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Low Lactose Yogurts and Milk Beverages by Ultrafiltration
Low Lactose Yogurts and Milk Beverages by Ultrafiltration F R A N K V. KOSIKOWSKI Department of Food Science
CorneH University Ithaca, N Y 14853
making. Such retentates stored for long periods without obvious changes, or spray dried and transported long distances, are used directly as viscous concentrates. They contain 18 to 20% protein and 4 to 5% lactose when made from skim milk. Diluting such highly plasticized retentates with water about 5 to 6 times, standardizing with fat, and making them with their naturally occurring low lactose, into fresh milk beverages and yogurts whose general composition and other characteristics could be observed was the present objective.
ABSTRACT
Skim milk retentates from ultrafiltration, containing approximately 20% protein, were diluted with water to 3.3 to 4.6% protein, standardized with cream to 1.38 to 2.60% fat, and homogenizedpasteurized. Such cooled milk beverages displayed good flavor and low lactose. Yogurts made from these low lactose milk beverages contained .31 to .61% lactose, a smooth viscous texture, and firm b o d y with clean, acid, slightly flat flavor. Samples were lower in mineral elements and calories than standard commercial yogurts. One low lactose yogurt contained 22 mg sodium and 31 cal per 100 g. Titratable acid and pH were comparable to fresh standard commercial yogurts but storage for 6 wk at 5 C showed no significant change in acidity. Bitterness occurred after the 1st wk in some lots of low lactose yogurt.
MATERIALS AND METHODS
Approximately 250-kg lots of pasteurized skim milk, processed fresh in the Cornell Dairy Plant, were concentrated selectively by direct ultrafiltration in an Abcor UF-22S unit with HFM (high flux membranes) with a molecular weight cut-off of 20,000. The skim milk was ultrafiltered at 50 C and 3.4 kg per cm 2 throughout concentration, and stored at - 2 0 C. When required for experiments, the highly concentrated frozen retentates were thawed overnight in a warm room and reconstituted with cold, clean tap water to varying protein between 3.3 to 4.6%, standardized with cream to 1.4 to 2.6% fat, then made into experimental yogurt lots. In several designed to increase flavor, 1% spray dried buttermilk (5.3% fat and 35.0% protein) and .04 to .4% sodium citrate (Na3C6Hs O 7 "2H20) were incorporated. Active individual cultures of Streptococcus tbermopbilus and Lactobacillus bulgarieus were used at 1.5% for each microorganism. A typical formula for 100 kg of experimental yogurt mix consisted of 44 kg retentate, 11 kg 40% fat cream, and 154 kg water along with dry buttermilk and sodium citrate, if required. The yogurt mix was heated to 65 C and homogenized (Manton-Gaulin) at 117 kg per cm 2, single stage. This hot mix was pasteurized at 75 C for 30 rain and cooled to 45 C. Then it was inoculated with active yogurt starter, filled into plastic cups with covers, and incubated at 43 C
INTRODUCTION
A need exists for low lactose milk and milk products (9, 16). Experimentally, hydrolysis of the lactose of milk by lactase has been the generally proposed mechanism to reduce lactose. Total carbohydrate and calories remain constant, and the product is sweeter (14, 15). Several reports (5, 11) cite the principles for making low lactose yogurts, using acid or neutral lactases, but no commercial milk products of this type have evolved. In parallel developments, ultrafiltration has emerged as a pragmatic means selectively to concentrate milk for cheese and manufacture of other dairy products (2, 4, 6, 13). An original concept by Maubois and Mocquot (12) suggested concentrating milk selectively 5 to 6 fold to produce a pre-cheese retentate requiring no further extensive whey separation for cheese Received May 22, 1978.
1979 J Dairy Sci 62:41-46
41
42
KOSIKOWSKI
TABLE 1. Composition of skim milk retentate and low lactose fat fortified milk beverage.
Components
Skim milk retentate (%)
Total protein Lactose Fat Ash Total solids
20.3 4.17 .93 2.27 27.60
for 3.5 to 4.0 h. Upon achieving a firm acid curd and a pH below 4.5 it was chilled rapidly t o 5 C. Yogurt and retentate samples were analyzed for c o m p o n e n t s in duplicate. Total solids were determined by drying overnight in a 100 C oven. Standard m e t h o d s of A O A C (1) were used for obtaining ash and total protein, the latter as Kjeldahl nitrogen. Fat was obtained by the standard Babcock test for milk with confirmation by the Mojonnier method. Mineral analyses were by photoelectric s p e c t r o m e t r y according to K e n w o r t h y (10), and lactose was calculated by difference. The pH values were obtained with a glass electrode p o t e n t i o m e t e r (Beckman Expandomatic). Titratable acidity, with N / 1 0 alkali and phenolphthalein, was expressed as percent lactic acid. Product flavor, texture, and appearance were judged by the a u t h o r using the official American Dairy Science score card as a guide.
