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Effect of Sodium Hexametaphosphate on Cottage Cheese Yields1
Effect of Sodium Hexametaphosphate on Cottage Cheese Yields 1
S. T. D Y B I N G , J. G. PARSONS, J. H. M A R T I N , 2 and K. R. SPURGEON Dairy Science Department
South Dakota State UniVersity Brookings 57007
ABSTRACT
INTRODUCTION
Sodium hexametaphosphate, a polyelectrolyte capable of precipitating whey proteins, was added to milk manufactured into cottage cheese to determine its effect upon yield and composition. Fresh skim milk, fortified with nonfat dry milk to 9% solids, was vat pasteurized and divided between two 200-liter vats. One vat served as a control and the other received either .05 or .2%, by weight, sodium hexametaphosphate prior to being made into cottage cheese by the short set culture procedure. Addition of .05% sodium hexametaphosphate to milk subsequently manufactured into cottage cheese increased yield of curd by .77% when yield was measured as kilogram 20% solids curd recovered per 100 kg milk and by 1.51% when measured as percent recovery of milk solids. The addition of .2% sodium hexametaphosphate to milk subsequently manufactured into cottage cheese increased yield of curd by 1.25% when yield was measured as kilogram of 20% solids curd recovered per 100 kg milk, by .12 kg of 20% solids curd recovered per kilogram milk solids, and by 2.45% when measured as percent recovery of milk solids. The increase in yield for both .05 and .2% added sodium hexametaphosphate was not shown to be increased recovery of whey proteins.
Major concerns of cottage cheese production are low yields and high whey disposal costs (13), an interesting situation as the protein in whey contributing to disposal cost could increase yield. The dissolved proteins in whey are mainly a-lactalbumin and 3-1actoglobulin. Because these proteins remain soluble during cottage cheese manufacture, they are lost and removed as part of the whey (13). Polyelectrolyres, such as carboxymethyl cellulose (CMC) and sodium hexametaphosphate (SHMP), can precipitate whey proteins, allowing them to be recovered by centrifugation (3, 6, 7, 9, 10, 11, 22, 26). If the technique of recovering whey proteins could be combined with procedures of making cottage cheese, while product quality is maintained, then the former waste item could become a profitable asset. The objective of this study was to explore the possibility that the polyelectrolyte, sodium hexametaphosphate, may increase the yield of cottage cheese. Therefore, yields and composition of cottage cheese made by a widely accepted culture procedure (23) were compared with the yield and composition of cottage cheese made from milk containing .05 or .2% sodium hexametaphosphate. MATERIALS AND METHODS Experimental Procedure
Received April 6, 1981. Published with the approval of the Director of the South Dakota Agriculture Experiment Station as Publication No. 1746 of the Journal series. 2Dairy Science Department, Clemson University, Clemson, SC 29631. 1982 J Dairy Sci 65:544--551
Fresh skim milk from the South Dakota State University Dairy Products Laboratory was transferred to a pasteurizing vat and heated to 43.3°C. Nonfat dry milk was added via a powder funnel to increase the solids-not-fat by .5% (wt/wt). The skim milk subsequently was vat pasteurized at 63°C for 30 min followed by immediate cooling to 4°C by a plate cooler. Finally, the skim milk was transferred into sani-
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HEXAMETAPHOSPHATE AND COTTAGE CHEESE YIELDS tized 37.8-liter milk cans and stored overnight at 3°C. The manufacture of the cottage cheese was initiated by splitting the processed skim milk equally between two sanitized 200 liter vats, with 141.75 kg in each (Figure 1). The temperature of the milk in both vats was raised to 32.2°C. Starter culture prepared from commercially available strains of lactic acid producing bacteria (19) then was added at 5.2% (wt/wt) and mixed thoroughly with the skim milk. Fifteen minutes after addition of the culture, 1 to 2 liters of milk were removed from the vat that was to receive the SHMP (Polyphos ®, Olin Chemicals, 120 Long Ridge Road, Stanford, CT 06904) and transferred to a sanitized stainless steel beaker containing the proper a m o u n t of previously weighed SHMP (either .05 or .2% of the weight of milk). The SHMP was stirred into the milk until it was completely dissolved. This solution then was returned to the vat and mixed thoroughly into the milk. Coagulator, consisting of 1 ml cottage cheese coagulator (Angevine-Funke, Inc., 3380 Tree Ct. Industrial Blvd., St. Louis, MO 63122) diluted to 20 ml with water was added to each vat 30 rain after it had received starter. When the pH of the coagulum dropped to 4.7 (TA .49
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to .51) the curd was cut with sanitized .64-cm knives. The curd then was allowed to sit undisturbed for 15 to 20 min to heal. The curd was then cooked. The temperature of the vat was increased by the following specific temperature intervals during 15 min periods: 2.8°C in the 1st 15 rain, 6.7°C for the 2nd 15 min, 5.6°C during the 3rd 15 min, and 6.7°C per 15 min to a final temperature of 54°C at the completion of cooking. Upon completion of cooking the curds Were held in the hot whey approximately 20 min. Before draining, the curd was allowed to sit unstirred for the last 5 min to allow the fines to settle. The whey was drained to the level of the curd and 76 liters of wash water added to the vat (4). The wash water was prepared previously by acidifying water to pH 5 with phosphoric acid, adding chlorine to 10 ppm and plate cooling the water to 4°C. The curd was allowed to remain 15 to 20 rain in the wash water, then the water was drained to the level of the curd, and a second wash of 114 liters wash water added. After 15 to 20 min the water was drained, and the curd was ditched for at least 30 min, and then mixed, sampled, and transferred to l l.4-1iter containers and weighed for yield determination. Samples of curd were frozen for later analyses. Sample Collection
FRESH SKIM MILK
l
FORTI F ICATION
l
PASTEURIZATION
BULK STARTER
Milk for cottage cheese making was sampled in duplicate. Whey and wash waters were collected in a tared 37.8 liter milk can, weighed, and thoroughly mixed. One sample of each whey and wash water was collected for determination of curd fines, and two additional whey samples were taken for compositional analysis. The curd was mixed thoroughly after draining, and duplicate representative samples were taken. All samples were stored in 532-ml Whirl-Pak plastic bags. Composition Analysis
IC ONTROL l
SODIUM H EX AMETAPHOSPHATE
SHORT SET COTTAGE CHEESE PROCESS Figure 1. Flow diagram of cottage cheese manufacturing process in 200-liter cheese vats.
