Department of Food Science, College of Agricultural Sciences, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.
J Agric Food Chem. 2011 Aug 24;59(16):8915-22. doi: 10.1021/jf201491k. Epub 2011 Jul 22.
Polyphenols are widely regarded as antioxidants, due in large part to their free radical scavenging activities and their ability to disrupt radical chain propagation. However, recent studies have demonstrated that the oxidation of some polyphenolic compounds, such as the tea-derived compound (-)-epigallocatechin-3-gallate (EGCG), results in the generation of reactive oxygen species that can potentially compromise the oxidative stability of food lipids under some conditions. In this present study, the rate of hydrogen peroxide (H(2)O(2)) generation and its stability, resulting from EGCG oxidation in Tween 80- and sodium caseinate-stabilized oil-in-water (O/W) emulsions in the presence of iron (25 μM Fe(3+) from FeCl(3)), were examined. Observed H(2)O(2) levels in protein-stabilized emulsions were significantly lower across all treatments as compared to surfactant-stabilized emulsions. The lower observed H(2)O(2) concentrations seen in the protein system are likely due to the antioxidant effects of the added proteins, which either prevented the generation of or more likely scavenged the peroxide. All protein-stabilized emulsions containing EGCG showed increases in carbonyl concentrations, a marker of protein oxidation, throughout the study. The H(2)O(2) scavenging activity of aqueous phase and interfacial caseinate and whey protein isolate (WPI) was also evaluated. Both proteins showed concentration-dependent scavenging of H(2)O(2) with caseinate displaying significantly higher scavenging abilities at all concentrations. These results suggest that food proteins may play an important role in mitigating the pro-oxidant effects of polyphenols.
多酚被广泛认为是抗氧化剂，这在很大程度上是由于它们的自由基清除活性以及它们破坏自由基链传播的能力。然而，最近的研究表明，一些多酚化合物的氧化，如茶衍生的化合物（-）-表没食子儿茶素-3-没食子酸酯（EGCG），会产生活性氧物种，这些物种在某些条件下可能会破坏食物脂质的氧化稳定性。在本研究中，考察了在铁（来自 FeCl3的 25 μM Fe3+）存在下，Tween 80 和酪蛋白酸钠稳定的油包水（O/W）乳液中 EGCG 氧化导致的过氧化氢（H2O2）生成速率及其稳定性。与表面活性剂稳定的乳液相比，在所有处理中，蛋白质稳定的乳液中观察到的 H2O2水平显著更低。在蛋白质体系中观察到的较低的 H2O2浓度可能是由于添加的蛋白质的抗氧化作用，这些蛋白质要么防止了过氧化物的生成，要么更可能清除了过氧化物。含有 EGCG 的所有蛋白质稳定的乳液在整个研究过程中羰基浓度（蛋白质氧化的标志物）均增加。还评估了水相和界面酪蛋白酸钠和乳清蛋白分离物（WPI）对 H2O2的清除活性。两种蛋白质均表现出对 H2O2的浓度依赖性清除，其中酪蛋白酸钠在所有浓度下均显示出更高的清除能力。这些结果表明，食物蛋白质可能在减轻多酚的促氧化作用方面发挥重要作用。
