淀粉颗粒聚集态结构与压力致熔融相变关系及机制研究

The application of the new type of green process technology in high value-added starch product development promotes the research on the pressure-induced melting phase transition of starch, which is often believed to have relations with crystal type of starch. However, there are differences in the ease or complexity of pressure-induced melting phase transition for starches with the same crystal types but different sources, indicating the pressure-induced melting phase transition properties may be decided by starch aggregation structure at multi-scales. In this subject, the spatial pattern of order-disorder structure transition for starch during pressure-induced melting will be firstly established by using microtechnique and infrared spectroscopy(IR). After that, the relationship between the aggregation structure of starch and pressure-induced melting phase transition properties will be illustrated by comparative studies and with the help of aggregation structure modification methods, such as chemical surface gelatinization, annealing, acidolysis, enzyme-recrystallization and heat-moisture treatment. The melting phase transition mechanisms for different source of starches will be discussed by in situ measurement of structural change in different density area of semicrystalline structure during pressure-induced melting by using synchrotron radiation small-angle x-ray scattering(SR-SAXS) in pressure system, as well as the analysis on interaction of water and starch molecule by using low field nuclear magnetic resonance (LR-NMR), IR and in situ Raman spectra in pressure system. This research is advantage to the improvement of aggregation structure model, as well as providing the basis of rational regulating of starch produces.

新型绿色加工技术在淀粉高值化产品开发上的应用促进了对压力体系下淀粉熔融相变过程的研究。通常认为压力致熔融相变过程与淀粉结晶类型密切相关，但结晶类型相同，植物来源不同的淀粉压力致熔融相变难易程度存在差异。推测压力致淀粉熔融相变特性由不同尺度聚集态结构决定。本课题将首先通过显微技术结合红外光谱技术确定压力致淀粉颗粒熔融相变过程中有序结构无序化的空间模式；其次借助表面化学糊化、韧化、酸解、酶解-重结晶、湿热处理等聚集态结构修饰方法，通过对比研究，明确淀粉聚集态结构与压力致熔融相变特性的关系；最后利用高压同步辐射X-射线散射技术对压力致淀粉熔融相变过程中半结晶区不同密度区域结构变化进行原位表征，结合低场核磁共振、红外光谱及高压拉曼光谱对水分与淀粉分子相互作用的研究，阐明压力致不同植物来源淀粉熔融相变机制。研究有助于进一步完善淀粉聚集态结构模型，并为淀粉相关产品性质的合理调控提供理论依据。

超高压是实现淀粉熔融相变的重要手段，在淀粉改性及淀粉质食品加工中广泛应用，但淀粉熔融相变难易程度受淀粉本身聚集态结构影响。为了分析淀粉聚集态结构与压力致熔融相变关系，本项目以具有不同结晶类型的马铃薯、玉米和豌豆淀粉为研究对象，在确定压力致淀粉颗粒熔融相变过程中有序结构无序化的空间模式的基础上，分析了表面化学糊化、韧化、酶解-重结晶、湿热处理等聚集态结构修饰方法对淀粉压力致熔融相变特性的影响。3种淀粉熔融相变规律研究表明，含有B型结晶的马铃薯淀粉和豌豆淀粉糊化较玉米淀粉难度更大，熔融相变过程中A型结晶有向B型结晶转化的趋势。相变过程中脐点处均容易作为结构破坏的起点，其中玉米淀粉较为明显，马铃薯淀粉还伴随着生长环的减弱，豌豆淀粉易形成由脐点延伸至表面的裂纹通道，进而破裂。研究表明，聚集态结构修饰能影响淀粉压力致熔融特性。韧化和湿热处理会使淀粉糊化压力增加或使压力糊化延迟，表明淀粉颗粒内部淀粉分子聚集的强化提升了淀粉压力耐受性。针对表面结构与其他淀粉具有明显差异的马铃薯淀粉，表面化学糊化使其耐压性有所降低，但作用效果并不明显，表明淀粉表层结构对压力耐受性影响并不突出。以直链淀粉含量较少的蜡质玉米淀粉为研究对象，糊化后通过酶解-重结晶法以及重复湿热处理制备了高结晶度A、B型淀粉微晶。通过对A、B型淀粉微晶的对比研究发现，与B型淀粉压力耐受性一般均高于A型淀粉压力耐受性不同，A型淀粉微晶的压力耐受性较B型更高，分析可能与A型微晶含水量少，空间稳定性更高相关。相关研究表明晶型尽管在一定程度上决定淀粉压力耐受性，但并不是唯一决定性因素，淀粉内部分子聚集程度对淀粉压力耐受性也具有明显影响。研究有助于进一步完善淀粉聚集态结构模型，并为淀粉相关产品性质的合理调控提供理论依据。