A comparison of cottage cheese made with and without the use of citric acid
by Marie Burgerova
A THESIS Submitted to the Graduate Faculty in partial fulfillment of the requirements for the degree
of Master of Science in Dairy Manufacturing at Montana State College
Montana State University
© Copyright by Marie Burgerova (1950)
Abstract:
Eighty vats of cottage cheese were made by the "short time" method, and 36 vats were made by the
"long time" method. Some of the vats of cheese were made with culture to which citric acid was added
before inoculation. Some of the cheese was made from skim milk to which amounts of citric acid
ranging from 0.002 to 0.3 percent were added before inoculation.
The volatile acids in the culture and in the cottage cheese were determined by the steam-distillation
method in which one liter of distillate was titrated against N/10 NaOH, using phenolphtalein as an
indicator. The number of milliliters of N/l0 NaOH required to titrate a liter of distillate was designated
as the "volatile acid number".
The "volatile acid numbers" of the cultures made with the addition of citric acid to the culture milk
were generally higher than those made without the addition of citric acid. High "volatile acid numbers"
in the cultures did not result in high "volatile acid numbers" in the cheese made from them.
The addition of 126 F water before heating the curd compared with heating and cooking the curd
without the addition of water did not influence the "volatile acid number" or the flavor of tho resulting
cottage cheese.
The addition of from 0.008 to 0.05 percent citric acid to the cheese milk before inoculation increased
the "volatile acid number" and the flavor of the resulting cottage cheese.
The cheese made by the "long time" method had a higher "volatile acid number" and a slightly more
desirable flavor than that made by the "short time" method.
Cottage cheese curd inoculated with culture and incubated for six hours before creaming had a better
flavor than cheese creamed with cultured cream or cheese to which uncultured sweet cream was
added. A COMPARISON OF COTTAGE CHEESE MADE WITH AND
WITHOUT THE USE OF CITRIC ACID
Uy'.
M arie BURGEROYA
A THESIS
Subm itted to th e G raduate F a c u lty
in
p a r t i a l f u l f i l l m e n t o f th e re q u ire m e n ts
f o r th e d eg ree o f
M aster o f S cien ce i n D a iry M an u factu rin g
at
Montana S ta te C ollege
Approved;
Bozeman, Montana
Ju n e, 195°
Ali, ;
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'IA '.I
j
3
C ty7- ^
2
TABLE OF COMTEUTS
ABSTRACT..............................................................
Page
3
INTRODUCTION.....................................................
I,.
HISTOR CAL.........................................................
5 .
EXPERT TINTA L .................................................................... H4.
D i s c u s s i o n - F R E S U L T S ....,.....................
28
SUMMARY AND CONCLUSIONS............................... 32
ACKNt'WLEDCXRrISTT ................................................ 35
LITERATURE CITED.............................................. 36
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94728
3
ABSTRACT
E ig h ty v a ts o f c o tta g e cheese w ere made by th e " s h o r t tim e" method,
and 56 v a ts w ere made by th e " lo n g tim e" m ethod. Some o f th e v a ts o f
ch eese were made w ith c u ltu r e to which c i t r i c a c id was added b e fo re
in o c u la tio n . Some o f th e cheese was made from skim m ilk to which amounts
o f c i t r i c a c id ra n g in g from 0.002 to 0 ,5 p e rc e n t were added b e fo re
in o c u la tio n .
The v o l a t i l e a c id s i n th e c u ltu r e and i n th e c o tta g e ch eese were
d eterm ined by th e s t e a m - d i s t i l l a t i o n method i n which one l i t e r o f
d i s t i l l a t e was t i t r a t e d a g a in s t 1 0 .0 HaOH, u s in g p h e n o lp h ta le in as an
i n d i c a t o r . The number o f m i l l i l i t e r s o f N/l0 NaOH re q u ire d to t i t r a t e
a l i t e r o f d i s t i l l a t e was d e sig n a te d a s th e " v o l a t i l e a c id num ber".
TIie " v o l a t i l e a c id numbers" o f th e c u ltu r e s made w ith th e a d d itio n
o f c i t r i c a c id to th e c u ltu r e m ilk w ere g e n e r a lly h ig h e r th a n th o se
made w ith o u t th e a d d itio n o f c i t r i c a c id . High " v o l a t i l e a c id numbers"
i n th e c u ltu r e s d id n o t r e s u l t in h ig h " v o l a t i l e a c id numbers" in th e
cheese made from them .
The a d d itio n o f 126 F w a te r b e fo re h e a tin g th e cu rd compared w ith
h e a tin g and cooking th e curd w ith o u t th e a d d itio n o f w a te r d id n o t
in flu e n c e th e " v o l a t i l e a c id number" o r th e f la v o r o f th e r e s u l t i n g
c o tta g e c h e e s e .
The a d d itio n o f from 0.008 to 0 .0 5 p e rc e n t c i t r i c a c id to th e
cheese m ilk b e fo re in o c u la tio n in c re a s e d th e " v o l a t i l e a c id number"
and th e f la v o r o f th e r e s u l t i n g c o tta g e c h e e s e .
The cheese made by th e " lo n g tim e" method had a h ig h e r " v o l a t i l e
a c id number" and a s l i g h t l y more d e s ir a b le f la v o r th a n t h a t made by th e
" s h o r t tim e" m ethod.
C o ttage cheese cu rd in o c u la te d w ith c u ltu r e and in c u b a te d f o r s ix
h o u rs b e fo re cream ing had a b e t t e r f la v o r th a n cheese creamed w ith
c u ltu r e d cream o r ch eese to which u n c u ltu re d sweet cream was added.
k
INTRODUCTION
C o ttag e ch eese has lo n g been re c o g n iz e d as a wholesome, n u t r i t i o u s ,
and econom ical f o r d .
I t was fo rm e rly made o n ly in th e home.
As more
p eople became aware o f i t s food v a lu e , d a ir y p la n ts s t a r t e d to manu­
f a c tu r e i t on a la r g e s c a l e .
C a re fu l, c o n tr o lle d methods i n th e p la n ts
produced a cheese o f more uniform t e x t u r e , body, and f la v o r th a n was
p o s s ib le when i t was made i n th e home.
I t has lo n g been known t h a t th e r e i s a good demand f o r c o tta g e
cheese w ith a p le a s in g f l a v o r .
Consumers a re a p p a re n tly more p a r tic u ­
l a r ab o u t th e f la v o r th a n th e te x tu r e o r g e n e ra l c o n s is te n c y .
This
demand has s tim u la te d i n t e r e s t in f la v o r re s e a rc h on c o tta g e c h e e se .
This work was u n d e rta k en i n an a tte m p t to improve th e f l a v o r in c o tta g e
cheese w ith o u t i n t e r f e r r i n g s e r io u s ly w ith body and te x tu r e c h a r a c te r ­
is tic s
5
HISTORICAL
S ince th e skim m ilk coagulum from w hich c o tta ,;e cheese i s made
i s so s im ila r to t h a t o f a c u ltu r e w hich i s used to improve th e f la v o r
o f m an u factu red d a ir y p ro d u c ts , i t fo llo w s t h a t th e c u ltu r e u sed to
s o t th e m ilk i s a v e ry im p o rta n t f a c t o r i n th e m anufacture o f c o tta @
cheese w ith a d e s ir a b le f l a v o r .
P rev io u s to i t s m an u factu re i n th e d a ir y p l a n t s , c o tta g e cheese
was made o f raw skim m ilk , h e ld a t room te m p e ratu re u n t i l c o a g u la te d ,
th e n cooked, d ra in e d , and s a l t e d .
This method produced a p ro d u c t
t h a t was la c k in g i n u n ifo rm ity and in d e s ir a b le f l a v o r .
f r e q u e n tly had an u n d e s ir a b le f l a v o r .
I t v e ry
T his in d ic a te s t h a t a good
c u ltu r e h a v in g a d e s ir a b le f la v o r i s n e c e s s a ry in th e m an u factu re o f
c o tta g e cheese to produce th e k ind o f f l a v o r d e s ire d by consum ers.
IIunziker (1 3 ) s t a t e s t h a t as e a r l y a s IG89 S to rch u sed pure
c u ltu r e s to improve th e f la v o r o f d a ir y p ro d u c ts ,
He added pure
c u ltu r e s t o ch u rn in g cream to improve th e f l a v o r o f th e r e s u l t i n g
b u tte r.
Conn ( 5 ) s tu d ie d th e e f f e c t o f r ip e n in g cream , p re v io u s to churn­
in g on th e f la v o r o f th e b u t t e r .
He p o in te d o u t t h a t cream rip e n in g
i s a complex p ro c e s s , and t h a t o th e r r e a c tio n s b e sid e s s o u rin g tak e
p la c e .
A ccording to h is f in d i n g s , th e r e sh o u ld be a d i s t i n c t i o n between
a c id and f l a v o r .
Acid i s developed from m ilk su g ar w h ile th e aroma
p ro b a b ly comes from o th e r s o u rc e s .
6
E xperim ents c a r r ie d on by Hammer and B a ile y ( 9 ) , S to ro h (2 2 ) ,
Boeldiout and O tt do V rie s ( 5 ) , and O rla -J e n s e n (19) proved t h a t a t
l e a s t two ty p e s o f organism s m ust be p r e s e n t in th e c u ltu r e to o b ta in
s a tis fa c to ry r e s u lts .
These two organism s were found to bo v e ry
d i f f e r e n t in t h e i r b io ch em ical f e a t u r e s , a lth o u g h t h e i r m o rp h o lo g ical
and c u l t u r a l c h a r a c t e r i s t i c s were v e ry much a l i k e .