R ESU LTS
Skim milk retentates
f r o m uttrafiltration,
Low lactose milk beverages (%) (1)
(2)
3.2 1.1 2.33 .42
3.88 1.1 2.00 .47
7.38
7.46
after a p p r o x i m a t e l y 5- to 6-fold dilution with water and i n c o r p o r a t i o n of milk fat, followed by h o m o g e n i z a t i o n and pasteurization, gave milk beverages of low lactose, Table 1, and clean good quality flavor. Three yogurts were made from such low lactose milk beverages in the first series, Table 2, with 3.32, 3.97, and 4.37% protein. Their lactose was .31, .40, a n d . 51%. The flavor of 1-wk old low lactose yogurt was clean and typical but slightly fiat. All these yogurts had firm bodies and s m o o t h texture but yogurts containing 3.97% protein most closely duplicated a good quality standard c o m m e r c i a l product. To m o d i f y flatness of flavor, new experimental lots of low lactose y o g u r t were supplem e n t e d with spray dried b u t t e r m i l k a n d / o r sodium citrate, Table 3. Small a m o u n t s of dry b u t t e r m i l k (1%) and sodium citrate (.04 to .4%) enhanced yogurt flavor w i t h o u t adversely affecting other qualities. However, holding some lots of yogurt at 5 C for a week or m o r e led to bitter flavor. F o r example, lots 2 and 3, Table 3, showed definite bitterness at 6 weeks.
TABLE 2. Composition of yogurts from reconstituted retentates of increasing protein content.a Total protein
Yogurt
Lactose
Fat
Ash
Total solids
Titratable acidity b
7.4 8.3 8.8
.98 ...c . . . . . .
pH
(%) A B C
3.32 3.97 4.37 a
-
.31 .40 .51
2.36 2.36 2.36
.49 .55 .59
4.15 ...
•
Original concentrated retentate -- 27.6% total solids, .93% fat, 20.3% protein, 2.27% ash, and 4.2% lactose.
blnitial acidity of fresh yogurt reconstituted retentate mix B = .13% TA and pH 6.78 and C = .15% TA and pH 6.78 - February 2, 1977. CNo analyses made. Journal of Dairy Science Vol. 62, No. 1, 1979
© t©
TABLE 3. Composition of yogurts from reconstitu t e d retentates s uppl e me nt e d with dried b u t t e r m i l k and sodium citrate, a
Yogurt supplemented with
Total protein
Lactose
Fat
Ash
Total solids
Titratable acid ityb
,< 0 0 pH
(%)
Z t~
Lot 1 -- April 14, 1977 D, Dry b u t t e r m i l k c E, Dry b u t t e r m i l k c and .4% sodium citrate
3.62 3.59
.45 .63
1.38 ] .38
.50 .71
6.8 7.1
.89 .90
4.02 4.38
Lot 2 -- April 22, 1977 F, Dry b u t t e r m i l k c and .040% sodium citrate
4.56
.55
2.59
.61
9.2
1.02
4.22
Lot 3 -- April 22, 1977 G, .040% Sodium citrate only
4.62
.48
2.60
.60
9.1
.91
4.45
F t~ <
t~ ~4
aorig inal concentrated retentate for Lots 1, 2, 3 = 19% protein, .3% fat. blnitial acidity of fresh yogurt retentate mix, F = .125% and pH 6.65 and G = .115% and pH 6.75.
,q
CDried b u t t e r m i l k used at 1% by wt.
>
F g < o Z Z O
44
KOSIKOWSKI
TABLE 4. Acidity changes in yogurts from reconstituted retentates stored at 5 C. Yogurts of tables 1-2
0
Weeks
A
.98
1
2
3
4
5
6
Titratable acidity, % 1.02
.91
.92
.93
.93
...a
B
. . .
1.11
1.00
1.02
1.02
1.02
...
