Ultrasound-induced modifications in structure, antioxidant activity and functionality of whey protein isolate-propolis polyphenol conjugates

In this study, whey protein isolate was conjugated with polyphenols via free radical reactions, using ultrasound treatment to enhance the bio-functional properties of the resulting conjugates. Ultrasound at 270 W for 20 min significantly improved the degree of conjugation compared to the traditional free radical method, as evidenced by higher levels of total phenolic and flavonoid content. Structural analysis revealed that the conjugates produced with ultrasound exhibited reduced α-helix content but increased β-turn and random coil structures, along with enhanced fluorescence intensity and surface hydrophobicity. Furthermore, the incorporation of ultrasound in the conjugation process significantly enhanced antioxidant activity and functional properties (p < 0.05), including thermostability, water solubility and emulsifying stability. These results highlight the potential of ultrasound-assisted conjugation to enhance protein-polyphenol interactions, opening new possibilities for applications in the food industry.