Hammer and B a ile y (9 ) found t h a t th e v o l a t i l e a c id i s an im p o rta n t
f a c t o r i n f la v o r developm ent.
S tre p to c o c c u s l a c t i s produced o n ly a
sm all amount o f v o l a t i l e a c id , w hereas a c u ltu r e o f good f l a v o r showed
c o n s id e ra b ly h ig h e r amounts o f v o l a t i l e a c id s .
Hammer (7 ) s tu d ie d th e ty p e s o f l a c t i c a c id in c u l t u r e .
The
p re se n c e o f i - l a c t i c a c id proved th e p re se n c e o f o th e r organism s th an
S, l a c t i s w hich produces o n ly d - l a c t i c a c id .
As in a c tiv e l a c t i c a c id
i s a m ix tu re o f d - l a c t i c a c id and 1- l a c t i c a c id , i t was obvious t h a t
th e o th e r organism s produce 1 - l n c t i c a c id .
Hammer (6 ) was a b le to
i s o l a t e th e s e organism s by in o c u la tin g l a c t i c a c id c u ltu r e on a g a r
s lo p e s and c a r r y in g i t th ro u g h a number o f t r a n s f e r s to e lim in a te
o th e r o rg a n ism s.
He named them S tre p to c o c c u s c itro v o ru s ( Louconostoc
o itr o v o r u s ) and S tre p to c o c c u s p a r a c itr o v o ru s ( Leuconostoc d e x tra n ic u m ).
S . p a ra c itr o v o ru s produces v a r ia b le amounts o f 1 - l a c t i o a c id , reddens
litm u s m ilk , and forms a c o m p a ra tiv e ly h ig h v o l a t i l e a c i d i t y .
S.
c itr o v o r u s does n o t produce l a c t i c a c id , does n o t redden litm u s m ilk .
and produces c o m p a ra tiv e ly low v o l a t i l e a c c i d i t y .
Both a re r e g u la r ly
7
found I n a a u ltu r o w ith et good f l a v o r , thou
nxmorouBe
jS. o itr o v o r u s Ic Iooo
TZonnor d e o o rib e d th o u ao t y p i c a l o L rop to o o eo i, b u t d i f f e r e n t
i n -Llioir a b i l i t y to f o r f e i t c i t r i c a c id to term v o l a t i l e o m p o m d c .
ler-nor and Dakor (1 0 ) found t h a t th o d l s t i n o t i o n botweon th e two
ty p e s Io n o t a sh a rp one, s in e o th o (c o u n t o f a c id produced by S ,
p a m c ltro v o v o o i s 8o v a r i a b l e
I n a s tu d y o f 12l| o u ltu ro o o f th o se
o r OBniffi to th o t o t a l a c i d i t i e s prod cod in n i l k v a rie d f r o n O«27 to
o «99 p o r o o it .
Van H e l , K luyvort end Dors (SL) s tu d ie d th o r e l a t i o n s h i p o f
a o o ty lu o th y lo o rb in o l and d la o o ty l to th e a re n a o f b u t t e r .
Sarv=Ioo
h a v in e ty p i c a l a re n a Qavo a n R o o ty ln o th y lo e rb in o l (CI3^-ClICIi-OG-C:^)
r o a o tio n , w h ile sa n p lo s la o ld n s on a re n a d id not*
A c lo s e c o r r o ln ti c n
boiwoon th e h i sh a re n a and th e p ro eaao e o f ao© fcylrse th y lc a rb in o l vma
n o te d ,
IIairavor, f r e s h l y p u r i f i e d a o o ty ln o th y lc a r b ln o l was found t o be
o d o r le s s .
!Then d la o o ty l (Cl^-CC-CO-CTt) was added to b u t t e r Ia o Id n s
i n a re n a , an v-m io ta k a b lo aroma became a p p a r e n t.
These I n v e s tl ^n to re
Or-UOludod Idiat d la o o ty l i s e i t h e r r e s p o n s ib le f o r th e f l a v o r o f b u t t e r
o r Io th e p r in c ip a l component c f th o a re n a m a te r ia l,
M lo h ao llan s F a m o rs and H am ar (Hi.) showed th e Im p o rtan ce o f
a c o ty ln e tiiy lo a r b in o l and d la o o ty l in l a c t i c a c id c u l t u r e s .
C u ltu re s
Im vinc e s a t i s f a c t o r y f l a v o r o o n ta in o d c o m p a ra tiv e ly I a r . o amounts
o f tliooo m a te ria ls , whereas e u ltu ro s Inoldnv flav o r c o n ta in e d r e la tiv e ly
sm all amounts o r none a t a l l .
abol and Hamer ( I ) sta ted th at ripenIng o f la c t ic acid cu ltu re
O
I n w lv o e a o o rlo o o f o h e n lo e l ohan oe t h a t a ro th e r e s u l t o f LIio n o tio n
Cf
La
'.W - L y 1-OO
of
u o to r la - r - n l l y p re sen , end th a t c e r t a i n o f th e
0 " T'oo.'dn f o r id rc -OUit- f o r th e o'a m o to r 1s t Io flenr r o f th o c u lt- r e *
Harmor and Sherwood (LH) found t h a t o - e i le ra b lo tv -o m to o f
w l a f '. l o G olds a ro
'T sen
In ra.’ lk*
produced
rotiueoti In a c u ltu r e ftr m th e o l ri-c no Id *,• r o i l y
Co him t i e : o f 3 , l a c t l o o I a- cos- e la te d nr, G nlon
oed e u ltx r o e c o n ta in In ^ I a r O cry u n to o f
o l n t l l o n o ’v .
c o o r d '"13 to t l i o i r f In d ia a , Jio v o l a t i l e f o ld s Sa a M lH ily rip e n e d
o u l to re o re a o o tly node up o f c o o t Io a c id w ith a c o a l I m o u n t o f
I r I t c I o l '«
o o'
In a c u ltu r e w’ Lh a low Q o id lty i Lho
c In r or
o
ro e
Is o e tlo a d d .
v o l a t i l e Gold produced Ir/ S» l a a t t o o '-.slo ts
and G l i t t l e o o o tlo fie ld ,
'
CT-O- OOU
r ' " ood by j , I-
- I ’d i r
he s
"ho v o l a t i l e a d d
c I t r ’c r o l l to t ' ; - LIT;,
c. Ic o a
or, v Iono oxorfc e r o o tr a -> >••
m
oc .toe-.' ta I
c o t Ur-
Is
b a o tlc a d d
I ho e e o n o in to J
th e ■o ld
o r lo s o f Lho r f p e n ln
>retiuoti
orfo. L e o , i/h ilo th e
iovclopaont Ty S.
a r l o t l n o In th e r o l a t i o ’ Qhip betwoon Mio
oe ! ' t i e s Gt d i f f e r e n t
11 a n o in t o f
s t l y o f p rrp lo r-le a d d
G ceooiatod n r r^an le n s pm duoo th e v o l a t ’ I e no Id*
I roIT o .
orews L o f iro lo a lo
th e v o l a t i l e a o ld f o r Cd by th e a ss.v o le Led
o r GRio-C i s - io s tly o o o tlo v o id ,
-Of t l
ro -
I a -J w I a t l I e
e tc o '-.Tdleeve t h a t
th e r Bone le to d o r a i l o re do o le o t o r th e --not p e r t l a t e In th e rV.-on’ ■
O tf
o r V- , w lille Gi. I u o t l e o o ritro le the f o r e
0.
n tlo u durl-r.
Lho e a r ly
9
E a rn e r (O) s tu d ie d th e in flu e n c e o f carbon d io x id e on th e f la v o r
of a c u ltu re .
Carbon d io x id e i s produced by th e a s s o c ia te organism s
in r e l a t i v e l y sm all q u a n titie s and d if f u s e s in to th e a i r o r rem ains
i n s o lu t i o n .
The in flu e n c e o f carbon d io x id e on th e f l a v o r o f a
c u ltu r e can be in c re a s e d by adding c i t r i c a c id to th e c u ltu r e m ilk .
The mechanisms in v o lv e d in th e p ro d u c tio n o f Cj, compounds by
th e f la v o r organism s from c i t r i c a c id w ere s tu d ie d by many i n v e s t i ­
g a to rs (8 ) .
Some o f them b e lie v e t h a t a c e tic a c id and carbon d io x id e
a re form ed from c i t r i c a c id a t a h ig h pH, w h ile th e Cr compounds a re
produced o n ly a t a r e l a t i v e l y low pH.
A ccording to o th e r s , th e p r i ­
mary compound formed i s a c o ty ln e th y lc a r b in o l.
At a Iotv pH i t ten d s
to a ccu m u late, and some o f i t i s o x id is e d to d i a c e t y l .
A t a h ig h pH
i t i s r a p id ly reduced to 2 , 3 -b u ty le n e g ly c o l.
A ccording to Beynum and P e tte ( 2 ) , a c e ta ld e h y d e i s form ed from
p y ru v ic a c id w hich comes from c i t r i c a c id .
From a c e ta ld e h y d e , a c e tic
a c id and e th y l a lc o h o l a re produced in a n e u t r a l medium.
A cety lm eth y l-
c n rb in o l i s formed a n a e r o b ic a lly from a c e ta ld e h y d e in an a c id medium.,
w h ile d ia c o ty l i s form ed a e r o b ic a lly .
Both compounds can be reduced
to 2 , 3 -b u ty le n e g ly c o l.
