热加工过程中淀粉有序结构的变化及与酶消化性的关联机理研究

Starch digestion is of great importance for human nutrition and health, and it is mainly related to the changes of ordered structure of starch during processing. Previous studies mainly focus on the changes of ordered structure of starch crystallites during processing and their effect on starch digestibility, with little information available on the effect of ordered structure of amorphous starch on starch digestibility. In this project, the partially and fully gelatinized starch samples will be prepared by concisely controlling the parameters of thermal processing. The multi-scale ordered structure of these gelatinized starch samples will be characterized by a combination of various modern techniques, especially the ordered structure of amorphous starch samples, which will be analyzed for the first time by the spectroscopy method. The in vitro enzymatic digestibility of these gelatinized starch samples will also be determined. Based on the above results, the correlation model between ordered structure of starch samples and enzymatic digestibility will be built using a multivariable statistical analysis. To reveal the mechanisms underlying digestibility of processed starch, equations for kinetics of enzyme absorption to starch and enzyme catalytic hydrolysis of starch, and surface plasma resonance (SPR) technique will be used. With all the information obtained above, the key factor that determines the digestibility of processed starch will be elucidated. The outcome of this project is of great fundamental significance to reveal the correlation mechanisms between ordered structure and digestibility of starch, and to provide a theoretical guidance for concise modulation of nutrition and digestion during food processing.

淀粉的消化性对于人类的营养和健康至关重要，其与加工过程中淀粉有序结构的变化密切相关。前期的研究主要集中在加工过程中晶体有序结构的变化及对其消化性的影响，对于无定型有序结构对淀粉消化性的影响还鲜有报道。本项目拟通过精确控制热加工参数，制备具有不同有序结构的部分和完全凝胶化态的淀粉样品，利用先进的多尺度结构表征方法对其有序性进行系统表征，尤其是首次通过光谱学等手段对无定型淀粉的有序结构进行分析；同时对不同凝胶化态淀粉样品的体外酶消化性进行测定，最后通过多变量统计分析等数学手段构建淀粉有序结构与消化性之间的关联模型。通过淀粉-酶吸附动力学，水解动力学及表面等离子体共振（SPR）技术等理论和实验相结合的方法对其消化性机理进行解析，最终阐明影响加工淀粉体外酶消化性的关键因子。本项目的实施对于揭示加工淀粉有序结构与其消化性的关联机理具有重要的理论意义，为实现食品加工过程精准营养消化调控提供理论指导。

加工食品中淀粉的消化性主要取决于其在加工过程中有序结构的变化。因此，深入理解热加工过程中淀粉结构演变及对其消化性的影响对于食品加工过程营养品质控制具有重要理论和实际意义。项目针对热加工过程中淀粉有序结构变化及对其酶消化性影响机制中的关键科学问题开展了一系列富有创新性的工作，主要研究内容及结果如下：.（1）揭示了热加工初期淀粉凝胶化过程中“晶体有序结构”的演变规律及对淀粉酶消化性的影响机制。结果表明水热处理导致颗粒内部不稳定晶体到整体晶体的破坏，而超高压处理则从内到外均匀地破坏晶体结构。马铃薯和莲子淀粉消化性与凝胶化程度显著正相关，而小麦淀粉消化性与凝胶化程度没有线性关系，通过激光显微共聚焦技术分析淀粉与酶的结合过程，首次直接证明影响淀粉消化性的关键限速步骤是淀粉与酶的接触/结合而非随后的催化水解。.（2）明晰了热加工后期凝胶化淀粉“短程分子有序性”的变化规律及对其功能性质和酶消化性的影响机制。结果表明XRD（16.7和20.7o处半峰宽）和Raman光谱（480, 1131和1080 cm-1处峰面积和强度）可以用于表征凝胶化淀粉短程分子有序性。随着加热温度及水分含量的升高，凝胶化淀粉短程分子有序性逐渐降低，促进了酶与其接触/结合并导致淀粉消化性升高。凝胶化淀粉短程分子有序性的降低增强了链的移动性及结晶重排，导致回生程度增加，但短程分子有序性过低会降低其结晶成核潜力并抑制回生，使回生淀粉凝胶强度降低及消化性升高。.（3）阐释了食品加工过程中淀粉与其他营养素（如蛋白质或脂质）以及小分子活性成分互作对淀粉消化性的影响机理。结果表明热加工能够提高淀粉-脂质复合物短程分子有序性进而降低其消化性。适度水解面筋蛋白通过与淀粉和α-淀粉酶相互作用阻碍酶与底物接触/结合和降低酶活来抑制淀粉消化。咖啡和不同茶提取物能够与酶结合影响其酶活并降低淀粉消化性，红茶提取物对淀粉消化性具有最强抑制作用，主要由于红茶中更高含量的茶黄素对α-淀粉酶活抑制作用更强的。