Physical Characteristics of Frozen Desserts Made from Ultrafiltered Milk and Various Carbohydrates

Physical Characteristics of Frozen Desserts Made from Ultrafiltered Milk and Various Carbohydrates WAYNE G. GElLMAN and DONALD E. SCHMIDT1 Dairy Products Technology Center California Polytechnic State University San Luis Obispo 93407 ABSTRACT

Milk fat, milk SNF, carbohydrates, emulsifiers, and stabilizers affect the flavor, body, and texture of ice cream. Proteins bind water. fats provide smoothness, carbohydrates affect sweetness and freezing temperature (20). stabilizers bind water, and emulsifiers increase fat dispersion. Stabilizers may bind water and proteins via hydrogen bonding (16). A mix in which all of these ingredients are balanced is essential for the production of quality ice cream (1).

Ultrafiltered whole milk retentate was used to make UF frozen desserts. All frozen desserts had 12% fat, 11.5% milk SNF, 13% sucrose, 4% com syrup solids, .25% stabilizer, and .25% salt. Traditional ice cream, in which NDM provided milk SNF, was the control. Lactose, glucose, and fructose (1.65 and .85% by weight) were added to UF frozen desserts to replace, in part, lactose lost during UF. One UF frozen dessert was made without the addition of alternative sugars. Mixes were pasteurized (74°C for 30 min), homogenized (13,800 kPa, first stage; 3450 kPa, second stage). and frozen in a batch freezer. Generally, UF frozen desserts had 2.24 times as much protein and 65% less lactose than the NDM ice cream. Lactose concentrations in UF desserts were 2.2% compared with 6.6% for the NDM ice cream. The NDM ice creams were significantly softer than all of the UF desserts. Hardness was reduced, and melt (measured by conversion to liquid) was influenced by the type and amount of alternative carbohydrate added to the mix. Fructose had the greatest effect. (Key words: ultrafiltration, frozen dessert, carbohydrate)

UF

INTRODUCTION

Some of the ingredients used to make ice cream mix are milk, cream, condensed milk N~M, dri~ .whey, sugar, dextrose, com syrup soh~s, s~bI1Izers, emulsifiers, and flavorings. VanIlla Ice cream contains not less than 10% milk fat and 20% total milk solids (1).

Received September 20, 1991. Accepted lune 3, 1992. IPresent address: Lochhead Manufacturing Company, Paso Robles, CA 93446. 1992 J Dairy Sci 75:2670-2675

Ultrafiltration has been used to recover proteins from whey and to concentrate milk prior to cheese manufacture. Compared with evaporation, UF reduces space requirements and equipment costs. Milk concentrated via UF has fewer defects related to extended heating than heat-evaporated milk (6, 7). Furthermore, UF, in combination with diafiltration, can be used to alter ratios of protein to lactose (4). Retentates have been used to replace milk SNF, normally obtained from NOM or condensed milk in frozen desserts and in frozen yogurts (3, 5, 6, 7, 12, 17). Kosikowski and Masters (9), Masters and Kosikowski (12), and Hofi (7) reported that desserts made from retentates received body and texture scores comparable with those of commercial ice creams. The high protein content of UF frozen desserts resulted in harder body, but smoother texture, than that of traditional ice cream. Investigations in which milk SNF was replaced with UF retentate indicate that smoother textures (5, 7), lower overruns (8), higher freezing points (5, 7, 8, 19), and harder body (5, 6, 7, 8, 9,10, II, 19) are common results. In addition, the UF ice creams exhibited greater heat-shock stability and better flavor and storage properties than traditional ice creams or ice creams made with whey protein concentrates (9). Desserts made from retentates exhibited excellent melting qualities (5, 6). High protein in the UF desserts increases the water-binding capacity

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FROZEN DESSERTS MADE WITH ULTRAFll.TRATION

and could possibly reduce the amount of stabilizers needed (8, 19). Protein-carbohydrate Interaction

