Effect of heat treatment on functional properties of walnut protein and enzymatic hydrolysis products of walnut meal

In this study, using walnut meal as raw materials, the walnut protein was extracted by acid precipitation and alkaline extraction, and the enzymatic hydrolysis product was prepared by alkaline protease. The effects of different heat treatment methods (untreated, 65 ℃/30 min, 72 ℃/10 s, 85 ℃/10 min, 95 ℃/10 min) on the emulsification, foaming and antioxidant properties of walnut protein and enzymatic hydrolysis products of walnut meal were determined. The results showed that the foaming property of walnut protein was the highest at 95 ℃/10 min, and that of enzymatic hydrolysis product was the highest at 72 ℃/10 s. The emulsification property of walnut protein was optimal at 95 ℃/10 min, and the emulsification property of enzymatic hydrolysis product was optimal at 65 ℃/30 min. With the increase of heat treatment temperature, the total reducing power, 1,1-diphenyl- 2-picrylhydrazyl (DPPH) and hydroxyl radical scavenging rates of walnut protein showed no obvious linear trend. The total reducing power was the highest at 85 ℃/10 min, and the superoxide anion radical scavenging rate was the lowest at 95 ℃/10 min. At 95 ℃/10 min, the scavenging rate of superoxide anion radical was decreased by 24% compared with the untreated group. Considering comprehensively, the heat treatment methods of 85 ℃/10 min treatment of walnut protein and 72 ℃/10 s treatment of enzymatic hydrolysis products showed the optimal functional properties.