C D E F G
._ '.89 .90 1.02 .91
1.12 .91 .91 1.04 .92
1.05 .93 .89 1.16 .94
1.07 .92 .93 1.10 1.00
1.07 .95 .94 1.11 1.00
1.04 .99 .94 1.12 .99
".97".94 1.11 1.03
A B C D E F G
4.15 ... -.4.02 4.38 4.22 4.45
4.02 4.15 4.12 4,08 4.32 4.21 4.45
4.11 4.15 4.20 4.11 4.30 4.25 4.45
4.10 4.20 4.20 4.09 4.35 4.32 4.49
4.11 4.15 4.22 4.11 4.42 4,32 4.59
pH 4.11 4.12 4.21 4.12 4.38 4.25 4.50
... ... - . -
4,18 4.48 4.41 4.50
aNo analyses. Their fresh, o n e day old samples were free o f t h e defect. Initial acidities o f the freshly made, low lactose milk beverages, prior t o y o g u r t m a n u facture, were less t h a n t h o s e o f n o r m a l fresh milk due to a r e d u c e d solid-not fat c o n t e n t . Titratable acidity o f the low lactose milk beverages were .11 to .13% and pH was 6.65 to 6.75. Plain, low lactose y o g u r t s during the 1st w k had titratable acidities o f .90 to 1.12%, d e p e n d ing u p o n p r o t e i n and milk-solid-not-fat, and a pH 4.0 to 4.15, Table 4. A d d i t i o n o f dry b u t t e r m i l k did n o t change m a r k e d l y the pH,
but t h a t o f s o d i u m citrate, alone, raised t h e pH f r o m 4.02 to 4.38, Table 4. Low lactose yogurts, s t o r e d 6 wk at 5 C, changed little in titratable acidity and pH. In t h r e e u n s u p p l e m e n t e d y o g u r t s n o change oc ~ curred f r o m the 2nd t o 5th wk. Dry b u t t e r m i l k and sodium citrate-supplemented yogurts b e h a v e d similarly t h r o u g h 6 wk. When y o g u r t s were held up to 8 wk, m o l d b e c a m e visible.
Mineral Elements
for
Several low lactose y o g u r t s w e r e analyzed m a j o r minerals, Table 5. P h o s p h o r u s ,
TABLE 5. Mineral elements of yogurts from reconstituted retentates.
Element
Yogurt F supplemented with dry buttermilk and sodium citrate
Yogurt G supplemented with sodium citrate only
Low fat plain commercial yogurt a
Whole milk plain commercial yogurt a
144 183 234 70
95 121 155 46
(rag/100 g) Phosphorus Calcium Potassium Sodium
108 132
80 95
124
104
45
22
aUSDA Handbook No. 8-1, revised November 1976. Journal of Dairy Science Vol. 62, No. 1, 1979
LOW LACTOSE YOGURTS AND MILK BEVERAGES BY ULTRAFILTRATION calcium, potassium, and sodium were lower in such yogurts than in commercial low fat yogurt containing added skim milk powder. Sodium was significantly lower than in the others. Low lactose yogurt G supplemented with .04% sodium citrate, for example, was 67% lower in sodium. Calcium reduction compared to the same yogurt was 48% but compared to normally calcium-rich whole milk was only 21%. The calcium to phosphorus ratio (1.0 to .84) was similar to whole milk and to commercial yogurts. Calories
Calories of all low lactose yogurts were less than those of standard commercial yogurts. Three low lactose yogurts, A and B, Table 1, and D, Table 2, ranging from 3.32 to 3.97% protein, after arbitrary adjustment to 1.55% fat. gave calculated calories of 30.1, 32.1, and 33.1 calories/100 g. These are compared to the 63 cal reported for 1.55% fat commercial yogurt fortified with skim milk powder (18). If computed as fruited low lactose yogurts with added sugar, they gave a lower percentage reduction in calories but which was, nevertheless, striking. DISCUSSION
Milk retentates universally have been used directly in their concentrated state for dairy products. In this study, the concept was to dilute highly concentrated, 20% protein, skim milk retentates with water into milk beverages containing about 3.5 to 4.5% protein. Resulting milk beverages and yogurts were low in lactose, as a natural consequence, and also, low in sodium and calories compared with commercial low fat, fortified yogurt. This suggests a potential for a new kind of low lactose fresh milk beverage not hydrolyzed by added lactase enzymes. Feeding trials with humans reported by Jones et al. (9) showed that milks whose lactose was reduced 75% by lactase hydrolysis were accepted highly and tolerated by most of the sensitive subjects. Lactose in the yogurts from the current investigation was reduced by 90 to 94% but not by hydrolysis. Commercial yogurts are abnormally high in lactose. Goodenough and Kleyn (8) reported that pre-yogurt bases averaged 8.5% lactose and yogurts 5.8
45
