Calcium Supplementation of Cottage Cheese

Calcium Supplementation of Cottage Cheese L. A. SHELEF and R. J. R Y A N Department of Nutrition and Food Science Wayne State University Detroit, MI 48202 ABSTRACT

Cottage cheese (100 g) provides only 6% of the calcium Recommended Daily Allowance for adults. Samples of fresh cheese were supplemented with calcium salts (chloride, lactate, or phosphate monobasic) to double the calcium content of the cheese to approximately 145 mg/100 g, and the effects of the supplementation on taste and microbial stability were studied. Supplementations did not affect pH or microbial stability during 21 d of refrigerated storage. Sensory evaluation results of a 12member taste panel showed higher flavor and preference scores for control than for all supplemented samples (P<.05) but no difference in odor, color, or texture. Overall, chloride appeared to be preferable for calcium content supplementation because only .26% (wt/wt) of the salt was required to obtain the desired calcium content level and the mineral was evenly distributed in the cheese. INTRODUCTION

Increases in the dietary calcium have been recommended in recent years for control of osteoporosis, hypertension, and other conditions. Although most dairy products are considered good sources of dietary calcium, as well as phosphorus, cottage cheese is lower in these two minerals than most others. Creamed or low fat cottage cheese, for example, contains 60 mg calcium content/100 g, approximately half the level in fluid milk. In both the conventional and the direct acidification procedures ("directly set") employed in the dairy industry today, calcium content is only partially retained by the formed curd. Calcium in acid whey tends to

Received January 7, 1988. Accepted June 10, 1988.

1988 J Dairy Sci 71:2618-2621

be higher (103 mg/lO0 g) than in sweet whey (47 mg/100 g) (7) because of the solvent action of hydrogen ions on the calcium phosphate of casein. Cottage cheese is a popular and desirable constituent of the diet of a large segment of the population, being high in protein (ca. 13%) and low in fat (1 to 4%). Being low in calories (ca. 100 cal/100 g), cottage cheese is particularly popular among women. However, 100 g of cottage cheese provide only 6% of the calcium Recommended Daily Allowance (RDA) for adults (5). Because calcium intake is low in general, and is inadequate among women (6), to explore means of providing more calcium content in cottage cheese appears desirable. Current federal standards do not permit calcium supplementation of cheese. The addition of a small quantity of calcium to milk from which cheese is made (.02% by weight, calculated as anhydrous calcium chloride), which is permitted, is intended as a coagulation aid (1). The present study was undertaken to test the feasibility of supplementation of cottage cheese with calcium to levels found in milk (approximately twofold increase). Specifically, the purposes of the study were to compare calcium supplementation of commercial cottage cheese with GRAS (generally recognized as safe) calcium salts, to evaluate the effects on taste and microbial stability, and to measure calcium stability in the cheese during refrigerated storage. MATERIALS AND METHODS

Cottage cheese (Farm Maid, Detroit, MI), small curd, Grade A, 4% milk fat, was purchased at local stores. Food grade calcium salts examined included the chloride, lactate, carbonate, gluconate (Mallinckrodt, St. Louis, MO), and phosphate monobasic (FMC Inc., Philadelphia, PA). Homogenized whole milk purchased locally was the carrier of the calcium salts.

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CALCIUM ADDED TO COTTAGE CHEESE Calcium salts, at quantities to provide a supplementation of approximately 70 mg calcium/100 g of cheese, were weighed, combined with milk (10 ml/500 g cheese) in a 1-L beaker, stirred, and heated, if needed, to dissolve the salt. Cottage cheese was added and the contents thoroughly mixed and divided in 100-g portions into sterile 150-ml beakers. The beakers were covered with aluminum foil and stored at 4°C. Control samples contained cheese and milk and were prepared in a similar manner. Replicate samples from the freshly prepared mixes were removed immediately after preparation and stored in the freezer in propylene screw top vials for Ca analysis. All cheese preparations were refrigerated for up to 3 wk and removed for analysis once a week. To test the levels of calcium in the cheese upon storage, samples from the top, middle, and b o t t o m thirds, and a mixture of the total contents were removed from duplicate containers into screw top vials and kept frozen until tested. The remaining mixed cheese was centrifuged at 5000 rpm for 10 min (IEC Centra-7R, Needham Heights, MA) and the whey collected for calcium analysis. Calcium was analyzed in all cheese samples and whey after ashing as follows: a 1-g sample was ashed overnight in a muffle furnace (Thermolyne, model F-A1625) at 600°C. The ash was treated with approximately 3 ml of nitric acid (trace element free), dried on a hot plate to evaporate the acid, dissolved in approximately 3 ml He1 (trace element free), and diluted 10x and 100x. Lanthanum chloride (.5%) was added to suppress phosphate interference. Calcium in the samples was read at peak wavelength of 422.7 nm using a Perkin Elmer (Norwalk, CT) atomic absorption spect r o p h o t o m e t e r (model 5000). Cheese pH was measured directly by immersing the glass electrode (Beckman pH meter model 3500, Beckman Instruments, Fullerton, CA) into thoroughly mixed samples. Measurements were taken immediately after preparation of the mixes and once a week thereafter during refrigerated storage. Microbial counts in control and supplemented cheese samples were determined once a week as follows: Aliquots (11 g) were removed from the thoroughly mixed cheese and transfeted to a sterile blender. Sterile .1% peptone water (99 ml) was added and the contents were