Procedures were identical for determination of total solids, fat, solids-not-fat, lactose, ash, phosphorus, and calcium in milk, curd, and whey samples. Determination of total solids was by the Mojonnier m e t h o d as described by A t h e r t o n and Newlander (2). F a t analysis was by the Association of Official Analytical Chemists (AOAC) Roese-Gottlieb m e t h o d ( 1 ) w i t h solids-not-fat calculated as the difference beJournal of Dairy Science Vol. 65, No. 4, 1982
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DYBING ET AL.
tween the total solids and fat. Protein c o n t e n t of the curd was determined by Mickelsen's procedure (15) of blending 25 g of curd with 75 g of .05 M sodium hydroxide prior to analysis. The AOAC Kjeldahl procedure (1) then was used to determine the nitrogen (protein) and the Rowland procedure (18) to fractionate the milk. The ash content was determined by the AOAC official method (1). Lactose was determined as the difference between the solids-not-fat and the sum of the total of protein and ash. The samples for mineral analyses were prepared by dry ashing, then dissolved in 2 ml concentrated ( 3 7 % ) h y d r o chloric acid, and diluted to 100 ml with distilled water. Phosphorus was determined by a colorimetric procedure (16). Calcium was determined by atomic absorption spectrophotometry of the sample prepared in the same manner as for the phosphorus determination. Quantification of the curd lost as fines was determined by Satterness's modification (19) of Rabb's procedure (17). Expression of Yield
Yields were expressed as kilogram 20% solids curd per 100 kg milk, kilogram 20% solids curd per kilogram milk solids, and percent recovery of milk solids in the curd.
Statistical Analysis
Statistical analysis of the data utilized the least squares analysis of variance of a two factor (added SHMP and replication) design experiment. The main effect of added SHMP was tested by the interaction of SHMP and replication (20). R ESU LTS AN D D ISCUSSION Cheese Milk Composition
The potential yield of cottage cheese is related directly to the composition of the starting milk, particularly to the quantity of casein. The composition of the milk used in this study is given in Table 1. The total solids content of the skim milks was higher than expected for skim milk. Although normally the total solids content of skim milk is 9.5% (8, 19), the milk used for level 1 skim milk, .05% SHMP and control, had a total solids content of 10.33%. The total solids for level 2 skim milk, .2% SHMP and control, was also high at 10.26%. The high total solids was due to the high fat content of the milk used, 1.17 and 1.26% fat, respectively, for the .05 and .2% SHMP skim milks versus the target fat content of .1%. Inefficiency of the separator in re-
TABLE 1. Composition of skim milk in manufacture of cottage cheese,a Level 2c
Level i b Component
Mean
SD
Total solids Fat Solids-not-fat Total protein Casein protein Whey protein Lactose Ash
10.33 1.17 9.16 2.81 2.28 .54 5.62 .73
.51 .27 .44 .18 .17 .04 .31 .02
88.98 106.46
13.15 17.77
Mean
SD
10.26 1.26 8.99 2.91 2.36 .54 5.36 .73
.30 .32 .38 .09 .10 .03 .42 .01
92.08 114.50
6.67 13.99
(%)
(mg/100 ml) Phosphorus Calcium
aMeans of 8 replications. b.05% Sodium hexametaphosphate and control. c.2% Sodium hexametaphosphate and control. Journal of Dairy Science Vol. 65, No. 4, 1982
HEXAMETAPHOSPHATE AND COTTAGE CHEESE YIELDS moving fat from relatively small amounts of milk was responsible for this high fat content. Fortification of the skim milks with nonfat dry milk increased the solids-not-fat (SNF) to 9.16% for the .05% SHMP milk and 8.99% for the .2% SHMP skim milk, which was close to the target 9.00%. However, protein content of both skim milks was lower than the expected 3.5% total protein, 2.8% casein, and .7% whey protein (8). The .05% SHMP skim milk contained 2.81% total protein, 2.28% casein, and .54% whey protein, and the .2% SHMP skim milk contained 2.91% total protein, 2.36% casein protein, and .54% whey proteins. Lactose was higher for both experimental skim milks than has been reported: 5.62% for the .05% SHMP milk and 5.36% for the .02% SHMP skim milk versus the reported average 4.9% (8). The low protein content may have been from the summer milk when the protein content is usually the lowest (12). Another factor is that dairy animals are being selected and bred to produce offspring genetically capable of yielding larger quantities of milk which contains smaller percentages of protein. This is a problem currently facing milk processors (25). The increase in lactose may have been caused
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by fortifying the milk with nonfat dry milk, which is concentrated skim milk added to increase the protein in the milk and contains 52.3% lactose (8). The ash content of all milks was .73%, close to the expected .7% (8). Phosphorus and calcium in the experimental milks were within the range commonly reported. The phosphorus content of the .05% SHMP milk was 88.98 rag/100 ml and the .2% SHMP milk contained 92.08 mg/100 ml versus reports ranging from 90 to 112 mg/100 ml (8). The calcium content for the .05% SHMP was 102.46 mg/100 ml and 114.50 mg/100 ml for the .2% SHMP milk. Although reported averages are around 120 to 121 mg/100 ml, Feeley et al. (5) noted a wide variation of mineral quantities in milk. They found that milk contained calcium ranging from 101 to 137 mg/100 ml.
Curd Composition
Composition of cottage cheese curds is in Table 2. Composition of curds as a group differed from average cottage cheese curd composition. Total solids of cottage cheese curd is usually 21% (8). However, the mean total solids of curds in our study, 26.14, 25.36,
TABLE 2. Composition of curd resulting from the manufacture of cottage cheese with and without sodium hexametaphosphate (SHMP).a,b Level 1 Component
Level 2
Control
.05% SHMP
26.14 4.80 15.20 11.99 11.72 .28 2.73 .48
25.36 5.15 14.85 11.02 10.69 .33 3.04 .79* *
Control
.2% SHMP
24.59 5.27 14.73 12.82 12.48 .34 1.39 .52
24.88 4.33** 15.67"* 10.76" * 10.39"* .36 3.68 ** 1.24"*
150.86 66.81
381.01 ** 240.91"*
(%) Total solids Fat Solids-not-fat Total protein Casein protein Whey protein Lactose Ash
(mg/lO0 ml) Phosphorus
Calcium
163.94
70.16
235.05 * *
136.71"*
aAll curd components except total solids are calculated to a 20% total curd solids basis. bMeans of 8 replications2 **Treatment different from control, highly significant (P<.01). Journal of Dairy Science Vol. 65, No. 4, 1982
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DYBING ET AL.
