The regulation mechanism of ultrasonic treatment on alkali-induced egg white protein gel: Structure, molecular characteristics and intermolecular forces distribution.

Egg white protein can be cross-linked to form a gel under alkali induction, which is typically represented by the preserved eggs from Chinese traditional food. The effects of ultrasonic at different intensities (50 W, 100 W, 200 W, and 300 W) on alkali-induced egg white protein (EWP) gel were investigated. The gel strength rose significantly by 26.08 % upon treatment with 50 W, but it gradually declined as the intensity increased. Meanwhile, the structure unfolding and molecular aggregation of EWP were affected by ultrasonic. Compared with 300 W, 50 W could enhance surface hydrophobicity and decrease total free sulfhydryl group content more during gel formation. Selective solubility experiment confirmed that ultrasonic reduced the formation of ionic bonds, which slightly slowed down the initial gelation. Simultaneously, 50 W promoted the formation of more disulfide bonds, which helped to improve the strength of the final gel, while the same effect was not observed at 300 W. In general, moderate ultrasonic can effectively improve the alkali-induced EWP gel properties, which provides theoretical support for developing high quality preserved eggs and protein gel foods.