Ultrasound-assisted glycosylated pea protein isolate for lutein nanoencapsulation: Structural characterization, stability enhancement, and interaction mechanisms

Ultrasonic pre-treatment can significantly accelerate the reaction rate of glycosylation, improve the efficiency of protein modification, and avoid the disadvantage of long-time required by traditional glycosylation. Moreover, this method has mild reaction conditions, which can reduce the destruction of essential amino acids. Therefore, this study aimed to modify pea protein isolate (PPI) with ultrasound-assisted glycosylation by xylose. The effects of protein-to-xylose ratios on the structural and functional properties of PPI were systematically examined. The results demonstrated that ultrasonic pretreatment could improve the glycosylation grafting efficiency, and the structure and properties of modified PPI (UPPIXs) underwent significant changes. Modified PPI with protein-to-xylose ratio of 2:1 (UPPIX-2:1) exhibited superior solubility, emulsifying and foaming characteristics. Subsequently, UPPIXs were used to fabricate lutein-loaded nanoparticles (UPPIXs-LUT), and their characteristics were analyzed. The results indicated that nanoparticle prepared with UPPIX-2:1 displayed the highest encapsulation efficiency (89.46 %). Spectral analyses, fluorescence quenching, and thermodynamic studies confirmed that hydrophobic interactions dominated nanoparticle formation. Antioxidant activity and stability assessments showed that UPPIXs-LUT possessed excellent antioxidant properties, and improved stability under light, heat, storage, and pH. This study provides a theoretical foundation to use self-assembled glycosylated protein nanoparticles as an efficient delivery system for hydrophobic nutrients.