Ultrasound-assisted ethanol induced gelation of egg white: Effects on gel properties, water distribution and microstructure

This study explored the mechanism by which ultrasound (0-180 W) assisted ethanol (25 % and 30 %) enhances the gel properties of egg white gel (EWG). The results showed that ultrasonic treatment (stabilized at 120 W) prominently improved hardness, springiness and water holding capacity (WHC) (approximately 2 times, 1.5 times and 1.3 times higher than those of control group). Notably, the gel properties of EWG30% group consistently outperformed those of EWG25% group. The results of physicochemical properties revealed that ultrasound-assisted ethanol treatment promoted the aggregation of soluble particles (the particle sizes was 3.10 and 1.69 times larger than that in EWG25% and EWG30%; while the solubility was increased by 29.69 % and 66.19 %, respectively). Disulfide bonds were identified as the predominant intermolecular force in the gels, accounting for over 70 %, while hydrogen bond content increased approximately 2.5-fold following treatment. The free water in EWGs exhibited a shift toward immobile water. SDS-PAGE analysis illustrated that lysozyme and ovomucoid participated in the aggregation process. Regarding gel structure, the β-sheet increased by 2.66 % and 15.48 % at ethanol concentrations of 25 % and 30 %, respectively, accompanied by a reduction in fluorescence intensity, further confirming ultrasound-assisted ethanol induced aggregation of egg white protein (EWP). Meanwhile, the gel microstructure became more compact, forming a highly ordered network directly correlated with the enhanced gel properties. Collectively, these findings demonstrate that ultrasound-assisted ethanol induction is an effective modification strategy for enhancing the gel properties of egg white, providing valuable insights for its practical applications.