H ichael i e n , e t a h , ( I ? ) found t h a t th e s a t i s f a c t o r y pH f o r p ro ­
d u c tio n o f n c o ty lm e th y lc a rb in o l
and d ia c e ty l can be e s ta b lis h e d by
o th e r a c id s a s w e ll as by l a c t i c a c id .
He added d i f f e r e n t amounts
o f d i f f e r e n t a c id s to pure c u ltu r e s and determ ined th e amounts o f
10
d ia c e ty l and a c e ty lm o th y lc a rb in o l.
Ite s u lts o f h is e x p erim en t shew
t h a t o th e r a c id s a re more s a t i s f a c t o r y th a n l a c t i c a c id f o r th e p ro ­
d u c tio n o f a c e ty lm e th y lc a rb in o l and d ia c o ty l by th e a s s o c ia te d
o rg a n ism s.
The p ro d u c tio n was h ig h e s t when c i t r i c a c id was added.
The r e s u l t s w ith l a c t i c a c id w ere c o m p a ra tiv e ly low.
gave h ig h e r y ie ld s th a n l a c t i c a c id .
S u lf u r ic a c id
M ix tu res o f l a c t i c a c id and
s u l f u r i c a c id gave th e same y ie ld s a s s u l f u r i c a c id a lo n e .
M ichaeliam and Hammer ( 15) sheaved t h a t a d d itio n o f l a c t i c a c id
to S . c itr o v n r u s a n d _S. p a ra c itr o v o ru s c u ltu r e in c re a s e d th e v o l a t i l e
a c id p ro d u c tio n .
The in c r e a s e v a rie d w ith d i f f e r e n t s t r a i n s .
It
was s m a lle s t w ith th o se p ro d u cin g a co n sp icu o u s change in th e
t i t r a ta b le a c i d i t y and g r e a t e s t w ith th o s e p ro d u cin g l i t t l e change.
The same in c r e a s e was o b ta in e d when t a r t a r i c , p h o sp h o ric , o r s u lf u r ic
a c id s wore added.
The in c re a s e in d ia c e ty l and a c e ty lm e th y lc a rb in o l
a f t e r a d d itio n o f a c t r i c a c id shows t h a t th e a s s o c ia te d organism s
can fe rm e n t more c i t r i c a c id th a n i s n o rm a lly p re s e n t in m ilk ,
Toens and Hammer (2 3 ) s tu d ie d th e r e l a tio n s h ip betw een th e a i r
su p p ly and a c id developm ent in c u l t u r e s .
A ccording to t h e i r fin d in g s
h ig h a c i d i t y o c cu rred in r e s t r i c t e d a i r su p p ly , w h ile in te rm e d ia te
a c i d i t i e s w ere observed w ith abundant a i r s u p p ly .
R ice (21) re p o rte d t h a t a e r a tio n r e t a r d s th e l a c t i c a c id f e r ­
m e n ta tio n o f m ilk a g r e a t d e a l when th e fe rm e n ta tio n i s accom plished
by b a c t e r i a b e lo n g in g to th e jS. I a c t i s group.
11
IIio h a e lia n and Hazmier (1 6 ) found t h a t oxygen su p p ly i s im p o rta n t
i n th e p ro d u c tio n o f d i a c e t y l .
in c re a s e d th e y ie ld o f d i a c e t y l .
P a ssin g oxygen th ro u g h th e c u ltu r e
A d d itio n o f a c e ty lm e th lc n rb in o l to
c u ltu r e d id n o t in c r e a s e th e amount o f d ia c e ty l e i t h e r w ith o r w ith ­
o u t th e tre a tm e n t w ith oscygen.
This seemed t o in d ic a te t h a t th e
fo rm a tio n o f d ia c e ty l from a c o ty lm e th y lc a rb in o l in a c u ltu r e i s n o t
d i r e c t chem ical o x id a tio n b u t r e s u l t s from th e a c tio n o f th e organism s*
Brewer, e t
were a b le t o in c r e a s e th e p ro d u c tio n o f d ia c e ty l
by growing th e c u ltu r e under an a i r p re s s u re o f t h i r t y pounds, o r
m ore, p e r sq u are in c h .
A g ita tio n was n e c e s s a ry sin c e p re s s u re w ith o u t
a g i t a t i o n d id n o t in c r e a s e th e d ia c e ty l c o n te n t.
In some o a se s th e
In c re a s e in d i a c e t y l was accompanied by an in c re a s e in a c e t y Imoth y ] c a r b in o l.
A ccording to P r i l l and Hammer (2 0 ) , v a rio u s f a c to r s in c re a s e d
th e c o n te n t o f d ia c e ty l in c u l t u r e s .
Shaking o f rip e n e d c u ltu r e
r e s u lte d in s i g n i f i c a n t in c r e a s e , w h ile la c k o f a e r a tio n caused a
d ecrease.
H olding rip e n e d c u ltu r e a t v a rio u s te m p e ra tu re s r e s u lte d
in an in c r e a s e , b u t th e b e s t r e s u l t s w ere o b ta in e d when th e c u ltu r e s
wore h e ld a t a low te m p e ra tu re .
D ia c e ty l c o n te n t was in c re a s e d by-
lo w e rin g th e pH o f th e c u ltu r e by adding s u lf u r ic a c id .
L ikew ise as
l i t t l e a s 0*008 p e rc e n t o f c i t r i c a c id r e s u l t e d in an in c r e a s e o f
d ia c o t y l.
Hammer (8 ) s t a t e d t h a t th e number o f th e a s s o c ia te d organism s
a t th e tim e a low pH i s reach ed i s v e ry im p o rta n t.
I f th e number i s
12
s n a i l , th e amount o f d ia c e ty l produced i s s m a ll, and th e c u ltu r e
la c k s fla v o r*
An e x c e s siv e number o f th e organism s p r e s e n t b e fo re
th e p ro p e r pH i s reached w i l l d e s tro y c i t r i c a c id b e fo re th e c o n d itio n s
a r e fa v o ra b le f o r accu m u latio n o f d i a c e t y l .
The amount o f d ia c e ty l
and a c e ty lm e th y lc a rb in o l s t a r t s to d e c re a se a s soon as tho maximun
amount i s re a c h e d .
The re d u c tio n can be d elay ed by k eep in g th e c u l­
tu r e a t a lew te m p e ra tu re .
For some tim e th e r e even can be an in c re a s e
i f c i t r i c a c id i s s t i l l p r e s e n t.
I f a sm all amount o f c i t r i c a c id i s
added to th e c u ltu r e a t th e tim e o f c o o lin g , th e in c re a s e con be made
more pronounced.
Toons and Hammer (2 3 ) s tu d ie d th e in flu e n c e o f th e rip e n in g
te m p e ra tu re .
8 9 »6 F .
Good c u ltu r e s were o b ta in e d i n th e range from 6U»U to
The m ost fa v o ra b le te m p e ra tu re s w ere from 70 to 72 F , when
re a so n a b ly ra p id growth was o b ta in e d .
A t h ig h e r te m p e ra tu re , th e
h e a t r e s i s t a n t organism s t h a t s u rv iv e p a s te u r iz a tio n had a g r e a te r
chance to develop and to in flu e n c e th e developm ent o f th e c u ltu r e
o rg a n ism s.
W ith low te m p e ra tu re s , i t was d i f f i c u l t to o b ta in ra p id
r ip e n in g , as th e growth o f th e organism s was d e lay e d .
C o n stan t
te m p e ra tu re s r e s u l t e d i n b e t t e r c u ltu r e s th a n f lu c tu a tin g tem pera­
tu re s .
Hammer and Baker ( I l ) found slo w er c o a g u la tio n and a c id d ev elo p m ent in m ilk s h e a te d to lij.5 F f o r JO m in u te s th an in m ilk s h e a te d
to c o n s id e ra b ly h ig h e r te m p e ra tu re s .
A t th e h ig h e r p a s te u r iz in g
13
te m p e ra tu re s chance f o r growth o f th e organism s r e s i s t i n g p a s te u r iz a ­
t i o n Y1TS n o t as g r e a t, s in c e th e s e organism s a re s u s c e p tib le to a c id ,
and t h e i r growth i s i n h i b i t e d by a more r a p id a c id p ro d u c tio n •
The
same r e s u l t s were o b ta in e d a t 160 P f o r 30 m in u tes a s a t h ig h e r
te m p e ra tu re s used f o r th e same p e rio d ,
Toens and Hammer (23) were a b le to compare slow and r a p id
c o a g u la tio n .
There i s a d e f i n i t e ad v an tag e o f ra p id c o a g u la tio n
o f s t a r t e r s over slow c o a g u la tio n .
Rapid c o a g u la tio n gave b e t t e r
c u ltu r e s more f r e q u e n tly th a n slow c o a g u la tio n .
Tic p e rio d o f
in c u b a tio n o f a s a t i s f a c t o r y c u ltu r e was found to be a b o u t 15 to
26 h o u rs and th e amount o f inoculum one p e r c e n t.
The most fa v o ra b le
a c i d i t y o f th e c u ltu r e f o r th e maximum developm ent o f f l a v o r and aroma
a t th e end o f r ip e n in g , was found to be 0 ,0 0 to 0,9 0 p e r c e n t.
From th e r e s u l t s r e p o r te d , i t i s e v id e n t t h a t th e r e a re many
f a c t o r s t h a t in flu e n c e th e d e s i r a b i l i t y o f c u l t u r e s .
