Changes in Mixtures of Whey Protein and κ-Casein Due to Heat Treatments

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Abstract
Polyacrylamide disc electrophoresis was investigated to determine its effectiveness in the resolution of the whey proteins and assess the effect of heat on the milk protein system. The major whey protein bands are [beta]-lactoglobulin-A and -B, [alpha]-lactalbumin, bovine serum albumin (BSA), and the immune globulins in decreasing order of mobility. A complex occurs between [kappa]-casein and [beta]-lactoglobulin when they are mixed in equal parts by weight in a solution of milk salts and heated to 74.5 C for 30 min. They interact completely when heated to 85 C under the same conditions. This type of complex did not occur with [alpha]-lactalbumin or BSA when heated with [kappa]-casein at 74.5 or 85 C for 30 min. One common electrophoretic band was formed by heating [beta]-lactoglobulin-A and -B to 74.5 or 85 C for 30 min. The slower electrophoretic mobility may be due to increased molecular size or a change in molecular configuration during heating. This protein does not occur naturally in milk whey.