Enzymes in Food and Beverage Processing

5 Use of Lactase in the Manufacture of Dairy Products

Downloaded by UNIV OF MICHIGAN ANN ARBOR on February 18, 2015 | http://pubs.acs.org Publication Date: June 1, 1977 | doi: 10.1021/bk-1977-0047.ch005

J. H . WOYCHIK and V. H . HOLSINGER Eastern Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Philadelphia, Pa. 19118

The p o t e n t i a l f o r l a c t a s e a p p l i c a t i o n in the manufacture o f d a i r y products has been recognized f o r many years. Lactase (β-D -galactosidase) hydrolyzes m i l k l a c t o s e i n t o its c o n s t i t u e n t mono saccharides, glucose and galactose. Chemical and p h y s i c a l changes that occur as a r e s u l t of l a c t o s e h y d r o l y s i s provide the r a t i o n a l e f o r its a p p l i c a t i o n . The p r i n c i p a l changes are reduced l a c t o s e content, increased carbohydrate solubility, increased sweetness, higher osmotic pressure, reduced viscosities, and more r e a d i l y fermentable sugar. Enzymatic h y d r o l y s i s o f l a c t o s e i n d a i r y foods would improve product q u a l i t y and provide low-lactose products f o r the l a c t o s e i n t o l e r a n t segment o f the population. A v a i l a b l e Lactases E f f o r t s to utilize l a c t a s e s f o r the manufacture o f hydrolyzed l a c t o s e (HL) products have been r e s t r i c t e d p r i m a r i l y by the l a c k of s u i t a b l e , commercially a v a i l a b l e , enzymes. Lactases a r e found i n p l a n t s , animals and microorganisms (Table I ) , but only micro bial sources can be used commercially. The pH optima of the m i c r o b i a l l a c t a s e s are q u i t e v a r i e d . The two enzymes of commer cial value a r e i s o l a t e d from the fungus, A s p e r g i l l u s n i g e r (1), and the yeast, Saccharomyces lactis (2), and differ widely i n t h e i r p r o p e r t i e s , p a r t i c u l a r l y in pH optimum (Table I I ) . The S. lactis enzyme (pH optimum o f 6.8-7.0) i s i d e a l l y s u i t e d f o r the h y d r o l y s i s o f l a c t o s e i n m i l k and sweet whey (pH 6.6 and 6.1, r e s p e c t i v e l y ) ; l a c k o f stability below pH 6.0 precludes its appli cation to a c i d whey (pH 4.5). The A. n i g e r l a c t a s e (pH optimum 4.0-4.5) has good pH stability, but the fall-off in r e l a t i v e activity at pH values above 4.5 l i m i t s i t s usefulness p r i m a r i l y to a c i d whey. Both o f these l a c t a s e s are a v a i l a b l e commercially i n p u r i f i e d form.

67 In Enzymes in Food and Beverage Processing; Ory, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

ENZYMES

68

IN FOOD A N D

BEVERAGE

PROCESSING

Table I Lactase D i s t r i b u t i o n

Plants Phaseolus v u l g a r i s , k e f i r g r a i n s , almonds, t i p s of w i l d r o s e s ,


and seeds of soybeans, a l f a l f a and

coffee.

Animal I n t e s t i n a l brush border

(pH

optimum 5.5-6.0).

Microbial B a c t e r i a (pH optimum 6.5-7.5) Fungi (pH optimum 2.5-4.5) Yeasts

(pH optimum 6.0-7.0)

Table I I P r o p e r t i e s of A. n i g e r and S^. l a c t i s Lactases

A. pH Optimum

4.0-4.5

Temperature Optimum pH

Stability

Half-life

niger

55°C 3.0-7.0

S.

lactis

6.8-7.0 35°C 6.0-8.5

(Days) at 50°C

Whole A c i d Whey 5% Lactose

8 100

In Enzymes in Food and Beverage Processing; Ory, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.


