蛋白/生物表面活性剂复合界面调控乳液稳定及消化的机理研究

The interfacial adsorption behavior of protein-surfactant mixtures and the structural properties of mixed interfacial layers are believed to play important roles in emulsion stability and lipid digestion. In this study, protein and biosurfactant as emulsifiers could competitively adsorb at the oil/water interface and form mixed interfacial layers. To modify the structural properties of mixed interfacial layers, the interactions between protein and biosurfactant molecular and their interfacial compatibility were strengthened by heat-induced structural changes of protein, which is controlled by protein aggregation behavior. These changes could improve emulsion stability and regulate lipid digestion. The detailed researches were described as follow: ①The interactions between protein and biosurfactant in the bulk were investigated; ②Dynamic drop shape analysis was used to evaluate the adsorption behavior of protein-biosurfactant mixtures at the oil-water interface and the dilatational rheology of mixed interfacial layers. How the intermolecular interactions between protein and biosurfactant influent their interfacial adsorption behaviors and structural properties of mixed interfacial layers was discussed, and the underlying mechanism was proposed; ③The changes in emulsion stability during the storage and the evolution of emulsion digestion during in vitro digestion were monitored, especially the interfacial rheology of protein-biosurfactant mixtures and the kinetics of lipid digestion. The relation among the structural properties of mixed interfacial layers, emulsion stability,and emulsion digestibility were established, which would provide the food industry with a possibility to successful development of functional food emulsion.

蛋白质-乳化剂复合体系的界面吸附行为和界面膜结构是影响乳液稳定性及乳液脂肪消化进程的关键因素。本项目以蛋白质和生物表面活性剂为研究主体，利用二者的界面竞争吸附行为构建复合界面膜，试图通过控制蛋白质热聚集行为定向修饰其分子结构，改变两类分子间相互作用和界面相容性，从而修饰复合界面膜结构，达到改善乳液稳定性，调节脂肪消化的目的。研究内容包括：①表征蛋白质与生物表面活性剂在体相中的相互作用；②采用滴形分析法表征复合体系的界面吸附动力学和界面膜流变学特性，揭示界面分子相互作用对界面吸附行为、界面膜结构的调控机制；③研究复合乳液的物理稳定性和消化过程，重点表征体外模拟消化过程中界面流变特征的变化和乳液脂肪消化动力学。本项目将从复合界面膜结构修饰的角度揭示其与乳液稳定/失稳、乳液消化特性之间的内在关联性，为开发新型功能食品提供新思路和理论指导。

食品乳液在加工和货架期内常发生失稳，严重影响其品质，是食品工业中亟待解决的技术问题。具有高界面活性的小分子乳化剂与能够形成粘弹性良好界面膜的蛋白质常共存于食品乳液中。复合乳液失稳可能与二者在界面上的竞争吸附/解析及不兼容性相关，研究蛋白-乳化剂复合体系相互作用及界面吸附行为对于克服乳液失稳具有重要的意义。本项目以大豆蛋白和生物表面活性剂（甜菊甙和鼠李糖脂）为对象，试图定向修饰其分子结构，系统研究蛋白热诱导和乙醇诱导聚集行为，揭示了大豆蛋白及生物表面活性剂的相互作用机制，研究二者的界面竞争吸附行为，意在提高其界面相容性，构建流变特性良好的复合界面膜，从而改善乳液稳定性。.主要研究发现包括：1）在中性及酸性pH下，低浓度乙醇均可诱导大豆蛋白发生自组装纤维聚集，醇诱导蛋白展开是蛋白纤维化的前提条件；2）热诱导纤维聚集体在中性pH发生强烈絮凝，糖接枝修饰不影响纤维聚集动力学，但可有效改善其pH稳定性和泡沫稳定性，纤维聚集体/多糖复合物的乳化性质明显改善；3）热处理诱导无定形聚集体的出现减小了界面吸附速度、表面压和界面粘弹模量，有利于形成多层界面结构，可有效改善蛋白的泡沫及乳液稳定性；4）大豆蛋白/生物表面活性剂在体相和界面相发生非特异性分子间弱疏水相互作用，表现出降低表面张力的协同作用及稳态的界面弹性行为，构建了兼具一定刚性和柔韧的复合界面层，可以有效改善蛋白的泡沫/乳液稳定性。.该项目大致完成了项目计划书的主要研究内容，基本达到预期的研究目标，并取得了一些研究成果，特别是在揭示植物蛋白聚集行为及其与生物表面活性剂相互作用机制方面所获得的发现。截至2016年12月，标注本项目基金资助并在国内外食品类主流期刊上发表学术论文11篇，其中SCI论文7篇。本项目的完成将阐述分子结构、复合界面膜结构和乳液稳定性之间的内在关系，探讨乳液稳定/失稳的调控机理，为新型乳液食品的开发提供理论基础与技术支撑。