羟自由基氧化对海鲈鱼肌原纤维蛋白生化特性及其乳化性能的影响

采用羟自由基氧化体系对海鲈鱼肌原纤维蛋白进行体外模拟氧化,研究羟自由基氧化氧化对肌原纤维蛋白生化特性和乳化性能影响。结果显示:随氧化时间的延长,羰基含量、表面疏水性和肌原纤维蛋白(MPI)平均粒径增加,总巯基和活性巯基含量下降,生色氨基酸含量减少,二聚酪氨酸含量在4 h达到最大值。H2O2浓度在1 mmol/L时上述指标变化显著,H2O2浓度在5 mmol/L和10 mmol/L条件下,前4 h乳化活性和乳化稳定性显著下降,活性巯基含量较对照组分别下降了51.93%和65.88%,MPI平均粒径较对照组分别增加了47.87%和72.38%,4 h后变化不明显,且不同氧化剂浓度之间差异性显著。SDS-PAGE电泳图谱表明经羟自由基氧化后蛋白质发生交联,形成大量高分子凝集体,在200 ku上方区域堆积,肌球蛋白重链含量减少。结果表明,羟自由基氧化体系能使海鲈鱼肌原纤维蛋白结构发生改变,导致其乳化性能下降。

Effects of Hydroxyl Radical Oxidation on the Biochemical Characteristics and Emulsifying Properties of Myofibrillar Proteins from Sea Bass

The effect of hydroxyl radical oxidation on the biochemical characteristics and emulsifying properties of myofibrillar proteins were investigated by in vitro simulant oxidation experiments. The results showed that with increasing oxidation time, the carbonyl content, surface hydrophobicity, and average particle size of myofibrillar protein isolate from sea bass were increased, the content of total sulfhydryl group, active sulfhydryl group, and chromophore amino acids were decreased, and the content of tyrosine dimer reached a maximum value at 4 h. These indicators changed significantly when the H2O2 concentration was 1 mM. When the H2O2 concentrations were 5 and 10 mM, during the first 4 h, emulsifying activity and emulsifying stability were significantly decreased; the active sulfhydryl group content were decreased by 51.93% and 65.88%, respectively, compared to that in the control group; the average particle sizes of myofibrillar protein isolate were increased by 47.87% and 72.38%, respectively, compared to the control group. After 4 h, no significant changes were observed, but significant differences were detected among different oxidant concentrations. Sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed that after hydroxyl radical oxidation, the proteins were cross-linked to form a large number of high-molecular-weight aggregates, which were accumulated in the region of over 200 ku. The content of myosin heavy chain was reduced. These results show that the hydroxyl radical oxidation system can change the structure of myofibrillar proteins in sea bass, leading to a decline in their emulsifying capacities.