24.59, and 24.88%, were high. The major factor contributing to this increase was the high fat content of the starting skim milk which resuited in high fat in cottage cheese curd. Level 1 cottage cheese curd, .05% SHMP and control, contained 5.15 and 4.80% fat, respectively, higher than the average cottage cheese curd fat content of .4% (8). Although total solids increased, the high curd fat caused protein to be below normal 16.9% (8). Significant differences (P<.01) between cottage cheese curds made from milk with and without SHMP at .05% were in ash, phosphorus, and calcium fractions. Treatment of milk with .05% SHMP with subsequent manufacture into cottage cheese produced a curd containing higher ash (by .31%), phosphorus (by 71.11 mg/100 ml), and calcium (by 66.55 mg/100 ml). Differences (P<.01) between .2% SHMP and its control cottage cheese were in fat, solidsnot-fat, total protein, casein, lactose, ash, phosphorus, and calcium fractions. The addition of .2% SHMP to milk subsequently made into cottage cheese produced a curd higher in solids-not-fat (by .94%), lactose (by 2.29%), ash (by .72%), phosphorus (by 230.15 mg/100 ml), and calcium (by 174.10 mg/100 ml), and lower in fat (by .94%), total protein (by 2.06%), and casein (by 2.09%). The decrease in total protein appears from the decrease in casein. The effect of SHMP upon cottage cheese was to produce a curd containing larger quantities of ash, phosphorus, calcium, and lactose. The greater the amount of SHMP added, the greater the increase of these curd components in the cottage cheese. However, with increasing addition of SHMP, the possibility increases that the curd would have lower percentages of casein and fat. The increase in ash agreed with findings of Mathur and Shahani (14), who noted an increase in ash content of whey protein concentrates prepared by precipitation with polyelectrolytes including SHMP. The increase in curd phosphorus and calcium has been reported by Wong et al. (24), who noted that adding SHMP to milk manufactured into cottage cheese increased the phosphorus and calcium, producing a nutritiously more desirable calcium to phosphorus ratio (1:1.5) compared to that of regular cottage cheese (1:3.4). Although the whey protein fractions Journal of Dairy Science Vol. 65, No. 4, 1982
were higher in the SHMP curds (.02 and .05%), these differences were not statistically significant (P> .05).
Whey Composition
Composition of whey is in Table 3. Whey contained higher percentages of total solids, fat, and lactose, and lower quantities of total proteins than reported in (13, 19). The average composition of cottage cheese (acid) whey is 6.5% total solids, .04% fat, .75% total protein, 4.9% lactose, .4% lactic acid, and .80% ash (13). However, our whey had compositional ranges of 6.68 to 6.98% total solids, .22 to .36% fat, .48 to .55% total protein, 5.24 to 5.41% lactose, and .66 to .73% ash. Whey originating from cottage cheese made with and without .05% SHMP, level 1, showed no significant differences (P>.05) between any of the components. However, whey originating from cottage cheese made with .2% SHMP contained significantly higher total solids, .3%, (P<.05) and fat, .13% (P<.01) than its control. The lower quantities of fat in .2% SHMP curd and the correspondingly larger amounts of fat in its whey indicated that addition of large amounts of SHMP may cause some loss of fat from cheese curd. However, because cottage cheese is normally made from skim milk, fat loss would not be a problem. The SHMP whey contained smaller quantities of whey protein (.03%), but the difference was not significant (P<.O5). Yield Lost as Curd Fines
The amount of curd lost in the whey as curd fines is in Table 4. The observed curd fine losses for all whey were lower than the fine losses of 1.55 kg 20% solids curd per 100 kg milk reported by Satterness et al. (19) for fortified skim milk manufactured into cottage cheese by the short set culture method. No significant difference in yield lost as curd fines in the whey and both wash waters occurred between cottage cheese treated with .05% SHMP and its control, level 1. No significant difference in the yield lost as curd fines were evident in the whey and wash waters of .2% SHMP cottage cheese and its control, level 2. The addition of SHMP to milk subsequently made into cottage cheese curd did not cause or protect from shattering
HEXAMETAPHOSPHATE AND COTTAGE CHEESE YIELDS
549
TABLE 3. Composition of whey resulting from manufacture of cottage cheese with and without sodium hexametaphosphate (SHMP). a Level 1 Component
Control
Level 2 .05% SHMP
Control
.2% SHMP
6.68 .23 6.44 .51 .08 .43 5.24 .70
6.98* .36* * 6.62 .48 .09 .40 5.41 .73
(%) Total solids Fat Solids-not-fat Total protein Casein protein Whey protein Lactose Ash
6.78 .24 6.54 .55 .08 .46 5.34 .66
6.72 .22 6.50 .51 .06 .45 5.30 .69
73.93 109.37
75.99 100.41
(m~lOOml) Phosphorus Calcium
73.53 104.20
87.24 80.75
aMeans of 8 replications. *Treatment different from control, significant (P<.05). **Treatment different from control, highly significant (P<.01).
of the curd, as reflected in yield lost as curd fines. Cottage Cheese Yield
Yields of cheese are in Table 5. Cottage cheese m a d e f r o m milk containing .05% SHMP s h o w e d higher yields (P<.05) w h e n expressed as kilogram 20% solids curd per 100 kg o f milk (.77 increase) and as p e r c e n t recovery of total solids (1.51% increase). While recovery o f curd as kilogram 20% solids curd per kilogram milk was higher for the .05% SHMP cottage
cheese than its control (.07 increase), the difference was n o t great enough to be significant (P>.05). T h e r e f o r e , the addition of .05% SHMP to milk for cottage cheese increased b o t h a m o u n t of curd that could be m a d e f r o m a given a m o u n t of milk and recovery of milk solids. The addition of .2% SHMP to cottage cheese milk increased yields (P<.05) w h e n measured by all three m e t h o d s : 1.25 kg m o r e 20% curd per 100 kg milk, .12 kg m o r e 20% curd per kg milk solids, and 2.45% greater recovery o f milk solids. Because of the high fat c o n t e n t of the curd,
TABLE 4. Average yield lost as curd fines in cottage cheese whey and wash waters, a Level 2
Level 1
Source of yield loss
Control
.05% SHMP
Control
.2% SHMP
(Yieldlost(kg20% solid curd/lO0 kgmilk)) Whey First wash Second wash Total
.67 .25 .18 1.10
.73 .24 .23 1.20
.61 .20 .20 1.01
.55 .24 .18 .96
aMeans of 8 replications. Journal of Dairy Science Vol. 64, No. 4, 1982
DYBING ET AL.
550 TABLE 5. Cottage cheese yields,a
Level 2
Level 1 Yield method
Control
.05% SHMP
Control
.2% SHMP
kg 20% curd per 100 kg milk kg 20% curd per kg milk solids Percent recovery of milk solids
21.71 2.11 42.12
22.48* 2.18 43.63*
21.82 2.13 42.60
23.07* 2.25* 65.05*
aMeans of 8 replications.