lactose, both significantly higher than whole milk. This results from skim milk powder fortification to improve body. The present experimental low lactose yogurts displayed satisfactory firmness, viscosity, and free whey at low milk solids. Properties of the natural low lactose yogurts were typical of standard commercial yogurt except for some flktness in flavor and, during storage, the appearance of bitterness among several lots (F, G), and a lack of acidity change from that established in the 1-wk old product. Flatness was decreased by adding dried buttermilk or sodium citrate or both. Improvement might, also, result by limiting lactose reduction to 1%. The pattern and origin of bitterness was not uncovered. It may be related to mold contamination, visibily observed from 6 to 8 wk, to the low total solids and high initial acid, or to some inherent property of the retentate in question. This suggests the need for more study. Standard commercial yogurt generally increases in titratable acidity from .9 to 1.7% after manufacture. This change contrasts with the almost stationary acidity of .9 to 1.1% in the experimental yogurts during 6 wk holding at 5 C, indicating lactose as a limiting factor. This may be a significant factor in improving keeping quality. Since this paper was presented for publication, Toppino et al. (17) reported in an abstract that yogurts from 1:2.5 concentrated ultrafiltered and diluted milks showed no increase in acidity above 1.1% for more than 7 days. Diluting highly concentrated milk retentates with water, a concept not to be confused with diafiltration concentration techniques described by Covacevich and Kosikowski (3, 4), apparently creates fundamental changes in protein micelle relationships. Otherwise, it is difficult to explain why firm, highly viscous acid curds are produced in yogurts made from them and containing only 7.4% total solids and 3.3% protein, Table 1. Furthermore, in preliminary studies of the same low lactose milk beverages, standardized to 3.5% fat, and set with standard amounts of rennet at normal temperatures for Cheddar cheese, curd formation was instantaneous. Also when skim milk retentates, without added fat, were diluted to about 5:1 acceptable cottage cheese was made. The curds cooked out Journal of Dairy Science Vol. 62, No. 1, 1979
46
KOSIKOWSKI
quickly during h e a t i n g t o give discrete, soft curds and an a p p a r e n t high yield. Such interesting c h e e s e m a k i n g characteristics o f low lactose milk beverages p r o d u c e d b y u l t r a f i l t r a t i o n encourages f u r t h e r research in t h e area.
REFERENCES
1 AOAC. 1970. Official methods of analysis, l l t h ed. Association of Official Agricultural Chemists, Washington, DC. 2 Chapman, H. R., V. E. Bines, F. A. Glover, and P. J. Skudder. 1974. Use of milk concentrated by ultrafiltration for making hard cheese, soft cheese and yogurt. J. Soc. Dairy Tech. 27:151. 3 Covacevich, H. R., and F. V. Kosikowski. 1977. Skimmilk concentration for cheesemaking by alternative ultrafiltration procedures. J. Food Sci. 42:1359. 4 Covacevich, H. R., and F. V. Kosikowski. 1977. Cream cheese by ultrafiltration. J. Food Sci. 42:1362. 5 Engel, W. G. 1973. The use of lactase to sweeten yogurt without increasing calories. Cultured Dairy Prod. J. 8:6. 6 Fenton-May, R. I., C. G. Hill, Jr., E. H. Amundson, M. H. Lopez, and P. D. Auclair. 1972. Concentration and fractionation of skimmilk by reverse osmosis and ultrafiltration. J. Dairy Sci. 55:1561. 7 Glover, F. A. 1971. Concentration of milk by ultra filtration and reverse osmosis. J. Dairy Res. 38:373. 8 Goodenough, E. R., and D. A. Kleyn. 1976. Qualitative and quantitative changes in carbohy-
Journal of Dairy Science Vol. 62, No. 1, 1979
drates during the manufacture of yogurt. J. Dairy Sci. 59:45. 9 Jones, D. V., M. C. Latham, F. V. Kosikowski, and G. Woodward. 1976. Symptom response to lactose - reduced milk in lactose-intolerant adults. Amer. J. Clin. Nutr. 29:633. 10 Kenworthy, A. L. 1960. Photoelectric spectrometer analysis of plant materials. Report of the Annu. Meeting of the 1960 Amer. Soc. Horticultural, March. 11 Kosikowski, F. V., and L. E. Wierzbicki. 1971. Low lactose yogurt from microbial lactase (/3-galactosidase) applications. J. Dairy Sci. 54:764. 12 Maubois, J. L., and G. Mocquot. 1971. Preparation of cheese from liquid precheese obtained by ultrafiltration of milk. Le Lait 51:495. 13 Maubois, J. L., and G. Mocquot. 1975. Application of membrane ultrafiltration to preparation of various types of cheese. J. Dairy Sci. 58:1001. 14 Paige, D. M., T. M. Bayless, S. S. Huang, and R. Wexler. Lactose hydrolyzed milk. Amer. J. Clin. Nutr. 28:818. 15 Rand, A., and P. Linklater. 1973. The use of enzymes for the reduction of lactose levels in milk products. Aust. J. Dairy Tech. 28:63. 16 Skala, I., V. Lamacora, and F. Pirk. 1971. Lactosefree milk as a solution of problems associated with dietetic treatment of lactose intolerance. Digestion 4:326. 17 Toppino, P. M., R. Nanni, and A. Cabrini. 1978. Preparation of yogurt with low acid content keeping quality at 25 and 4°C. Page 832 in Brief communications 20th International Dairy Congress, Paris. June 26-30. 18 USDA Handbook 8-1. 1976. Composition of dairy products. Washington, DC.
