THERMALLY INDUCED CHANGES IN EGG-WHITE PROTEINS

The heat-induced aggregation of egg white protein and conformational change of heat-denatured egg white protein at a high pH value were investigated. The flexibility and surface hydrophobicity of egg white protein increased with increasing temperature. The results of the changes in sulfhydryl groups in egg white protein during heating and SDS-PAGE indicated that sulfhydryl-disulfide interchange between the heat-denatured egg white protein had occurred. The change in CD spectra of heat-denatured egg white protein was interpreted as the result of increase in beta-sheet structure in sacrifice of helical structure. The partially unfolded stable structure of heat-denatured egg white protein was predicted from the cooperativity of the guanidine hydrochloride denaturation curves. It was concluded from these results that heat-induced soluble egg white aggregates were built from the partially unfolded molecules which contain a considerable amount of secondary structure and were cross-linked with a continuous disulfide cross-linked network and that the network of the beta-sheet structure was strengthened by the exposed hydrophobic residues.