b r o w n s l i m e .
T h e a d d i t i o n of s o r b i c a c i d to t h e w a s h w a t e r a p p e a r e d to
i n c r e a s e t h e s h e l f - l i f e of c o t t a g e c h e e s e i n o c u l a t e d w i t h G. c a n d i d u m a n d P e n , f r e q u e n t a n s b y a p p r o x i m a t e l y 2 to 4 d a y s , r e s p e c t i v e l y .
T h is w as the only com pound show ing b eneficial effects.

T r e a t m e n t of D r e s s i n g M a t e r i a l s

T h e d e s i r e d c o n c e n t r a t i o n s of t h e v a r i o u s a c i d s a d d e d t o t h e
d r e s s i n g m a t e r i a l w e r e d e t e r m i n e d by p r e l i m i n a r y s t u d i e s .

A pprox­

i m a t e l y 0 . 1 5 p e r c e n t c i t r i c a n d l a c t i c a c i d s w e r e fo u n d t o r e d u c e
t h e pH of t h e c r e a m i n g m i x t u r e t o 5 . 2 , w h i c h a l l o w e d s u f f i c i e n t
s a f e t y f a c t o r b e f o r e r e a c h i n g t h e i s o - e l e c t r i c p o i n t of t h e p r o t e i n
in the c re a m in g m ix tu re .

A c o n c e n t r a t i o n of 0 .1 0 p e r c e n t s o r b i c

a c id w as ad d ed to th e c r e a m

w i t h o u t a n y d e t r i m e n t a l e f f e c t on t h e

f l a v o r of t h e c r e a m e d c h e e s e .

Two p e rc e n t s t a r t e r was u sed as

r e c o m m e n d e d b y M a r q u a r d t ( 1 9 5 3 , 1954), a n d o n l y s l i g h t l y a f f e c t e d
t h e pH o f t h e c r e a m i n g m i x t u r e .
T h e a d d i t i o n of c i t r i c a n d s o r b i c a c i d s t o t h e c r e a m i n g
m ixtures

of s a m p l e s i n o c u l a t e d w i t h A c h . b u t y r i i n c r e a s e d t h e

s h e l f - l i f e a p p r o x i m a t e l y 2 d a y s o v e r t h e r e m a i n d e r of t h e t r e a t e d
sam p les.

118

S o r b i c a c i d a d d e d t o t h e c r e a m i n g m i x t u r e of c h e e s e i n o c u ­
l a t e d w ith A c h . e u r y d i c e i n c r e a s e d th e s h e l f - l i f e a p p r o x i m a t e l y 4 to
6 days lo n g e r th an the o th e r s a m p le s .
F avorable resu lts
in o c u la te d w ith Ach.

a r e show n for s o rb ic acid in c h e e s e

e u r y d i c e , w h i l e t h e a c i d s h o w e d no b e n e f i c i a l

e ffe c t in t h e s a m p l e s i n o c u l a t e d w ith Ach. b u ty ri.
T a b l e X X I I i n d i c a t e s t h a t t h e u s e of s o r b i c a c i d a d d s a p p r o x ­
i m a t e l y 4 d a y s , w h i l e i n c o r p o r a t i o n of c i t r i c a n d l a c t i c a c i d s a n d
s t a r t e r a d d a p p r o x i m a t e l y 2 d a y s t o t h e s h e l f - l i f e of c o t t a g e c h e e s e
in o c u la te d w ith A le, m e t a l c a l i g e n e s .
T h e e n t i r e s e r i e s of s a m p l e s i n o c u l a t e d w i t h B. f i r m u s a n d
t h e u n i n o c u l a t e d c o n t r o l d e v e l o p e d m o l d i n 6 t o 10 d a y s .

Sorbic

a c id a p p e a r e d to give b e tte r r e s u l t s th an any o th e r com pound used
ag ain st th is n a tu ra l contam inant.

T h e l o w pH of t h e c h e e s e p r o b ­

a b l y r e t a r d e d t h e b r o w n s l i m e d e v e l o p m e n t of B. f i r m u s , b u t
allow ed the m old co n tam in an t to grow readily.
S a m p le s in o c u la te d w ith E. coli exhibited a so m e w h a t lo n g e r
s h e lf - lif e w ith all of th e a d d itiv e s.

Sorbic acid w as th e m o st ef­

f e c t i v e , g i v i n g a n i n c r e a s e of 4 d a y s , w h i l e t h e o t h e r s g a v e a n
i n c r e a s e of 2 d a y s w h e n c o m p a r e d t o t h e i n o c u l a t e d c o n t r o l .