*Treamaent different from control, significant (P<.05).
these yields were higher than normal. However, if the fat content of the curd, expressed as 20% solids, is subtracted from the kilogram 20% solids per 100 kg milk, the results should reflect contents of regular cottage cheese. The new yields for the .05% SHMP and control curds were 17.33 and 16.91%, and the .02% SHMP and control curd yields were 18.74 and 16.55%. These yields are within the expected range of 14 to 18% (19) and still show that SHMP increased yield of cottage cheese. Effects of adding SHMP to cottage cheese milk were to produce increased yields of curd containing more ash, phosphorus, and calcium. The curd produced with .2% SHMP also contained less fat and casein but a greater quantity of lactose. An increase in curd yield but decrease in curd fat and casein was an unexpected result. The fat missing in the curd appeared in the whey and was assumed to have been lost. However, the casein missing in the curd was not measured in the whey; the SHMP whey casein was .01 to .2% lower than the control whey. Because the recovery of lactose was determined by difference, the increase in lactose may account for other milk components not recorded in the composition analysis. Greater incorporation of the whey proteins into the curd may have produced part of the increase in yield when SHMP was added to the milk. With SHMP addition, whey proteins decreased in whey (.01 and .03%) and increased in curd (.02 and .05%). Hence, there was a small recovery of the whey proteins as curd, but it was not a significant increase (P<.05) over the controls. The inability to reduce the pH of the milk to the levels used in some of the procedures for recovering whey proteins from whey with Journal of Dairy Science Vol. 65, No. 4, 1982
polyelectrolytes, pH 3.0 (10) and 3.2 (11, 26), may explain the lack of significant whey protein recovery. The desired effect was that pH during the manufacture of cottage cheese (4.7) would be low enough with the quiescent coagulation of the milk to allow significantly greater protein recovery. However, a pH of 3.0 to 3.2 would be undesirable, because casein becomes increasingly soluble as the pH goes below 4.6 (21). Further studies are needed to evaluate properties of polyelectrolytes and cottage cheese to recover the whey proteins. ACKNOWLEDGMENT
This work was supported in part by funds from Dairy Research Inc., Rosemont, IL. REFERENCES
1 Association of Official Analytical Chemists. 1975. Official methods of analysis. 12th ed. Washington, DC. 2 Atherton, H. V., and J. A. Newlander. 1977. Chemistry and testing of dairy products. 4th ed. Avi Publ. Co., Inc., Westport, CT. 3 Bough, W. A., and D. R. Landes. 1976. Recovery and nutritional evaluation of proteinaceous solids separated from whey by coagulation with chitosan. J. Dairy Sci. 59:1874. 4 Emmons, D. B., D. C. Beckett, J. N. Campbell, and E. S. Humbert. 1978. Reduced washing of cottage cheese and increased recovery of whey solids. Cult. Dairy Prod. J. 13(2): 13. 5 Feeley, R. M., P. E. Criner, E. W. Murphy, and E. W. Toepfer. 1972. Major mineral elements in dairy products. J. Am. Diet. Assoc. 61:505. 6 Gordon, W. G. 1945. Method for the separation of protein from animal matter containing protein in water-soluble form. US Patent 2,377,624. 7 Hansen, P.M.T., J. Hidalgo, and I. A. Gould. 1971. Reclamation of whey protein with carboxymethylcellulose. J. Dairy Sci. 54:830.
HEXAMETAPHOSPHATE AND COTTAGE CHEESE YIELDS 8 Hargrove, R. D., and J. A. Alford. 1974. Composition of milk products. In Fundamentals of dairy chemistry. 2nd ed. B. H. Webb, A. H. Johnson, and J. A. Alford, ed. Avi Publ. Co., Inc., Westport, CT. 9 Hidalgo, J., and P.M.T. Hansen. 1971. Selective precipitation of whey proteins with carboxymethylcellulose. J. Dairy Sci. 54:1270. 10 Hidalgo, J., J. Kruseman, and H. U. Bohren. 1973. Recovery of whey proteins with sodium hexametaphosphate. J. Dairy Sci. 56;988. 11 Hill, R. D., and J. G. Zadow. 1974. The precipitation of whey proteins by carboxymethylcellulose of differing degrees of substitution. J. Dairy Res. 41:373. 12 Johnson, A. H. 1974. The composition of milk. In Fundamentals of dairy chemistry. 2nd ed. B. H. Webb, A. H. Johnson, and J. A. Alford, ed. Avi Publ. Co., Inc., Westport, CT. 13 Kosikowski, F. V. 1979. Whey utilization and whey products. J. Dairy Sci. 62:1149. 14 Mathur, B. N., and K. M. Shahani. 1979. Use of total whey constituents for human food. J. Dairy Sci. 62:99. 15 Mickelsen, R. 1974. Factors affecting yields of cottage cheese. Contrib. 903, Dept. Dairy and Poultry Sci., Kansas State Univ., Manhattan. 16 Morrison, W. R. 1964. A fast simple and reliable method for the microdetermination of phosphorus in biological materials. Analy. Biochem. 7:218.
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17 Rabb, J. A., Jr., B. J. Liska, and C. E. Parmelee. 1964. A simple method for estimating curd fines in cottage cheese whey. J. Dairy Sci. 47:92. 18 Rowland, S. J. 1938. The determination of the nitrogen distribution in milk. J. Dairy Res. 9:42. 19 Satterness, D. E., J. G. Parsons, J. H. Martin, and K. R. Spurgeon. 1978. Yields of cottage cheese made with cultures and direct acidification. Cult. Dairy Prod. J. 13(1):8. 20 Steele, R.G.D., and J. H. Torrie. 1960. Principles and procedures of statistics. McGraw-Hill Book Co., Inc., New York, NY. 21 Tuckey, S. L. 1964. Properties of casein important in making cottage cheese. J. Dairy Sci. 47: 324. 22 Vorobyev, A. I. 1962. Coagulation of milk and ripening o f cheese (using calcium phosphates and calcium chlorides). Proc. 16th Int. Dairy Congr., Copenhagen, B, 576. 23 Wi!ster, C. H. 1974. Practical cheesemaking. 12th ed. Oregon State Univ. Bookstore, Inc., Corvallis. 24 Wong, N. P., D. E. LaCroix, W. A. Mattingly, J. H. Vestal, and J. A. Alford. 1976. The effect of manufacturing variables on the mineral content of cottage cheese. J. Dairy Sci. 59:41. 25 Yee, J. J. 1976. A study of milk composition in South Dakota. M.S. thesis. South Dakota State Univ., Brookings. 26 Zadow, J. G., and R. D. Hill. 1975. The precipitation of proteins by carboxymethylcellulose. J. Dairy Res. 42:267.
