Studies on the Flavor of Creamed Cottage Cheese1

S T U D I E S ON T H E F L A V O R O F C R E A M E D C O T T A G E C H E E S E ~ D. W. MATHER 2 AND F. J. BABEL Dairy Department, Purdue University, Lafayette, Indiana SUMMARY The biaeetyl contents of 41 samples of commercial creanled cottage cheese, obtained from retail stores, varied from 0 to 3.2 p.p.m.; 73.1% of samples contained less than 1.0 p.p.m, and 95.1% contained less than 2.0 p.p.m. When cottage cheese is manufactured by the long-set method, the maxinmm amount of biacetyl capable of being produced by a lactic culture is not attained at the time of cutting the curd (pit 4.7). During cottage cheese manufacture there is a partition of the milk constituents and flavor compounds. The whey fraction contains considerably more citric acid, lactose, biacetyl, and acetyhnethylcarbinol than the curd. However, a proportionate amount of the biacetyl present at the time of cutting is retained by the cheese and the use of a culture producing considerable biaeetyl results in cheese with a correspondingly higher biacetyl content. The addition of citric acid to a creaming mixture for cottage cheese did not result in an increased biacetyl content when the cheese was held at 45 ° F. The addition of both citric acid and lactic culture to a creaming mixture for cottage cheese increased the biacetyl content when the holding temperature was 45 ° F., but a sour flavor was evident after several days' storage.

The d a i r y i n d u s t r y is s t r i v i n g c o n s t a n t l y to m a n u f a c t u r e u n i f o r m d a i r y products. The f a c t o r s which m u s t be considered i n j u d g i n g u n i f o r m i t y v a r y somewhat a m o n g the different d a i r y p r o d u c t s . W i t h most p r o d u c t s , flavor, composition, a n d p h y s i c a l c h a r a c t e r i s t i c s are i m p o r t a n t considerations. M u c h progress has been a t t a i n e d in the m a n u f a c t u r e of c r e a m e d cottage cheese with u n i f o r m composition a n d p h y s i c a l characteristics. Less progress has been m a d e i n s t a n d a r d i z i n g the flavor. This is i n d i c a t e d r a t h e r c l e a r l y b y the d a t a i n Table 1, which show the b i a e e t y l c o n t e n t s of 41 samples of creamed cottage cheese o b t a i n e d f r o m r e t a i l stores. S i m i l a r data have been r e p o r t e d b y other investigators (5, 9). TABLE 1 Biacety! contents of 41 samples of creamed cottage cheese Biaeetyl content

No. o2 samples

(p.p.m.) 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

Biacetyl content

No. of samples

(p.p.m.) 2 2 9 3 4 5 1 2 1

0.9 1.1 1.2 1.3 1.4 1.9 2.6 3.2

1 1 2 3 1 2 1 1

Received for publication January 19, 1959. 1Published with the approval of the Director of the Purdue Agricultural Experiment Station as Journal Series Paper No. 1387. Portion of a thesis prepared by the senior author in partial fulfillment of the requirements for the degree of Doctor of Philosophy. Present address: Breakstone Foods, Inc., Walton, New York. 809

8]0

D.W.

M A T H E R AND F. J. B A B E L

I t is recognized that biacetyl is not the only flavor contributor to creamed cottage cheese but that it is an i m p o r t a n t one (5, 6, 9). The studies reported here were designed to provide information on various factors which influence the biacetyl content of creamed cottage cheese. METHODS

Biacetgl a~d acetglmethglcarbbwl. The colorimetric method of Prill and H a m m e r (8) was used for the estimation of biaeetyl and acetyhnethylcarbinol in cultures and cottage cheese. Color intensity was measured with a Beckman spectrophotometer (Model B) at a wave length of 530 m~. Dimethylglyoximate was used in constructing the standard curve. Citric acid. The chromatographic method of Bulen el al (1), as modified by F r a z e u r (2), was used for the estimation of citric acid. Lactose. The method of P e r r y and Doan (7) was used to determine lactose in milk, culture, whey, and cottage cheese. Color intensity was measured with a Beckman spectrophotometer (Model B) at a wave length of 520 m~. Volatile acids. A 50-g. sample of product was steam-distilled after the addition of 3 ml. of 1 N sulfuric acid. The first 100 ml. of distillate was titrated with 0.1 N sodimn hydroxide, using phenolphthalcin as indicator. Manufacture of cottage cheese. Cottage cheese was made according to the long-set method outlined by Hales (3). When creamed, a 12% fat creaming m i x t u r e was added at the rate of one p a r t creaming mixture to two parts cheese. The creamed cheese was salted at the rate of 1%.. RESULTS