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blended for 30 s. Total aerobes were determined by plating appropriate dilutions using plate count agar (Difco, Detroit, MI). Plates were incubated at 35°C for 48 h and cells counted. For yeast and mold enumeration, an antibiotic solution of chlorotetracycline He1 and chloramphenicol (500 mg each in 100 ml phosphate buffer) was added to plate count agar (2 ml/100 ml) before pouring the plates. Colonies were counted after incubation for 5 d at 23°C (2). Sensory evaluations of the cheese were conducted after 21 d of refrigerated storage b y quantitative descriptive analysis using score sheets. Evaluations were made by a 12-member panel of graduate students of food and nutrition, who regularly consume cottage cheese. Sensory characteristics scored, on a 1 to 5 scale, were flavor and odor (fresh to off) and color, texture, and overall rating according to preference (from most to least acceptable). A section for comments was also included in the evaluation. Four replicate samples were used for Ca and pH determinations and duplicate samples for enumeration of microorganisms. Calcium and sensory evaluation data were analyzed b y one-way analysis of variance technique. RESULTS AND DISCUSSION

Table 1 presents data on the chloride, lactate, and phosphate calcium salts, percent calcium in the salts, the amount needed to raise the Ca content of cheese by 70 mg/100 g, and the effect of the added salts on the cheese pH. Measurements of pH showed that fresh cottage cheese had a pH of 4.9 -+ .1. Cottage cheese freshly supplemented with the chloride, lactate, and phosphate salts effected a slight decrease in pH, to 4.64, 4.81, and 4.67, respectively. These pH remained essentially unchanged over the 21 d of storage at 5°C. Although both carbonate and gluconate salts were initially included in the study, they were unsuitable Ca sources because of their poor solubility. Cottage cheese contained 75 mg calcium/ 100 g (Table 2). Supplementation of the cheese with the chloride, lactate, or phosphate monobasic salts elevated the Ca content to a mean of 150.5,128.0, and 134.6 mg/100 g, respectively. The disagreement with the calculated values (145 mg/100 g) was apparently caused by the Journal of Dairy Science Vol. 71, No. 10, 1988

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SHELEF AND RYAN

TABLE 1. Salts employed in calcium supplementation of cottage cheese and their effect on pH.

Salt

Molecular weight

Ca

Amount ~

(%)

(g/100 g cheese)

CaC12 .2H 20 CaC 6 Hlo 06 .5H~ O Ca(H2 PO4 )2 "H20

147.02 308.31 252.09

27.25 13.00 15.89

.26 .54 .44

Cheese pH 2

4.64 4.81 4.67

xFor supplementation of 70 mg Ca/100 g cheese. 2 Fresh cottage cheese pH was 4.91.

actual degree of h y d r a t i o n of the salts. In general, the mineral c o n t e n t was distributed evenly within the container, but tended to be lower in the whey. Levels measured at each sampling period in the w h e y of samples supp l e m e n t e d with the lactate or phosphate salt were different (P<.05) f r o m levels in the o t h e r cheese fractions (Table 2). T o t a l aerobes in fresh cottage cheese ranged f r o m 3 × 103 to 8 x 103/g; yeast and m o l d counts were < 1 0 / g . A f t e r 21 d of storage t o t a l aerobic counts increased by less than one log cycle. The added calcium salts did not influence bacterial growth, and differences b e t w e e n numbers were n o t significant a m o n g the treatments. Sensory evaluation results are summarized in Table 3. Average o d o r scores for the f o u r samples were n o t statistically different f r o m each other (P>,05). However, average flavor and preference scores of Ca-supplemented vs. control cottage cheese were significantly different (P<.05). Nonetheless, over 50% o f the panel c o m m e n t e d that the slightly tangy flavor

of the Ca-supplemented samples was not perceived as objectionable. Color and texture were u n a f f e c t e d by the treatments. A l t h o u g h s u p p l e m e n t a t i o n decreased cheese pH slightly, the anions, rather than pH difference (<.2 units), are t h o u g h t to have affected the taste. CONCLUSIONS