CorneH University Ithaca, N Y 14853
making. Such retentates stored for long periods without obvious changes, or spray dried and transported long distances, are used directly as viscous concentrates. They contain 18 to 20% protein and 4 to 5% lactose when made from skim milk. Diluting such highly plasticized retentates with water about 5 to 6 times, standardizing with fat, and making them with their naturally occurring low lactose, into fresh milk beverages and yogurts whose general composition and other characteristics could be observed was the present objective.
ABSTRACT
Skim milk retentates from ultrafiltration, containing approximately 20% protein, were diluted with water to 3.3 to 4.6% protein, standardized with cream to 1.38 to 2.60% fat, and homogenizedpasteurized. Such cooled milk beverages displayed good flavor and low lactose. Yogurts made from these low lactose milk beverages contained .31 to .61% lactose, a smooth viscous texture, and firm b o d y with clean, acid, slightly flat flavor. Samples were lower in mineral elements and calories than standard commercial yogurts. One low lactose yogurt contained 22 mg sodium and 31 cal per 100 g. Titratable acid and pH were comparable to fresh standard commercial yogurts but storage for 6 wk at 5 C showed no significant change in acidity. Bitterness occurred after the 1st wk in some lots of low lactose yogurt.
MATERIALS AND METHODS
Approximately 250-kg lots of pasteurized skim milk, processed fresh in the Cornell Dairy Plant, were concentrated selectively by direct ultrafiltration in an Abcor UF-22S unit with HFM (high flux membranes) with a molecular weight cut-off of 20,000. The skim milk was ultrafiltered at 50 C and 3.4 kg per cm 2 throughout concentration, and stored at - 2 0 C. When required for experiments, the highly concentrated frozen retentates were thawed overnight in a warm room and reconstituted with cold, clean tap water to varying protein between 3.3 to 4.6%, standardized with cream to 1.4 to 2.6% fat, then made into experimental yogurt lots. In several designed to increase flavor, 1% spray dried buttermilk (5.3% fat and 35.0% protein) and .04 to .4% sodium citrate (Na3C6Hs O 7 "2H20) were incorporated. Active individual cultures of Streptococcus tbermopbilus and Lactobacillus bulgarieus were used at 1.5% for each microorganism. A typical formula for 100 kg of experimental yogurt mix consisted of 44 kg retentate, 11 kg 40% fat cream, and 154 kg water along with dry buttermilk and sodium citrate, if required. The yogurt mix was heated to 65 C and homogenized (Manton-Gaulin) at 117 kg per cm 2, single stage. This hot mix was pasteurized at 75 C for 30 rain and cooled to 45 C. Then it was inoculated with active yogurt starter, filled into plastic cups with covers, and incubated at 43 C
INTRODUCTION
A need exists for low lactose milk and milk products (9, 16). Experimentally, hydrolysis of the lactose of milk by lactase has been the generally proposed mechanism to reduce lactose. Total carbohydrate and calories remain constant, and the product is sweeter (14, 15). Several reports (5, 11) cite the principles for making low lactose yogurts, using acid or neutral lactases, but no commercial milk products of this type have evolved. In parallel developments, ultrafiltration has emerged as a pragmatic means selectively to concentrate milk for cheese and manufacture of other dairy products (2, 4, 6, 13). An original concept by Maubois and Mocquot (12) suggested concentrating milk selectively 5 to 6 fold to produce a pre-cheese retentate requiring no further extensive whey separation for cheese Received May 22, 1978.
1979 J Dairy Sci 62:41-46
41
42
KOSIKOWSKI
TABLE 1. Composition of skim milk retentate and low lactose fat fortified milk beverage.
Components
Skim milk retentate (%)
Total protein Lactose Fat Ash Total solids
20.3 4.17 .93 2.27 27.60
for 3.5 to 4.0 h. Upon achieving a firm acid curd and a pH below 4.5 it was chilled rapidly t o 5 C. Yogurt and retentate samples were analyzed for c o m p o n e n t s in duplicate. Total solids were determined by drying overnight in a 100 C oven. Standard m e t h o d s of A O A C (1) were used for obtaining ash and total protein, the latter as Kjeldahl nitrogen. Fat was obtained by the standard Babcock test for milk with confirmation by the Mojonnier method. Mineral analyses were by photoelectric s p e c t r o m e t r y according to K e n w o r t h y (10), and lactose was calculated by difference. The pH values were obtained with a glass electrode p o t e n t i o m e t e r (Beckman Expandomatic). Titratable acidity, with N / 1 0 alkali and phenolphthalein, was expressed as percent lactic acid. Product flavor, texture, and appearance were judged by the a u t h o r using the official American Dairy Science score card as a guide.
