CHARACTERISTICS OF HEAT-INDUCED TRANSPARENT GELS FROM EGG-WHITE BY THE ADDITION OF DEXTRAN SULFATE

Heat-induced egg white gels containing polysaccharides were formed at pH 6.5, and the physicochemical properties were investigated. The hard ness, water-holding capacity, and transparency of egg white gel marked ly 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 actio n of DS on heat gelation of egg white,appeared mainly due to chemical interactions rather than physical entanglement. Dilute solutions of eg g 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 aggregate s consisted of ovalbumin, ovotransferrin, and lysozyme. The addition o f 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.