To study the hydroxyl radical oxidation (HRO) effects on properties and structure of the walnut protein, the alkali extraction-acid precipitation method was implemented to extract WP, and then oxidized with hydroxyl radical generated by Fe / H2O2/ Asc system. Various patterns of carbonyl, thiol, endogenesis fluorescence, particle size, and functional properties of WP with different degrees of oxidation were studied. The results showed that the solubility, free thiol, and endogenesis fluorescence intensity were decreased with the increase of H2O2 concentration, and the largest drop was 45.6%, 28.2%, and 34.8%, respectively. The water holding capacity (WHC), mean particle size, and carbonyl content of WP were increased with the H2O2 concentration, and reached 136.6%, 12.7% and 88.9%, respectively. The emulsifying activity index (EAI), emulsifying stability index (ESI), foaming property (FP), and oil holding capacity (OHC) were first increased and then decreased, and the maximum was 108.8%, 53.4%, 42.6%, and 146.0%, respectively. Scanning electron microscope (SEM) showed a tight structure of WP with low concentration oxidation (0.1 mmol/L), while the morphology became loose and the porosity increased with high concentration oxidation (15 mmol/L). Taken together, hydrogen peroxide oxidation has a large effect on the functional properties and structure of WP, and better emulsifying and foaming property could be obtained by low concentration oxidation.
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