S ince b u t t e r
c u ltu r e s a re u sed to c o a g u la te th e slcim m ilk in th e m an u factu re of
c o tta g e choose, i t would be re a so n a b le to e x p e c t t h a t th e c u ltu r e
should have an in flu e n c e on th e f la v o r o f th e r e s u l t i n g c h e e s e .
t h i s a ssu m p tio n , th e fo llo w in g ex p erim en ts wore u n d e rta k e n .
On
EXPEPJI1ETrrAL
C ottage cheese was made from f r e s h skim m ilk s e p a ra te d from th e
whole m ilk produced by th e Montana S ta te C o lleg e d a ir y h e rd .
The
w hole m ilk was o f h ig h q u a l i t y w ith an a v erag e sta n d a rd b a c t e r i a
p l a t e co u n t o f l e s s th a n 10,000 organism s p e r m l.
The skim m ilk was
p a s te u r iz e d a t II4.5 F f o r pO m in u tes and c o o led to a te m p e ratu re
low er th a n 50 F«
The ch eese was made in a s p e c i a l l y d esig n ed th r e e -
com partm ent e x p e rim e n ta l cheese v a t in w hich th r e e b a tc h e s o f c o tta g e
ch eese co u ld be made a t one tim e u n d er th e same te m p e ra tu re c o n tr o l.
I n two o f th e com partm ents cheese was made v a ry in g one o r more o f
th e c o n s t i t u e n t s .
A cheek b a tc h was made i n th e t h i r d com partm ent.
Tliroe d i f f e r e n t com m ercial c u ltu r e s w ere c a r r ie d .
skim m ilk was p a s te u r iz e d a t 200 F f o r one h o u r.
Tiie c u ltu r e
A fte r c o o lin g , th e
m ilk was in o c u la te d w ith a sm all amount o f m other c u ltu r e and in cu b ated
a t 72 F o v er n i g h t .
The n e x t m orning, th e c u ltu r e s were p u t in th e
r e f r i g e r a t o r and h o ld a t lj.0 F b e fo re th e y wore used f o r making th e
c o tta g e c h e e s e .
Some o f th e v a ts o f c o tta g e cheese w ere made by th e " s h o r t
tim e" method i n which seven p e rc e n t o f c u ltu r e was added to th e
m ilk and s o t a t 90 F, th e m ilk c o a g u la te d , and th e curd c u t i n from
3% to U i h o u rs from th e tim e o f s e t t i n g .
O th er v a ts o f ch eese were
made by th e 1lo n g tim e" method in w hich -g p e rc e n t o f c u ltu r e was
added to th e m ilk and s e t a t 72 F .
Tlie c u ltu r e d m ilk was allo w ed
15
to sta n d f o r from Il+ to 16 h o u rs , u s u a lly o v e m ig h t u n t i l i t c o a g u la te d .
TIie c o a ru lu n vms c u t m th 3 /l| in c h curd Im ives and allow ed to s ta n d
f o r te n m in u te s , a f t e r w hich s u f f i c i e n t w a te r h e a te d to 126 F was
added to some o f th e b a tc h e s to cover th e cu rd w h ile th e o th e rs were
cooicod wi shout th e a d d itio n o f w a te r .
H e atin g was th e n s t a r t e d a t
th e r a t e I F r i s e i n te m p e ra tu re e v ery f o u r m in u te s , and th e h e a tin g
c o n tin u e d u n t i l th e te m p e ra tu re o f th e whey re a ch e d 126 F,
TIie cheese
was cooked a t 126 F, a f t e r w hich th e whey was d ra in e d end c o ld w a te r
e q u iv a le n t to th e amount o f whey d ra in e d from th e cheese was added.
The cheese was s t i r r e d , th e w a te r removed, and th e cheese allo w ed
to d r a in over n i g h t , a f t e r w hich i t was removed and h o ld in th e
r e f r i g e r a t o r a t Uo F f o r a b o u t LiQ h o u rs b e fo re i t was an aly zed f o r
v o l a t i l e a c id c o n te n t and sco red f o r f l a v o r .
The a c i d i t y o f th e
co agulun a t th e tim e o f c u t t i n g , th e method o f c u ttin g , th e s iz e o f
c u rd , th e co o k in g , d r a in in g , end w ashing c f th e curd was c a r r i e d o u t
a s u n ifo rm ly as was p o s s ib le re g a r d le s s o f w h eth er th e ch eese was
made by th e " s h o r t tim e" o r by th e " lo n g tim e" m ethod.
The v o l a t i l e a c id s i n th e cheese w ere determ ined by th e d i s ­
t i l l a t i o n method used by Hammer and B a ile y ( 9 ) .
This method c o n s is ts
o f s t e a m - d i s t i l l i n g 250 grams o f m a te r ia l t o be te s t e d a f t e r th e
a d d itio n o f l rj ml 1C/ 1 s u l f u r i c a c id , and t i t r a t i n g th e f i r s t 1000
ml o f d i s t i l l a t e w ith N/lO sodium h y d ro x id e u sin g p h e n o lp h ta le in as
an i n d i c a t o r .
B efore a n a l y s i s , th e sample o f th e cheese was made
u n ifo rm by m ixing i t th o ro u g h ly in a m ech an ical b le n d e r.
F iv e
26
hundred ml o f d i s t i l l e d w a te r wore added t o th e 2^0 grams o f choose to
lteep th e cheese from b u rn in g o n to th e f l a s k .
ment u sed i s shown i n f ig u r e I .
The d i s t i l l a t i o n e q u ip ­
The amount o f v o l a t i l e a c id was e x p re ss ed
in ml o f T/lO ITaOH re q u ire d to t i t r a t e th e a c id in one l i t e r o f d i s .111 a t e .
The number o f m i l l i l i t e r s o f IIaOH re q u ire d to t i t r a t e one
l i t e r o f d i s t i l l a t e was d e sig n a te d no th e " v o l a t i l e a c id num ber".
In o rd e r to determ in e w h eth er o r n o t th e skim m ilk o r th e
d i s t i l l e d w a te r had any m a te r ia l e f f e c t on th e t i t r a t i o n s , p re lim in ­
a r y d i s t i l l a t i o n s w ere made on th ro e sam ples o f skim m ilk and th r e e
sam ples o f d i s t i l l e d w a te r in th e same way ns th e d i s t i l l a t i o n s were
nado on th e c o tta g e ch o o se.
T able
.
The r e s u l t s a re shown in ta b le I .
" ! ! ! ! l i t e r s o f Ti/lO ITaOII r e q u ire d t o t i t r a t e one l i t e r of
d i s t i l l a t e o b ta in e d from skim m ilk and from d i s t i l l e d
w a te r .
T r ia l
No.
M a te ria l
Amount
d is tille d
skim m ilk
d i s t i l l e d w a te r
skim m ilk
d i s t i l l e d w a te r
skim m ilk
d i s t i l l e d w a te r
I
2
Z
J
250
500
250
500
250
500
g
ml
g
ml
g
ml
ml H/10 ITaOH
( v o l a t i l e a c id number)
2 .0
________ 1V7
1 .9
1*6
2 .2
_______________ 1.7
S ix t r i a l s were made on growing c u ltu r e s in d i f f e r e n t l o t s o f
s Icim m ilk u s in g a d i f f e r e n t amount o f c i t r i c a c id in th e c u ltu r e
m ilk in each t r i a l .
tria ls .
The same k ind o f c u ltu r e was used in a l l s ix
In two o f th e t r i a l s no c i t r i c a c id was added to th e c u l­
tu r e m ilk .
In th e o th e r fo u r t r i a l s a sm all p e rc en ta g e o f c i t r i c
a c id was added to th e m ilk b e fo re i t was in o c u la te d .
Tlie rip e n e d
F ig u re I .
D i s t i l l a t i o n a p p a ra tu s u sed in making th e v o l a t i l e a c id d e te rm in a tio n s .
J a t e r was b o ile d in f l a s k A by means o f a h o t p l a t e . Tvvo hundred f i f t y grams o f cheese
to w hich I^ ml o f I y l s u l f u r i c a c id and j}00 ml o f d i s t i l l e d w a te r was added was b o ile d
in f l a s k B. The steam from f l a s k A was p assed th ro u g h th e cheese in f l a s k B. Tie
steam c a r r y in g th e v o l a t i l e a c id s from f l a s k B was condensed in th e w a te r cooled
condensor C and cau g h t in l i t e r f l a s k D.
c u ltu re s
rere an aly zed f o r v o l a t i l e a c id .
The c u ltu r e s w ere a ls o
te s t e d q u a l i t a t i v e l y f o r th e u re s e ro e o f a c e ty lv .e th y lo a r h in o l by
th e c r e a tin e t e s t (1 3 ) .
The c r e a tin e t e s t was made by a d d in - 3 .? ml o f 6 U sodium
h y d ro x id e and a sm all amount o f c r e a tin e to 2 .5 ml o f c u ltu r e in a
t e s t tu b e and. m ixing th o ro u g h ly .
A fte r 30 m in u te s, th e p in k band
formed a t th e top o f th e m ix tu re was m easured in m illi m e t e r s .
The
r e s u l t s o f th e /{8 h our o ld c u ltu r e s a rc g iv en in ta b le I I .
Table I I .
M i l l i l i t e r s o f ll/lO NaOH re q u ire d to t i t r a t e one l i t e r of
c u ltu r e d i s t i l l a t e and th e r e s u l t s o f th e c r e a t i n e t o s t
on sam ples o f c u ltu r e when d i f f e r e n t amounts o f c i t r i c
a c id w ere added t o th e c u ltu r e m ilk b e fo re in o c u la tio n .
T r i a l : F la v o r o f
j P e rc e n t o f c i t No.
