Effects of l-arginine/l-lysine modifications on the protein structure, binding interactions, and functional properties of soy protein hydrolysate

This study investigated the effects of different concentrations (0%, 0.1%, 0.5%, and 1.0%) of l-arginine/l-lysine on the structural and functional properties of soy protein hydrolysate (SPH) extracted using enzyme-assisted extraction processing. The addition of l-arginine and l-lysine increased the pH, solubility, fluorescence intensity, and surface hydrophobicity of SPH and decreased its turbidity, particle size, and α-helix content, thus changing its secondary and tertiary structure without affecting the molecular-weight distribution. The pattern of intra-particle interactive forces and molecular docking studies indicate that hydrogen bonds may be the primary driving force for the binding of l-arginine/l-lysine with SPH. Overall, l-arginine and l-lysine significantly improved the antioxidant activities, foaming abilities, and emulsifying properties of SPH. The addition of 1% (w/v) l-arginine and 1% (w/v) l-lysine caused a significant decrease in the 1,1-diphenyl-2-picrhydrazyl radical scavenging activity and foaming activity and stability of SPH, respectively. Notably, at the same concentration, l-arginine better improved the functional properties of SPH than did l-lysine. Therefore, this study confirms the advantage of using basic amino acids as protein modifiers and could facilitate the application of SPH in the food industry.