耐热型高直链化淀粉亚微晶体系的构建及慢消化机理研究

As one kind of functional carbohydrates, slowly digestible starch (SDS) generally leads hot interest to scientists in the area of Diet Structure and Health. Researchers have widely reported that the SDS products prepared from A-type native starch and B-type retrograded starch, have disadvantages in the low yield of SDS and low thermal stability during food processing. Therefore, we plan to develop a new approach to produce SDS with high thermal stability, based on the formation of the debranched starch submicrocrystal system. The project first plans to grade and purify amylose with higher molecule weight and purity, by investigating physically unfolding starch clusters, enzyme debranching, and alcohol-alcohol precipitation. Several aspects then have been planed for consideration. First, the effect of the compatibility between host (debranched starch) and guest (cyclodextrins and their derivatives), the molar ratio of host to guest, inclusion conditions, and recrystallization temperature and time on the formation law of the debranched starch submicrocrystal system will be examined. Second, the thermally stable principle of the submicrocrystal system is planned to explore, and the slow digestible mechanism of the designed submicrocrystal system with high thermal stability will be interpreted. These studies can provide some scientific basis for preparing SDS products with high thermal stability and promoting the theory in slow digestibility of the debranched starch submicrocrystal system.

慢消化淀粉（SDS）作为新型功能性食品碳水化合物，为当前膳食结构与维持人体健康领域的研究热点。本项目基于现有慢消化淀粉以A-型原淀粉和B-型结晶淀粉为主要组分，存在SDS含量低、热稳定性差等问题，拟构建耐热型SDS形成新途径与方法—即构建高直链化淀粉亚微晶体系。项目从研究淀粉物理解簇、酶法脱支、醇-醇梯度沉淀分级出高直链化淀粉入手，研究主体（高直链化淀粉）聚合度分布、客体（环糊精及其衍生物）的不同空腔与侧链、主客体摩尔比、络合温度、结晶速率、结晶温度、结晶时间等关键因素对高直链化淀粉亚微晶体系形成的影响规律，解析目标亚微晶体系的晶体类型、晶胞参数、晶系特征与其耐热特征的关联性，并阐明耐热型高直链化淀粉亚微晶体系的慢消化机理，为耐热型SDS制备新途径、新方法的建立及慢消化理论的创新提供科学依据。

基于A-型和B-型结晶慢消化淀粉淀粉存在SDS含量低、热稳定性差等问题，本项目构建了耐热型SDS形成新途径与方法—即构建高直链化淀粉亚微晶体系。首先建立聚乙二醇逐步沉淀分级方法，结合酶法限制脱支手段，实现多分散性（PDI）为1.4、重均分子量（Mw）为1.2×106～1.8×106 g/mol的高直链化淀粉提纯制备；基于主客体分子间（内）次级键变化，构建了环糊精及其衍生物、普鲁兰多糖诱导淀粉结晶类耐热高直链化亚微晶体系，其SDS含量达到45.8%以上；建立并运用淀粉荧光修饰、晶胞结构解析方法，从片晶晶系由六角晶系转化为正交晶系导致水分子均匀分布的角度，阐明了高直链化淀粉亚微晶体系的耐热原理；在排除环糊精及其衍生物分子通过抑制体外模拟酶水解活性导致高直链化淀粉慢消化性提高基础上，发现高直链化亚微晶体系的零散结晶区对酶水解的抗性是其具有显著慢消化特点的重要原因。基于上述理论创新，开发出淀粉分级方法、基于淀粉荧光修饰的晶体结构解析方法、基于挤压作为生物反应器的结晶转化技术、环糊精诱导淀粉结晶技术等专利技术，实现3类低升糖指数淀粉产品在兴贸玉米有限公司改线投产，为我国1亿糖尿病患者膳食提供了新途径。