Characteristics of Heat-Induced Transparent Gels from Egg White by the Addition of Dextran Sulfate

Abstract

Heat-induced egg white gels containing polysaccharides were formed at pH 6.5, and the physicochemical properties were investigated. The hardness, water-holding capacity, and transparency of egg white gel markedly increased in the presence of dextran sulfate (DS) at a weight ratio of 0.05 to the protein. The effects were not observed by the addition of dextran (DX). Scanning electron microscopy showed that a very fine network structure had been formed in the gel containing DS. The action of DS on heat gelation of egg white appeared mainly due to chemical interactions rather than physical entanglement. Dilute solutions of egg white alone and egg white containing DX formed insoluble aggregates by protein interactions through disulfide cross-links during heating. From SDS−PAGE analysis with 2-mercaptoethanol, the insoluble aggregates consisted of ovalbumin, ovotransferrin, and lysozyme. The addition of DS inhibited formation of insoluble aggregates in egg white solution during heating. The inhibitory effect of DS would be ascribed to the formation of firmer and transparent egg white gels. Keywords: Egg white; dextran sulfate; transparent gel; microstructure; aggregation