5.

woYCHiK

AND

HOLSiNGER

Lactase in Dairy Manufacturing

69

P u r i t y , a v a i l a b i l i t y , and cost of l a c t a s e s are important c o n s i d e r a t i o n s i n any f u l l - s c a l e enzymatic process f o r l a c t o s e h y d r o l y s i s . Consequently, although l a c t o s e h y d r o l y s i s can be achieved most simply by the a d d i t i o n of s o l u b l e enzyme to milk or whey, immobilized enzyme technology has been evaluated with l a c tases i n an e f f o r t to improve the economics of l a c t o s e h y d r o l y s i s 0,-4,5,6). While e f f o r t s have been made to develop a s a t i s f a c t o r y immobilized process f o r the S^. l a c t i s l a c t a s e (2), i t s s t a b i l i t y f o l l o w i n g immobilization has not been s u f f i c i e n t to warrant i t s use. Problems a s s o c i a t e d w i t h p r o t e i n adsorption to a v a r i e t y of enzyme support systems and maintaining acceptable column s a n i t a t i o n l e v e l s working with n u t r i t i v e substrates, such as m i l k or sweet whey, f u r t h e r l i m i t i t s usefulness. I t would appear that batch treatment with s o l u b l e enzyme would be the method of choice f o r HL d a i r y products made with S_. l a c t i s l a c t a s e . In c o n t r a s t , the A. n i g e r l a c t a s e has proven to be adaptable to use i n immobilized forms and has been bound to a wide v a r i e t y of s o l i d supports ( 3 , 4 , 2 î i , £ ) · Depending on the substrates used and operating c o n d i t i o n s , o p e r a t i o n a l h a l f - l i v e s from 8 to 100 days have been obtained. Although some o p e r a t i o n a l problems s t i l l e x i s t , there i s l i t t l e doubt that the A. n i g e r l a c t a s e can be used s u c c e s s f u l l y i n immobilized systems. Applications The h y d r o l y s i s of l a c t o s e i n whole or skim milk, best accomp l i s h e d by batch treatment with S. l a c t i s l a c t a s e , can be achieved by incubation with 300 ppm l a c t a s e at 32°C f o r 2.5 hr (10), or at 4°C f o r 16 hr (11). H y d r o l y s i s l e v e l s of 70-90% are obtained and the m i l k can be processed i n t o a v a r i e t y of products or used d i r e c t l y as a beverage. Some of the advantages and d i s advantages i n a p p l i c a t i o n of l a c t a s e s i n the manufacture of d a i r y products and processes f o l l o w . F l u i d and Dried M i l k Products Beverage Products. In recent years, numerous s t u d i e s (12, 13,14) have e s t a b l i s h e d a p a t t e r n of l a c t o s e i n t o l e r a n c e among nôh^aucasian c h i l d r e n and a d u l t s that i s a t t r i b u t a b l e to low i n t e s t i n a l l a c t a s e l e v e l s . F l a t u l e n c e , cramps, d i a r r h e a , and p o s s i b l y a general impairment i n normal d i g e s t i v e processes may accompany l a c t o s e i n t o l e r a n c e . The i n a b i l i t y of i n d i v i d u a l s to hydrolyze l a c t o s e can have serious i m p l i c a t i o n s i n n u t r i t i o n programs based on milk products. The HL m i l k prepared i n our l a b o r a t o r y f o r beverage use was evaluated i n terms of i t s p h y s i c a l and o r g a n o l e p t i c p r o p e r t i e s . The f a c t that HL m i l k i s sweeter than normal milk posed some problems i n d e f i n i n g i t s f l a v o r i n t a s t e panel t e s t i n g . Based on f l a v o r scores (Table I I I ) i t was evident that a r e c i p r o c a l r e l a t i o n s h i p e x i s t e d between the amount of l a c t o s e hydrolyzed i n the


70

ENZYMES

IN FOOD A N D

BEVERAGE

PROCESSING


product and i t s f l a v o r score. I t was c l e a r that judges t r e a t e d the marked sweetness as a " f o r e i g n " f l a v o r . A d d i t i o n a l t a s t e panel s t u d i e s showed that h y d r o l y s i s of 30, 60 and 90% l a c t o s e had the same e f f e c t on f l a v o r of m i l k as the a d d i t i o n of 0.3, 0.6, and 0.9% sucrose. Paige et a l . (15) reported that Negro adolescents found m i l k with 90% of i t s l a c t o s e hydrolyzed q u i t e acceptable to d r i n k , although the m a j o r i t y of the group surveyed judged i t sweeter than c o n t r o l m i l k .

