Influence of sucrose on cold gelation of heat-denatured whey protein isolate

Abstract

A solution of heat-denatured whey proteins was prepared by heating 100 g kg−1 whey protein isolate (WPI) at pH 7.0 to 75 °C for 15 min in the absence of salt. Heat treatment caused the globular protein molecules to unfold, but electrostatic repulsion opposed strong protein–protein aggregation and so prevented gel formation. When the heat-denatured whey protein solution was cooled to room temperature and mixed with 15 mM CaCl2, it formed a gel. We investigated the influence of the presence of sucrose in the protein solutions prior to CaCl2 addition on the gelation rate. At relatively low concentrations (0–100 g kg−1), sucrose decreased the gelation rate, presumably because sucrose increased the aqueous phase viscosity. At higher concentrations (100–300 g kg−1), sucrose decreased the gelation rate, probably because sugar competes for the water of hydration and therefore increases the attraction between proteins. These data have important implications for the application of cold-setting WPI ingredients in sweetened food products such as desserts. © 2000 Society of Chemical Industry