果胶结构对淀粉老化性质的影响规律和作用机理研究

The retrogradation of starch during storage influences starch-based products strongly. Controlling retrogradation of starch by adding polysaccharides has been a research hotspot. However, the influence law and mechanism of polysaccharides on retrogradation of starch is not clear. Considering abundance of polysaccharides and starch, it is hard to investigate the law and mechanism by a systematic study. In this project, pectins with different structural characteristics (molecular weight, degree of methoxylation, degree of branching, and hydrophobicity) will be selected as representative polysaccharides, which will be prepared by kinds of physicochemical methods such as dynamic high pressure microfluidizaiton, saponification, acid hydrolysis and alkylation. After preparation, their structure will be characterized by traditional chemical methods combing with modern instrumental analysis. Pectins with different structures will then be mixed with three representative starches (rice starch, potato starch and pea starch) respectively. Short-term retrogradation will be determined by RVA and dynamic rheology. Long-term retrogradation will be analyzed by texture analyzer, DSC and X-ray. The retrogradation mechanism will be investigated by determination of leached amylose, interaction force experiment, FTIR, determination of water migration and distribution, scanning electron microscope, HPSEC, and molecular simulation. Then mathematical statistics such as Principal Component Analysis will be applied to analysis the influence law and mechanism of pectin (polysaccharides) structure on retrogradation of starch, which will promote the development of theory of starch retrogrdation, and provide theoretical guidance for improving quality of starch-based products.

淀粉储藏期老化严重影响淀粉质食品品质，添加多糖来控制淀粉的老化已成为国内外的研究热点。目前多糖对淀粉老化特性的影响规律和作用机理尚不清楚。面对海量的多糖和淀粉种类，进行系统研究探讨其规律和机理是难以实现的。本项目拟采用物理化学手段（微射流、皂化、稀酸水解和烷基化修饰）制备不同分子结构(分子量、酯化度、支链度、疏水性)的果胶为代表性多糖。采用传统化学法结合现代仪器分析表征果胶和淀粉的分子结构信息。以不同结构果胶与三种代表性淀粉（大米、马铃薯和豌豆淀粉）复配成混合体系，通过RVA和动态流变测定考察短程老化；质构、DSC和X衍射测定长程老化；渗漏直链淀粉量测定、相互作用测定、红外、水分迁移和分布测定、扫描电镜、绝对分子量表征、结合分子模拟探讨淀粉老化机理。采用主成分分析等数理统计手段分析果胶（多糖）结构对淀粉老化性质的影响规律和机理，从而促进淀粉老化理论的发展，为淀粉质食品品质改良提供理论指导。

添加亲水胶体调控淀粉的理化性质成为国内外科研人员的研究热点。果胶是一类结构多样的植物多糖，果胶结构对淀粉理化性质的影响规律和机理尚不清楚。本项目研究了果胶半乳糖醛酸、酯化度、分子量和酰胺化度等结构对淀粉糊化、老化和流变性质的影响，通过多元线性回归分析总结了果胶结构对淀粉性质的影响规律，表明峰值黏度和谷值黏度主要受酯化度的影响；崩解值主要与半乳糖醛酸呈正相关，与酰胺化度呈负相关；影响回复值的两个主要因素是半乳糖醛酸（负相关）和分子量（正相关）。对于老化性质，半乳糖醛酸越大越能抑制淀粉的老化，且对短期老化的影响更大；果胶酯化结构和酰胺结构的存在促进了淀粉的老化；分子量越大越能促进淀粉的短期老化而抑制长期老化。流变性质表明果胶的添加增强了混合体系的黏性，提高了淀粉凝胶的剪切稳定性。采用分子动力学模拟探讨了果胶半乳糖醛酸含量、酯化度、酰胺化度和分子量影响淀粉老化性质的潜在机理：果胶分子的存在改变了淀粉分子链段的运动能力，改变果胶与淀粉间非键相互作用强弱，同时也影响了淀粉分子链段的运动空间，进而改变了淀粉在老化过程中的定向迁移。研究结果为淀粉质食品品质改良提供理论指导，为深入研究其他亲水胶体影响淀粉老化性质的机制提供理论借鉴。