Journal of Dairy Science VoI. 65, No. 4, 1982
S. T. D Y B I N G , J. G. PARSONS, J. H. M A R T I N , 2 and K. R. SPURGEON Dairy Science Department
South Dakota State UniVersity Brookings 57007
ABSTRACT
INTRODUCTION
Sodium hexametaphosphate, a polyelectrolyte capable of precipitating whey proteins, was added to milk manufactured into cottage cheese to determine its effect upon yield and composition. Fresh skim milk, fortified with nonfat dry milk to 9% solids, was vat pasteurized and divided between two 200-liter vats. One vat served as a control and the other received either .05 or .2%, by weight, sodium hexametaphosphate prior to being made into cottage cheese by the short set culture procedure. Addition of .05% sodium hexametaphosphate to milk subsequently manufactured into cottage cheese increased yield of curd by .77% when yield was measured as kilogram 20% solids curd recovered per 100 kg milk and by 1.51% when measured as percent recovery of milk solids. The addition of .2% sodium hexametaphosphate to milk subsequently manufactured into cottage cheese increased yield of curd by 1.25% when yield was measured as kilogram of 20% solids curd recovered per 100 kg milk, by .12 kg of 20% solids curd recovered per kilogram milk solids, and by 2.45% when measured as percent recovery of milk solids. The increase in yield for both .05 and .2% added sodium hexametaphosphate was not shown to be increased recovery of whey proteins.
Major concerns of cottage cheese production are low yields and high whey disposal costs (13), an interesting situation as the protein in whey contributing to disposal cost could increase yield. The dissolved proteins in whey are mainly a-lactalbumin and 3-1actoglobulin. Because these proteins remain soluble during cottage cheese manufacture, they are lost and removed as part of the whey (13). Polyelectrolyres, such as carboxymethyl cellulose (CMC) and sodium hexametaphosphate (SHMP), can precipitate whey proteins, allowing them to be recovered by centrifugation (3, 6, 7, 9, 10, 11, 22, 26). If the technique of recovering whey proteins could be combined with procedures of making cottage cheese, while product quality is maintained, then the former waste item could become a profitable asset. The objective of this study was to explore the possibility that the polyelectrolyte, sodium hexametaphosphate, may increase the yield of cottage cheese. Therefore, yields and composition of cottage cheese made by a widely accepted culture procedure (23) were compared with the yield and composition of cottage cheese made from milk containing .05 or .2% sodium hexametaphosphate. MATERIALS AND METHODS Experimental Procedure
Received April 6, 1981. Published with the approval of the Director of the South Dakota Agriculture Experiment Station as Publication No. 1746 of the Journal series. 2Dairy Science Department, Clemson University, Clemson, SC 29631. 1982 J Dairy Sci 65:544--551
Fresh skim milk from the South Dakota State University Dairy Products Laboratory was transferred to a pasteurizing vat and heated to 43.3°C. Nonfat dry milk was added via a powder funnel to increase the solids-not-fat by .5% (wt/wt). The skim milk subsequently was vat pasteurized at 63°C for 30 min followed by immediate cooling to 4°C by a plate cooler. Finally, the skim milk was transferred into sani-
544
HEXAMETAPHOSPHATE AND COTTAGE CHEESE YIELDS tized 37.8-liter milk cans and stored overnight at 3°C. The manufacture of the cottage cheese was initiated by splitting the processed skim milk equally between two sanitized 200 liter vats, with 141.75 kg in each (Figure 1). The temperature of the milk in both vats was raised to 32.2°C. Starter culture prepared from commercially available strains of lactic acid producing bacteria (19) then was added at 5.2% (wt/wt) and mixed thoroughly with the skim milk. Fifteen minutes after addition of the culture, 1 to 2 liters of milk were removed from the vat that was to receive the SHMP (Polyphos ®, Olin Chemicals, 120 Long Ridge Road, Stanford, CT 06904) and transferred to a sanitized stainless steel beaker containing the proper a m o u n t of previously weighed SHMP (either .05 or .2% of the weight of milk). The SHMP was stirred into the milk until it was completely dissolved. This solution then was returned to the vat and mixed thoroughly into the milk. Coagulator, consisting of 1 ml cottage cheese coagulator (Angevine-Funke, Inc., 3380 Tree Ct. Industrial Blvd., St. Louis, MO 63122) diluted to 20 ml with water was added to each vat 30 rain after it had received starter. When the pH of the coagulum dropped to 4.7 (TA .49
545
to .51) the curd was cut with sanitized .64-cm knives. The curd then was allowed to sit undisturbed for 15 to 20 min to heal. The curd was then cooked. The temperature of the vat was increased by the following specific temperature intervals during 15 min periods: 2.8°C in the 1st 15 rain, 6.7°C for the 2nd 15 min, 5.6°C during the 3rd 15 min, and 6.7°C per 15 min to a final temperature of 54°C at the completion of cooking. Upon completion of cooking the curds Were held in the hot whey approximately 20 min. Before draining, the curd was allowed to sit unstirred for the last 5 min to allow the fines to settle. The whey was drained to the level of the curd and 76 liters of wash water added to the vat (4). The wash water was prepared previously by acidifying water to pH 5 with phosphoric acid, adding chlorine to 10 ppm and plate cooling the water to 4°C. The curd was allowed to remain 15 to 20 rain in the wash water, then the water was drained to the level of the curd, and a second wash of 114 liters wash water added. After 15 to 20 min the water was drained, and the curd was ditched for at least 30 min, and then mixed, sampled, and transferred to l l.4-1iter containers and weighed for yield determination. Samples of curd were frozen for later analyses. Sample Collection
FRESH SKIM MILK
l
FORTI F ICATION
l
PASTEURIZATION
BULK STARTER
Milk for cottage cheese making was sampled in duplicate. Whey and wash waters were collected in a tared 37.8 liter milk can, weighed, and thoroughly mixed. One sample of each whey and wash water was collected for determination of curd fines, and two additional whey samples were taken for compositional analysis. The curd was mixed thoroughly after draining, and duplicate representative samples were taken. All samples were stored in 532-ml Whirl-Pak plastic bags. Composition Analysis
IC ONTROL l
SODIUM H EX AMETAPHOSPHATE
SHORT SET COTTAGE CHEESE PROCESS Figure 1. Flow diagram of cottage cheese manufacturing process in 200-liter cheese vats.