Table I I I F l a v o r Scores of Hydrolyzed-Lactose

Milk

% Lactose Hydrolyzed

F l a v o r Score

0

37.0

30

37.0

60

36.7

90

36.2

In a d d i t i o n to overcoming the problems of the l a c t o s e i n t o l erant, h y d r o l y s i s of l a c t o s e i n m i l k i s advantageous f o r the p r e p a r a t i o n of m i l k concentrates. A h i g h l y a t t r a c t i v e method of p r e s e r v i n g whole m i l k i s f r e e z i n g a 3:1 concentrate. The products keep much longer than f l u i d m i l k under normal r e f r i g e r a t i o n and, when r e c o n s t i t u t e d , have a f l a v o r v i r t u a l l y i n d i s t i n g u i s h able from f r e s h milk. However, concentrates prepared from normal m i l k have a tendency to t h i c k e n and coagulate on standing. T h i s p r o t e i n d e s t a b i l i z a t i o n r e s u l t s from c r y s t a l l i z a t i o n of l a c t o s e which has been brought to i t s s a t u r a t i o n p o i n t i n the concentrat i o n process. E a r l y research (16) showed that l a c t o s e h y d r o l y s i s l e d to improvement i n the p h y s i c a l s t a b i l i t y of the concentrates during storage. However, h y d r o l y s i s of 90% of l a c t o s e alone d i d not i n c r e a s e storage s t a b i l i t y by more than one month over the c o n t r o l (Figure 1 ) . HL samples heat t r e a t e d at 71°C f o r 30 min a f t e r canning showed only a moderate r i s e i n v i s c o s i t y a f t e r 9 months storage (lower c u r v e ) . Organoleptic e v a l u a t i o n showed no d i f f e r e n c e i n f l a v o r score of the r e c o n s t i t u t e d concentrate with 90% of i t s l a c t o s e hydrolyzed and a f r e s h whole m i l k c o n t r o l with sucrose added. S i m i l a r l y , l a c t o s e c r y s t a l l i z a t i o n was avoided when skim m i l k concentrates were prepared from HL m i l k and stored at c o l d temperatures.


5.

woYCHiK A N D HOLSiNGER

Ldddse in Dairy Mdnufdcturing

71


Dried Products. No problems were encountered i n the manuf a c t u r e of m i l k powder from HL whole m i l k . However, HL skim m i l k powder, with a major p o r t i o n of i t s l a c t o s e hydrolyzed, had a tendency to s t i c k to the hot metal s u r f a c e s of the dryer at temperatures s i g n i f i c a n t l y lower than r e g u l a r skim m i l k s t i c k s (60 vs 75°C) at comparable moisture l e v e l s . Thus, the surfaces of the powder c o l l e c t i n g apparatus need to be h e l d below 60°C to avoid the s t i c k i n g problem. Cultured Products. C u l t u r e d products have long been thought to c o n t a i n low l e v e l s of l a c t o s e because of i t s fermentative u t i l i z a t i o n . However, w h i l e the lower l e v e l s of l a c t o s e may make these products more compatible to the l a c t o s e i n t o l e r a n t , the p r a c t i c e of f o r t i f y i n g yogurt with l a c t o s e r e s u l t s i n r e s i d u a l l e v e l s as high as 3.3-5.7% (17). Gyuricsek and Thompson (18) reported that among yogurts prepared from l a c t a s e t r e a t e d m i l k i n which more than 90% of the l a c t o s e was hydrolyzed, the HL yogurts set more r a p i d l y than c o n t r o l s d i d and had good a c c e p t a b i l i t y . Advantages claimed f o r the a p p l i c a t i o n of l a c t a s e i n yogurt manuf a c t u r e i n c l u d e a c c e l e r a t e d a c i d development, which reduces the r e q u i r e d set-time, and a r e d u c t i o n of " a c i d " f l a v o r by the glucose and g a l a c t o s e , which made the p l a i n yogurt more acceptable to consumers. Supplying s t a r t e r c u l t u r e organisms with glucose and g a l a c tose, r a t h e r than l a c t o s e , as an energy source can be expected to r e s u l t i n a l t e r e d carbohydrate u t i l i z a t i o n patterns and metabo l i t e production. 0 L e a r y and Woychik (19,20) undertook a study to d e f i n e the m i c r o b i a l and chemical changes that might occur i n c u l t u r e d d a i r y products manufactured from HL milk. They reported that t y p i c a l sugar concentrations i n the HL m i l k f o r yogurt are glucose, 2.6%; g a l a c t o s e , 2.3%; l a c t o s e , 2.0%. Decrease i n pH accompanied fermentation i n the c o n t r o l and HL milk; l e s s time was r e q u i r e d to reach pH 4.6 i n the HL m i l k than i n the c o n t r o l (Figure 2). The f a s t e r a c i d development i n the HL m i l k i s a r e s u l t of a h i g h er i n i t i a l r a t e o f fermentation. These f i n d i n g s support the decreased set-times reported by Gyuricsek and Thompson (18). The growth curves of the mixed s t a r t e r c u l t u r e c o n s i s t i n g of Streptococcus t h e r m o p h i l i s and L a c t o b a c i l l u s b u l g a r i c u s shown i n Figure 3 demonstrate that l a c t o s e h y d r o l y s i s has no e f f e c t on the symbiotic growth r e l a t i o n s h i p s of the s t a r t e r organisms. The c a r bohydrate u t i l i z a t i o n p a t t e r n s by the c u l t u r e s i n the two yogurts were d i f f e r e n t . The values i n Table IV show that almost twice as much galactose was c a t a b o l i z e d i n the c o n t r o l milks as i n HL milk. At the same time, the t o t a l amount of l a c t i c a c i d produced by the s t a r t e r organisms was greater i n the HL m i l k . These f i n d ings r e f l e c t a l t e r e d patterns of metabolite production r e s u l t i n g from the u t i l i z a t i o n of a greater p r o p o r t i o n of the t o t a l a v a i l able sugar i n the form of glucose. f


