Effect of Dry Heat and Mild Alkaline Treatment on Functional Properties of Egg White Proteins

Abstract

Physicochemical properties exhibited by the dried egg white protein molecule during the dry heat treatment at low water activity were assessed. Gelling properties of dried egg white proteins were greatly improved by heating in the dry state at a mild alkaline pH (under 9.50). The surface hydrophobicity increased with heating time, and sulfhydryl−disulfide exchange was accelerated at a mild alkaline dry heating. The proteins were deamidated by this treatment with no effect on solubility and hydrolysis. After 15 days of storage of the proteins in the dry state, the deamidation rate reached 12.2%. However, dry heating at higher pH (>9.50) caused detrimental effect on egg white proteins, resulting in the formation of insoluble aggregates by polymerization. Increasing solubility due to the deamidation of the denatured proteins and the reaction can be an important factor for forming excellent firm gels of dried egg white proteins. Thus, the combination of dry heating and deamidation under controlled pH values offers a new approach to improve the functional properties of food proteins and to study the structure−function relationship. Keywords: Egg white; gelation; elasticity; dry heating; pH; deamidation; alkali treatment