: th e c u ltu r e ; r i c a c id added
!
i
I
i ' '
' good
none
good
none
...goodh'drfe
'......
f a.......................
ir
none
----v e ry good
'0 .0 0 8
[ v e ry good
0 .0 1
good
0.008
v o ry good
0.01
t good
o.d3
v e ry good
0.05
v e ry good
,
0.03
. v e ry good
,
0.05
...
: ml Il/lO HaOH
: Depth o f c o lo r
: ( v o l a t i l e a c id t band i n th e
s number)
i c r e a tin e t e s t
t
t in mm
!
!
10.5
2
t
:
9
2
0
S
2
q
17 .1
I
18 .If
k
5
,
13.7
S
17.7
21 .7
5
$
3 5 .1
5
,
2 4 .5
5
%
:
2 9 .3
5
X
Ti.y
7.9
5
Four t r i a l s w ere made on making th re e b a tc h e s o f cheese in a
th ree-co m p artm en t choose v a t .
V arying amounts o f c i t r i c a c id were
added to th e c u ltu r e m ilk a t th e tim e o f in o c u la tio n , b u t no c i t r i c
a c id was added to th e skim m ilk from w hich th e cheese was made.
A ll
19
fo u r b a tc h e s ’//ore made by th e " s h o r t tim e" m ethod.
The p ro c e d u re
d u rin g m an u factu re o f th e d i f f e r e n t v a ts i n each t r i a l ’//as k e p t as
u n iform as p o s s ib le .
The o n ly v a r ia b le was th e amount o f c i t r i c
a c id u se d ,
TIio r e s u l t s a re shown in t a b le I I I ,
Table I I I ,
M i l l i l i t e r s o f N/10 TIaOH r e q u ire d to t i t r a t e one l i t e r
o f c u ltu r e d i s t i l l a t e and one l i t e r o f cheese d i s t i l l a t e
made w ith th e c u l t u r e . D if f e r e n t amounts o f c i t r i c
a c id w are added to th e c u ltu r e m ilk b e fo re in o c u la tio n
and none to th e skim m ilk from w hich th e cheese was made.
T ria l s fla v o r of
: Percent; o f S ml IT/10 IIaOH
Ho,
th e c u ltu r e : c i t r i c a c id : re q u ire d f o r
• added
: c u ltu r e d i s t
: tilla te
:
i ( v o l a t i l e a c id
i
: num ber)
S
:
:
i
«
:
:
good
;
none
8 .)
t
10
v e ry good
:
0 .0 0 1
14.8
:
v e ry good
:
0 . 00b
;
# .4
v e ry good
:
none
:
8 .5
11
v e ry good
,
0.001
i
16.5
v e ry good
i
0.005
3 0 .7
:
v o ry good
:
none
10 .1
I
12
v e ry good
:
0.001
:
1 7 .1
v o ry good
i
0.005
:
2 5 .4
v e ry good
:
0 .0 1
;
3 2 .7
v
o
ry
good
:
0 .0 1
S
13
4 0 .5
v e ry good
:
0 .0 1
2 8 .1
i
: ml "ll/lO"
. HaOH r e : q u ire d
i fo r
i cheese
: d is till: a te
I (v o la tile
I a c id
; num ber)
i 3*5
: 3 .4
;
I 4 .4
I 4a
I 6 *6
: 2 .7
i 2 .3
2 4 .3
2 3 .6
I 5 .2
: 5 .4
: Comment
: on th e
i fla v o r
: o f th e
i cheese
:
I
:
2
f
I fla t
* fla t
$ fla t
fla t
i
f
la t
:
f
l
at
;
f
l
a
t
i
f
l
a
t
i
f
l
a
t
$
: fla t
2 fla t
$ fla t
Table IV g iv e s th e r e s u l t s on s ix t r i a l s , a t o t a l o f tw elv e v ats
o f cheese made by th e " s h o r t tim e" method when v a ry in g amounts o f
c i t r i c a c id w ere added t o th e cheese m ilk .
I n o rd e r to d eterm in e
w h eth er th e a d d itio n o f 126 F w a te r b e fo re h e a tin g th e cu rd and th e
Table 1 7.
I I i l l i l i t e r s o f N/lO HaOH re q u ire d to t i t r a t e one l i t e r o f d i s t i l l a t e from u n d ilu te d
whey, d ilu te d whey, w ashing w a te r , ana th e f in i s h e d choose made by th e " s h o r t tim e"
m ethod.
(A) cheeso made w ith a d d itio n o f 126 F w a te r and w ith w ashing_______________
V o la tile a c id number
T r ia l i F la v o r o f
: P e rc e n t o f
ml N/10 NaOE re q u ire d : ml N/10 NaOH r e No.
% th e c u ltu r e : c i t r i c a c id
to t i t r a t e th e d ilu te d
quirod. to c i t r a t e
:
: added to th e
whey
th e w ashin w a te r
:
: cheese m ilk
X
none
14 : v e ry good
:
4 .8
1.6
none
:
15 : good
5 .9
1.7
16 : v e ry good
t
0.008
8 .5
1.6
0.008
17 : v e ry good
13.6
1.8
18 : v e ry good
0 .0 1
5*9
1.6
19 % good
0 .0 1
12.3
1.7
: ml N/10 HauH
2 re q u ire d to
* t i c ra te th e
cheese
•
3 .5
2 .7
9 .9
10.8
11.3
:
1 0 .4
O
(B) cheese made w ith o u t a d d itio n o f 12' w a te r and w ith o u t washinr
v o l a t i l e a c id number
T r ia l : F la v o r o f
P e rc e n t o f c i t r i c
ml /lO TIaOH re q u ire d to : ml /1 0 HaOH re q u ire d to
Ho.
: th e c u ltu r e
a c id added to th e
t i t r a t e u n d ilu te d whey
: t i t r a t e th e cheese
:
cheese m ill;
14 : v e ry good
none
6 .2
T T
15 : good
none
5 .4
3 .4
16 : v e ry good
0.008
7 .3
10.3
17 : v e ry good
0.008
14.1
9 .2
10 : v e ry good
0 .0 1
10.1
19.3
19 * good
0 .0 1
12 J i
11.9
Pl
w ashing c f th e cooked curd in c re a s e s th e lo s s o f v o l a t i l e a c id s ,
c h eese was made e x a c tly th e sane in two com partm ents o f th e cheese
v a t w ith th e seme c u ltu r e and skim m ilk .
To th e cheese in one com­
p a rtm e n t, 126 F w a te r was added b e fo re h e a tin g , and th e c u rd was
washed a f t e r i t was cooked and d ra in e d .
No warm w a te r was added to
th e cu rd i n th e o th e r compartment b e fo re h e a tin g , and th e cu rd was
n o t washed a f t e r i t was cooked end d ra in e d .
The u n d ilu te d whey and
th e d ilu te d whey, th e wash w a te r, and th e choose w ere a n a ly z e d f o r
v o l a t i l e a c id s .
Ton t r i a l s , each c o n ta in in g th ro e b a tc h e s o f c h e e s e , w ere made
by th e n s h o r t tim e" method w ith one ty p e o f c u ltu r e c o n ta in in g no
added c i t r i c a c id .
V arying amounts o f c i t r i c a c id w ere added t o th e
cheese m ilk b e fo re i t was in o c u la te d .
The r e s u l t s , given in ta b l e V,
in d ic a te t h a t th e maximum and minimum p e rso n t a as o f c i t r i c a c id
t h a t could "bo added t o th e m ilk to produce cheese o f d e s ir a b le f la v o r
and body c h a r a c t e r i s t i c s i s from 0.008 to 0 , 0 5 .
F u r th e r t r i a l s w ere co n d u cted , u s in g th r e e d i f f e r e n t com m ercial
c u ltu r e s and v a ry in g th e p e rc e n ta g e o f c i t r i c a c id added to th e m ilk
from w hich th e cheese was made w ith in th e in d ic a te d optimum ra n g e .
Six t r i a l s , each c o n ta in in g two b a tc h e s o f c h ee se, and e i g h t t r i a l s ,
each c o n ta in in g th r e e b a tc h e s o f c h ee se, w ere made u s in g th r e e
d iff e r e n t c u ltu re s .
V arying amounts o f c i t r i c a c id w ith in th e optimum
range in t a b le V w ere added to th e m ilk from which th e ch eese was
made by th e " s h o r t tim e" m ethod.
The r e s u l t s a re given in ta b l e VI,
22
Table V,
M i l l i l i t e r s o f Il/lO ITaOH re q u ire d to t i t r a t e one l i t e r o f
cheese d i s t i l l a t e in te n t r i a l s where d i f f e r e n t amounts o f
c i t r i c a c id were added to th e skim m ilk from w hich th e
ch eese was made by th e " s h o r t tim e" m ethod.
T r ia l s F la v o r o f
. th e c u ltu r e
Mo.
