Ultrasonic treatment improves the heat aggregation behavior of degreased egg yolk powder: Functional and structural effects

The poor solubility of degreased egg yolk powder (DEYP) significantly limits its industrial applications. While ultrasonic combined enzymatic (UE) modification effectively enhances DEYP's functional properties, the essential heat treatment required for sterilization and enzyme inactivation induces protein aggregation, leading to a drastic solubility reduction (from 90.54 g/100 g-63.48 g/100 g). The current study investigated the effect of ultrasonic treatment on the functional properties of ethanol-degreased yolk powder (ET-DEYP) and supercritical fluid CO2-degreased yolk powder (SF-DEYP) after heat sterilization. The results showed that ultrasonic treatment (300 W, 10 min) significantly improved the solubility of modified ET-DEYP (95.22 g/100 g) and enhanced emulsifying and foaming properties. Particle size distribution, SEM, and SDS-PAGE analyses confirmed that ultrasonic treatment broke up the heat-induced aggregates. Further analysis revealed that ultrasonic treatment increased the solubility of modified DEYPs by reducing the size of the particles, increasing surface negative charge and hydrogen bonding, and reducing surface hydrophobicity. This study demonstrates that ultrasonic treatment effectively restores the functional properties of modified DEYPs post-heat sterilization. It highlights ultrasonic treatment as a technology for depolymerizing heat aggregates, offering an effective method for producing modified DEYPs with significant applicability in the food industry.