119
S o r b i c a c i d a d d e d t o t h e c r e a m i n g m i x t u r e a l s o a p p e a r e d to
i n c r e a s e t h e s h e l f - l i f e of c o t t a g e c h e e s e i n o c u l a t e d w i t h E. f r e u n d i i
by a p p r o x im a te ly 2 days.
T h e d a ta sh o w n in T a b le XXVI a r e in sig n ific a n t fro m the
s t a n d p o i n t of M. c a n d i d u s a n d M, c o n g l o m e r a t u s , s i n c e n e i t h e r of
t h e s e o r g a n i s m s p r o d u c e v is ib le s p o ila g e in co ttag e c h e e s e o th er
th an f r e e whey.
The resu lts

s h o w n in T a b le XXVII d e m o n s t r a t e th e

effective­

n e s s of s o r b i c a c i d i n i n h i b i t i n g t h e p a r t i c u l a r m o l d w h i c h c o n t a m i n ­
a te d th e s a m p l e s in o c u la te d with P s.
was in c re a s e d ap p ro x im a te ly
pound.

desm olyticum .

The shelf-life

6 d a y s b y t h e a d d i t i o n of t h i s c o m ­

T h e l o w p H of t h e c h e e s e a t t h e t i m e of i n o c u l a t i o n p r o b a b l y

p r e v e n t e d d e v e l o p m e n t of t h e t a p i o c a s l i m e c h a r a c t e r i s t i c of P s .
desm olyticum .
and C ollins

T h i s o b s e r v a t i o n i s s u b s t a n t i a t e d by E l l i k e r (1952)

(1955a).

L a c tic a c id in th e d r e s s i n g

e n c o u r a g e d t h e d e v e l o p m e n t of

g r e e n s l i m e in s a m p l e s in o c u la te d w ith P s. f l u o r e s c e n s .

A fter 6

d a y s , g r e e n s l i m e d e v e l o p e d in t h e s a m p l e c o n t a i n i n g l a c t i c a c i d .
T h e l o w p H of t h e c o t t a g e c h e e s e c u r d a t t h e t i m e of i n o c u ­
l a t i o n w i t h P s . f r a g i p r o b a b l y p r e v e n t e d p r o d u c t i o n of t h e t y p i c a l
brow n slim e,

and m old grow th o c c u r r e d instead.

120

T h e s a m p l e s in o c u la te d with P s. tr a lu c id a and containing
s t a r t e r a n d s o r b i c a c i d h a d a s h e l f - l i f e of 2 a n d 10 d a y s , r e ­
s p e c tiv e ly , lo n g e r th an th e in o c u la te d control.

The spoilage again

w a s d u e t o m o l d g r o w t h , w i t h t h e e x c e p t i o n of t h e s a m p l e c o n t a i n ­
ing s o r b i c a c id w h ich w h e y e d -o ff.

S o rb ic acid effectiv ely inhibited

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

T h e l o w p H of

t h e o r i g i n a l c h e e s e p r o b a b l y p r e v e n t e d t h e d e v e l o p m e n t of t h e
brow n s lim e p ro d u c e d by P s . tra lu c id a .
S orbic acid w as

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

p i n k s l i m e of R. f l a v a a s t h e i n c o r p o r a t i o n of t h i s c o m p o u n d i n ­
c r e a s e d t h e s h e l f - l i f e a p p r o x i m a t e l y 10 d a y s .
T h e a d d i t i o n of s o r b i c a c i d t o t h e c r e a m i n g m i x t u r e i n ­
c r e a s e d t h e s h e l f - l i f e of c o t t a g e c h e e s e i n o c u l a t e d w i t h M u c o r
p l u m b e u s b y a p p r o x i m a t e l y 8 d a y s w h e n c o m p a r e d to t h e i n o c u l a t e d
control.
C i t r i c a n d l a c t i c a c i d s a n d s t a r t e r in t h e c r e a m i n g m i x t u r e
i n c r e a s e d th e s h e l f - l i f e of c o tta g e c h e e s e in o c u la te d w ith Pen, f r e q u e n t a n s b y a p p r o x i m a t e l y 2 d a y s , w h i l e t h e a d d i t i o n of s o r b i c a c i d
to th e d r e s s i n g i n c r e a s e d th e s h e lf - lif e by 6 days.
S o r b i c a c i d a d d e d to t h e c r e a m i n g m i x t u r e w a s e f fe c tiv e in c o n ­
t r o l l i n g s p o i l a g e o f c o t t a g e c h e e s e d u e t o G. c a n d i d u m , a s t h e s h e l f - l i f e
w a s i n c r e a s e d 4 d a y s b y t h e a d d i t i o n of t h i s c o m p o u n d .

