Influence of sucrose on NaCl-induced gelation of heat denatured whey protein solutions

A solution of heat-denatured whey proteins was prepared by heating 10 wt.% whey protein isolate at pH 7.0 to 80 degrees C for 10 min in the absence of salt. This treatment caused the globular protein molecules to partially unfold and aggregate. When the heat-denatured whey protein solution was cooled to room temperature and mixed with 200 mM NaCl it formed a gel. The influence of sucrose (0 to 10 wt.%) in the protein solutions prior to NaCl addition on the gelation rate was investigated. At relatively low concentrations (0-8 wt.%) sucrose decreased the gelation rate, presumably because sucrose increased the aqueous phase viscosity. At higher concentrations (> 8 wt.%) sucrose increased the gelation rate, probably because it decreased the thermodynamic affinity of the globular proteins for the aqueous solution, which increased the attraction between proteins. This data has important implications for the application of cold-setting whey protein ingredients in sweetened food products such as deserts and beverages. (C) 2000 Elsevier Science Ltd. All rights reserved.