羟自由基氧化对草鱼肌原纤维蛋白结构和凝胶性质的影响

摘要

以草鱼肉为研究对象,采用芬顿反应体系(H2O2浓度分别为0.1、1.0、5.0、10.0 mmol/L)产生不同浓度·OH对其肌原纤维蛋白进行模拟氧化,研究·OH氧化对草鱼肌原纤维蛋白结构及凝胶性质的影响.结果表明,氧化使肌原纤维蛋白羰基含量显著增加(P＜0.05),当氧化剂H202的浓度为10.0 mmol/L时,羰基含量比对照组增加了111.35％;随着H2O2浓度的提高,肌原纤维蛋白总巯基、活性巯基、游离氨基含量显著下降(P＜0.05);二聚酪氨酸水平和表面疏水性显著增加(P＜0.05).十二烷基硫酸钠-聚丙烯酰胺凝胶电泳分析表明氧化使蛋白质分子间发生交联和聚集,产生了分子质量大于200 ku的蛋白聚集体.可见,·OH氧化使草鱼肌原纤维蛋白中巯基、酪氨酸、色氨酸等氨基酸残基发生了显著氧化修饰,蛋白质分子产生了交联和聚集,蛋白质构象发生了显著变化.此外,氧化可进一步影响肌原纤维蛋白的凝胶性质,使其凝胶网络结构变疏松、凝胶孔隙增大,凝胶中部分不易流动水转变为自由水,最终导致凝胶强度和凝胶持水性显著降低.%In this paper,myofibrillar protein from grass carp was artificially oxidized in hydroxyl radical-generating system with H2O2 concentrations of 0.1,1.0,5.0 and 10.0 mmol/L,and the effect of oxidization on the structural characteristics and gel properties of myofibrillar protein was investigated.The results showed that the carbonyl content increased significantly (P ＜ 0.05) after oxidization by 111.35％ compared to the initial value when the concentration of H2O2 was 10.0 mmol/L.With the increase in H2O2 concentration,the total thiol group level,free thiol group level,and free amine content decreased significantly (P ＜ 0.05),while bityrosine content and surface hydrophobicity increased significantly (P ＜ 0.05).The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) result showed that hydroxyl radical oxidation could induce the crosslinking and aggregation of protein molecules,thereby forming aggregates with molecular mass higher than 200 ku.The above results indicated that the thiol group,tymsine and tryptophane residues of myofibrillar protein were modified after hydroxyl radical oxidation,thus leading to a significant change in protein structure.In addition,the gel properties of myofibdllar protein were also influenced by oxidation,the network structure of the gel was damaged,and the portable water in the gel was converted to free water.These changes finally induced apparent decreases in the gel strength and water-holding capacity.