Effect of Peroxyl-Radicals-Induced Oxidative Modification in the Physicochemical and Emulsifying Properties of Walnut Protein

In this paper, the effects of peroxyl radical oxidation on the physicochemical and functional properties of walnut protein were investigated. Walnut protein isolate (WPI) containing 2,2 '-azobis(2-amidinopropane) dihydrochloride (AAPH) was oxidatively stressed under aerobic conditions in peroxyl radical-generating media. Incubation of walnut protein with increasing concentration of AAPH resulted in gradual carbonyl generation and free sulfhydryl group degradation. The results of surface hydrophobicity implied that oxidation leads to protein aggregation thus decreasing protein solubility in an AAPH concentration-dependent manner (P < 0.05). Emulsifying properties exhibited a significant increase (P < 0.05) at AAPH concentrations up to 0.2 mM and higher AAPH concentrations reduced the emulsifying capacity of WPI. These results indicate that appropriate oxidation is helpful to improve the emulsifying properties of protein, and with an increase of oxidation degree, emulsifying functional will damage.