Ferme~tatio~l prod~cts for~ed by lactic c~d!~tres i~ skimmilk at 70 ° F. Lactic cultures grown in skimmilk produce several compounds which have an effect on flavor. The rates of formation of lactic acid, biacetyl, and volatile acids, all of which influence flavor, are shown in Table 2. The amounts of lactose and citric acid fermented, as well as the amount of acety]methylcarbinol formed, are given also. Rate of acid production is shown b y titratable acidity and p H determinations. A decrease in lactose occurred as the titratablc acidity increased and p H decreased, but even a f t e r 24 hr. of incubation considerable lactose was still present. Biacetyl increased very little during incubation for 10 hr., but for the next 6 hr. appreciable amounts were formed. Acetyhuethylcarbinol increased throughout the incubation period; however, large increases were evident only a f t e r 8 hr. of incubation. Volatile acids also accumulated t h r o u g h o u t the incubation period and large increases were noted a f t e r 10 hr. of incubation. The citric acid content decreased throughout the incubation period and only 0.02% remained a f t e r 24 hr. Partition of citric acid, lactose, biacetgl, a~td acetylmethylcarbinol during the manufacture of cottage cheese. The data presented in Table 3 indicate how certain milk constituents and fermentation products are partitioned between the curd and whey. Two trials are included, one with a culture which produced considerable biacetyl, and the o~her with a culture which produced only a small

FLAVOR OF COTTAGE CHEESE

811

TABLE 2 Fermentation products formed by a lactic culture in skimmilk at 70 ° F. Incu bation time

Titratable acid

(hr.)

(%)

0 1 2 3 5 6 7 8 9 10 12 13 14 15 16 24

0.18 0.18 0.19 0.19 0.22 0.26 0.30 0.35 0.44 0.52 0.68

0.77 0.82 0.84 0.89 0.97

pit

Lactose

Biaeetyl

Aeetylmethylcarbinol

(%)

(p.p.m.)

(p,p.m.)

5.3 5.3 5.3 5.3 5.3 5.1 5.2 5.1 5.1 5.0 4.9 4.5 4.5 4.5 4.5 4.4

0.2

6.44 6.42 6.38 6.29 6.27 6.10 5.81 5.55 5.37 5.15 4.83 4.69 4.59 4.58 4.56 4.44

0.2 0.1 0.1 0.2 0.1 0.3 0.4 0.3 0.5 1.1 1.5 2.1 2.3 2.8 2.5

Volatile acid

Citric aeid

(ml. 0.1 N NaOH)

(%)

1.0 1.2 1.5 1.7 1.8 1.9 2.7 3.0

0.18 0.20 0.25 0.27 0.37 0.39 0.52 0.55

7.1

0.63

13.1 30.1 42.9 57.9 89.7 97.2 103.5

0.70 1.20 1.47 1.72 2.12 2.73 3.52

0.14 0.13 0.12 ...... 0.11 0.09 0.09 0.08 0.05 0.02

a m o u n t . I n b o t h lots, n m c h of t h e c i t r i c a c i d was f e r m e n t e d p r i o r to c u t t i n g t h e coagulum. The remaining citric acid was removed largely with the whey. In L o t 1, 1 5 . 1 % of t h e l a c t o s e w a s f e r m e n t e d p r i o r to c u t t i n g , a n d 9 . 5 % i n L o t 2. A l t h o u g h m o s t of t h e l a c t o s e w a s c o n t a i n e d in t h e w h e y f r a c t i o n , a c o n s i d e r a b l e p o r t i o n was p r e s e n t in t h e w a s h e d a n d d r a i n e d c u r d . T h e b i a c e t y l c o n t e n t of t h e e o a g u l u m j u s t p r i o r to c u t t i n g , a n d of t h e w h e y , w e r e p r a c t i c a l l y i d e n t i c a l , i n d i c a t i n g t h a t b i a c e t y l f o r m e d b y t h e f e r m e n t a t i o n of c i t r i c a c i d w a s r e m o v e d l a r g e l y b y t h e w h e y f r a c t i o n . T h e c u r d c o n t a i n e d less t h a n o n e - h a l f t h e p e r c e n t a g e of b i a c e t y l c o n t a i n e d i n t h e w h e y . P a r t i t i o n of a c e t y l m e t h y l c a r b i n o l f o l l o w e d t h e s a m e g e n e r a l t r e n d as b i a c e t y l .

