Fabrication of multifunctional biomaterial through conjugation between whey protein isolate and punicalagin.

This study explores the feasibility of ultrasound-assisted covalent conjugation between punicalagin-rich polyphenol (PRP) and whey protein isolate (WPI), compared with the conventional free-radical grafting method, which is time-consuming. Ultrasound-assisted conjugation between PRP and WPI reduced the interaction time from 24 h in the conventional method to 20 min, while maintaining a high PRP grafting content (56.44 mg/g). Changes in the ratios of free amino, Thiol, and tyrosine groups, as well as decreased fluorescence intensity relative to native WPI, indicated the formation of WPI-PRP conjugates. SDS-PAGE analysis revealed intensified 40-55 kDa bands, representing covalently linked WPI-PRP. The molecular docking study indicated that the WPI-PRP conjugates also formed hydrogen bonds. Functionally, WPI-PRP conjugates had high thermal stability, antioxidant, antimicrobial, and emulsion activities compared to WPI. Finally, WPI-PRP conjugates could be used as delivery systems for bioactive compounds in the food and pharmaceutical sectors.