I
t
:
20
21
22
25
. v e ry
j v e ry
. v e ry
: Good
{ v e ry
. v e ry
. v e ry
, v e ry
. v e ry
. v e ry
j good
. v e ry
:
2h
25
26
27
28
29
good
good
good
good
good
good
good
good
good
good
G ood
good
i good
: v e ry
. v e ry
. v e ry
. v e ry
s v e ry
. v e ry
I v e ry
: v e ry
: good
: good
j v e ry
: v e ry
: v e ry
: good
: v e ry
•
good
good
good
good
good
good
good
good
good
good
good
good
, ml Il/lO IJaOH re- ' 1 F la v o r o f th e
t P e rc e n t o f
c i t r i c a c id : q u ire d f o r th e
1 cheese
added
,
cheese
d
i
s
t
i
l
l
I
;
j a te
I
:
, ( v o l a t i l e a c id
t
:
, number)
;
I
none
v e ry f l a t
t
,
3 .5
i
0,002
v
e ry f l a t
I
S
7 .9
:
v
e ry f l a t
o.ooU
s
6 . 9 ..................... :
i
none
v
e ry f l a t
1
W
T
I
:
0.002
v
e
ry f l a t
,
6 .8
t
:
o.ooU
:
9 .2
• v e ry f l a t
I
:
2 .7
> none
1 v e ry f l a t
0.002
I
6»k
t
< v e ry f l a t
O.OOli
v e ry f l a t
«
8
.1
I
v
e ry f l a t
0.006
:
i
9 .U
i
good
J
1 0 .1
0,008
:
1
0 .0 1
good
I
:
1 0 .4
?
6.006
v
e ry f l a t
:
8 .8
:
1
f
l
at
0.008
I
I
9 .9
$
0 .0 1
f
l
at
i
:
9 .0
;
v
e
ry f l a t
0.006
:
«
I
9 ^ ~
good
0.008
I
s
10.8
1
0 .0 1
good
i
:
11.3
$
0.03
good
;
:
13 .1
:
0.05
good
I
»
lk .h
I
0 .1
f
la t
:
t
6 .5
I
good
$
0.03
i
1 5 .1
1
0 .0 5
good
*
i
i
15.5
0 .1
f
la t
>
t
9 .1
:
0.03
f
l
at
t
t
10*6
:
t
0 .0 5
good
1
*
1 6.9
i
0 .1
fla t
:
7 .1
:
t
0 .2
fla t
i
s
5 .1
i
0 .2
fla t
i
:
6 .3
t
fla t
t
0 .3
:
5 .9
23
Table V I.
M i l l i l i t e r s o f N/lO HaOH r e q u ire d to t i t r a t e one l i t e r
o f d i s t i l l a t e from cheese made by th e " s h o r t tim e" m ethod.
The choose was made vri th th ro e d i f f e r e n t c u ltu r e s and
v-rith c i t r i c a cid added to th e skim m ilk .
T r ia l j F la v o r o f
: P e rc e n t o f s ml U/lO ITaOH : F la v o r :
Ho.
th e c u ltu r e
c itric
r e q u ir e d f o r
sco re
a c id added
th e ch eese
o f th e
d is tilla te
cheese
( v o l a t i l e a c id curd
num ber)
CULTURE A
Good
1 0.1
0.008
38
23
v e ry rood
0 .0 1
104
38
Good
0.008
3 7 .5
9 .9
O ),
dLl
frpod
0 .0 1
9 .8
3 7.5
v e ry good
0.000
10.8
38
25
0 .0 1
v e ry good
38
11.3
v
e
ry
good
0,03
1 3 .1
38
OZ
v e ry good
0.05
38
1U 4
v e ry good
0.03
1 5 .1
38
v e ry good
0.05
15.5
3 8 .5
good
0.03
10 4
3
7 .5
CO
v e ry good
0 .0 5
16 .9
3 8 .5
CULTURE B
v e ry good
10.5
0.000
38
good
0 .0 1
30
11.8
38
v e ry good
0.05
13.0
38
v e ry good
11 .1
0.008
38
v e ry good
0 .0 1
12
31
38
v e ry good
0.03
1U.2
38
v e ry good
0.008
9 .1
3 7 .5
good
0 .0 1
10.2
32
3 7 .5
good
0.03
11.7
3 7 .5
v e ry good
0.05
17.1
3 8 .5
v e ry good
0.05
33
38
15 .u
v e ry good
0.05
3 8 .5
16.3
CULTURE C
good
0.008
8 .1
37
good
0 .0 1
3k
9 .4
3 7 .5
good
0.03
7 .1
3 6 .5
good
0.008
7 .5
3 6 .5
good
0 .0 1
35
7 .9
3 6 .5
9 .1
37
.. .& °A _________ 0.03
good
0.008
6 .9
35
good
0 .0 1
0 .2
36
37
good
0.03
8 .5
3 6 .5
good
0.05
10.8
37
good
0 .0 5
12 .1
37
37
rood
0 .5
9 ,9
______
F la v o r of
th e cheose
good
good
fla t
fla t
good
good
good
good
good
good
fla t
good
good
good
good
good
good
good
fla t
fla t
fla t
good
good
good
fla t
fla t
fla t
fla t
fla t
fla t
fla t
fla t
fla t
fla t
fla t
fla t
In an a tte m p t to d eterm in e w hich o f th e two m ethods, th e " s h o r t
tim e" o r th e " lo n g t i n e " , would produce a h ig h e r v o l a t i l e a c i d i t y ,
th e ex p erim en t re c o rd e d i n t a b le YI was re p e a te d u s in g th e " lo n g time"
method*
Uio same amounts o f c i t r i c a c id and th e same th r e e c u ltu r e s
were u s e d ,
Tlie r e s u l t s a re re p o rte d i n ta b l e H I ,
The com parison of
th e " s h o r t tim e" and th e " lo n g tim e" m ethods i s given i n ta b le V III,
Three ways o f cream ing were t r i e d i n o rd e r to d eterm in e w h eth er
th e f l a v o r o f th e cheese could be im proved.
Three o n e -q u a rt g la ss
j a r s w ere f i l l e d w ith cheese from th e same b a tc h .
The amount o f
cream n e c e s s a ry was p re p a re d and th en d iv id e d in to th ro e p o r ti o n s .
Two p o r tio n s o f cream were p la c e d i n th e r e f r i g e r a t o r , w h ile th e
t h i r d was in o c u la te d w ith te n drops o f c u ltu r e and in c u b a te d a t 72 F
f o r s ix h o u rs ,
Two j a r s o f cheese wore p u t in th e r e f r i g e r a t o r .
The
t h i r d j a r was ln o o u la to d w ith te n te a s p o o n fu ls o f c u ltu r e and in cu b ­
a te d a t 72 F f o r s ix h o u rs ,
At th e end o f t h i s tim e th e j a r s o f
cheese w ere combined w ith the cream .
Gne j a r c o n ta in in g u n tre a te d
curd and u n tr e a te d cream serv ed as a ch eck .
In th e second j a r ,
c u ltu r e d cheese was mixed w ith p la in cream .
The t h i r d j a r , c o n tain ed
p la in c h e e se , and c u ltu r e d cream .
A ll th ro e j a r s w ere h o ld over
n ig h t in th e r e f r i g e r a t o r and th e v o l a t i l e a c id d eterm in ed on a
250 gram sample o f onoh th e n e x t day.
and a f t e r cream ing.
The cheese was sc o re d b e fo re
The r e s u l t s o f f iv e t r i a l s a re shewn i n ta b le IX*
25
-a b le ' IT .
M l l l i l i t e r s o f 1T/lO ITaOH r e q u ire d to t i t r a t e one l i t e r
o f d i s t i l l a t e from cheese made by th e " lo n g tim e" m ethod.
The cheese was made w ith th r e e d i f f e r e n t c u ltu r e s and
T dth c i t r i c a c id added to tiie sldLm m ilk .
T r ia l : F la v o r o f : P e rc e n t o f : ml N/10 HaOH
Y la v o r : F la v o r o f
Ho.
th e c u l­
c i t r i c a c id
r e q u ire d f o r
sc o re
th e choose
tu r e
added
cheese d i s t i l l ­ o f th o
a te
cheese
( v o l a t i l e a c id
ourd
num ber)
CULTUfiB A
v e ry good
0.008
fla t
11 .9
3 7 .5
v e ry good
0 .0 1
38
H i. I
good
38
good
0 .0 ?
good
16 »9
39
v e ry good
0.008
good
12. t r
38
v e ry good
0 .0 1
good
39
38
13.3
0 .0 1
v e ry good
good
15.8
3 0 .5
good
0.008
good
1 2 .5
3 8 .5
W
v e ry good
0 .0 1
good
14.6
3 8 .5
v e ry good
o .o ? ................
good
39
17.5
v e ry good
0.05
good
1 7 .4
3 9 .5
Iil
v e ry good
0.05
1 8 .1
good
3 9 .5
good
0 .0 5
18.3
good
39.
CULTURE B
v e ry good
0.000
15.2
good
3 3 .5
v e ry good
h2
0 .0 1
good
13.5
38
v e ry good
0 . 0?
good
10.5
39
good
0.008
11.7<
fla t
3 7 .5
good
0 .0 1
good
U5
14.9
3 0 .5
good
0 .0 ?
18.3
good
40
v e ry good
1 2 .1
0.008
good
38
v e ry good
0 .0 1
13.8
good
bh
3 8 .5
good
0 .0 ?
1 9 /)
good
40
v e ry good
0 .0 5
good
15/ '
39
good
0 .0 5
good
to
17 .1
39
good
0.05
good
16.5
3 8 .5
CULTURE C
good
0.008
9 .2
fla t
37
good
0 .0 1
to
fla t
36
7 .3
good
0 .0 ?