R ESU LTS
Skim milk retentates
f r o m uttrafiltration,
Low lactose milk beverages (%) (1)
(2)
3.2 1.1 2.33 .42
3.88 1.1 2.00 .47
7.38
7.46
after a p p r o x i m a t e l y 5- to 6-fold dilution with water and i n c o r p o r a t i o n of milk fat, followed by h o m o g e n i z a t i o n and pasteurization, gave milk beverages of low lactose, Table 1, and clean good quality flavor. Three yogurts were made from such low lactose milk beverages in the first series, Table 2, with 3.32, 3.97, and 4.37% protein. Their lactose was .31, .40, a n d . 51%. The flavor of 1-wk old low lactose yogurt was clean and typical but slightly fiat. All these yogurts had firm bodies and s m o o t h texture but yogurts containing 3.97% protein most closely duplicated a good quality standard c o m m e r c i a l product. To m o d i f y flatness of flavor, new experimental lots of low lactose y o g u r t were supplem e n t e d with spray dried b u t t e r m i l k a n d / o r sodium citrate, Table 3. Small a m o u n t s of dry b u t t e r m i l k (1%) and sodium citrate (.04 to .4%) enhanced yogurt flavor w i t h o u t adversely affecting other qualities. However, holding some lots of yogurt at 5 C for a week or m o r e led to bitter flavor. F o r example, lots 2 and 3, Table 3, showed definite bitterness at 6 weeks.
TABLE 2. Composition of yogurts from reconstituted retentates of increasing protein content.a Total protein
Yogurt
Lactose
Fat
Ash
Total solids
Titratable acidity b
7.4 8.3 8.8
.98 ...c . . . . . .
pH
(%) A B C
3.32 3.97 4.37 a
-
.31 .40 .51
2.36 2.36 2.36
.49 .55 .59
4.15 ...
•
Original concentrated retentate -- 27.6% total solids, .93% fat, 20.3% protein, 2.27% ash, and 4.2% lactose.
blnitial acidity of fresh yogurt reconstituted retentate mix B = .13% TA and pH 6.78 and C = .15% TA and pH 6.78 - February 2, 1977. CNo analyses made. Journal of Dairy Science Vol. 62, No. 1, 1979
© t©
TABLE 3. Composition of yogurts from reconstitu t e d retentates s uppl e me nt e d with dried b u t t e r m i l k and sodium citrate, a
Yogurt supplemented with
Total protein
Lactose
Fat
Ash
Total solids
Titratable acid ityb
,< 0 0 pH
(%)
Z t~
Lot 1 -- April 14, 1977 D, Dry b u t t e r m i l k c E, Dry b u t t e r m i l k c and .4% sodium citrate
3.62 3.59
.45 .63
1.38 ] .38
.50 .71
6.8 7.1
.89 .90
4.02 4.38
Lot 2 -- April 22, 1977 F, Dry b u t t e r m i l k c and .040% sodium citrate
4.56
.55
2.59
.61
9.2
1.02
4.22
Lot 3 -- April 22, 1977 G, .040% Sodium citrate only
4.62
.48
2.60
.60
9.1
.91
4.45
F t~ <
t~ ~4
aorig inal concentrated retentate for Lots 1, 2, 3 = 19% protein, .3% fat. blnitial acidity of fresh yogurt retentate mix, F = .125% and pH 6.65 and G = .115% and pH 6.75.
,q
CDried b u t t e r m i l k used at 1% by wt.
>
F g < o Z Z O
44
KOSIKOWSKI
TABLE 4. Acidity changes in yogurts from reconstituted retentates stored at 5 C. Yogurts of tables 1-2
0
Weeks
A
.98
1
2
3
4
5
6
Titratable acidity, % 1.02
.91
.92
.93
.93
...a
B
. . .
1.11
1.00
1.02
1.02
1.02
...