Lonergan (11) documented that frozen storage of reduced-lactose UP retentate destabilized the casein. The stability of the casein in frozen concentrated milk appears to depend on the hydrogen-bonding potential of the carbohydrates in the retentate (13). The stronger and more numerous the hydrogenbonding sites, the more stable is the system (14). Freezing-point depression of sugars also affects protein stability. Stability of casein in the presence of xylose, sucrose, raffinose, and glucose was studied by Minson et al. (13). Freezing-point depression affected protein stability when hydrogen-bonding potential was equal, although casein stability improved as hydrogen bonding increased. During diafiltration, protein is concentrated, and soluble components are removed. An 87% decrease in riboflavin did not affect protein stability, nor did the reduction of soluble calcium (13). Lonergan (11) concluded that water-soluble minerals and vitamins had no significant effect on casein stability. Moon et al. (15) suggest that depletion of carbohydrates in cryocasein resulted in low surface activities and decreased emulsifying capacity. In the present study, the effect of addition of low concentrations of lactose, glucose, and fructose on melt, body, and texture of UP frozen deserts was investigated. MATERIALS AND METHODS Milk

Milk standardized to 4.5% milk fat was provided by the dairy plant at California Polytechnic State University, San Luis Obispo. Milk was pasteurized at 73.8°C for 16 s, homogenized single stage (Series 1000; Cherry Burrell, Inc., Cedar Rapids, IA) (13,800 kPa), and stored at 4°C.

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pressure of 800 kPa, and outlet pressure of 600 kPa. A total of 390 kg of milk was processed: 250 kg of permeate were removed, 215 kg of softened water (49°C) were added to the retentate, and 243 kg of diluted permeate were removed. Retentate was concentrated to about 28% total solids, standardized to 26.5% total solids with undiluted permeate, cooled to 4SC, and stored cold until used. Mix Formulation

The base mix contained 12% fat, 11.5% milk SNF, 13% sucrose, 4% corn syrup solids, .25% stabilizer, and .25% salt (5). The base formulation was as follows: retentate, 82.50%; sucrose, 13.00%; corn syrup solids, 4.00%; KONTROU~ stabilizer (Germantown Mfg., Inc., Broomall, PA), .25%; and salt, .25%. Retentate provided milk SNF and milk fat. Salt was added to lower the freezing point and to improve the flavor and mouthfeel (1). Lactose, glucose, and fructose were each added to UP base mix before processing at .83 or 1.65% (wtlwt). Equivalent retentate was removed to maintain proportions. A traditional mix was prepared using the same sweetener and stabilizer system, except that skim milk and NDM provided milk SNF, and cream provided milk fat. Manufacturing Process

Ingredients were blended, pasteurized (74°C for 30 min), cooled to 60°C, homogenized at 13,800 and 3450 kPa in the first and second stages, cooled to 4°C, and stored overnight. Mixes were flavored with 7.78 ml of singlestrength vanilla extract (Lochhead Manufacturing Co., Paso Robles, CA)/L of mix. Mix was frozen in an batch freezer (model 40; Emery Thompson, Bronx, NY). Overrun was 70 to 75% as determined by the method outlined by Arbuckle (1). Packaging was in 1.89-L (.5-gal) cartons and in 113-g (6-oz) cups. Frozen desserts were placed in a -28.8°C hardening room for 24 h and then transferred to a -22°C freezer.

UF Ultrafiltration was performed with a DDS pilot plant (model 36-2.25; Niro Atomizer, Hudson, WI) UP unit fitted with a DDS 2000 polysulfone 20,000 molecular weight cutoff, spiral wound membrane. The system was operated in a batch mode at 49°C, constant inlet

Compositional Analysis

Mixes were analyzed for total solids, fat, protein, lactose, and ash. Microwave oven procedure was used to determine total solids (18). The Pennsylvania modified Babcock method [AOAC 16.177 for cream (2)] was Journal of Dairy Science Vol. 75, No. 10, 1992

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GEll..MAN AND SCHMIDT

used for fat analysis. Protein detenninations were by dye binding [method 18.IIC (18)] (model 3010-020; UDY Corp., Fort Collins, CO). A YSI model 27 instrument (Yellow Springs Instrument Co., Yellow Springs, OR) with an immobilized galactose oxidase enzyme membrane was used to detennine lactose. Ash was determined by method 18.4 (18).

