Conformation and Oxidative Damage of Lipid Molecules in Membrane Models of Food and Biological Systems

本文研究了分散体系中脂质在油水界面上的构象与氧化的关系。通过DSC、FT-IR和表面压等方法对甘油三酯在油水界面上的分子取向进行了分析，发现不饱和脂肪酸在界面上呈松散堆积状态。然而，添加表面活性晶体增加了甘油三酯分子在界面处的分子取向。研究了乳化体系中羟基自由基对脂肪酸酯的氧化作用。结果表明，氧化程度与脂肪酸的结构没有直接关系，而与乳化所用的乳化剂有关。与使用非离子表面活性剂相比，使用离子表面活性剂增加了脂肪酸酯的氧化程度。蛋白质稳定的乳状液氧化机理与表面活性剂稳定的乳状液不同。这些r 关于我们 结果表明，影响脂质氧化的主要因素不是脂质本身的构象，而是脂质与乳化剂在界面上的相互作用。为了获得界面处乳化剂的物理状态和相互作用的信息，研究了脂肪氧合酶在不同乳化剂稳定的乳状液中的反应。在由蛋白质稳定的乳液中观察到高的氧合速率，而在由表面活性剂稳定的乳液中观察到非常低的氧合速率。吸附蛋白质在界面处形成二维网络结构，蛋白质分子的横向扩散受到高度限制。脂氧合酶可能能够从界面处的二维网络中的缝隙中吸取底物脂质。而表面活性剂在界面处容易扩散，迅速向界面能级高的地方移动，可以填充界面。对于脂氧合酶来说，从这样一个被表面活性剂密集填充的界面中吸取底物脂质可能是困难的。本研究结果将为构建真实的食品中安全、有效的抗氧化体系提供基础性研究成果。少

Relation between conformation and oxidation of lipids at the oil-water interface in dispersed systems has been investigated. Analyzes of molecular orientation of triglycerides at the oil-water interface by DSC,FT-IR and surface pressure measurements revealed that unsaturated fatty acids were loosely packed at the interface. However, the addition of surface active crystals increased the molecular orientation of triglyceride molecules at the interfaces. The oxidation of various kinds of fatty acid esters induced by hydroxyl radical in emulsion systems was studied. The obtained results have shown that the degree of oxidation does not directly relate to the structure of fatty acid, but to the emulsifiers used for emulsification. The use of ionic surfactants increased the degree of oxidation of fatty acid esters as compared to the use of non ionic surfactants. The oxidation mechanism in emulsions stabilized by proteins were different from that in emulsions stabilized by surfactants. These r … More esults indicate that the important factor is not the conformation of lipids itself, but the interaction of lipid and emulsifiers at the interfaces in relation to the oxidation of lipids. In order to obtain the information on the physical states and interaction of emulsifiers at the interface, Iipoxygenase reaction in emulsions stabilized by various emulsifiers was investigated. The high oxygenation rates were observed in the emulsions stabilized by proteins, whereas the oxygenation rate was very low in the emulsion stabilized by surfactants. It is thought that adsorbed proteins form the two-dimensional network structure at the interfaces in which the lateral diffusion of protein molecule is highly restricted. Lipoxygenase may be able to draw the substrate lipid from the crevice in the two dimensional network at the interface. However, surfactants are easy to diffuse at the interface to move rapidly the place with high interfacial energy level and can fill the interface. It may be difficult for lipoxygenase to draw the substrate lipid from such an interface densely filled by surfactants. The results obtained through this research project may become fundamental findings for the construction of the safe and efficient antioxidant systems in real foods. Less