E f f e c t of addition of citric acid to creamed cottage cheese on the biacetyl content. S i n c e b i a c e t y l is f o r m e d b y f e r m e n t a t i o n o f c i t r i c a c i d in m i l k b y l a c t i c c u l t u r e s , a n e x p e r i m e n t was c o n d u c t e d to d e t e r m i n e t h e effect of a d d i t i o n of c i t r i c a c i d to c r e a m e d c o t t a g e c h e e s e on t h e b i a c e t y l c o n t e n t . A b a t c h of c o t t a g e cheese w a s d i v i d e d i n t o t h r e e l o t s a m ! t r e a t e d as f o l l o w s : L o t 1, n o t r e a t m e n t ; TABLE 3 Partition of citric acid, lactose, biacetyl, and acetyhnethslcarbinol during the manufacture of cottage cheese Citric acid

Lactose

(%) Product

(%)

(p.p.m.)

Lot 1

Lot 2

Lot ]

Lot 2

Skimmilk

0.13

0.14

5.3

5.3

Coagulum prior to cutting Whey Washed cm'd Thoroughly drained curd

0.55 0.08 0.01 0.01

0.08 0.09 0.04 0.04

4:5 4.7 1.8 1.7

4:8 4.9 2.0 2.0

Culture

Biacetyl Lot 1 Lot 2

Acet?qmethylcarbinol

(p.p.m.) Lot 1

Lot 2 82.4 30.1

.;:8

0:6

9~:S

2.3 2.3 1.0 1.0

1.1 1.2 0.5 0.6

55.7

52.7

22.8

29.0 24.2

19.0 16.2

S]~

D . W . MATH]~R AND F. J. BABEL

Lot 2, one part by weight of creaming mixture containing 12% fat was added to two parts cottage cheese; Lot 3, treated the same as Lot 2 except that 0.15% citric acid was added. The citric acid was added as a 15% solution. Samples of each lot were stored at 45 ° F. and analyzed at intervals for biacetyl, aeetylmethylearbinol, and pH. Results of these analyses are given in Table 4. TABLE 4 Effect of addition of citric acid to creamed cottage cheese on the biacetyl content Lot I C o t t a g e cheese AcetylD a y s held methylat 45 ° :F. ]Biacetyl carbinol

Lot 2 C r e a m e d c o t t a g e cheese

pit

(p.p.m.) (p.p.m.) 0 2 4 6 8~ 13 ~

1.4 1.5 1.4 1.5 1.4 1.2

16.4 16.5 15.6 18.1 17.8 5.6

AeetylmethylB i a c e t y l carbinol

pH

(p.p.m.) (p.p.m.) 4.57 4.69 4.64 4.65 4.65 4.79

1.2 1.2 0.9 1.2 1.2 0.9

6.2 12.0 9.1 11.0 10.0 5.7

Lot 3 C r e a m e d c o t t a g e cheese plus citric acid AeetylmethylB i a c e t y l carbinol

pH

(p.p.m.) (p.p.m.) 4.88 4.91 4.9l 4.93 4.85 4.88

1.0 1.1 1.0 1.0 1.2 0.8

4.6 12.1 13.4 13.8 21.2 12.8

4.65 4.71 4.69 4.70 4.79 4.69

L o t 2, slightly sour ; L o t 3, sour. b All lots spoiled.

Lot 1 remained quite constant in biaeetyl content throughout the 13-day holding period. Only small fluctuations were noted in the aeetylmethylcarbinol content for eight days, but a large decrease occurred at 13 days. The p H increased from 4.57 to 4.79 during the holding period. Lot 2 also remained quite constant in biacetyl, but the aeetyhnethylearbinol content fluctuated. An increase in carbinol was evident after two days and a large decrease at 13 days. The p H at 0 and 13 d a y s ' storage was identical. Lot 3, with added citric acid, remained constant in biacetyl content for eight days and then decreased. The carbinol content increased for eight days and then a large decrease was apparent. The p i t showed only slight variations.

