Stabilization of Calcium-Sensitive (α ) Casein by Kappa-Casein: Effect of Chymotrypsin and Heat on Kappa-Casein

Abstract

Kappa-casein is characterized by its ability to stabilize the calcium -sensitive casein so that it does not precipitate with calcium chloride. A precipitation test measuring this property of kappa-casein showed that some preparations of kappa-casein were heat-stable, that is, after heating (90[degree]C. for 15 minutes) they retained their ability to stabilize the calcium-sensitive casein, whereas others were heat-labile. The latter were adequate stabilizers before heating but after heating had lost much or all of this property. Chymo-trypsin (1: 28,500) at pH 7 transformed kappa-casein from the heat-stable to the heat-labile form. The results suggest that the protease in milk which is associated with acid-precipitated casein be investigated for a similar role.