Calcium s u p p l e m e n t a t i o n of creamed cottage cheese to levels typically present in milk was d e m o n s t r a t e d . The use of the chloride, lactate, or p h o s p h a t e monobasic salts resulted in p r o d u c t s with elevated calcium content, and s u p p l e m e n t a t i o n did not appreciably affect pH, microbial stability, or o d o r o f the refrigerated cheese. A l t h o u g h taste scores and preference scores of cheese w i t h o u t added calcium were superior and statistically different f r o m all calcium supplemented samples, the latter were judged acceptable. Overall, s u p p l e m e n t a t i o n of cheese with the chloride salt appears to be preferable: because of its low molecular weight in comparison to

TABLE 2. Calcium content in cottage cheese (control) and after supplementation with three calcium salts. Calcium in cheese (mg/100 g) Fraction

Control

SD

CaC1a

SD

CaC6 H10 06

Mixture Top Bottom Whey

75.7

5.8 a 5.2 a 2.3 a 4.6 a

150.5 149.6 151.8 136.9

6.0 a 6.1 a 5.4 a 7.9 a

128.0 120.1 109.8 99.5

77.9 83.8 68.7

SD 8.2 a 10.8 a 5.7 a 2.6 b

Ca(H2 P04 )2

SD

134.6 136.4 135.2 108.2

2.6 a 4.4 a 5.2 a 5.9 b

a'bMeans within a column with different superscripts are significantly different (P<.05). 1Each value is a mean of four replicates. Journal of Dairy Science Vol. 71, No. 10, 1988

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TABLE 3. Sensory evaluation scores for control and calcium supplemented cottage cheese.1 Score Treatment

Odor

SD

Taste

SD

Preference

SD

Control CaCI2 .2H 20 CaC 6 Hi0 06 • 5 H 20 Ca(H 2 PO 4 )~ "H 20

1.33 1.50 1.58 1.75

.49 a .67 a .67 a .75 a

1.17 2.00 2.00 2.33

.39 a .85 b .85 b .78 b

1.42 2.92 2.33 2.08

.67 a 1.16 b .98 b 1.08 b

a'bMeans within a column with different superscripts are significantly different (P<.05). 1Means of scores from a 12-member taste panel (1 = most acceptable, 5 = least acceptable).

t h e o t h e r t w o salts, s u p p l e m e n t a t i o n r e q u i r e d a d d i t i o n o f t h e smallest a m o u n t (.26%, w t / w t ) . T h e s u p p l e m e n t e d mineral was readily inc o r p o r a t e d into t h e cheese and evenly dist r i b u t e d in the cheese and w h e y . Moreover, since s o d i u m chloride is usually a d d e d to cheese, r e d u c t i o n o f t h e s o d i u m chloride c o n t e n t c o u p l e d w i t h calcium c h l o r i d e supp l e m e n t a t i o n should i m p r o v e t a s t e scores for t h e p r o d u c t . A t t e m p t s t o reduce t h e salt c o n t e n t in c o t t a g e cheese to restrict d i e t a r y intake o f s o d i u m have b e e n r e p o r t e d in t h e literature (3, 4, 8). R e d u c i n g t h e s o d i u m chloride c o n t e n t in c o t t a g e cheese while supp l e m e n t i n g it w i t h calcium c h l o r i d e will o f f e r t w o n u t r i t i o n a l b e n e f i t s to p e o p l e c o n s u m i n g c o t t a g e cheese.

ACKNOWLEDGMENT

T h e a u t h o r s t h a n k K-L. C. J e n for assistance in analyzing t h e data.

REFERENCES

1 Anonymous. 1986. Code Fed. Reg. Title 21, Section 133.129(b), p. 184. 2 American Public Health Association. 1985. Standard methods for the examination of dairy products. 15th ed. G. H. Richardson, ed. Washington, DC. 3 Demott, B. J. 1986. Influence of added calcium chloride upon flavor of cottage cheese. Cult. Dairy Prod. J. 21:10. 4 Demott, B. J., J. P. Hitchcock, and O. G. Sanders. 1984. Sodium concentration of selected dairy products and acceptability of a sodium substitute in cottage cheese. J. Dairy Sci. 67:1539. 5 Food and Nutrition Board. 1980. Recommended Daily Allowances. 9th rev. ed. Natl. Acad. Sci., Natl. Res. Counc., Washington, DC. 6 Schuette, S. A., and H. M. Linkswiler. 1984. Calcium in present knowledge in nutrition. 5th ed. Nutrition Found., Inc. Washington, DC. 7 United States Department of Agriculture. 1976. Composition of foods: Dairy and egg products. Agric. Handbook No. 8-1, Agric. Res. Serv., Washington, DC. 8 Wyatt, C. J. 1983. Acceptability of reduced sodium in breads, cottage cheese and pickles. J. Food Sci. 48:1300.

Journal of Dairy Science Vol. 71, No. 10, 1988