羟自由基氧化对核桃蛋白性质和结构的影响

Effect of hydroxyl radical oxidation on properties and structure of walnut protein

为研究羟自由基氧化对核桃蛋白性质和结构的影响,以碱溶酸沉法提取核桃蛋白,经铁/过氧化氢/抗坏血酸体系氧化产生羟自由基,分析不同氧化程度核桃蛋白的羰基、巯基、内源荧光、粒径和功能性质的变化规律。结果表明,随着H_(2)O_(2)浓度的增大,核桃蛋白的溶解性、游离巯基和内源荧光强度呈下降趋势,最大降幅分别为45.6%、28.2%和34.8%;持水性、平均粒径和羰基随H_(2)O_(2)浓度的增大而逐渐增加,最大增幅分别为136.6%、12.7%和88.9%;核桃蛋白的乳化性、乳化稳定性、起泡性和持油性呈先增大后减小的趋势,最大增幅分别为108.8%、53.4%、42.6%和146.0%;电镜扫描结果显示经低浓度羟自由基(0.1 mmol/L)氧化可使核桃蛋白的结构更紧密,而高浓度羟自由基氧化(15 mmol/L)则使其形态变疏松,孔隙率增大。该研究表明羟自由基氧化会影响核桃蛋白的功能性质和结构,而适度氧化可获得具较好乳化性和起泡性的核桃蛋白。

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/H_(2)O_(2)/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 H_(2)O_(2)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 H_(2)O_(2)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.