中低水分含量下小麦淀粉相转变中的分子解组装机制及与淀粉消化性的相关性研究

The digestibility of starch is of particular importance for human nutrition and health. Most starch consumed by human has undergone some form of processing or cooking with water, which results in the phase transitin and structural disruption of starch granules. The digestibility of processed starchy foods is largely dependent on the degree of starch molecular disassembly. Most food systems are processed in limited water conditions. As a result, the deep understanding of molecular disassembly of starch at low to intermediate water content during phase transition and its consequent effect on starch digestibility is particularly significant scientifically and practically.. This study will address a critical knowledge gap in food science and nutrition concerning the molecular disassembly mechanism of wheat starch at low to intermediate water content during phase transition and how the degree of starch molecular disassembly influences the digestibility of starch. Firstly, the project will study the phase transition of starch granules at low to intermediate water content measured by differential scanning calorimetry (DSC). Secondly, the swelling behavior of starch granules and disassembly process of different levels of starch microstructure during DSC phase transition will be extensively studied by simulating the same experimental conditions used in DSC measurements (same water content and heating procedures). The molecular disassembly mechanism of starch granules during DSC phase transitions at low to intermediate water content will be elucidated. Finally, the effect of degree of starch molecular disassembly on starch digestibility will be studied. The outcome of this project will provide theoretical platform to the food industry for the optimization of food processing and improvement of healthy starch in processed foods.

淀粉的消化性能对于人类的营养和健康至关重要。绝大多数淀粉在被食用之前都要与水一起经过一定形式的加工或烹饪,导致淀粉颗粒发生相转变伴随着颗粒有序结构的破坏。加工淀粉类食品的消化性能主要取决于淀粉在加工相转变过程中的分子解组装程度。绝大多数的食品系统都是在中低水分含量下加工的，淀粉的凝胶化过程非常复杂。因此，深入解析中低水分含量下淀粉相转变过程中的分子解组装机制及与淀粉消化性能的相关性具有重大的理论和实践指导意义。.本项目拟研究小麦淀粉颗粒在低中水分含量下相转变过程中的分子解组装机制及与淀粉消化性能的相关性。研究淀粉颗粒在中低水分含量下的DSC相转变行为；通过模拟与DSC相转变相同的实验条件，深入研究淀粉颗粒在DSC相转变过程中的溶胀行为以及不同分子尺度微观结构的变化规律，阐明中低水分含量下淀粉颗粒在DSC相转变过程中的分子解组装机制；研究相转变过程中淀粉的分子解组装行为对淀粉消化性能的影响

淀粉的消化性能对于人类的营养和健康至关重要。加工淀粉类食品的消化性能主要取决于淀粉在加工相转变过程中的分子解组装程度。绝大多数的食品系统都是在中低水分含量下加工的，淀粉的凝胶化过程非常复杂。因此，深入解析中低水分含量下淀粉相转变过程中的分子解组装机制及与淀粉消化性能的相关性具有重大的理论和实践指导意义。本项目的主要研究内容如下：.①分析和表征了用于实验材料的几种小麦淀粉；以分离制备的小麦淀粉为原料，系统研究了宽范围水分含量下小麦淀粉的DSC相转变特性，明确了中低水分含量下小麦淀粉凝胶化转变随水分含量变化的规律。.②首次创新性地使用快速粘度分析仪（RVA）模拟DSC加热条件制备了在不同水分含量下，加热到不同温度下淀粉的凝胶化样品。通过DSC测定上述制备淀粉样品的热转变特性，红外（FTIR）和拉曼（Raman）光谱表征淀粉中双螺旋结构的短程有序性，X-射线衍射表征晶体的长程有序性，小角X-射线散射（SAXS）测定淀粉中结晶和无定型片层的周期性结构，扫描电子显微镜（SEM）测定淀粉样品的微观形貌。通过DSC相转变规律，结合DSC加热过程中淀粉的多尺度结构变化结果，阐明了不同水分含量下（尤其是中低水分含量下）淀粉相转变过程中的分子解组装机制。.③以小麦淀粉和山药淀粉为原料，制备了不同水分含量下（64%，55%，46%，37%，28%，19%）在100 oC下加热不同时间（5, 10, 20和30 min）的凝胶化淀粉样品。通过DSC、ATR-FTIR红外光谱、Raman光谱、XRD以及扫描电镜表征淀粉在加热过程中淀粉分子的解组装机制，用改进的Englyst方法测定不同方式处理后的淀粉样品的消化性。研究结果表明，淀粉的凝胶化程度或结构有序性不是凝胶化淀粉消化性的关键限速因子。