1 0 .1
fla t
3 7 .5
good
0.006
fla t
7 .1
35
good
0 .0 1
to
fla t
9 .1
3 6 .5
good
0 . 0?
fla t
9/
37
good
0.006
8 .1
f
la t
3 6 .5
good
to
0 .0 1
8 .6
f
l
at
3 7 .5
good
0 . 0?
f
l
a
t
0 .7
37
good
0.05
9 .2
f
l
a
t
3 6 .5
good
0.05
to
fla t
1 1 .4
3 7 .5
good
0.05
10.6
f
la t
3 6 .5
Table V I I I e
A com parison o f th e a c id numbers and f la v o r s c o re s c f th e cheese made by th e " s h o r t
tim e" a id th e " lo n e tim e" method when d i f f e r e n t p e rc e n ta g e s o f c i t r i c a c id w ere
added to th e cheese m ilk#
P e rc e n ta g e s o f c i t r i c a c id added to th e cheese d l k
0 .0 1
0.03
0.000
0.0 5
Method o f ;
m a n u fa c tu re :
C ul­
ture:
used
s h o r t tim e : V o la tile 10 .1 9 .9 10.8
lo n g ' Ine ;
,1 1 .9 12.0 12.8
A
B
C
:
:
:
:
:
:
:
:
:
s h o r t tin e
I n g tim e
a c id
s lio rt tim e
lo n g tim e
numbers
,
:
10J i 11.3 9 . 9 : 13.1 15.1 10. 6 : I ': . U 15.5 16.9
I ’4 .1 13.3 li i .6 : 16.9 15.6 1 7 .9 : I »k 18.1 13,C
,1 0 .5 1 1 .1 9 . 1; 1 1 .8 1 2 .0 1 0 .2 : I 3 .8 lU .2 I l * ? : I ? . I I5.I4 1 6 . 3
:1 3 .2 11.0 1 2 .1 : 13.5 lL . 1 3 .0 : 10.5 16.3 1 9 .6 : 15.6 I ? . I 16.9
8.1
9*2
7 .5
7 .1
6 .9 :
8 . 1:
9 . U 7 .9
7 .3 -2 i L
8 .2 : 7 .1
8 .6 : 10.1
:
s h o r t tim e : F la v o r
lo n g tim e :
: sc o re
s h o r t tim e :
lo n g tim e : o f th e
:33
:3 7 »5
:
:38
:3 8 .5
s h o r t tim e : cheoso
lo n g tim e : cu rd
:37
:37
37*5 38
38
3 8 .5
38
33
38
38
3 7 .5 : 33
3 8 .5 : 39
:
30
37 »5 33 38
3 7 .5 : 50
3 7 .5 38
38 3 8 .5 3 8 .5 : 39
:
3 6 .5 35
3 7 .5 3 6 .5 37 : 3 6 .5
35
3 6 .5 s 34
3 6 .5 3 7 .5 : 5 7 .5
9 .1
9 /3
0.5$ 10.8 12.1 9 .9
8 .7 : 9 .2 I l J j 10.6
:
38
3 7 .5 : 38
3 8 ,5 3 8 .5
3 8 .5 39 : 3 9 .5 3 9 .5 39 .5
38
kO
3 7 .5
40
3 3 .5 38
39
39
37
37
3 6 .5
37
37
37
3 6 .5
36 .5 3 7 .5 3 6 .5
3 8 .5
38 .5
27
Tablo IX .
T r ia l
No.
50
51
52
55
5k
C onparison o f th e m i l l i l i t e r s o f Ii/lO UaOH re q u ire d t o t i t ­
r a te one l i t e r o f cheese d i s t i l l a t e o b ta in e d b e fo re and
a f t e r th e cheeso was crooned in th r e e d i f f e r e n t w ays.
F la v o r
sc o re
b e fo re
cream­
in g
ml Ii/lO UaOH
re q u ire d to
t i t r a t e th e
cheeso d i s ­
t i l l a t e b e fo re
c roam ing
( v o l a t i l e a c id
number)
" W
bo
bo
57
57
57
57
57
58
58
58
38
SG
58
_____
..
.
19.6
19.6
19*6
9 .8
9 .8
9 .8
910
9*8
9 .8
"' i w
l Ju 3
1 4 . 5 ...........
1I4..5
14.5
L!4.5
Method o f “ ml H/lO
F la v o r
cream ing
re q u ire d sco re
to t i t ­
a fte r
(I) #
r a t e th e cream ­
cheeso
in g
d is till­
a te
a fte r
cream ing
A.
"W
19.7
B.
19.5
5 9 .5
C.
18.5
3 9 ,5
A.
57
9^9
B.
10.2
57
c.
10.8
5 7 .5
A.
9 .8
57
B*
57
9 .5
C.
11.2
5 7 .5
A.
lb .8 “
58
B.
58
3J|..5
C.
15^
5 8 .5
A.
58
15.9
B«
lb . I
58
C.
16.1
5 8 .5
VfA - p la in c h eeso —u n tr e a te d cream
B - p la in c h ee se — c u ltu r e d cream
C - c u ltu r e d c h eese—u n tr e a te d cream
F lav o r
o f th e
choose
good
b itte r
b itte r
good
good
good
good
good
m e ta llic
good
good
good
good
good
good
28
DISCUSSIOIT OF HSSULTS
IVhon 500 ml sam ples o f d i s t i l l e d w a te r and 2$0 grams sam ples
o f skim m ilk were steam d i s t i l l e d and t i t r a t e d , am all though q u ite
c o n s ta n t v o l a t i l e a c id numbers r e s u lte d ( t a b l e I ) .
The a c id v a lu e s
f o r d i s t i l l e d w a te r w ere p ro b a b ly due to two f a c t o r s :
( l ) th e pH
a t w hich th e p h e n o lp h ta le in in d ic a to r changes c o lo r , and ( 2 ) th e
m echanical c a rry o v e r o f a sm all amount o f s u l f u r i c a c id d u rin g th e
d is tilla tio n ,
P h e n o lp h ta le in changes c o lo r a t pH 8 .4 t o 10, and
th u s th e s o lu tio n would have to he s l i g h t l y on th e b a s ic s id e b e fo re
th e change would o c c u r.
However, t h i s would n o t acco u n t f o r a v ery
la r g e p o r tio n o f th e 1 ,9 ml re q u ire d to t i t r a t e a l i t e r o f w a te r
d is tilla te .
S ince th e d i s t i l l a t i o n a p p a ra tu s was n o t equipped w ith
a vapor t r a p , some o f th e a c id was p ro b a b ly m e c h a n ic a lly c a r r ie d
over in to th e d i s t i l l a t i o n f l a s k .
Thus m ost o f the base r e q u ire d to
t i t r a t e a w a te r sample r e a c te d to n e u t r a l i z e t h i s a c id ,
Tlie sm all
a d d itio n a l amount o f base re q u ire d to t i t r a t e a l i t e r o f skim
m ilk d i s t i l l a t e p ro b a b ly re a c te d w ith th e v o l a t i l e a c id s d i s t i l l e d
from th e skim m ilk ,
TIiese a c id v a lu e s sh o u ld be k e p t i n mind when
i n t e r p r e t i n g th e r e s u l t s o f th e a c id number o b ta in e d by d i s t i l l i n g
c u ltu r e s o r c o tta g e choose,
Tlie d i s t i l l a t i o n o f tw elve c u ltu r e s t e s t e d by th e c r e a t i n e t e s t
showed v a r ia tio n s o f th e amount o f v o l a t i l e a c id s in e oh c u ltu r e
( ta b le I I ) .
In g e n e r a l, th e v o l a t i l e a c id numbers o b ta in e d w ere in
d i r e c t r e l a t i o n to th e amount o f c i t r i c a c id added to th e c u l t u r e .
29
Tho c r e a tin e t e s t showed a d if f e r e n c e in th e dep th o f th e p in k band
o n ly between c u ltu r e s made w ith and w ith o u t added c i t r i c a c i d .
o u t added c i t r i c a c id , th e band was 2 mm deep in each c a s e .
W ith­
Regard­
l e s s o f th e amount o f c i t r i c a c id added, th e p in k band m easured 5 mm
i n a l l c a se s e x c e p t one.
H irh " v o l a t i l e a c id numbers" in th e c u ltu r e s d id n o t r e s u l t in
h ig h " v o l a t i l e numbers" in th e c o tta g e ohoeso made from them .
--'von
when c u ltu r e s w ith a v e ry good f la v o r which had h ig h " v o l a t i l e a c id
numbers" wore used to make th e c h e e se , th e co rre sp o n d in g ch eese had
a r e l a t i v e l y low " v o l a t i l e a c id number" ( t a b l e I I I ) .
The v a r ia tio n s
in th e " v o l a t i l e a c id numbers" o f th e cheeso d id n o t a g ree w ith th e
v a r i a t i o n s o f th e " v o l a t i l e a c id number" o f th e c u l t u r e s .
TIio f la v o r
o f th e cheese was c r i t i c i s e d as f l a t by an ex p erien c e d ch eese ju d g e.
P resum ably, th e w ashing o f th e curd r e s u l t e d in a lo s s o f v o l a t i l e
a c id .
I t i s re a so n a b le to e x p e c t t h a t some o f th e v o l a t i l e a c id s
w hich a re w a te r s o lu b le a re l o s t in th e l i q u i d d u rin g th e p ro c e ss
o f making th e c h e e se .
However, th e " v o l a t i l e a c id numbers" o f th e
cheeso made w ith a d d itio n o f w a te r and w ith o u t a d d itio n o f w a te r do
n o t show a s i g n i f i c a n t v a r i a t i o n ( t a b l e IV ).
The amount o f v o l a t i l e
a c id s n o t o n ly i n th e cheese b u t a ls o i n th e whey in c re a s e d when
c i t r i c a c id was added to th e cheese m ilk .