Procedures were identical for determination of total solids, fat, solids-not-fat, lactose, ash, phosphorus, and calcium in milk, curd, and whey samples. Determination of total solids was by the Mojonnier m e t h o d as described by A t h e r t o n and Newlander (2). F a t analysis was by the Association of Official Analytical Chemists (AOAC) Roese-Gottlieb m e t h o d ( 1 ) w i t h solids-not-fat calculated as the difference beJournal of Dairy Science Vol. 65, No. 4, 1982
546
DYBING ET AL.
tween the total solids and fat. Protein c o n t e n t of the curd was determined by Mickelsen's procedure (15) of blending 25 g of curd with 75 g of .05 M sodium hydroxide prior to analysis. The AOAC Kjeldahl procedure (1) then was used to determine the nitrogen (protein) and the Rowland procedure (18) to fractionate the milk. The ash content was determined by the AOAC official method (1). Lactose was determined as the difference between the solids-not-fat and the sum of the total of protein and ash. The samples for mineral analyses were prepared by dry ashing, then dissolved in 2 ml concentrated ( 3 7 % ) h y d r o chloric acid, and diluted to 100 ml with distilled water. Phosphorus was determined by a colorimetric procedure (16). Calcium was determined by atomic absorption spectrophotometry of the sample prepared in the same manner as for the phosphorus determination. Quantification of the curd lost as fines was determined by Satterness's modification (19) of Rabb's procedure (17). Expression of Yield
Yields were expressed as kilogram 20% solids curd per 100 kg milk, kilogram 20% solids curd per kilogram milk solids, and percent recovery of milk solids in the curd.
Statistical Analysis
Statistical analysis of the data utilized the least squares analysis of variance of a two factor (added SHMP and replication) design experiment. The main effect of added SHMP was tested by the interaction of SHMP and replication (20). R ESU LTS AN D D ISCUSSION Cheese Milk Composition
The potential yield of cottage cheese is related directly to the composition of the starting milk, particularly to the quantity of casein. The composition of the milk used in this study is given in Table 1. The total solids content of the skim milks was higher than expected for skim milk. Although normally the total solids content of skim milk is 9.5% (8, 19), the milk used for level 1 skim milk, .05% SHMP and control, had a total solids content of 10.33%. The total solids for level 2 skim milk, .2% SHMP and control, was also high at 10.26%. The high total solids was due to the high fat content of the milk used, 1.17 and 1.26% fat, respectively, for the .05 and .2% SHMP skim milks versus the target fat content of .1%. Inefficiency of the separator in re-
TABLE 1. Composition of skim milk in manufacture of cottage cheese,a Level 2c
Level i b Component
Mean
SD
Total solids Fat Solids-not-fat Total protein Casein protein Whey protein Lactose Ash
10.33 1.17 9.16 2.81 2.28 .54 5.62 .73
.51 .27 .44 .18 .17 .04 .31 .02
88.98 106.46
13.15 17.77
Mean
SD
10.26 1.26 8.99 2.91 2.36 .54 5.36 .73
.30 .32 .38 .09 .10 .03 .42 .01
92.08 114.50
6.67 13.99
(%)
(mg/100 ml) Phosphorus Calcium
aMeans of 8 replications. b.05% Sodium hexametaphosphate and control. c.2% Sodium hexametaphosphate and control. Journal of Dairy Science Vol. 65, No. 4, 1982
HEXAMETAPHOSPHATE AND COTTAGE CHEESE YIELDS moving fat from relatively small amounts of milk was responsible for this high fat content. Fortification of the skim milks with nonfat dry milk increased the solids-not-fat (SNF) to 9.16% for the .05% SHMP milk and 8.99% for the .2% SHMP skim milk, which was close to the target 9.00%. However, protein content of both skim milks was lower than the expected 3.5% total protein, 2.8% casein, and .7% whey protein (8). The .05% SHMP skim milk contained 2.81% total protein, 2.28% casein, and .54% whey protein, and the .2% SHMP skim milk contained 2.91% total protein, 2.36% casein protein, and .54% whey proteins. Lactose was higher for both experimental skim milks than has been reported: 5.62% for the .05% SHMP milk and 5.36% for the .02% SHMP skim milk versus the reported average 4.9% (8). The low protein content may have been from the summer milk when the protein content is usually the lowest (12). Another factor is that dairy animals are being selected and bred to produce offspring genetically capable of yielding larger quantities of milk which contains smaller percentages of protein. This is a problem currently facing milk processors (25). The increase in lactose may have been caused
547
by fortifying the milk with nonfat dry milk, which is concentrated skim milk added to increase the protein in the milk and contains 52.3% lactose (8). The ash content of all milks was .73%, close to the expected .7% (8). Phosphorus and calcium in the experimental milks were within the range commonly reported. The phosphorus content of the .05% SHMP milk was 88.98 rag/100 ml and the .2% SHMP milk contained 92.08 mg/100 ml versus reports ranging from 90 to 112 mg/100 ml (8). The calcium content for the .05% SHMP was 102.46 mg/100 ml and 114.50 mg/100 ml for the .2% SHMP milk. Although reported averages are around 120 to 121 mg/100 ml, Feeley et al. (5) noted a wide variation of mineral quantities in milk. They found that milk contained calcium ranging from 101 to 137 mg/100 ml.
Curd Composition
Composition of cottage cheese curds is in Table 2. Composition of curds as a group differed from average cottage cheese curd composition. Total solids of cottage cheese curd is usually 21% (8). However, the mean total solids of curds in our study, 26.14, 25.36,
TABLE 2. Composition of curd resulting from the manufacture of cottage cheese with and without sodium hexametaphosphate (SHMP).a,b Level 1 Component
Level 2
Control
.05% SHMP
26.14 4.80 15.20 11.99 11.72 .28 2.73 .48
25.36 5.15 14.85 11.02 10.69 .33 3.04 .79* *
Control
.2% SHMP
24.59 5.27 14.73 12.82 12.48 .34 1.39 .52
24.88 4.33** 15.67"* 10.76" * 10.39"* .36 3.68 ** 1.24"*
150.86 66.81
381.01 ** 240.91"*
(%) Total solids Fat Solids-not-fat Total protein Casein protein Whey protein Lactose Ash
(mg/lO0 ml) Phosphorus
Calcium
163.94
70.16
235.05 * *
136.71"*
aAll curd components except total solids are calculated to a 20% total curd solids basis. bMeans of 8 replications2 **Treatment different from control, highly significant (P<.01). Journal of Dairy Science Vol. 65, No. 4, 1982
548
DYBING ET AL.