E N Z Y M E S IN FOOD A N D B E V E R A G E PROCESSING


72

Figure 2.Change of pH with time during yogurt production


5.

w o Y C H i K A N D HOLSiNGER

73

Ldctdse in Ddiry Mdnufdcturing

Table IV Galactose U t i l i z a t i o n i n C o n t r o l and HL Yogurts

Control


CHO

(%)

HL

Galactose

(%)

CHO

(%)

Galactose

Initial

7.11

3.50

7.01

3.30

Final

5.23

2.73

5.20

2.95

% Utilized

1.88

0.77

1.81

0.35

(%)

The a c c e l e r a t e d a c i d production by yogurt c u l t u r e organisms i n HL milk was a l s o observed by Gyuricsek and Thompson (18) with c u l t u r e s used i n cottage cheese manufacture. Advantages of using HL m i l k reported (18) i n c l u d e reduced s e t t i n g - t i m e , l e s s curd s h a t t e r and reduced l o s s of f i n e s , a more uniform curd, and use of lower cook-out temperatures. With the exception of improved s t a r t e r c u l t u r e s and more automated equipment, few m o d i f i c a t i o n s have been developed f o r improving the manufacture or a c c e l e r a t i n g the r i p e n i n g of Cheddar cheese. Thompson and Brower (11) extended the use of HL milk to the manufacture of Cheddar cheese and found that l a c t o s e h y d r o l y s i s modified the process c o n s i d e r a b l y . The f a s t e r a c i d development reduced renneting times and s i g n i f i c a n t l y reduced curd cooking and cheddaring times. With equivalent times i n cure, the HL Cheddar was s u p e r i o r to c o n t r o l cheeses i n f l a v o r , body, and texture and more r a p i d l y developed these c h a r a c t e r i s t i c s c l o s e r to that of o l d e r c o n t r o l cheeses. The improved q u a l i t i e s were a t t r i b u t e d to the e f f e c t s of l a c t o s e h y d r o l y s i s . The body and t e x t u r e changes may be the r e s u l t of increased osmolarity accompanied by reduced c a s e i n s o l v a t i o n . The a c c e l e r a t e d r i p e n i n g may be a t t r i b u t a b l e to increased l e v e l s of enzymes r e l e a s e d i n t o the cheese by higher b a c t e r i a l populations when glucose i s a v a i l able as a growth s u b s t r a t e . Whey U t i l i z a t i o n The nation's cheese i n d u s t r y annually produces over 32 b i l l i o n pounds of whey, of which l i t t l e more than h a l f i s u t i l i z e d . In the case of l a c t o s e , t h i s excess production over u t i l i z a t i o n represents approximately 600 m i l l i o n pounds which could conceivably be converted i n t o s a l a b l e products. M o d i f i c a t i o n of whey by l a c t a s e h y d r o l y s i s could o f f e r new avenues f o r whey


74

E N Z Y M E S IN

FOOD AND

B E V E R A G E PROCESSING

utilization. Two of the most promising processes appear to be conversion to l a c t o s e - d e r i v e d s i r u p s and fermentative u t i l i z a tion.


