微波协同无机盐对麦胚膜结合脂肪酶及其界面活性的调控机制

In view of the fact of short shelf life of wheat germ and whole wheat flour products, as well as the deficiency of the current theoretical research on low-moisture material in microwave food processing, this study is designed to carry out a theoretical research on microwave stabilization, focusing on the key scientific matter in cereal germ microwave processing, namely the correlation between the catalytic efficiency and composition of lipid-water interfaces, which is the catalytic site of lipase, the relationship between lipases structure and catalytic function. Heat stable membrane-bound wheat germ lipase, the key enzyme that affects the germ stability, are took as the main research object to study the cooperative action in microwave and inorganic salts during wheat germ stabilization, from the aspects of the composition and structure of lipid-water interfaces and the relationship between the catalytic efficiency and interface structure, the interacting between lipase micro structure and macro effect. The dielectric properties of wheat germ and its typical components, the characteristics of low moisture in wheat germ and composition complexity of wheat germ are fully considered. Methods like bioelectromagnetics, modern structural biology analysis, interfacial enzymatic analysis methods and data fusion technology are well combined. Then, reasons for membrane-bound lipase inactivated by microwave and inorganic salts are explained on molecular level, and the mathematical interrelationship among state variable, microwave field response, lipid-water interfaces, micro structure and macro effect during wheat germ microwave stabilization is built. Thus, a key problem in low-moisture food processing by microwave will be solved, offering solid theoretical foundation to development of wheat germ and whole wheat flour processing industry.

针对小麦胚芽与全麦粉产品货架期短、以及食品微波加工理论关于低水分物料研究的不足，课题围绕麦胚脂肪酶微波钝化过程中的关键科学问题，即：脂肪酶催化场所--油水界面组成与催化效率的关联、脂肪酶结构与催化功能的关系，展开微波钝酶基础理论研究。课题充分考虑麦胚低水分特征与组成复杂性，以影响麦胚稳定性的关键酶--膜结合脂肪酶为对象，麦胚及其典型组分的介电性分析为基础，将生物电磁学、结构生物学、界面酶学分析方法以及数据融合技术等有机结合，系统探讨微波与无机盐协同作用下，油水界面组成与结构变化、及其与酶催化效率的关联；脂肪酶多层次分子结构、宏观性能变化以及多元分子间的交互影响规律。最终，实现耐热膜结合脂肪酶受微波与无机盐协同钝化的分子解释，并构建微波过程参数-微波场响应-界面组成-微观结构-宏观效应之间的量化关联。从而，完善低水分食品物料的微波稳定化基础理论，为全麦粉与麦胚深加工产业发展提供技术支撑。

针对小麦胚芽与全麦粉产品货架期短、以及食品微波加工理论关于低水分物料研究的不足，展开微波钝酶基础理论研究。课题系统探讨了麦胚的介电性能及无机盐增强效应，分析了脂肪酶耐热性、以及无机盐对其活性的影响，研究了微波协同无机盐对脂肪酶结构与功能、以及对脂肪酶催化场所——油水界面活性的影响规律。研究表明，微波频率、水量、脂肪对小麦胚芽的介电特性具有重要影响，Na+对其有明显的增强效果。无机盐通过改变脂肪酶高级结构降低了其活性，微波钝酶作用主要源于其热效应；Na+对麦胚脂肪酶的微波钝化具有增效作用，其钝化过程可采用一级动力学（Logistic和Boltzmann模型）进行拟合。脂肪酶的作用底物和产物对其界面活性影响程度不同，三油酸甘油酯＞单油酸甘油酯＞油酸；不同浓度无机盐离子对麦胚脂肪酶界面活性影响效果不同，Na+更有利于抑制酶的界面活性；不同温度、界面环境条件下，无机盐离子对麦胚脂肪酶界面活性影响效果不同，无机盐降低了三油酸甘油酯或油酸存在时的油水界面张力，其中Na+抑制作用明显；温度主要通过影响G''改变界面流变性质，30 ℃时抑制效果最佳。研究成果完善了低水分食品物料的微波稳定化基础理论，为全麦粉与麦胚深加工产业发展提供了技术支撑。