Ultrasound-mediated modulation of non-covalent interactions between whey protein isolate fibrils and Hericium erinaceus polysaccharides: Structural characteristics and interfacial properties.

This study examined how ultrasound processing regulates the fibrils of whey protein isolate (WPIF, 1.0%) and the non-covalent interactions with Hericium erinaceus polysaccharide (HEP, 0.25-1.5%). This process was aimed at elucidating the underlying mechanism of how it affects the structural and functional characteristics of the complex. Spectroscopic analysis showed that both WPIF and ultrasound-treated WPIF (UWPIF) formed complexes with HEP mainly through hydrogen bonding and electrostatic interactions. Concurrently, the protein structure shifted from β-sheet-rich conformations toward more disordered random coil structures, thereby improving dispersibility. Compared to WPIF, UWPIF showed a stronger fluorescence quenching behavior when bound to HEP as a result of the ultrasound process, which exposed additional binding sites. Furthermore, UWPIF showed optimum emulsifying performance at a reduced HEP concentration (0.75%), with an emulsifying activity index (EAI) of 50.2 m2/g and an emulsifying stability index (ESI) of 93.5 min. Its foam formation capacity (FA) and foam stability (FS) were 77.1% and 53.0%, respectively. In contrast, WPIF required the HEP concentration of 1.0% to achieve peak performance (EAI: 42.2 m2/g; ESI: 75.8 min; FA: 67.4%; FS: 48.3%). The UWPIF-HEP (0.75%) complex exhibited the lowest air-water interfacial tension (6.1 mN/m), indicating enhanced surface activity related to foaming behavior. Furthermore, ultrasound treatment and HEP addition significantly improved the antioxidant activity of the fibrils. Simplified molecular docking and MD simulations suggested stronger monosaccharide-level binding propensity of β-lactoglobulin than α-lactalbumin, with hydrogen bonding, electrostatic interactions, and van der Waals interactions contributing to the stabilization of protein-monosaccharide complexes. This study provides a theoretical foundation for the use of ultrasound in altering the interfacial functionality of protein fibril-polysaccharide complexes.