Desirable characteristics of casein peptides with simultaneously enhanced emulsion forming ability and antioxidative capacity in O/W emulsion

Abstract

This study aimed to explore the desirable characteristics of casein hydrolysates with simultaneously enhanced emulsion forming and antioxidative ability in oil-in-water (O/W) emulsion. Effects of physicochemical properties of casein hydrolysates prepared by trypsin, alcalase, and neutrase on physical and oxidative stability of O/W emulsion were studied, and potential antioxidant peptides were characterized by UPLC-MS/MS and bioinformatics analysis. Results showed that casein hydrolysates at a lower degree of hydrolysis (DH) produced by trypsin displayed higher zeta potential absolute values (−31.7 mV), smaller particle size (170.75 nm) and improved antioxidant properties compared to alcalase and neutrase, and could form more stable emulsion with d4,3 of 0.39–0.41 μm at a broader range of DH. Additionally, compared with sodium caseinate (NaCas), the oxidation of emulsion was significantly retarded during the storage progress prepared by the trypsin hydrolysates at DH of 4.49% alone or with Tween 20. Peptidomics indicated that the trypsin hydrolysates contained more peptides with basic amino acids at C-terminal and aromatic amino acids at N-terminus, which exhibited cationic amphiphilic properties with grand average of hydrophilicity values (GRAVY) of −0.5 ∼ +0.5 and pI > pH 7.0. This could contribute to their better emulsion formation and inhibition of lipid oxidation ability by producing dense interfacial layers with peptides interactions or excluding metal ions in O/W emulsions. These results suggested that casein hydrolysates at lower DH prepared by trypsin owned potential amphiphilic antioxidant peptides, which were desired to enhance the stability and functional activity of O/W emulsion.