Method for loading liposomes with soybean protein isolate hydrolysate influences the antioxidant efficiency of liposomal systems: Adding after liposomes formation or before lipid film hydration

This research investigated the method for loading liposomes with soybean protein isolate hydrolysate (SPIH) to create stable and antioxidative protein hydrolysate-containing liposomes. SPIH (SPIH-AF) prepared via a twostep hydrolysis by alcalase and flavourzyme was added at different concentrations to liposomes by two methods. More effective adsorption of SPIH-AF onto liposomal membrane occurred when it was added at 0.5 mg/ mL and distributed in both the inner and outer water phases (addition before lipid film hydration), or added at lower concentrations (< 0.192 mg/mL) and distributed in the outer water phase (addition after liposomes formation). SPIH-AF concentration and distribution directly influenced its early rate of inhibition on lipid oxidation and membrane properties. SPIH-AF in the outer water phase functioned more effectively to inhibit lipid oxidation products accumulation. The interactions between SPIH-AF and liposomes altered SPIH-AF's secondary structures. Compared with Trp-liposomes interactions, Tyr-liposomes interactions were more sensitive to SPIHAF concentration and distribution. SPIH-AF distribution affected strongly the electrostatic interactions (but weakly the hydrophobic interactions). Tyr/Trp-liposomes interactions were more powerful when SPIH-AF was located in both the inner and outer water phases at higher concentrations.