Ultrasound-assisted free radical grafting of sesamol onto whey protein isolate: Structural modifications, functional enhancements, and antioxidant properties

This study fabricated conjugates of whey protein isolate (WPI) and sesamol using an ultrasound-assisted free radical method. This approach significantly reduced the reaction time from 24 h to 90 min relative to the conventional free radical method, while achieving a comparable sesamol binding equivalent (4.65 mg/g). Structural analyses (amino acid side-chains, FTIR, XRD, surface hydrophobicity) revealed chemical modifications, as supported by reduced free thiol/amino groups and altered protein conformation under ultrasound. Molecular docking suggested potential hydrogen bonds and hydrophobic interactions between sesamol and WPI. Particle size and ζ-potential measurements revealed formation of larger, stable aggregates. Furthermore, WPI-sesamol conjugates exhibited superior functional properties, including protein solubility and emulsifying capacity, as well as enhanced antioxidant activity (DPPH• and ABTS⁺• scavenging), with ultrasound-assisted treatment yielding the most pronounced improvements. The ultrasound-assisted method establishes an efficient strategy for producing WPI-sesamol conjugates with superior functionality and antioxidant capacity, highlighting their potential as novel food ingredients.