Use of Lactase in the Manufacture of Dairy Products

Abstract

The potential for lactase application in the manufacture of dairy products has been recognized for many years.Lactase (β-D -galactosidase) hydrolyzes milk lactose into its constituent mono saccharides, glucose and galactose.Chemical and physical changes that occur as a result of lactose hydrolysis provide the rationale for its application. The principal changes are reduced lactose content, increased carbohydrate solubility, increased sweetness, higher osmotic pressure, reduced viscosities, and more readily fermentable sugar. Enzymatic hydrolysis of lactose in dairy foods would improve product quality and provide low-lactose products for the lactose intolerant segment of the population. Available LactasesEfforts to utilize lactases for the manufacture of hydrolyzed lactose (HL) products have been restricted primarily by the lack of suitable, commercially available, enzymes. Lactases are found in plants, animals and microorganisms (Table I), but only micro bial sources can be used commercially. The pH optima of the microbial lactases are quite varied. The two enzymes of commer cial value are isolated from the fungus, Aspergillus niger (1), and the yeast, Saccharomyces lactis (2), and differ widely in their properties, particularly in pH optimum (Table II). The S. lactis enzyme (pH optimum of 6.8-7.0) is ideally suited for the hydrolysis of lactose in milk and sweet whey (pH 6.6 and 6.1, respectively); lack of stability below pH 6.0 precludes its appli cation to acid whey (pH 4.5).The A. niger lactase (pH optimum 4.0-4.5) has good pH stability, but the fall-off in relative activity at pH values above 4.5 limits its usefulness primarily to acid whey. Both of these lactases are available commercially in purified form.

Carbohydrases

“…In the case of ripened cheeses, lactase supplementation significantly shortens the ripening process and reduces costs, while also enhancing flavor development. Other enzymes such as proteases that accompany lactase also may contribute to the ripening process (Woychik and Holsinger, 1977;Barker and Shirley, 1980;Coughlan and Charles, 1980;Moore, 1980;Nijpels, 1981;Böing, 1982;Burgess and Shaw, 1983;Crueger and Crueger, 1984;Moulin and Galzy, 1984;Mahoney, 1985;Swaisgood and Horton, 1989).…”