Effect of addition of citric acid a~d lactic culture to creamed cottage cheese on the biacetyl content. The failure to obtain a large increase in biacetyl when citric acid was added to creamed cottage cheese suggested the lack of a sufficient number of organisms capable of fermenting the acid. Therefore, an experiment was conducted to study the effect of additions of citric acid and lactic culture. The culture selected produced considerable biacetyl in cultured buttermilk. The data obtained in this experiment are given in Table 5. Lots 1, 2, and 3 were prepared in the same manner as in the previous experiment. Lot 4 was similar to Lot 3, except that the creaming mixture contained 2 ~ lactic culture. All lots were held at 45 ° F. and analyzed for biacetyl, acetylmethylcarbinol, and p H at various intervals. The cottage cheese used in the preparation of these lots contained an appreciable amount of biacetyl and when held uncreamed (Lot 1) it maintained approximately the same biaeetyl content. The acetylmethylearbinol content increased slightly for six days and then decreased to its approximate original

TABLE 5 Bincetyl content of cottage cheese, creamed cottage cheese, creamed cottage cheese p l u s citric acid, ttlld creamed cottage cheese p]us citric acid and lactic culture D,~ys held at 4 5 ° F . 0

2

Tr(mtmcnt

4

6

9

0

2

4

6

:Biacctyl

Acctylmethylcarbinol

(p.p.m,)

(p.p.m.)

9

0

2

4

(;

9

pl I

1,ot I. Cott;~gc cheese

1.3

1.5

1.5

1.4

1.4

6.9

7.6

]0.l

10.4

6.4

4.77

4.80

4.76

4.75

4.89

:Lot 2. (~t'e:lmed cott~lge chce,~e

1.0

1.0

] .1

] .0

] ,0

6.6

8.3

5.4

7.(;

11.6

5.10

5.08

5.14

5. I (~

5.14

Creamed cott~lgc cheese [)Ills citric ~Lcid

:1.0

1.0

] .0

0.8

0.8

6.6

7.0

7.3

6.2

5.7

4.7(;

4.80

4.~:~

4.~:~

4.~:,'

1,or 4. Crc~mcd cott:,gc chccsc I)lUs citric acid :lnd b~ctic culture a

0.8

1.8

3. l

2.9

2.2

9.0

27.6

82.4

78. l

34.8

4.80

4.68

4.43

4.50

4.46

I ,or ;4.

" I , o t 4 sour :it f o u r d a y s ; I n d t h e r e a f t e r .

814

D. w . M A T H E I ~ A N D F. J . B A B E L

value at nine days. The p H remained quite constant for six days, with a definite increase being noted at nine days. The addition of cream to cottage cheese (Lot 2) decreased the biacetyl content by about one-third, the extent of dilution by the creaming mixture. Slight variations were found in the carbinol content, the most important being an increase at nine days. No apparent change occurred in pH. The addition of citric acid to the creaming mixture (Lot 3) did not give an increase in biaeetyl or carbinol, but it did decrease the p H by about 0.3 unit. Addition of both citric acid and lactic culture to the creaming mixture (Lot 4) resulted in an increase in biacetyl which reached a maximum in four days, then decreased. The earbinol content showed exactly the same trend as the biacetyl content. The p H decreased after holding for four days and a sour flavor was noted at this time. DISCUSSION