Sirups. The low sweetness l e v e l of l a c t o s e r e l a t i v e to sucrose does not allow much d i r e c t competition; however, a cons i d e r a b l e increase i n sweetness r e s u l t s f o l l o w i n g h y d r o l y s i s of l a c t o s e . R e l a t i v e sweetness i s dependent on s e v e r a l f a c t o r s , the p r i n c i p a l one being c o n c e n t r a t i o n . Table V l i s t s the sweetness of s e v e r a l sugars at 10% concentrations r e l a t i v e to sucrose.

Table V R e l a t i v e Sweetness of 10% Aqueous Sugar

Sugar

Solutions

Sweetness

Sucrose

100

Lactose

40

Glucose

75

Galactose

70

(%)

Thus, the a v a i l a b i l i t y of HL wheys increases the p o t e n t i a l f o r producing l a c t o s e - d e r i v e d s i r u p s . HL s i r u p s have been prepared by Guy (21) using both hydrolyzed wheys and l a c t o s e s o l u t i o n s . Deproteinized and demineralized s i r u p s concentrated to 65% t o t a l s o l i d s e x h i b i t e d good s o l u b i l i t i e s , showed no mold growth, and had good humectant p r o p e r t i e s . A ready a p p l i c a t i o n f o r these s i r u p s was found i n caramel manufacture where the HL s i r u p showed the same s t a b i l i z i n g e f f e c t against sucrose c r y s t a l l i z a t i o n as d i d " i n v e r t " sugar. Further a p p l i c a t i o n s f o r these s i r u p s await development by food t e c h n o l o g i s t s . Fermentation. U t i l i z a t i o n of whey as a fermentation subs t r a t e , e s p e c i a l l y f o r s i n g l e c e l l p r o t e i n s (22,23,24) and a l c o h o l production (25), has been studied e x t e n s i v e l y . A major o b s t a c l e to broader u t i l i z a t i o n of whey as a fermentation medium has been the f a c t that r e l a t i v e l y few organisms are able to u t i l i z e l a c t o s e . Several yeasts were evaluated f o r a l c o h o l production i n whey (26) and, although Kluyveromyces f r a g i l i s was found to be the most e f f i c i e n t , only 55% of the l a c t o s e was converted to a l c o h o l . The low conversion l e v e l has been a t t r i b u t e d



Lactdse in Ddiry Mdnufdcturing


8.0 h

L. bulgoncus, LH MILK L. bulgoricus, CONTROL MILK

5.0

S. thermophilic, LH MILK S. thermophillus, CONTROL MILK 1

2 TIME,

3 HOURS

4

Figure 3. Growth of yogurt cultures in control and HL milks

TIME, HOURS Figure 4. Alcohol production by K. fragilis in control and HL acid whey



