微波效应致莲子淀粉与绿原酸多尺度复合及其老化行为解析

Lotus seed starch, a special high-amylose starch, easily undergoes retrogradation during food processing. This change results in a deterioration in the quality of lotus seed products, which severely restricts the development and application of highly processed lotus seed products. The nature of lotus seed starches will be analyzed in this present project. First, a numerical simulation method will be applied to reveal the molecular behavior of lotus seed starch in a non-uniform flow field. Starch pasting properties will be investigated under the synergistic effects of microwave irradiation and chlorogenic acid based on the movement profile of a free energy surface on a molecular surface. Then, paramagnetic resonance will be employed to determine the intermediate form of molecular free radicals in a starch-chlorogenic acid-water ternary system by using microwave irradiation field. This technique will be then combined with high-dimensional nuclear magnetic technique to analyze the interaction of the molecular force in this ternary system and to quantitatively illuminate the effects of microwave irradiation on the molecular energy levels and the relaxation time of starch complexes. Molecular dynamics will be employed to simulate the docking form of starch-chlorogenic acid and to interpret the multi-scale composite mechanism of starch and chlorogenic acid. Finally, cryo-electron microscopy will be applied to observe the molecular rearrangement and determine the related laws controlling the formation of starch-chlorogenic acid complexes during starch retrogradation. The topology of recrystallization of lotus starch-chlorogenic acid complexes will beanalyzed and calculated by combinational use of different modern spectrum technology. Retrogradation kinetic models of starch will be then established to explain the retrograde behavior of lotus starch-chlorogenic acid complexes. This project will provide some scientific basis in support of innovation in starch retrogradation’s control theory and the development of highly processed products that use lotus seeds.

莲子淀粉为高直链特异性淀粉，在加工中极易老化返生而导致产品品质劣变，严重制约了莲子深加工产品的开发与应用。本项目以莲子淀粉为研究对象，首先利用数值模拟手段揭示非均匀流动场内莲子淀粉的分子行为，依据自由能面在分子表面移动规律探究微波场与绿原酸协同作用下的淀粉糊化特性；然后采用顺磁共振技术测定微波辐射场内淀粉-绿原酸-水三元体系中分子自由基中间产物，并结合高维核磁技术分析该体系中的分子力互作形式，定量阐述微波作用对淀粉复合物分子能级和弛豫时间的影响，运用分子动力学手段模拟淀粉-绿原酸对接形式，阐释淀粉与绿原酸多尺度复合机制；最后借助冷冻电镜观察淀粉-绿原酸复合物在淀粉老化过程中的分子重排规律，借助现代光谱技术分析计算莲子淀粉-绿原酸复合物重结晶的拓扑结构，构建淀粉老化动力学模型，解析莲子淀粉-绿原酸复合物的老化行为。本项目可为淀粉回生控制理论的创新及莲子深加工产品开发提供一定的科学依据。

莲子属典型易老化回生淀粉基食品，前期研究发现微波场使莲子淀粉单分子链与酚类组分发生特异性结合，显著降低莲子中的抗性淀粉含量。基于此，本项目深入研究微波场内绿原酸与莲子淀粉的互作行为，主要结果如下：.（1）研究微波场内绿原酸对莲子淀粉介电响应的影响。结果表明：微波场中混合体系具有更强的微波能转化效率，在不同微波功率下，绿原酸与淀粉将形成不同类型的结合方式，且只有在较高微波功率条件时绿原酸才能主动干预淀粉内部链的重组。.（2）从多尺度角度对复合体系的精细结构开展研究。结果表明：绿原酸以多种形式参与淀粉分子的重排（非包合型、V7型和单纯物理包埋）。有序结构变化表明，氢键作用是稳定复合体系的主要作用力，而直链淀粉是绿原酸分子作为氢键供体的主要结合位点。螺旋结构和纳米聚集结构研究表明，由于绿原酸空间位阻较大，形成的复合结构难以形成自相似有规立构，这表明绿原酸分子能抑制淀粉分子的有序重排。.（3）在多尺度复合结构的研究基础上，利用分子动力学模拟技术解析复合体系力学特性与复合物精细结构的关联性。结果表明，在淀粉体系中，结构灵活度较高的单螺旋组分更容易发生构象变化，此时绿原酸插入到糖链的螺旋状空腔内，而双螺旋结构无法形成凹槽，绿原酸仅附着于双链螺旋的表面。.（4）研究复合体系特异性结构与其老化行为之间的构效关系。结果表明，微波环境中，绿原酸分子能够增强断链反应，促使莲子淀粉内部B2和B3链断裂成小分子片段，导致莲子淀粉在老化过程中形成更为稳定的凝胶连续相，防止凝胶胶束单元的崩溃。.综上，本项研究揭示了微波技术与绿原酸协同作用对莲子淀粉老化的抑制机理，对于推动微波技术在分子层面上调控淀粉基食品的加工特性提供了理论依据。