Non-covalent interactions of modified walnut protein isolate with proanthocyanidins: binding mechanisms, function, and stability

This study investigated the binding mechanism, functional properties, and stability of non-covalent complexes of proanthocyanidins (PA) (0, 1.0, 2.0, 4.0, and 8.0 mg/mL) with modified walnut protein isolate (MWalPI) at different concentrations. The results showed that the turbidity, binding amount, and particle size of the MWalPI-PA complexes all increased with increasing PA concentration. The secondary structure of MWalPI unfolds, showing a decrease in the β-sheet content to 46.19 % and an increase in the β-turn content to 25.15 %. The fluorescence quenching mechanism of the MWalPI-PA complex was identified as a static quenching mechanism, and hydrophobic interactions and hydrogen bonding were the primary factors driving the binding of MWalPI to PA. When the PA concentration was 4.0 mg/mL, the zeta potential of the MWallPI-PA composite reached the maximum, and the emulsification and stability of MWallPI-PA increased by 1.05 times and 0.41 times, respectively. The stability results also indicate that MWalPI-PA exhibits good storage stability, thermal stability, light stability, and digestive stability at a PA concentration of 4.0 mg/mL. These findings provide a theoretical foundation for the non-covalent binding of MWalPI-PA, expanding the potential applications of MWalPI and PA in the food industry. • Non-covalent·complexes·(MWalPI-PA) were prepared. • PA formed complexes with MWalPI through hydrophobic and electrostatic interactions. • The fluorescence quenching mechanism of the MWalPI-PA complex is static quenching. • Interaction changed the secondary structure of MWalPI and enhanced emulsification. • The highest retention of PA was observed at PA concentrations of 4.0 and 8.0 mg/mL.