C D E F G
._ '.89 .90 1.02 .91
1.12 .91 .91 1.04 .92
1.05 .93 .89 1.16 .94
1.07 .92 .93 1.10 1.00
1.07 .95 .94 1.11 1.00
1.04 .99 .94 1.12 .99
".97".94 1.11 1.03
A B C D E F G
4.15 ... -.4.02 4.38 4.22 4.45
4.02 4.15 4.12 4,08 4.32 4.21 4.45
4.11 4.15 4.20 4.11 4.30 4.25 4.45
4.10 4.20 4.20 4.09 4.35 4.32 4.49
4.11 4.15 4.22 4.11 4.42 4,32 4.59
pH 4.11 4.12 4.21 4.12 4.38 4.25 4.50
... ... - . -
4,18 4.48 4.41 4.50
aNo analyses. Their fresh, o n e day old samples were free o f t h e defect. Initial acidities o f the freshly made, low lactose milk beverages, prior t o y o g u r t m a n u facture, were less t h a n t h o s e o f n o r m a l fresh milk due to a r e d u c e d solid-not fat c o n t e n t . Titratable acidity o f the low lactose milk beverages were .11 to .13% and pH was 6.65 to 6.75. Plain, low lactose y o g u r t s during the 1st w k had titratable acidities o f .90 to 1.12%, d e p e n d ing u p o n p r o t e i n and milk-solid-not-fat, and a pH 4.0 to 4.15, Table 4. A d d i t i o n o f dry b u t t e r m i l k did n o t change m a r k e d l y the pH,
but t h a t o f s o d i u m citrate, alone, raised t h e pH f r o m 4.02 to 4.38, Table 4. Low lactose yogurts, s t o r e d 6 wk at 5 C, changed little in titratable acidity and pH. In t h r e e u n s u p p l e m e n t e d y o g u r t s n o change oc ~ curred f r o m the 2nd t o 5th wk. Dry b u t t e r m i l k and sodium citrate-supplemented yogurts b e h a v e d similarly t h r o u g h 6 wk. When y o g u r t s were held up to 8 wk, m o l d b e c a m e visible.
Mineral Elements
for
Several low lactose y o g u r t s w e r e analyzed m a j o r minerals, Table 5. P h o s p h o r u s ,
TABLE 5. Mineral elements of yogurts from reconstituted retentates.
Element
Yogurt F supplemented with dry buttermilk and sodium citrate
Yogurt G supplemented with sodium citrate only
Low fat plain commercial yogurt a
Whole milk plain commercial yogurt a
144 183 234 70
95 121 155 46
(rag/100 g) Phosphorus Calcium Potassium Sodium
108 132
80 95
124
104
45
22
aUSDA Handbook No. 8-1, revised November 1976. Journal of Dairy Science Vol. 62, No. 1, 1979
LOW LACTOSE YOGURTS AND MILK BEVERAGES BY ULTRAFILTRATION calcium, potassium, and sodium were lower in such yogurts than in commercial low fat yogurt containing added skim milk powder. Sodium was significantly lower than in the others. Low lactose yogurt G supplemented with .04% sodium citrate, for example, was 67% lower in sodium. Calcium reduction compared to the same yogurt was 48% but compared to normally calcium-rich whole milk was only 21%. The calcium to phosphorus ratio (1.0 to .84) was similar to whole milk and to commercial yogurts. Calories
Calories of all low lactose yogurts were less than those of standard commercial yogurts. Three low lactose yogurts, A and B, Table 1, and D, Table 2, ranging from 3.32 to 3.97% protein, after arbitrary adjustment to 1.55% fat. gave calculated calories of 30.1, 32.1, and 33.1 calories/100 g. These are compared to the 63 cal reported for 1.55% fat commercial yogurt fortified with skim milk powder (18). If computed as fruited low lactose yogurts with added sugar, they gave a lower percentage reduction in calories but which was, nevertheless, striking. DISCUSSION
Milk retentates universally have been used directly in their concentrated state for dairy products. In this study, the concept was to dilute highly concentrated, 20% protein, skim milk retentates with water into milk beverages containing about 3.5 to 4.5% protein. Resulting milk beverages and yogurts were low in lactose, as a natural consequence, and also, low in sodium and calories compared with commercial low fat, fortified yogurt. This suggests a potential for a new kind of low lactose fresh milk beverage not hydrolyzed by added lactase enzymes. Feeding trials with humans reported by Jones et al. (9) showed that milks whose lactose was reduced 75% by lactase hydrolysis were accepted highly and tolerated by most of the sensitive subjects. Lactose in the yogurts from the current investigation was reduced by 90 to 94% but not by hydrolysis. Commercial yogurts are abnormally high in lactose. Goodenough and Kleyn (8) reported that pre-yogurt bases averaged 8.5% lactose and yogurts 5.8
45