Statistical Analysis

The design of the experiment was a randomized block. There were three replications. Analytical tests were performed in triplicate. Minitab Release 6.1 (Minitab Inc, State College, PA) was used to perform ANOVA and to calculate mean values. Duncan's multiple range test (P > .05) was performed after ANDVA analysis when appropriate.

PhysIcal Analysis of Ice Cream

Hardness was measured using a cone penetrometer using a 35-g model p cone (model l2-Z-11; Precision Scientific, Inc., Chicago, fi.,) (1, 10, 19). The 113-g cups of dessert were tempered to -I6.6"C, and testing was performed at 22"C. Each test required less than 1 min. Melt was measured by modifying the method described by Arbuckle (1). A 113-g sample of tempered dessert was placed on a lOO-mesh metal screen in an 25.5"C gravity convection incubator (Blue M Stabl Therm; General Signal Co., Blue Island, fi.,) to simulate ambient summer temperatures, and the volume of melted liquid collected in a graduated cylinder was recorded every 5 min for 80 min. Sensory Evaluation

Samples were evaluated for flavor, body, and texture by 11 experienced judges. Differences in product attributes were recorded.

RESULTS Mix Composition

Frozen dessert mixes 1 and 2 contained lactose added at 1.65 and .83%; mixes 3 and 4 contained glucose added at 1.65 and .83%; and mixes 5 and 6 contained fructose added at 1.65 and .83%. Control UP contained no added lactose. The traditional mix was prepared with NOM providing milk SNF and with the same sweeteners as the UP control. The compositions of mixes are in Table 1. Differences were not significant (P > .05) between total solids, fat, and ash contents. Total solids ranged from 39.92 to 41.05%. Differences were significant between the protein contents of UP desserts and NOM ice cream. The mean protein content of the UP desserts was 8.93 versus 3.98% for NOM mix. Protein contents among UP desserts were not significantly different (P > .05). Lactose for UP desserts was 2.2 versus 6.6% for NOM ice

TABLE 1. Composition of mixes made with alternative sweeteners for the production of UP retentate desserts compared with traditional ice cream made from NOM. I Sample

Total solids

Protein

Fat

Lactose

Ash

6.6" 2.2 b 2.3 b 2.2b 2.2b 2.1 b 2.2b 2.2 b .10

1.18" 1.12" 1.11" 1.12" 1.11" 1.09" 1.08" 1.09" .04

(Mean %) NOM Mix UP Control UP Mix 1 UP Mix 2 UP Mix 3 UP Mix 4 UP Mix 5 UP Mix 6 SE

39.92" 40.38" 41.04" 40.82" 41.05" 40.94" 40.93" 40.95" .56

3.98" 8.61 b 8.93b 9.01 b 8.94b 8.93b 9.02b 9.05b .39

12.08" 12.25" 12.15" 12.34" 12.05" 12.30" 12.05" 12.05" .23

".bMeans within the same column followed by the same letters are not significantly different (P < .05). IMix 1 = 1.65% lactose; mix 2 = .83% lactose; mix 3 = 1.65% glucose; mix 4 .:: .83% glucose; mix 5 fructose; and mix 6 = .83% fructose. All mixes contained 13% sucrose and 4% com syrup solids.

