Soy protein isolate/dextran glycation conjugates: Fabrication through ultrasound-assisted cyclic continuous reaction and their applications as carriers of anthocyanins

The precise control of browning and enhancement of Maillard reaction kinetics to improve the surface functionality and nutrient encapsulation efficiency of soy proteins remains a significant challenge. This research presents an ultrasound-assisted cyclic reaction method (1-7 cycles) to synthesize soy protein isolate/dextran (SPI/D) conjugates with enhanced grafting degree and functionality during the Maillard reaction. The technique significantly increased the grafting degree to 65.92 % by the seventh cycle, with minimal browning. Structural analysis showed tighter secondary and more relaxed tertiary structures, leading to a diminished exposure of hydrophobic moieties and an enhancement in solubility, emulsification, foaming, and antioxidant capacity. These functional improvements notably bolstered the SPI/D conjugates' ability to encapsulate anthocyanins (ANs). Particularly, after seven cycles, SPI/D demonstrated a marked enhancement in the thermal, storage, and light stability of ANs. Additionally, it reduced the susceptibility of ANs to degradation by hydrogen peroxide, Fe³⁺ ions, and gastrointestinal simulated digestion (p < 0.05), which was attributed to their relatively higher hydrophobic residues, hydrogen bonds, and hydrophobic interactions. This strategy provides new insights into soy protein design, highlighting the potential to augment surface functionality and nutrient encapsulate efficiency by controlling the browning degree and enhancing Maillard reaction kinetics.