Mechanistic insights into ultrasound‑improved foaming properties of freeze‑thawed egg white: From macroscopic rheology to interfacial proteomics.

Repeated freeze-thawed (F-T) cycles critically damaged the foaming properties of egg white, thereby constraining its application in the food industry. This study investigated the effect of ultrasonic pretreatment in restoring the foaming property of egg white protein (EWP) subjected to repeated F-T cycles. A comprehensive analysis was conducted from the perspectives of foam behavior, physicochemical and interfacial properties, protein structure and interfacial proteomics. The results demonstrated that ultrasonic pretreatment (360 W, 10 min) effectively maintained foaming properties of egg white that underwent eight F-T cycles (EWP8-FTC) compared with those of fresh EWP. Moreover, ultrasonic pretreatment reduced the foaming ability (FA) from 41.35% to 18.56%, while concomitantly enhancing foam stability (FS) by 32.69%. Furthermore, there was no significant difference (p > 0.05) in the FA of ultrasonically pretreated egg white that underwent eight F-T cycles (UEWP8-FTC) compared with those of EWP. Ultrasound reduced the particle size of EWP, enhanced molecular flexibility, increased the content of free sulfhydryl groups and surface hydrophobicity, as well as optimized secondary structure. In addition, it regulated the adsorption behavior of interfacial proteins such as lysozyme C, mucin-5B, clusterin and Ovodefensin A1 at the air-water interface. This study elucidated the molecular mechanism by which ultrasound modulates interfacial protein adsorption, providing a theoretical reference for improving the quality of frozen egg white and promoting its high‑value industrial applications.