Journal of Dairy Science Vol. 75, No. 10, 1992

= 1.65%

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FROZEN DESSERTS MADE WITH ULTRAFILTRATION

TABLE 2. Penetration depths and overrun for UP desserts made with alternative sweeteners and NDM ice cream.! Sample

Penetration

Overrun

Draw temperature

(mm)

(%) 74.68 71.58 71.58 73.88 70.98 74.78 71.48 72.68 6.0

-3.00a -1.50b -1.54b -1.55 b -1.57 b -1.65 b -1.60b -1.63 b .28

157.898 76.92b 83.74c 82.61 c 85.15c 86.37c 92.38d 90.67d 6.16

NDM Mix UP Control UP Mix I UP Mix 2 UP Mix 3 UP Mix 4 UP Mix 5 UP Mix 6 SE

('C)

8,b.c,dMeans within a column followed by the same letters are not significantly different (P > .05). lMix I = 1.65% lactose; mix 2 = .83% lactose; mix 3 = 1.65% glucose; mix 4 = .83% glucose; mix 5 fructose; and mix 6 = .83% fructose. Each mix contained 13% sucrose and 4% corn syrup solids.

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Figure 1. Melt profiles of UP desserts containing added lactose (A), fructose (8), glucose (C), and comparison (D) of all added sugars. Journal of Dairy Science Vol. 75, No. 10, 1992

2674

GEll..MAN AND SCHMIDT

cream. Lactose concentrations for the UF mixes were not significantly different (P> .05) based on results of the testing technique used. Overrun and Hardness

Overruns for the ice cream samples ranged from 70.9 to 74.8% and were not significantly different (P > .05) (fable 2). The hardness of the frozen desserts, indicated by decreased penetration, resulted in significant differences (P > .05) (Table 2). Mean penetration depths ranged from 7.69 to 9.24 mm for UF desserts. The NDM samples had a mean penetration of 15.78 mm. Multiple range tests indicated that the amount and type of carbohydrate used influenced the hardness of UF desserts. The addition of lactose to mixes 1 and 2 did not significantly (P > .05) reduce hardness from the UF control mix. The addition of glucose to mixes 3 and 4 resulted in significant differences (P < .05) from the other UF variables. The amount of glucose added had little effect. Mixes 5 and 6, which had fructose added, were significantly softer (P < .05) than other UF desserts. The effect of variables-such as overrun, draw temperature (-3.0·C for NDM mix and -1.5 to -1.65·C for

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UF mixes), and total solids-did not result in significant interactions (P > .05). Differences in frozen dessert hardness could not be explained by the effect of alternative sweeteners on the calculated percentage of frozen water in the frozen dessert. Arbuckle (1) suggested that depression of the freezing point and, hence, the percentage frozen water are affected by the molecular weight of the carbohydrate added. Therefore, glucose and fructose should have had an equal effect on product hardness. Because this was not the case, other reactions, perhaps those between carbohydrate and protein, influenced product hardness. In the preparation of cryocasein, the percentage of sugar present affected protein stability (13, 14). The effect of protein and carbohydrate interactions in relation to ice cream hardness deserves additional investigation. Melt

The amounts of melted mix collected from the UF desserts were significantly different (P < .05) from those of the NDM ice cream. The liquid was collected from NDM ice cream within 5 min, but the UF desserts did not

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Figure 2. Comparison of melt and hardness characteristics of UF desserts and traditional ice cream. Bars with different letters (a, b, c) are significantly different (P < .05). Journal of Dairy Science Vol. 75, No. 10, 1992

FROZEN DESSERTS MADE WITH ULTRAFILTRAnON

release any fluid for 30 min. Although the initiation of fluid release was slower for the UF desserts, total conversion to liquid was more complete and faster than for the traditional ice cream. The amounts of mix collected from the UP desserts with the added sugars were not significantly different (P > .05) from one another. But, as seen in Figure 1, the average amounts of liquid collected over time were not identical. Figure 2 shows that, as the softness of the dessert increased, so did the amount of melted mix after 45 min. However, the relationship between the two attributes was not direct or proportional. Sensory Analysis

The judges determined that sensory attributes of the UF and NDM ice creams were similar, but UF desserts tended to receive more positive comments on flavor, body, and texture than the NDM ice cream. CONCLUSIONS

The type of carbohydrate added to lactosereduced UF desserts affected the hardness of the product. The softening of the UF products could not be accounted for by the effect of calculated freezing-point depression, as evidenced by differences between fructose and glucose variables. Melting profiles of UF desserts were different from those of traditional products. Initiation of melt, as indicated by fluid collected, was slower but occurred at a faster rate and was more complete. Additional work is needed to determine why the addition of small amounts of different carbohydrates affected the physical characteristics of frozen dessert prepared from lactose-reduced retentate. ACKNOWLEDGMENTS

Funding for this project was provided by the California Dairy Foods Research Center and the National Dairy Promotion and Research Board. Leslie Cooper edited this manuscript. REFERENCES 1 Arbuckle, W. S. 1986. Ice Cream. 3rd ed. AVI Publ. Co., Westport, CT.

