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

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 degrees C for 15 min in the absence of salt. Heat treatment caused the globular protein molecules to u nfold, but electrostatic repulsion opposed strong protein-protein aggregati on and so prevented gel formation. When the heat-denatured whey protein sol ution 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 prot ein solutions prior to CaCl2 addition on the gelation rate. At relatively l ow concentrations (0-100 g kg(-1)), sucrose decreased the gelation rate, pr esumably because sucrose increased the aqueous phase viscosity. At higher c oncentrations (100-300 g kg(-1)), sucrose decreased the gelation rate, prob ably because sugar competes for the water of hydration and therefore increa ses the attraction between proteins. These data have important implications for the application of cold-setting WPI ingredients in sweetened food prod ucts such as desserts. (C) 2000 Society of Chemical Industry.