Effect of peptide–phenolic interaction on the antioxidant capacity of walnut protein hydrolysates

Summary Walnut antioxidant peptides and phenolic compounds ( POH s) commonly coexist in walnut protein hydrolysates ( WPH s). However, the peptide–phenolic interaction and its effects on antioxidant activities of WPH s remain unknown. Fluorescence and dynamic light scattering were used to study the peptide–phenolic interaction in WPH ‐ POH mixtures (W‐P) with different POH / WPH ratios; antioxidant abilities of POH only solution, WPH only solution and W‐P were measured with three assays: DPPH radical scavenging, Fe 2+ chelation and linoleic acid peroxidation inhibition. Results showed that initially POH s bonded to hydrophobic sites of peptides; subsequently, when POH / WPH ratio exceeded 1:120 (w/w), POH s changed the conformation and average particle size of peptides. Their interaction could at most increase WPH s’ capability in scavenging DPPH radical (44.9%), chelating Fe 2+ (36.1%) and inhibiting linoleic acid oxidation (87.5%) at the POH / WPH ratio (w/w) point of 1:12. This research offered a guidance in the production of WPH s with high functionality.