Tlie lo s s was s m a lle s t in
b o th c a se s when no c i t r i c a c id was added, and th e lo s s in c re a s e d when
a h ig h e r p e rc e n ta g e o f v o l a t i l e a c id s was p r e s e n t.
From th e " v o l a t i l e
30
a c id number" o b ta in e d from th e wash w a te r , i t i s in d ic a te d t h a t quick
w ashing does n o t cause f u r t h e r lo s s o f v o l a t i l e a c id s in th e c h e e se .
The " v o l a t i l e a c id number" in th e t h i r t y v a ts o f ch ee se made
w ith v a ry in g amounts o f added c i t r i c a c id show t h a t cheese made
w ith o u t any a d d itio n o f c i t r i c a c id was f l a t and la ck e d f l a v o r .
c o n ta in e d o n ly a sm all amount o f v o l a t i l e a c id s .
It
The a d d itio n o f
0 .0 0 2 , OeQOz1I., and 0.006 p e rc e n t o f c i t r i c a c id caused an in c re a s e
in th e " v o l a t i l e a c id number" o f th e c h e e s e , ( ta b le V ).
However,
t h i s in c r e a s e was a p p a r e n tly to o sm all to r e s u l t i n a good f la v o r
oh o ese, b ecause cheese made w ith th e s e amounts o f added c i t r i c a c id
s t i l l la ck e d f l a v o r .
A d e f i n i t e improvement in th e f la v o r was
observed w ith th e a d d itio n to cheese m ilk o f 0.008 t o 0 .0 5 p e rc e n t
o f c i t r i c a c id .
A d dition o f c i t r i c a c id t o th e cheoso m ilk beyond
th e s e amounts r e s u lte d in cheeso w ith a f l a t f l a v o r .
S ince th e optimum amount o f c i t r i c a c id ap p ears to l i e between
0.008 and 0 ,0 5 p e r c e n t, a d d itio n a l t e s t s w ere made o v er t h i s range
u s in g th r e e d i f f e r e n t c u ltu r e s ( ta b l e YI j .
The r e s u l t s show t h a t
b o th c u ltu r e A and B r e s u lte d in good f la v o r c h e e se .
r e s u l t s w ere o b ta in e d w ith c u ltu r e C,
and la c k e d f l a v o r .
U n s a tis f a c to r y
s in c e th e ch eeses w ere f l a t
C o n sid e rin g o n ly th e r e s u l t s o b ta in e d w ith c u ltu re
A and B, i t i s a p p a re n t t h a t w h ile th e " v o l a t i l e a c id numbers" were
p r o p o r tio n a l to the amount o f c i t r i c a c id added to th e m ilk , th e
f l a v o r s c o re s rem ained f a i r l y c o n s ta n t.
51
A d d itio n a l t r i a l s were made in making cheese by th e Mlo n g tim e"
method w ith th e sane th r e e c u ltu r e s b y adding c i t r i c a c id over th e
in d ic a te d optimum ra n g e .
Again c o n s id e rin g o n ly c u ltu r e A and B,
i t ap o a rs t h a t th e r e i s b u t l i t t l e d if f e r e n c e between e i t h e r th e
f l a v o r o r th e " v o l a t i l e a c id number" o f b a tc h e s made w ith d i f f e r e n t
p e rc e n ta g e s o f added c i t r i c a c i d ( t a b l e V I I ) .
Comparisons o f th e r e s u l t s o f the two methods ( t b io V I I I ) ,
a g a in e x c lu d in g c u ltu r e C, show t h a t in e v e ry case e x c e p t one th e
" v o l a t i l e a c id number" and th e f la v o r s c o re s were h ig h e r when th e
" lo n g tim e" method was u sed .
E xcept in t r i a l jjO w here a c u ltu r e p ro d u cin g a b i t t e r f la v o r
was e n c o u n te re d , c u ltu r in g th e cheese b e fo re cream ing ap p eared to
improve th e f la v o r o f th e r e s u l t i n g p ro d u c t ( t a b l e I X) .
T h is r e s u l t
was a ls o in d ic a te d by th e in c r e a s e in a c id number o f th e b a tc h e s
t r e a t e d by t h i s m ethod.
In th e o th e r two m ethods, p la in cream ing
and cream ing w ith c u ltu r e d o r \am, th e f la v o r sco re o f th e cheese
rem ained th e same, and th e a c id number in c re a s e d o n ly v a ry s l i g h t l y
if at all.
. Il
32
SUMMARY AtID CONCLUSIONS
T h ir ty - f o u r t r i a l s , c o n s is tin g o f 80 v a ts o f c o tta g e c h e e se ,
were made by th e " s h o r t tim e" m ethod, and 12 t r i a l s , c o n s is tin g
o f 36 v a ts o f c o tta g e c h e e se , were made by th e "lo n g tim e" m ethod.
Some o f th e v a ts o f th e cheese were made w ith c u ltu r e to vh ic h
c i t r i c a c id was added to th e c u ltu r e m ilk b e fo re in o c u la tio n .
Some
o f th e v a ts w ere made w ith cheese m ilk to which c i t r i c a c id was
added b e fo re in o c u la tio n , and some were made w ith cheese m ilk to
w hich no c i t r i c a c i d was added.
The v o l a t i l e a c id s i n th e cheese w ere determ ined by th e steam
d i s t i l l a t i o n method and t i t r a t i o n made on th e f i r s t l i t e r o f d i s t i l l a t e d c o lle c te d from th e c o n d en se r.
The l i t e r o f d i s t i l l a t e was
t i t r a t e d a g a in s t N/1 0 MaOH u sin g p h e n o lp h ta le in as a n i n d i c a t o r and
th e number o f m i l l i l i t e r s o f a l k a l i re q u ire d was d e sig n a te d a s th e
" v o l a t i l e a c i d num ber",
TIie " v o l a t i l e a c id numbers" o f th e c u ltu r e s made w ith th e
a d d itio n o f c i t r i c a c id t o th e c u ltu r e m ilk were g e n e r a lly h ig h e r
th a n th e c u ltu r e s made w ith m ilk to which no c i t r i c a c id was added.
High " v o l a t i l e a c id numbers" in th e c u ltu r e s d id n o t r e s u l t in
h ig h " v o l a t i l e a c id numbers" in th e cheese made w ith them .
V ats o f cheese made by th e a d d itio n o f 126 F w a te r b e fo re h e a tin g
began d id n o t r e s u l t in cheese w ith a h ig h e r " v o l a t i l e a c id number"
th a n th e v a ts t h a t were cooked w ith o u t th e a d d itio n o f w a te r .
33
Clieoso made b y a d d in g c i t r i c a c id t o t h e choose m ilk h ad a
b e t t e r f l a v o r th a n c h e e se made w ith m ilk t o w h ich no c i t r i c a c id was
added.
ih e a d d i t i o n o f fro m 0 .0 0 2 to 0 .0 0 6 p e r c e n t c i t r i c a c i d t o th e
c h e e se m ilk r e s u l t e d i n an in c r e a s e i n " v o l a t i l e a c id n u m b er," b u t
th e in c r e a s e d am ount d id n o t seem t o be s u f f i c i e n t t o r e s u l t i n an
im proved f l a v o r .
The a d d i t i o n o f 0 .0 0 8 t o 0 .0 5 p e r c e n t o f c i t r i c a c i d to th e
c h e e so m ilk b e f o r e in o c u l a t i o n in c r e a s e d th e " v o l a t i l e a c i d number"
and a l s o im proved th e f l a v o r o f th e r e s u l t i n g c h e e s e .
H ig h e r
p e r c e n ta g e s o f c i t r i c a c id d id n o t seem to g iv e s a t i s f a c t o r y r e s u l t s .
The " v o l a t i l e a c i d number" o f th e ch e e so was somewhat h ig h e r
when th e c h e e se was made b y th e " lo n g tim e" m eth o d .
The f l a v o r
s c o re o f th e c h e e se a l s o seemed t o be a l i t t l e h ig h e r .
T hree d i f f e r e n t ways o f cream in g w ere u s e d i n o r d e r t o d e t e r ­
m ine w h e th e r o r n o t th e f l a v o r o f th e c h e e se c o u ld bo im proved w ith
c re a m in g .
C heese in o c u la te d w ith c u l t u r e and in c u b a te d f o r s i x h o u rs
b e f o r e cream in g showed an im provem ent i n t h e f l a v o r .
C u lt u r in g and
in c u b a tin g cream b e f o r e m ix in g i t w ith th e ch e e so and c rea m in g th e
c h e e s e w ith p l a i n cream w ith o u t any tr e a tm e n t d id n o t r e s u l t i n any
im provem ent i n t h e f l a v o r s c o r e s .
35
ACmOiJLED CEMENT
Tlae a u th o r w is h e s t o e x p r e s s h e r a p p r e c i a t i o n to th e C h em istry
D ep artm en t o f M ontana S t a t e C o lle g e f o r p r o v id in g th e n e c e s s a r y e q u ip ­
m e n t, and t o t h e D a iry I n d u s t r y D ep artm en t f o r p r o v id in g th e m a t e r i a l
u s e d t o p ro c u re th e d a ta u sed in t h i s t h e s i s .
The a u th o r a l s o
s i n c e r e l y a p p r e c i a t e s th e g u id a n ce and a d v ic e g iv en by D r. John A.
N elso n i n p r e p a r a t i o n o f th e t h e s i s , and t o M rs. Kay R o b e r ts , Mr.
John H, N e ls o n , J r . , and M iss M a rg a re t A n ack er f o r t h e i r c r i t i c i s m
and a d v ic e i n E n g lis h i n p r e p a r i n g th e t h e s i s .
36
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