甜菜果胶醇析行为的静电调控机理研究

Unveiling the mechanism on alcoholic precipitation of sugar beet pectins (SBP) is one of the critical problems in pectin chemistry. However, the mechanism has not been fully developed due to the limit research on the precipitation process of SBP. On the basis of interactions among SBP, counterions and solvent molecules within alcohol–water solution, SBP–counterions interaction therefore is employed to regulate the precipitation behavior of SBP by weakening its affinity with solvent molecules. Prior to alcoholic precipitation, SBP will be electrostatically bound with counterions in aqueous solution. Subtle change in the hydration properties of SBP will be subsequently analyzed using the combined technology of low field nuclear magnetic resonance and dynamic light scattering. In addition, the change in conformational transition and the decrease of particle size of SBP during precipitation process will be monitored via 13C nuclear magnetic resonance and dynamic light scattering, respectively. Consequently, correlation between SBP conformation and the critical ethanol concentration for SBP precipitation could be established. Through this research, electrostatic interactions involved in the alcoholic precipitation of SBP will be greatly emphasized, thereby adding knowledge to the mechanism on pectin precipitation by alcohol. Meanwhile, the scientific guidance will be provided for the precipitation of SBP in practice.

揭示甜菜果胶（SBP）的醇析机理具有重要科学意义，但因缺乏对SBP醇析过程的深入研究，SBP的醇析机理仍有待完善。基于SBP、反离子、溶剂分子间在醇–水溶液中的相互作用关系，本课题拟利用SBP–反离子静电相互作用以降低SBP与溶剂分子的亲附性，从而调控SBP的醇析行为。醇析前，先诱导SBP吸附反离子，之后采用低场核磁共振、动态光散射等技术，探索 SBP水合特性的变化规律；利用聚焦光束反射测量技术研究SBP醇析的临界乙醇浓度，并采用13C核磁共振、动态光散射等技术追踪SBP在醇析前的分子构象转变及粒度收缩，探索SBP的分子构象与临界乙醇浓度的关系，进而阐明SBP醇析行为的差异性。本项目有望从静电作用的角度上揭示SBP醇析行为的调控机理，完善SBP的醇析机理，并为SBP的生产实践提供科学指导。

果胶在醇-水溶液中经历分子链脱水、聚集、沉淀等系列的物理变化过程，涉及果胶分子间、果胶分子-溶剂分子间的复杂相互作用关系。本研究构建甜菜果胶、醇析助剂、乙醇溶液的醇析体系，通过金属离子、牛血清蛋白调节甜菜果胶的水合特性，进而揭示甜菜果胶在静电作用调控下的醇析行为，为完善甜菜果胶的醇析机理提供理论依据。具体研究内容如下：1.本项目研究了反离子、牛血清蛋白对甜菜果胶的流体动力学调控，利用果胶分子链与金属离子、牛血清蛋白的静电作用力弱化果胶分子链与溶剂分子的水合作用；2.特异性修饰甜菜果胶的甲氧基、乙酰基，评价了这两种取代基团对甜菜果胶水合特性和醇析特性的影响；3.制备并分析了甜菜果胶-金属离子、甜菜果胶-牛血清蛋白的共醇析复合物，结合醇析率曲线探究了甜菜果胶的醇析行为，并采用多种谱学技术分析半乳糖羧基的形态与结构变化。综合上述结果，本研究为甜菜果胶醇析工艺的改良、物化品质的提升提供了理论指导。项目资助发表文章15篇，申请/授权专利4项，培养博士、硕士研究生3名。