Dairy Chemistry And Biochemistry

336 DAIRY CHEMISTRY AND BIOCHEMISTRY

over chemical methods because they cause fewer side-reactions and conse-
quently give superior products, e.g. hydrolysis of starch.
Although relatively few enzymes are used in the dairy industry on a
significant scale, the use of rennets in cheesemaking is one of the principal
of all industrial applications of enzymes.
The applications of exogenous enzymes in dairy technology can be
divided into two groups:

1. Technological, in which an enzyme is used to modify a milk constituent
   or to improve its microbiological, chemical or physical stability.


2. Enzymes as analytical reagents. Although the technological applications
   are quantitatively the more important, many of the analytical applica-
   tions of enzymes are unique and are becoming increasingly important.

Since the principal constituents of milk are proteins, lipids and lactose,
proteinases, lipases and P-galactosidase (lactase) are the principal exogenous
enzymes used in dairy technology. Apart from these, there are, at present,
only minor applications for glucose oxidase, catalase, superoxide dismutase
and lysozyme. Lactoperoxidase, xanthine oxidase and sulphydryl oxidase
might also be included, although at present the indigenous form of these
enzymes is exploited.
The application of enzymes in food technology has been widely reviewed
(Fox, 1991; Nagodawithana and Reed, 1993). Reviews on applications of
exogenous enzymes in dairy technology include Fox and Grufferty (1991),
Fox (1993) and Brown (1993).

8.3.2 Proteinases

There is one major (rennet) and several minor applications of proteinases in
dairy technology.

Rennets. The use of rennets in cheesemaking is the principal application of
proteinases in food processing and is second only to amylases among
industrial applications of enzymes. The sources of rennets and their role in
milk coagulation and cheese ripening are discussed in Chapter 10 and will
not be considered here.

Accelerated cheese ripening. Cheese ripening is a slow, expensive and
partially uncontrolled process; consequently, there is increasing interest, at
both the research and industrial levels, in accelerating ripening. Various
approaches have been investigated to accelerate ripening, including a higher
ripening temperature (especially for Cheddar-type cheese which is usually
ripened at 6-8"C), exogenous proteinases and peptidases, modified starters
(e.g. heat-shocked or lactose-negative) and genetically engineered starters or