176 DAIRY CHEMISTRY AND BIOCHEMISTRY

native state. This has obvious advantages for the digestibility of the

caseins, the natural function of which is presumably nutritional and hence

easy digestibility in the ‘native’ state is important. The caseins are also

readily hydrolysed in cheese, which is important for the development of

cheese flavour and texture (Chapter lo). However, casein hydrolysates

may be bitter due to a high content of hydrophobic amino acids (small

hydrophobic peptides tend to be bitter). The caseins are readily hy-

drolysed by proteinases secreted by spoilage micro-organisms.

The caseins adsorb readily at air-water and oil-water interfaces due to

their open structure, relatively high content of apolar amino acid residues

and the uneven distribution of amino acids. This gives the caseins very

good emulsifying and foaming properties, which are widely exploited in

the food industry.

The lack of higher structures probably explains the high stability of the

caseins to denaturing agents, including heat.

(a)
Figure 4.18 Energy-minimized models of the tertiary structures of bovine asi- (a), p- (b)
and K- (c) caseins (from Kumosinski, Brown and Farrell, 1993a, b; Kumosinski and Farrell,
1994)