The flavor imparted by biacetyl to dairy products such as butter, cultured buttermilk, cultured sour cream, and various cheeses is considered desirable. However, the biacetyl content of dairy products has not been well standardized and this is particularly true of cottage cheese. The data in Table 1 confirm this statement and show a range of 0 to 3.2 p.p.m, biacetyl in retail samples of cottage cheese. A biaeetyl content of about 2 p.p.m, gives a pleasing flavor and seems to mask a sour f a v o r sometimes associated with cottage cheese. Although considerable research has been conducted on the chemical conspounds produced by lactic cultures growing in milk (4), the literature does not contain a complete analysis showing the amounts of lactose and citric acid fermented and changes in pH, titratable acidity, biacetyl, aeetylmethylcarbinol, and volatile acids as a result of these fermentations. Such an analysis is presented in Table 2. The first stage of cottage cheese nlanufaeture by the long-set method is quite similar to the manufacture of cultured butternfilk, since with both products heated skimmilk is inoculated x¥ith lactic culture and incubated at 70 ° F. The data presented in Table 2 were intended to show that with cultured buttermilk ripened to 0.80 to 0.85% titratable acidity, considerably more of the flavor compounds (biacetyl, volatile acids, etc.) are produced than at the cutting tinle for cottage cheese ( p H 4.7). Also, with cottage cheese there is a partition of the fermentation products and other milk constituents between the curd and whey. Such a partition does not occur in the manufacture of cultured buttermilk. The biacetyl content of the coagulum prior to cutting has an influence on the bia eetyl content of cottage cheese. A proportionate amount of the biaeetyl in the coagulum is retained by the cheese. This is shown by the data in Table 3, which were obtained by cultures having different capacities to produce biaeetyl. The fermentation of citric acid during setting of the cheese, and the loss of most of the remaining citric acid in the whey, result in cottage cheese having only a small amount of the compound from which to form additional flavor materials. Numerous studies (4) have indicated that citric acid is the source of biaeetyl. The biaeetyl content of cottage cheese held at 45 ° F. remains quite constant for several days. When creamed, the biaeetyl content also remains quite con-

FLAVOR OF COTTAGE CHEESE

815

stant, but it is decreased in proportion to the dilution with cream. The citric acid or citrates contained in the creaming mixture, as well as citric acid added to such a mixture, were not fermented to yield additional biacetyl. Failure to obtain an increase in biacetyl m a y be due to too high a p i t , small numbers of citric a c i d - f e r m e n t i n g organisms, failure of the organisms contained in the curd particles to reach the substrate, an unfavorable temperature, a n d / o r perhaps other factors. The addition of lactic culture to a creaming mixture containing added citric acid (Table 5) increased the biacetyl content of creamed cottage cheese. The increase f r o m an initial content of 0.8 p.p.m, to 3.1 p.p.m, in four days had a definite effect on flavor. However, the lactic culture also produced sufficient lactic acid d u r i n g the holding period to give the cheese a sour flavor. P e r h a p s a louver holding t e m p e r a t u r e would have decreased the amount of lactic acid produced, but 45 ° F. is a eommon holding t e m p e r a t u r e for cottage cheese in retail stores and in the home. REFEREN('ES (1) BL~LEN, W. A., VARI':ER, g. E., AND BUP,RELL, R. C. Separation of Organic Acids from Plant Tissues. Anal. Chem., 24: 187. 1959. (2) Fm'~zErJa, D. R. A 3~[ethod for the DetermiI~ation of Citric and Lactic Acids in Dairy Products. J. Dairy Sci, 41: 703. 1958. (3) tt_x~s, M. W. Sweet Cm'd Cottage Cheese. 3rd ed. Chr. H a n s e n ' s Laboratory, Inc., MiD waukee. 1957. (4) I-IA.~IMER,B. W., AND BABEL, F. J. Bacteriology of Butter Cultures: A Review. J. Dairy Sci., 26: 83. 1943. (5) ~-~EREI3f,A. T. :Flavor Production in Cottsge Cheese by 3Iicroorganisms. M.S. thesis, Purdue University. 1949. (6) PARKER, ]:~. B., AND ELLIKER, P. R. Effect of Spoilage Bacteria on Biacetyl Content and Flavor of Cottage Cheese. J. Dairy Sci., 36: 843. 1953. (7) PERRY, N. A., _~NDDOAN, F. J. A Picric Acid Method for the Simultaamous Determination of Lactose and Sucrose in Dairy Products. J. Dairy Sci., 33: 176. ]950. (~8) 1:)RILL, E. A., AND HAM~IER, B. W. A Colorimetric Method for the Mierodetermination of Biacety]. Iowa State Coll. J. Sci., 12: 385. 1938. (9) W_~LES, C. S., ~X~DH:~-~tO.~, L. G. Changes in the Biaeetyl Content of Creamed Cottage Cheese Caused by Organisms Associated with Spoilage. Food l~esearch, 22: 170. 1957.