76

E N Z Y M E S IN FOOD A N D B E V E R A G E PROCESSING

to a p o s s i b l e i n a b i l i t y o f the yeast to t o l e r a t e high a l c o h o l concentrations p o s s i b l y because of s e n s i t i v i t y of the yeast l a c tase to a l c o h o l . The a v a i l a b i l i t y o f whey having i t s l a c t o s e hydrolyzed to i t s c o n s t i t u e n t monosaccharides permitted an e v a l u a t i o n of nonlactose fermenting organisms such as Saccharomyces c e r e v i s i a e , which t o l e r a t e high a l c o h o l c o n c e n t r a t i o n s , f o r a l c o h o l production. O'Leary et a l . (27) evaluated HL wheys using c e r e v i s i a e and K. f r a g i l i s f o r comparison. Curves i l l u s t r a t ing a l c o h o l production by glucose-pregrown K. f r a g i l i s i n c o n t r o l and HL wheys are shown i n Figure 4. Ethanol production was more r a p i d i n HL whey during the f i r s t 24 h r fermentation, but l a t e r decreased so that the r a t e o f production was l e s s than that i n the c o n t r o l whey. The t o t a l y i e l d o f ethanol was s i m i l a r i n both cases and averaged 1.9%. Reducing sugar l e v e l s decreased at the same r a t e i n the f i r s t 24 hr fermentation, but l e s s u t i l i z a t i o n occured i n HL wheys i n the l a t e r stages of fermentation. The p a t t e r n o f sugar u t i l i z a t i o n i n the HL wheys (Figure 5) showed that although glucose disappeared r a p i d l y during the f i r s t 24 h r fermentation, there was l i t t l e change i n the galactose conc e n t r a t i o n during t h i s p e r i o d . Galactose u t i l i z a t i o n began only a f t e r 24 hr fermentation and i s t y p i c a l of a d i a u x i c p a t t e r n o f sugar u t i l i z a t i o n . A longer fermentation p e r i o d was r e q u i r e d i n the HL whey due to the d i a u x i c phenomenon. S_. c e r e v i s i a e , a nonlactose fermenting yeast, i s commonly used i n wine and beer production because of i t s a b i l i t y to w i t h stand r e l a t i v e l y high a l c o h o l concentrations. Growth curves of IS. c e r e v i s i a e , pregrown on glucose and on g a l a c t o s e , showed that s i m i l a r c e l l populations e x i s t e d i n HL whey f o r the f i r s t 48 hr growth, but d e c l i n e d t h e r e a f t e r , except that those pregrown on galactose increased s i g n i f i c a n t l y a f t e r the i n t i a l d e c l i n e . A l c o h o l production by these organisms i n the HL wheys showed a s i m i l a r p a t t e r n i n that comparable l e v e l s of a l c o h o l were a t t a i n e d a f t e r 48 h r (Figure 6 ) . A l c o h o l production by the g l u cose pregrown S_. c e r e v i s i a e began to decrease a f t e r 48 h r , whereas the g a l a c t o s e pregrown c e l l s continued t h e i r a l c o h o l production which reached a l e v e l twice that o f the glucosepregrown c e l l s . Sugar u t i l i z a t i o n c l o s e l y p a r a l l e l e d a l c o h o l production. S^. c e r e v i s i a e pregrown on glucose u t i l i z e d glucose r a p i d l y but d i d not u t i l i z e g a l a c t o s e . J3. c e r e v i s i a e pregrown on galactose s i m i l a r l y u t i l i z e d glucose but a l s o u t i l i z e d galactose a f t e r 96 h r . These s t u d i e s i n d i c a t e d that although l a c t o s e h y d r o l y s i s i n whey permits a l c o h o l production by organisms unable to ferment l a c t o s e , the galactose r e l e a s e d by h y d r o l y s i s i s not e f f i c i e n t l y u t i l i z e d . In model system s t u d i e s , the e f f i c i e n c y of converting sugar to a l c o h o l by K. f r a g i l i s was as f o l l o w s : glucose > l a c t o s e > g a l a c t o s e . Conclusions The d a i r y i n d u s t r y today has a v a i l a b l e e x i s t i n g technology f o r the a p p l i c a t i o n o f enzymatic h y d r o l y s i s of l a c t o s e i n m i l k




Lactase in Dairy Mdnufdcturing

J 10

*

1 " - - * Γ " 100 150

50

TIME, HOURS Figure 5. Change in sugar concentrations dur ing fermentation of HL acid whey by K. fragilis

10

50

100

150

200

TIME, HOURS Figure 6. Alcohol production in HL acid whey by glu cose-pregrown and gahctose-pregrown S. cerevisiae


78

E N Z Y M E S IN FOOD AND B E V E R A G E PROCESSING


and m i l k products. U t i l i z a t i o n of the l a c t a s e enzyme, i n e i t h e r " f r e e " o f immobilized systems, can r e s u l t i n q u a l i t y improvements i n a number o f products and y i e l d processing economies i n others. The a p p l i c a t i o n discussed i n t h i s report should be reviewed and assessed f o r p o t e n t i a l b e n e f i t s by d a i r y product manufactur ers i n t h e i r s p e c i f i c operations. Whey, i n p a r t i c u l a r , with i t s ever i n c r e a s i n g production, poses a s p e c i a l problem whose s o l u t i o n can be a t t a i n e d only through a p p l i c a t i o n of unconventional technology. I t i s b e l i e v e d that a p p l i c a t i o n o f l a c t a s e o f f e r s a p o t e n t i a l f o r i n n o v a t i v e whey u t i l i z a t i o n . Literature Cited 1. 2.