24.59, and 24.88%, were high. The major factor contributing to this increase was the high fat content of the starting skim milk which resuited in high fat in cottage cheese curd. Level 1 cottage cheese curd, .05% SHMP and control, contained 5.15 and 4.80% fat, respectively, higher than the average cottage cheese curd fat content of .4% (8). Although total solids increased, the high curd fat caused protein to be below normal 16.9% (8). Significant differences (P<.01) between cottage cheese curds made from milk with and without SHMP at .05% were in ash, phosphorus, and calcium fractions. Treatment of milk with .05% SHMP with subsequent manufacture into cottage cheese produced a curd containing higher ash (by .31%), phosphorus (by 71.11 mg/100 ml), and calcium (by 66.55 mg/100 ml). Differences (P<.01) between .2% SHMP and its control cottage cheese were in fat, solidsnot-fat, total protein, casein, lactose, ash, phosphorus, and calcium fractions. The addition of .2% SHMP to milk subsequently made into cottage cheese produced a curd higher in solids-not-fat (by .94%), lactose (by 2.29%), ash (by .72%), phosphorus (by 230.15 mg/100 ml), and calcium (by 174.10 mg/100 ml), and lower in fat (by .94%), total protein (by 2.06%), and casein (by 2.09%). The decrease in total protein appears from the decrease in casein. The effect of SHMP upon cottage cheese was to produce a curd containing larger quantities of ash, phosphorus, calcium, and lactose. The greater the amount of SHMP added, the greater the increase of these curd components in the cottage cheese. However, with increasing addition of SHMP, the possibility increases that the curd would have lower percentages of casein and fat. The increase in ash agreed with findings of Mathur and Shahani (14), who noted an increase in ash content of whey protein concentrates prepared by precipitation with polyelectrolytes including SHMP. The increase in curd phosphorus and calcium has been reported by Wong et al. (24), who noted that adding SHMP to milk manufactured into cottage cheese increased the phosphorus and calcium, producing a nutritiously more desirable calcium to phosphorus ratio (1:1.5) compared to that of regular cottage cheese (1:3.4). Although the whey protein fractions Journal of Dairy Science Vol. 65, No. 4, 1982
were higher in the SHMP curds (.02 and .05%), these differences were not statistically significant (P> .05).
Whey Composition
Composition of whey is in Table 3. Whey contained higher percentages of total solids, fat, and lactose, and lower quantities of total proteins than reported in (13, 19). The average composition of cottage cheese (acid) whey is 6.5% total solids, .04% fat, .75% total protein, 4.9% lactose, .4% lactic acid, and .80% ash (13). However, our whey had compositional ranges of 6.68 to 6.98% total solids, .22 to .36% fat, .48 to .55% total protein, 5.24 to 5.41% lactose, and .66 to .73% ash. Whey originating from cottage cheese made with and without .05% SHMP, level 1, showed no significant differences (P>.05) between any of the components. However, whey originating from cottage cheese made with .2% SHMP contained significantly higher total solids, .3%, (P<.05) and fat, .13% (P<.01) than its control. The lower quantities of fat in .2% SHMP curd and the correspondingly larger amounts of fat in its whey indicated that addition of large amounts of SHMP may cause some loss of fat from cheese curd. However, because cottage cheese is normally made from skim milk, fat loss would not be a problem. The SHMP whey contained smaller quantities of whey protein (.03%), but the difference was not significant (P<.O5). Yield Lost as Curd Fines
The amount of curd lost in the whey as curd fines is in Table 4. The observed curd fine losses for all whey were lower than the fine losses of 1.55 kg 20% solids curd per 100 kg milk reported by Satterness et al. (19) for fortified skim milk manufactured into cottage cheese by the short set culture method. No significant difference in yield lost as curd fines in the whey and both wash waters occurred between cottage cheese treated with .05% SHMP and its control, level 1. No significant difference in the yield lost as curd fines were evident in the whey and wash waters of .2% SHMP cottage cheese and its control, level 2. The addition of SHMP to milk subsequently made into cottage cheese curd did not cause or protect from shattering
HEXAMETAPHOSPHATE AND COTTAGE CHEESE YIELDS
549
TABLE 3. Composition of whey resulting from manufacture of cottage cheese with and without sodium hexametaphosphate (SHMP). a Level 1 Component
Control
Level 2 .05% SHMP
Control
.2% SHMP
6.68 .23 6.44 .51 .08 .43 5.24 .70
6.98* .36* * 6.62 .48 .09 .40 5.41 .73
(%) Total solids Fat Solids-not-fat Total protein Casein protein Whey protein Lactose Ash
6.78 .24 6.54 .55 .08 .46 5.34 .66
6.72 .22 6.50 .51 .06 .45 5.30 .69
73.93 109.37
75.99 100.41
(m~lOOml) Phosphorus Calcium
73.53 104.20
87.24 80.75
aMeans of 8 replications. *Treatment different from control, significant (P<.05). **Treatment different from control, highly significant (P<.01).
of the curd, as reflected in yield lost as curd fines. Cottage Cheese Yield
Yields of cheese are in Table 5. Cottage cheese m a d e f r o m milk containing .05% SHMP s h o w e d higher yields (P<.05) w h e n expressed as kilogram 20% solids curd per 100 kg o f milk (.77 increase) and as p e r c e n t recovery of total solids (1.51% increase). While recovery o f curd as kilogram 20% solids curd per kilogram milk was higher for the .05% SHMP cottage
cheese than its control (.07 increase), the difference was n o t great enough to be significant (P>.05). T h e r e f o r e , the addition of .05% SHMP to milk for cottage cheese increased b o t h a m o u n t of curd that could be m a d e f r o m a given a m o u n t of milk and recovery of milk solids. The addition of .2% SHMP to cottage cheese milk increased yields (P<.05) w h e n measured by all three m e t h o d s : 1.25 kg m o r e 20% curd per 100 kg milk, .12 kg m o r e 20% curd per kg milk solids, and 2.45% greater recovery o f milk solids. Because of the high fat c o n t e n t of the curd,
TABLE 4. Average yield lost as curd fines in cottage cheese whey and wash waters, a Level 2
Level 1
Source of yield loss
Control
.05% SHMP
Control
.2% SHMP
(Yieldlost(kg20% solid curd/lO0 kgmilk)) Whey First wash Second wash Total
.67 .25 .18 1.10
.73 .24 .23 1.20
.61 .20 .20 1.01
.55 .24 .18 .96
aMeans of 8 replications. Journal of Dairy Science Vol. 64, No. 4, 1982
DYBING ET AL.
550 TABLE 5. Cottage cheese yields,a
Level 2
Level 1 Yield method
Control
.05% SHMP
Control
.2% SHMP
kg 20% curd per 100 kg milk kg 20% curd per kg milk solids Percent recovery of milk solids
21.71 2.11 42.12
22.48* 2.18 43.63*
21.82 2.13 42.60
23.07* 2.25* 65.05*
aMeans of 8 replications.