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2 Association of Official Analytical Chemists. 1984. Official Methods of Analysis. 14th ed. AOAC, Arlington, VA. 3 Bundgaard, A. G. 1972. Hyperfiltration of skim milk for ice cream manufacture. Dairy Ind. 10:119. 4 Cheyran, M. 1986. Ultrafiltration Handbook. Technomic Publ. Co., Lancaster, P A. 5 GeHman, W., D. Schmidt, C. Herfurth-Kennedy, and J. Path. 1990. Production of frozen desserts from milk retentate. J. Dairy Sci. 73(Suppl. 1):75.(Abstr.) 6 Grow, K. P., H. A. Roberts, and I. J. Jeon. 1989. Evaluation of ice milks containing ultrafiltered skim milk solids. J. Dairy Sci. 72(Suppl. 1):130.(AbstL) 7 Hofi, M. A. 1989. The use of ultrafiltration in ice cream making. Egypt. J. Dairy Sci. 17:27. 8 Jensen. L. A., P. S. Tong, and L. Harris. 1989. Characteristics of frozen desserts containing retentate from ultrafiltration of skim milk. I. Mix composition and freezing. J. Dairy Sci. 72(Suppl. l):129.(Abstr.) 9 Kosikowski, F. V., and A. R. Masters. 1983. Preparation of ice cream, skim milk and cream made from whole milk retentates. J. Dairy Sci. 66(Suppl. 1): 99.(Abstr.) 10 Lee, F. Y. 1990. Effect of ultrafiltration retentates and whey protein concentrates on ice cream quality during storage. M.S. Thesis, Mississippi State Univ., Starkville. 11 Lonergan, D. A. 1983. Isolation of casein by ultrafiltration and cryodestabilization. J. Food Sci. 48: 1817. 12 Masters, A. R., and F. V. Kosikowski. 1986. Effect of protein and solids content on low lactose ice cream from ultrafiltered milk. J. Dairy Sci. 69(Suppl. 1): 78.(Abstr.) 13 Minson, E. I., 0. Fennema, and C. H. Admunson. 1981. Accelerated test for evaluating protein stability in frozen skim milk. J. Food Sci. 46:1592. 14 Minson, E. I., O. Fennema, and C. H. Admunson. 1981. Efficiency of various carbohydrates as cryoprotectants for casein in skim milk. J. Food Sci. 46:1597. 15 Moon, T. W., I. C. Peng, and D. A. Lonergan. 1989. Functional properties of cryocasein. J. Dairy Sci. 72: 815. 16 Neilson, B. J. 1978. Combined emulsifiers/stabilizers for ice cream. Gordian 78:176. 17 Parsons, J. G., S. T. Dybing, D. S. Coder, K. R. Spurgeon, and S. W. Seas. 1985. Acceptability of ice cream made with processed wheys and sodium caseinate. J. Dairy Sci. 68:2880. 18 Richardson, G. 1985. Standard Methods for the Examination of Dairy Products. 15th ed. Am. Publ. Health Assoc., Inc., Washington, DC. 19 Tong, P. S.• L. A. Jensen, and L. Harris. 1989. Characteristics of frozen desserts containing retentate from ultrafiltration of skim milk. II. Some physical properties. J. Dairy Sci. 72(Suppl. 1): 129.(Abstr.) 20 Wong, N. P., R. Jenness, M. Keeney, and E. H. Marth. 1988. Fundamentals of Dairy Chemistry. 3rd ed. Van Nostrand, New York, NY.

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