Heat-Induced Interaction between Crude κ-Casein and β-Lactoglobulin

Abstract

The effect of heat on the complexing of crude K-casein and B-lactoglobulin was studied by electrophoresis and ultracentrifugation. These proteins complexed when heated to 65[degree]C and higher when they were present in a system at pH 6.5, ionic strength 0.02. A 20-min. heat treatment of a 1:1 mixture of these proteins resulted in 3.4% of the B-lactoglobulin interacting with K-casein at 65[degree]C, 82.9% at 85[degree]C and 76.7% at 99[degree]C. Approximately 2.2 g of B-lactoglobulin may interact with 1.0 g of K-casein if an infinite ratio of B-lactoglobulin to casein is heated at 88[degree]C for 20-min.; only 1.4 g will interact at 99[degree]C. The complex has an S20 of 44-48 as compared to an S20 of 3.1 for B-lactoglobulin and 18 for K-casein. The P content of the complex was 0.2% corresponding to that of K-casein.