Isolation and Structure of Cotylenin E

²-Casein was modified by trypsin, chymosin or phosphoprotein phosphatase. Each modified ²-casein was fortified to the test-milk which was pretreated at 10°C by immobilized thermolysin to curdle non-enzymatically at 35°C. Fortification with chymosin-modified ²-casein, devoid of the hydrophobic moiety near the C-terminus, increased the curd tension as did native ²-casein. The test-milk fortified with trypsin-modified ²-casein, which has been deleted some part of the hydrophilic region near the N-terminus, had similar curd tension to unfortified test-milk. The test-milk fortified with dephosphorylated ²-casein, formed a softer curd than that with native ²-casein. Trypsin-modified ²-casein or dephosphorylated ²-casein retained its associative ability, but chymosin-modified ²-casein revealed negligible ability to associate.

These results led to the conclusion that the phosphoryl group on the hydrophilic moiety of ²-casein contributes to the increase in curd tension, while the hydrophobic moiety is responsible for the association of ²-casein.