蛋白-多酚复合物界面层及多糖网络结构对油凝胶稳定性影响机理研究

Exploring the way to produce oleogel with characteristics of plastic fats to substitute traditional solid lipid is one way to reduce the use of trans fat. Most research has been focused on using small molecular gelators or surfactants to make oleogel. Food polymers such as protein and natural polysaccharides have different varieties and special interfacial characteristics. Applying these renewable food materials in functional oleogel with polyunsaturated fatty acids has great economic value. Addition of polyphenol compounds in oleogel could restrict lipid oxidation. In this program, therefore, the self-assembly protein-polyphenol colloid nanocomplexes was formed and supplied as emulsifier. The emulsion was formed by complexation with polysaccharides. The polyphenol compound could be brought to the surface and the interfacial structure was intensified due to the adsorption of the colloidal compounds. The effect of different kinds of oil and drying methods on the structure and lipid oxidation of oleogel was evaluated. The interfacial and polymer structure were characterized and the binding and clustering morphology of oil were illustrated to build their link with the oleogel and lipid stability. The release of free fatty acid during in vitro digestion of oleogel was also evaluated to measure the controlling release ability of lipids in oleogel. This research will provide theoretical values for exploration the mechanism of food polymers to stabilize oleogel. In addition, it will provide a scientific basis for the application of antioxidant polyphenol in high-fat system.

寻求具有塑性脂肪特征的油凝胶制备方法替代食品传统固态油脂是减少食品中反式脂肪的重要途径之一。目前研究多使用小分子凝胶因子或表面活性剂制备油凝胶，而食品聚合物如蛋白和天然多糖种类众多且具有独特的界面特性，将此类可再生原料用于开发富含不饱和脂肪酸的油凝胶具有重要经济意义，此外油凝胶中引入抗氧化多酚可抑制油脂氧化。为此，本课题以蛋白-多酚制备胶体复合物作为乳化剂，与多糖复合制备乳浊液体系，将多酚携带至油滴界面构建抗氧化界面层增加界面层强度，评价油相种类、干燥方式对油凝胶稳定性的影响，表征乳浊液及油凝胶中蛋白-多酚界面层结构及多糖网状结构，明晰油凝胶制备过程中分子形态变化，揭示分子聚集及结合方式与油凝胶结构及油脂氧化的内在联系，同时评价油凝胶在模拟小肠消化过程中脂肪酸释放规律，本研究对明确食品聚合物结构的形成对油凝胶稳定性的影响具有重要理论价值，为抗氧化多酚在高油脂体系中的应用提供科学依据。

采用明胶与单宁酸、原花青素分别复合，研究了胶体复合物的性质，发现二者在pH 6，复配比例16:1时所得复合物粒径最小，二者结合为氢键相互作用为主的自发结合，形成复合物后蛋白结构展开，复合物抗氧化能力显著提升，降低界面张力能力增加。复合物可制备稳定的乳液，乳液粒径小于单独明胶制备的乳液，含有多酚的乳液在存储过程中具有较高的氧化稳定性。通过冷冻干燥明胶-多酚乳液可得到形态完整的固体脂，剪切后可制得稳定的弹性固体特征的油凝胶。研究了多糖对复合物体系和乳液及油凝胶性质的影响，发现在明胶-多酚乳液中加入多糖亚麻籽胶，可形成更加稳定的乳液，观察复合物的微观形态发现三者可形成明显的纳米颗粒，考察界面性质发现一定浓度的多酚对于复合物降低界面张力具有促进作用，而过高的多酚添加量反而不利于界面张力降低。蛋白-多酚-多糖三者复合物可在油滴表面形成独特的颗粒吸附的界面膜，具有皮克林吸附特性，可有效增加乳液界面稳定性，增强乳液的结构强度，乳液可通过烘箱干燥制备出柔软的固体油凝胶，油凝胶具有良好的触变回复性以及热稳定性，并可经过重新水化形成稳定的乳液。最后以三种植物油分别制备不同脂肪酸组成的植物油基油凝胶，并进行了储存实验，发现储存过程中大豆油基油凝胶流变性下降更加明显，亚麻籽油烘箱干燥制备的油凝胶更容易氧化，而单宁酸明显抑制了油凝胶中油脂的氧化程度。对三种植物油基油凝胶进行模拟体外消化，发现油凝胶中的游离脂肪酸释放量明显高于植物油，且β-胡萝卜素的生物利用度显著增加，表明油凝胶可作为一种良好的脂溶性生物活性物质载体。本项目研究对于将天然大分子聚合物和小分子抗氧化多酚在低饱和油凝胶中的应用奠定了基础，拓展了凝胶因子种类，揭示了复合物稳定油凝胶的机制，建立了聚合物基油凝胶宏观和微观稳定性的联系，具有较深的理论价值和广阔的应用前景。