Integrating spectroscopic techniques and molecular dynamics simulations to probe the interaction between hesperidin and soy protein isolate and the consequent functional improvements

Natural polyphenols, when combined with proteins, can endow proteins with unique functional properties. This research synthesized soybean protein isolate (SPI)-hesperidin (HP) complexes and systematically examined the contact between their structure and functional characteristics. The experimental findings demonstrated that the conjugation of SPI with HP resulted in a significant increase in particle size from 279.2 ± 1.4 nm to 377.6 ± 19.2 nm, accompanied by a marginal elevation of ζ-potential from −24.6 ± 1.3 mV to −22.0 ± 0.6 mV. The spectroscopic analyses, employing multiple techniques, showed that reduction in the α-helix and marked fluorescence quenching of SPI and brought about alterations in its secondary structure, characterized by a reduction in the α-helix and a corresponding increase in the β-sheet. Moreover, molecular docking and dynamics simulations provided compelling evidence that SPI formed complexes with HP via hydrogen bonding and hydrophobic interactions. In addition, Functional characterization studies revealed that at an HP concentration of 1.25 mg/mL, the complex exhibited enhanced protein flexibility (57.60%), surface hydrophobicity (41.72%), foaming activity (4.70%), and emulsifying activity (28.16%), whereas foam stability and emulsifying stability decreased by 5.79% and 12.91%, respectively. This research further illuminated the intricate interaction mechanism between proteins and polyphenols, shedding new light on the applications of SPI and HP in food.