SU M M A R Y AND CONCLUSIONS

The m ic ro o r g a n is m s iso lated from

spoiled cottage c h e e se

a n d a g a r e x p o s u r e p l a t e s w e r e i d e n t i f i e d a s f o ll o w s :

A chrom obacter

b u t y r i , A c h r o m o b a c te r e u r y d ic e , A lcalig en es m e ta lc a lig e n e s , B acillus
f irm u s , B acteriu m

e ry th ro g e n e s , C orynebacterium

filam entosum ,

E s c h e r ic h ia coli, E s c h e r ic h ia freundii, E s c h e r ic h ia in te rm e d iu m ,
M icrococcus a u ra n tia c u s,
g lo m eratu s,

M ic r o c o c c u s c a n d id u s , M ic r o c o c c u s con

M ic r o c o c c u s e p id e r m id is , M ic ro c o c c u s flavus, P s e u -

dom onas d esm o ly ticu m , P se u d o m o n as fluorescens,

Pseudom onas

f r a g i , P s e u d o m o n a s t r a l u c i d a , R h o d o to ru la f la v a , T o r u lo p s is C andida,
T o ru lo p sis v e r s a t i l i s , G eotrichum can d id u m , M ucor p lu m b eu s, M ucor
r a c e m o s u s , and P en icilliu m

frequentans.

N in eteen r e p re s e n ta tiv e o rg a n ism s w ere selected for fu rth er
s tu d y fro m th e tw e n ty -fiv e lis te d above.

When in o c u la te d into s t e r i l e

c o t t a g e c h e e s e c u r d , f i v e of t h e n i n e t e e n c u l t u r e s p r o d u c e d a p p r o x i ­
m a t e l y t h e s a m e d e g r e e a n d t y p e of d e f e c t i n p u r e c u l t u r e a s w h e n
c o m b i n e d w i t h S. l a c t i s .
S i x c u l t u r e s p r o d u c e d m o r e p r o n o u n c e d d e f e c t s in p u r e
c u l t u r e , w h ile s i x o t h e r s p r o d u c e d m o r e p r o n o u n c e d d e f e c ts when
c o m b in e d

with S. l a c t i s .

T h e d e g r e e of d e f e c t p r o d u c e d by t h e

121

122

n i n e t e e n o r g a n i s m s t e s t e d co u ld not be c o r r e l a t e d with the p r e s e n c e
o r a b s e n c e of S. l a c t i s .

H o w e v e r, r e d u c e d pH w as effective in r e ­

t a r d i n g t h e d e v e lo p m e n t of th e d e f e c ts .

In n i n e of e l e v e n i n s t a n c e s

w h e r e t h e r e w e r e d i f f e r e n c e s i n b o t h t h e d e g r e e of d e f e c t a n d t h e
p H , t h e d e f e c t s w e r e m o r e p r o n o u n c e d a t t h e h i g h e r pH l e v e l s r e ­
g a r d l e s s of w h e t h e r t h e s e w e r e p r o d u c e d b y t h e p u r e c u l t u r e s i n d i ­
v i d u a l l y o r w h e n c o m b i n e d w i t h S. l a c t i s .
T h e d ata p re s e n te d indicate that under n o rm a l c o m m e rc ia l
r e f r i g e r a t i o n , m a n y of t h e o r g a n i s m s s t u d i e d c o u l d m u l t i p l y in c o t ­
ta g e c h e e s e and c a u s e spoilage.
R e d u c e d p H l e v e l s c a u s e d r e d u c t i o n s in t h e g r o w t h of t h e
o r g a n i s m s in b ro th .

From

t h e d a t a , it m a y b e c o n c l u d e d t h a t pH

l e v e l s of 5 . 0 a n d b e l o w r e t a r d t h e g r o w t h of t h e m a j o r i t y of t h e
organism s

studied.

