The denaturation of whey proteins in a processed cheese environment

Abstract

The kinetics of whey protein denaturation at three pH values (pH 5.4, 5.7 and 6.0) was determined in processed cheese made from rennet casein/whey protein concentrate (RC-PC), or milk protein concentrate (MPC-PC). Samples were heated from 75 to 100 °C for up to 5400 s. Denaturation of both proteins was faster with increasing pH. The reaction order for β-lactoglobulin and α-lactalbumin denaturation was 1.5 and 1.0 respectively. There was a change in temperature dependence of the rate constants at about 85 °C for both proteins. Kinetic parameters were consistent with unfolding as rate-determining at low temperatures and aggregation as rate-determining at higher temperatures. β-Lactoglobulin denaturation was slower at low temperatures and faster at high temperatures for the MPC-PC when compared with RC-PC with a similar effect at all pH. α-Lactalbumin denaturation was more rapid for MPC-PC than RC-PC at all temperatures, with a greater difference at lower pH.