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

Walnut antioxidant peptides and phenolic compounds (POHs) commonly coexist in walnut protein hydrolysates (WPHs). However, the peptide–phenolic interaction and its effects on antioxidant activities of WPHs 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, Fe²⁺ chelation and linoleic acid peroxidation inhibition. Results showed that initially POHs bonded to hydrophobic sites of peptides; subsequently, when POH/WPH ratio exceeded 1:120 (w/w), POHs changed the conformation and average particle size of peptides. Their interaction could at most increase WPHs’ capability in scavenging DPPH radical (44.9%), chelating Fe²⁺ (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 WPHs with high functionality.