A c o n c e n t r a t i o n of 7 p e r c e n t s o d i u m c h l o r i d e w a s r e q u i r e d
t o i n h i b i t t h e m a j o r i t y of t h e o r g a n i s m s t e s t e d .
m a t e l y 1.5 p e r c e n t

salt is the m ax im u m

Since a p p r o x i­

concentration acceptable

i n c o t t a g e c h e e s e a n d a p p r o x i m a t e l y 4 . 0 p e r c e n t i s n o r m a l in c o t t a g e c h e e s e d r e s s i n g , it c a n be c o n clu d ed th at th e added s a lt h as
l i t t l e , i f a n y , e f f e c t on t h e s h e l f - l i f e of c o t t a g e c h e e s e .
H e a t i n g a t 143°

F.

f o r 30 m i n u t e s d e s t r o y e d a l l of t h e n i n e ­

te e n o r g a n is m s te s te d , except B acillus f ir m u s .

Subsequent heat

123

s t u d i e s s h o w e d t h a t o n ly tw o o r g a n i s m s w e r e d e s tr o y e d by h e a tin g
a t 120°

F . f o r 15 m i n u t e s i n s k i m m i l k , b u t o n l y t w o c u l t u r e s s u r ­

vived when

heated

at t h i s t e m p e r a t u r e and h o lding t i m e in whey.

T h i s s u g g e s t s t h a t t h e c o o k i n g p r o c e s s u s e d in m a n u f a c t u r i n g c o t ­
t a g e c h e e s e d e s t r o y s t h e m a j o r i t y of s p o i l a g e o r g a n i s m s .
A l l of t h e o r g a n i s m s e x c e p t B a c i l l u s f i r m u s w e r e d e s t r o y e d
b y 5 0 p a r t s p e r m i l l i o n of c h l o r i n e i n 5 m i n u t e s .

O n l y e l e v e n of

t h e n i n e t e e n c u l t u r e s w e r e d e s t r o y e d i n 25 p a r t s p e r m i l l i o n of
c h l o r i n e w i t h 10 m i n u t e s of e x p o s u r e .

F i f t y p a r t s p e r m i l l i o n of

q u a t e r n a r y w i t h 10 m i n u t e s of e x p o s u r e a l s o d e s t r o y e d o n l y e l e v e n
of the n in e te e n c u ltu re s .

The q u a te rn a ry was effective against

g r a m - p o s i t i v e o r g a n i s m s but not e ffe c tiv e a g a in s t th e g r a m - n e g a t i v e
types.

F i f t y p a r t s p e r m i l l i o n of i o d o p h o r w i t h 1 m i n u t e of e x ­

p o s u r e w a s e f f e c t i v e i n d e s t r o y i n g t h i r t e e n of t h e n i n e t e e n c u l t u r e s ,
and i n c r e a s e d e x p o s u r e s w e r e not sig n ifican tly m o r e effective.
io d o p h o r w as in effectiv e a g a in st the m old c u ltu re s te ste d .
t h e c o n d i t i o n s of t h i s s t u d y , c h l o r i n e w a s m o s t

The

Under

e ffe c tiv e , follow ed

by th e io d o p h o r and th e q u a te r n a ry com pounds.
O n l y a s m a l l n u m b e r of t h e o r g a n i s m s t e s t e d w a s d e s t r o y e d
a t p H 5 . 2 a n d a b o v e w i t h c o n c e n t r a t i o n s of 0 . 0 5 , 0 . 1 0 , a n d 0.2 5
percent

s o r b i c a c i d , w h i l e a t p H 5 . 0 a n d 4 . 8 , t h e v i a b i l i t y of t h e

124
c u l t u r e s w a s d e c r e a s e d c o n s i d e r a b l y a s th e s o r b ic acid content in ­
c re a se d from

0.05 t o 0 . 2 5 p e r c e n t .

T h e d a ta p r e s e n te d in d ic a te th at a c e tic , c itr ic , and so rb ic
a c i d s a d d e d t o t h e w a s h w a t e r i n c r e a s e d t h e s h e l f - l i f e of c o t t a g e
c h e e s e s ig n if ic a n tly w hen sp o ila g e w as c a u s e d by v a r io u s o r g a n is m s .
T h e d a t a a l s o s h o w t h a t t h e a d d i t i o n of s o r b i c a c i d a n d
s t a r t e r t o c o t t a g e c h e e s e d r e s s i n g i n c r e a s e d t h e s h e l f - l i f e of t h e
p r o d u c t s ig n i f i c a n t l y w hen th e c h e e s e w as in o c u la te d with v a r i o u s
spoilage o rg a n ism s.

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