Effect of pH during the dry heating on the gelling properties of egg white proteins

Abstract

Gel strength and elasticity of dried egg white proteins greatly increased by heating in the dry state at alkaline pH region (under 9.5) for a short period of time (3–5 days) without losing water solubility. Circular dichroism and differential scanning calorimetry spectrum revealed that the increased degree of denaturation found during preheating was accelerated in alkaline pH region. The polymerization of the proteins was also enhanced by alkaline dry heating through sulfhydryl-disulfide interchange. Alkaline dry heating resulted in high molecular weight polymer of partially unfolded egg white proteins which, in turn, contribute in the formation of low molecular weight and narrow molecular distribution of the aggregate found during the subsequent heat for gelation. Thus, heating of dried egg white proteins in the dry state at alkaline pH (under 9.5) is an effective method to obtain firm and elastic gels. The degree of unfolding of the proteins upon dry heating may play a crucial role in the gelling process of the proteins.