Interaction between Walnut Polyphenols and Protein and Its Antioxidant Activity

The mechanism of chemical bonding between walnut phenolic compounds and walnut protein of the walnut were explored in this paper. The walnut protein solution was first treated by solvent under alkaline and acidic conditions, and then ultrafiltration was carried out, and different bound polyphenols were obtained by destroying the interaction force between walnut protein-polyphenol compounds. The content and antioxidant activity of polyphenols were determined. The results showed that the contents of free polyphenols were 6.46, 6.27 mg/g respectively, accounting for 25.15% and 29.77% of the total phenols, the contents of non-covalent polyphenols were 11.31, 7.74 mg/g respectively, accounting for 44.02% and 36.75% of the total phenols, and the contents of covalent polyphenols were 7.92, 7.05 mg/g respectively, accounting for 30.83% and 33.48% of the total phenols.It was known that non covalent binding was the main form of interaction between polyphenols and protein complexes. Under pH3.5 and pH11 conditions, the scavenging rates of free polyphenols on DPPH free radicals were 82.34% and 43.68%, Fe2+ chelating ability were 71.88% and 49.96%, reducing power absorbance value were 1.157 and 0.857, inhibition of lipid peroxidation ability were 47.71% and 32.69%, respectively. Among the five different bound polyphenols, the antioxidant capacity of free polyphenols was significantly higher than that of other bound polyphenols (p<0.05).