The Role of Protein Denaturation, Extent of Proteolysis, and Storage Temperature on the Mechanism of Age Gelation in a Model System

Abstract

A model system was used to investigate the effects of heat treatment, storage temperature, and proteolysis on the gelation time of both unconcentrated and concentrated (evaporated) milks. For unconcentrated milks, increasing levels of whey protein denaturation retarded the gelation process. Elevated storage temperatures accelerated the gelation process, but only in cases where milk samples had been previously proteolyzed. The actual extent of proteolysis was not related to gelation time. In evaporated milk, increasing temperature and extent of proteolysis reduced gelation time. Samples that had no induced proteolysis also gelled. Age gelation in unconcentrated and concentrated milks is controlled by two different mechanisms. In unconcentrated milk, gelation is a two-stage process where proteolysis is followed by nonenzymatic physicochemical changes In concentrated milk, gelation occurrs by nonenzymatic physicochemical processes.