Dairy Chemistry And Biochemistry

MILK PROTEINS^163

L K-[K-CN-IPI [I major cnrhohydrate-free

and 9 minor carbohydrate

-containing pro~eins]

Figure 4.8 Heterogeneity of bovine casein.

4.5 Some important properties of the caseins

4.5.1 Chemical composition

The principal chemical and physicochemical properties of the principal milk

proteins are summarized in Table 4.2. Some of the properties of the caseins

are discussed in more detail below (see Swaisgood, 1992, for a review).

Amino acid composition. The approximate amino acid composition of the
main caseins is shown in Table 4.4. Amino acid substitutions in the principal
genetic variants can be deduced from the primary structures (Figures
4.9-4.12). Four features of the amino acid profile are noteworthy:

1. All the caseins have a high content (35-45%) of apolar amino acids (Val,
   Leu, Ile, Phe, Tyr, Pro) and would be expected to be poorly soluble in
   aqueous systems, but the high content of phosphate groups, low level of