lactose, both significantly higher than whole milk. This results from skim milk powder fortification to improve body. The present experimental low lactose yogurts displayed satisfactory firmness, viscosity, and free whey at low milk solids. Properties of the natural low lactose yogurts were typical of standard commercial yogurt except for some flktness in flavor and, during storage, the appearance of bitterness among several lots (F, G), and a lack of acidity change from that established in the 1-wk old product. Flatness was decreased by adding dried buttermilk or sodium citrate or both. Improvement might, also, result by limiting lactose reduction to 1%. The pattern and origin of bitterness was not uncovered. It may be related to mold contamination, visibily observed from 6 to 8 wk, to the low total solids and high initial acid, or to some inherent property of the retentate in question. This suggests the need for more study. Standard commercial yogurt generally increases in titratable acidity from .9 to 1.7% after manufacture. This change contrasts with the almost stationary acidity of .9 to 1.1% in the experimental yogurts during 6 wk holding at 5 C, indicating lactose as a limiting factor. This may be a significant factor in improving keeping quality. Since this paper was presented for publication, Toppino et al. (17) reported in an abstract that yogurts from 1:2.5 concentrated ultrafiltered and diluted milks showed no increase in acidity above 1.1% for more than 7 days. Diluting highly concentrated milk retentates with water, a concept not to be confused with diafiltration concentration techniques described by Covacevich and Kosikowski (3, 4), apparently creates fundamental changes in protein micelle relationships. Otherwise, it is difficult to explain why firm, highly viscous acid curds are produced in yogurts made from them and containing only 7.4% total solids and 3.3% protein, Table 1. Furthermore, in preliminary studies of the same low lactose milk beverages, standardized to 3.5% fat, and set with standard amounts of rennet at normal temperatures for Cheddar cheese, curd formation was instantaneous. Also when skim milk retentates, without added fat, were diluted to about 5:1 acceptable cottage cheese was made. The curds cooked out Journal of Dairy Science Vol. 62, No. 1, 1979
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KOSIKOWSKI
quickly during h e a t i n g t o give discrete, soft curds and an a p p a r e n t high yield. Such interesting c h e e s e m a k i n g characteristics o f low lactose milk beverages p r o d u c e d b y u l t r a f i l t r a t i o n encourages f u r t h e r research in t h e area.
REFERENCES
1 AOAC. 1970. Official methods of analysis, l l t h ed. Association of Official Agricultural Chemists, Washington, DC. 2 Chapman, H. R., V. E. Bines, F. A. Glover, and P. J. Skudder. 1974. Use of milk concentrated by ultrafiltration for making hard cheese, soft cheese and yogurt. J. Soc. Dairy Tech. 27:151. 3 Covacevich, H. R., and F. V. Kosikowski. 1977. Skimmilk concentration for cheesemaking by alternative ultrafiltration procedures. J. Food Sci. 42:1359. 4 Covacevich, H. R., and F. V. Kosikowski. 1977. Cream cheese by ultrafiltration. J. Food Sci. 42:1362. 5 Engel, W. G. 1973. The use of lactase to sweeten yogurt without increasing calories. Cultured Dairy Prod. J. 8:6. 6 Fenton-May, R. I., C. G. Hill, Jr., E. H. Amundson, M. H. Lopez, and P. D. Auclair. 1972. Concentration and fractionation of skimmilk by reverse osmosis and ultrafiltration. J. Dairy Sci. 55:1561. 7 Glover, F. A. 1971. Concentration of milk by ultra filtration and reverse osmosis. J. Dairy Res. 38:373. 8 Goodenough, E. R., and D. A. Kleyn. 1976. Qualitative and quantitative changes in carbohy-
Journal of Dairy Science Vol. 62, No. 1, 1979
drates during the manufacture of yogurt. J. Dairy Sci. 59:45. 9 Jones, D. V., M. C. Latham, F. V. Kosikowski, and G. Woodward. 1976. Symptom response to lactose - reduced milk in lactose-intolerant adults. Amer. J. Clin. Nutr. 29:633. 10 Kenworthy, A. L. 1960. Photoelectric spectrometer analysis of plant materials. Report of the Annu. Meeting of the 1960 Amer. Soc. Horticultural, March. 11 Kosikowski, F. V., and L. E. Wierzbicki. 1971. Low lactose yogurt from microbial lactase (/3-galactosidase) applications. J. Dairy Sci. 54:764. 12 Maubois, J. L., and G. Mocquot. 1971. Preparation of cheese from liquid precheese obtained by ultrafiltration of milk. Le Lait 51:495. 13 Maubois, J. L., and G. Mocquot. 1975. Application of membrane ultrafiltration to preparation of various types of cheese. J. Dairy Sci. 58:1001. 14 Paige, D. M., T. M. Bayless, S. S. Huang, and R. Wexler. Lactose hydrolyzed milk. Amer. J. Clin. Nutr. 28:818. 15 Rand, A., and P. Linklater. 1973. The use of enzymes for the reduction of lactose levels in milk products. Aust. J. Dairy Tech. 28:63. 16 Skala, I., V. Lamacora, and F. Pirk. 1971. Lactosefree milk as a solution of problems associated with dietetic treatment of lactose intolerance. Digestion 4:326. 17 Toppino, P. M., R. Nanni, and A. Cabrini. 1978. Preparation of yogurt with low acid content keeping quality at 25 and 4°C. Page 832 in Brief communications 20th International Dairy Congress, Paris. June 26-30. 18 USDA Handbook 8-1. 1976. Composition of dairy products. Washington, DC.