3. 4. 5. 6. 7. 8. 9.

10. 11. 12. 13. 14. 15.

16. 17. 18.

Woychik, J . Η., and Wondolowski, M. V. Biochim. Biophys. Acta (1972) 289, 347-351. Woychik, J . Η., Wondolowski, M. V., and Dahl, K. J . In "Immobilized Enzymes in Food and M i c r o b i a l Processes," Olson, A. C. and Cooney, C. L., e d i t o r s , 41-49, Plenum Press, New York, Ν. Y. (1974). Woychik, J . Η., and Wondolowski, M. V. J . M i l k Food Technol. (1973) 36, 31-33. W i e r z b i c k i , L. E., Edwards, V. Η., and Kosikowski, F. V. B i o t e c h n o l . Bioeng. (1974) 16, 397-411. P i t c h e r , W. H. J r . Am. Dairy Rev. (1957) 37, 34B, 34D, 34E. Pastore, Μ., M o r i s i , F., and Viglia, A. J . Dairy Sci. (1974) 57, 269-272. Hustad, G. O., Richardson, T., and Olson, N. F. J . D a i r y Sci. (1973) 56, 1111-1117. Olson, A. C., and Stanley, W. L. J . A g r i . Food Chem. (1973) 21, 440-445. Hasselburger, F. X., A l l e n , B., Paruchuri, Ε. Κ., Charles, Μ., and Coughlin, R. W. Biochem. Biophys. Res. Commun. (1974) 57, 1054-1062. Guy, E. J., Tamsma, Α., Kontson, Α., and H o l s i n g e r , V. H. Food Prod. Develop. (1974) 8, 50-60. Thompson, M. P., and Brower, D. P. Cultured Dairy Prod. J . (1976) 11, 22-23. Paige, D. Μ., Bayless, Τ. Μ., F e r r y , G. C., and Graham, G. C. Johns Hopkins Med. J . (1971) 129, 163-169. Rosensweig, N. S. J. Dairy Sci. (1969) 52, 585-587. Lebenthal, E., Antonowicz, I., and Schwachman, H. Amer. J . Clin. Nutr. (1975) 28, 595-600. Paige, D. Μ., Bayless, Τ. Μ., Huang, S., and Wexler, R. ACS Symposium S e r i e s , " P h y s i o l o g i c a l E f f e c t s of Food Carbohy d r a t e s , " (1974), 191. Tumerman, L., Fram, Η., and C o r n e l y , K. W. J . Dairy Sci. (1954) 37, 830-839. Anonymous. Cultured Dairy Prod. J . (1973) 8, 16-19. Gyuricsek, D. Μ., and Thompson, M. P. Cultured Dairy Prod. J. (1976) 11, 12-13.


5.

W O Y C H I K A N D HOLSINGER

19. 20. 21. 22. 23.


24. 25. 26.

27.

Lactase in Dairy Manufacturing

79

O'Leary, V. S., and Woychik, J. H. J. Food Sci. (1976) 41, 791-793. O'Leary, V. S., and Woychik, J. App. Environmental Micro biol. (1976) 32, 89-94. Guy, E. J. Abstract 71st Annual Meeting, Amer. Dairy Sci. Asso. (1976), D7. Wasserman, A. E., Hopkins, W. J., and Porges, N. Sewage and I n d u s t r i a l Wastes (1958) 30, 913-920. Wasserman, A. E., Hampson, J. W., A l v a r e , N. F., and A l v a r e , N. J. J. Dairy Sci. (1961) 44, 387-392. B e r n s t e i n , S., Tzeng, C. Η., and S i s s o n , D. F i r s t Chem. Congr. N. Amer. Cont. (1975) A b s t r a c t BMPC 68. Rogosa, Μ., Browne, Η. Η., and W h i t t i e r , E. O. J. Dairy Sci. (1947) 30, 263-269. O'Leary, V. S., Green, R., S u l l i v a n , B. C. and H o l s i n g e r , V. H. F i r s t Chem. Congr. N. Amer. Cont. (1975) Abstract BMPC 158. O'Leary, V.S., Sutton, C., Bencivengo, Μ., S u l l i v a n , B., and H o l s i n g e r , V. H. Unpublished.


Enzymes in Food and Beverage Processing

Recommend Documents