*Treamaent different from control, significant (P<.05).
these yields were higher than normal. However, if the fat content of the curd, expressed as 20% solids, is subtracted from the kilogram 20% solids per 100 kg milk, the results should reflect contents of regular cottage cheese. The new yields for the .05% SHMP and control curds were 17.33 and 16.91%, and the .02% SHMP and control curd yields were 18.74 and 16.55%. These yields are within the expected range of 14 to 18% (19) and still show that SHMP increased yield of cottage cheese. Effects of adding SHMP to cottage cheese milk were to produce increased yields of curd containing more ash, phosphorus, and calcium. The curd produced with .2% SHMP also contained less fat and casein but a greater quantity of lactose. An increase in curd yield but decrease in curd fat and casein was an unexpected result. The fat missing in the curd appeared in the whey and was assumed to have been lost. However, the casein missing in the curd was not measured in the whey; the SHMP whey casein was .01 to .2% lower than the control whey. Because the recovery of lactose was determined by difference, the increase in lactose may account for other milk components not recorded in the composition analysis. Greater incorporation of the whey proteins into the curd may have produced part of the increase in yield when SHMP was added to the milk. With SHMP addition, whey proteins decreased in whey (.01 and .03%) and increased in curd (.02 and .05%). Hence, there was a small recovery of the whey proteins as curd, but it was not a significant increase (P<.05) over the controls. The inability to reduce the pH of the milk to the levels used in some of the procedures for recovering whey proteins from whey with Journal of Dairy Science Vol. 65, No. 4, 1982
polyelectrolytes, pH 3.0 (10) and 3.2 (11, 26), may explain the lack of significant whey protein recovery. The desired effect was that pH during the manufacture of cottage cheese (4.7) would be low enough with the quiescent coagulation of the milk to allow significantly greater protein recovery. However, a pH of 3.0 to 3.2 would be undesirable, because casein becomes increasingly soluble as the pH goes below 4.6 (21). Further studies are needed to evaluate properties of polyelectrolytes and cottage cheese to recover the whey proteins. ACKNOWLEDGMENT
This work was supported in part by funds from Dairy Research Inc., Rosemont, IL. REFERENCES
1 Association of Official Analytical Chemists. 1975. Official methods of analysis. 12th ed. Washington, DC. 2 Atherton, H. V., and J. A. Newlander. 1977. Chemistry and testing of dairy products. 4th ed. Avi Publ. Co., Inc., Westport, CT. 3 Bough, W. A., and D. R. Landes. 1976. Recovery and nutritional evaluation of proteinaceous solids separated from whey by coagulation with chitosan. J. Dairy Sci. 59:1874. 4 Emmons, D. B., D. C. Beckett, J. N. Campbell, and E. S. Humbert. 1978. Reduced washing of cottage cheese and increased recovery of whey solids. Cult. Dairy Prod. J. 13(2): 13. 5 Feeley, R. M., P. E. Criner, E. W. Murphy, and E. W. Toepfer. 1972. Major mineral elements in dairy products. J. Am. Diet. Assoc. 61:505. 6 Gordon, W. G. 1945. Method for the separation of protein from animal matter containing protein in water-soluble form. US Patent 2,377,624. 7 Hansen, P.M.T., J. Hidalgo, and I. A. Gould. 1971. Reclamation of whey protein with carboxymethylcellulose. J. Dairy Sci. 54:830.
HEXAMETAPHOSPHATE AND COTTAGE CHEESE YIELDS 8 Hargrove, R. D., and J. A. Alford. 1974. Composition of milk products. In Fundamentals of dairy chemistry. 2nd ed. B. H. Webb, A. H. Johnson, and J. A. Alford, ed. Avi Publ. Co., Inc., Westport, CT. 9 Hidalgo, J., and P.M.T. Hansen. 1971. Selective precipitation of whey proteins with carboxymethylcellulose. J. Dairy Sci. 54:1270. 10 Hidalgo, J., J. Kruseman, and H. U. Bohren. 1973. Recovery of whey proteins with sodium hexametaphosphate. J. Dairy Sci. 56;988. 11 Hill, R. D., and J. G. Zadow. 1974. The precipitation of whey proteins by carboxymethylcellulose of differing degrees of substitution. J. Dairy Res. 41:373. 12 Johnson, A. H. 1974. The composition of milk. In Fundamentals of dairy chemistry. 2nd ed. B. H. Webb, A. H. Johnson, and J. A. Alford, ed. Avi Publ. Co., Inc., Westport, CT. 13 Kosikowski, F. V. 1979. Whey utilization and whey products. J. Dairy Sci. 62:1149. 14 Mathur, B. N., and K. M. Shahani. 1979. Use of total whey constituents for human food. J. Dairy Sci. 62:99. 15 Mickelsen, R. 1974. Factors affecting yields of cottage cheese. Contrib. 903, Dept. Dairy and Poultry Sci., Kansas State Univ., Manhattan. 16 Morrison, W. R. 1964. A fast simple and reliable method for the microdetermination of phosphorus in biological materials. Analy. Biochem. 7:218.
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17 Rabb, J. A., Jr., B. J. Liska, and C. E. Parmelee. 1964. A simple method for estimating curd fines in cottage cheese whey. J. Dairy Sci. 47:92. 18 Rowland, S. J. 1938. The determination of the nitrogen distribution in milk. J. Dairy Res. 9:42. 19 Satterness, D. E., J. G. Parsons, J. H. Martin, and K. R. Spurgeon. 1978. Yields of cottage cheese made with cultures and direct acidification. Cult. Dairy Prod. J. 13(1):8. 20 Steele, R.G.D., and J. H. Torrie. 1960. Principles and procedures of statistics. McGraw-Hill Book Co., Inc., New York, NY. 21 Tuckey, S. L. 1964. Properties of casein important in making cottage cheese. J. Dairy Sci. 47: 324. 22 Vorobyev, A. I. 1962. Coagulation of milk and ripening o f cheese (using calcium phosphates and calcium chlorides). Proc. 16th Int. Dairy Congr., Copenhagen, B, 576. 23 Wi!ster, C. H. 1974. Practical cheesemaking. 12th ed. Oregon State Univ. Bookstore, Inc., Corvallis. 24 Wong, N. P., D. E. LaCroix, W. A. Mattingly, J. H. Vestal, and J. A. Alford. 1976. The effect of manufacturing variables on the mineral content of cottage cheese. J. Dairy Sci. 59:41. 25 Yee, J. J. 1976. A study of milk composition in South Dakota. M.S. thesis. South Dakota State Univ., Brookings. 26 Zadow, J. G., and R. D. Hill. 1975. The precipitation of proteins by carboxymethylcellulose. J. Dairy Res. 42:267.
Journal of Dairy Science VoI. 65, No. 4, 1982