κ-Casein—β-Lactoglobulin Interaction in Solution When Heated

Abstract

Heating a mixture (0.5% of each) of β-lactoglobulin and κ-casein at pH 7 at 90 C 15 min led to interaction between the two proteins. Electrophoresis at pH 2.1 showed that, before heating, the components moved independently; whereas, after heating, a single component of intermediate mobility was observed. Ultracentrifuge examination of the heated mixture showed a new component with an S20 value of 45, three times greater than the S20 value of κ-casein. The ability of the κ-casein to stabilize calcium-sensitive casein was considerably reduced in the heated mixture. The clotting time of κ-casein by rennin was increased by the addition of β-lactoglobulin and was increased still further when the mixture had been heated. The clot formed by the action of rennin on the heated mixture contained the β-lactoglobulin as well as the κ-casein. © 1962, American Dairy Science Association. All rights reserved.