基于分子尺度的高静压致淀粉糊化机理研究

The quality of staple food can be improved by high hydrostatic pressure processing which reduced starch retrogradation and gelatinization temperature. To identify mechanism of starch gelatinization induced by high hydrostatic pressure, two kinds of starch from rice and corn are used for verifying each other. Molecular scale of starch gelatinized by high hydrostatic pressure and heat intend to be compared to each other on the same starch gelatinization degrees. Data of short-rang structure will be studied by detecting starch surface molecular, vibration of typical functional groups and chemical shift of typical carbon atoms using X-Ray Photoelectron Spectroscopy, Fourier Transform Infrared Spectroscopy and Nuclear Magnetic Resonance. To obtain information of long-rang structure, Gel Permeation Chromatography-Laser Light Scattering Analysis and High Performance Anion Exchange Chromatography will be used to analyzed molecular weight and distribution, chain length, conformation index, fine structure of amylopectin and branch point distribution. Using X-Ray Powder Diffractometry and Small Angle X-Ray Scattering, the aggregative state information such as crystal form, degree of crystallinity, thickness of semi-crystal layer and crystal layer is about to be determinate. The correlation of molecular scale and aggregative state will be studied by comparison of short-rang structure and long-rang structure with aggregative state. Contrasting with the corresponding structure of starch gelatinized by heat on the same starch gelatinization degrees, the mechanisms differences between pressure-induced gelation and heat-induced gelation will be explained. Mechanism of starch gelatinization induced by high hydrostatic pressure will be illuminated, and model of type A starch gelatinized by high hydrostatic pressure will be proposed. After the project is finished, the application of high hydrostatic pressure in staple food will be popularized.

高静压处理降低淀粉糊化温度和回生速度，可提升主食产品品质。为明确高静压致淀粉糊化机理，项目以大米和玉米淀粉为研究对象，通过高静压和热处理获得相同糊化度的淀粉；采用X-射线光电子能谱、傅里叶变换红外光谱和核磁共振，分析淀粉表面分子、特征官能团的振动、特征碳原子的化学位移，获得近程结构数据；采用凝胶渗透色谱-激光光散射联用和高效阴离子交换色谱，分析分子量及其分布、链长、构象指数、支链淀粉精细结构、分支点分布，获得远程结构数据；采用X-射线衍射和小角X-射线散射等分析晶型、结晶度、半结晶层和结晶层厚度等，获得聚集态数据。对比淀粉近程、远程结构和聚集态结构，阐明分子尺度与聚集态结构变化的关联性；比较相同糊化度下热处理淀粉的对应结构，阐明高静压和热处理淀粉糊化机理的差异；完善高静压致淀粉糊化的机理，从淀粉的分子尺度层面提出高静压致A型淀粉糊化模型。项目完成后可促进高静压技术在主食领域的推广。

高静压可降低淀粉糊化温度和延缓回生，提升产品品质。为明确高静压致A型淀粉糊化机制，项目以大米和玉米淀粉为研究对象，通过高静压和热处理获得相同糊化度的淀粉；采用傅里叶变换红外光谱和固态核磁共振，分析淀粉特征官能团的振动和特征碳原子的化学位移，获得近程结构数据；采用凝胶渗透色谱-激光光散射联用和高效阴离子交换色谱，分析分子量及其分布、链长及其分布获得远程结构数据；采用X-射线衍射和小角X-射线散射分析晶型、结晶度、半结晶层和结晶层厚度等，获得聚集态结构数据。研究内容（1）比较相同糊化度下高静压和热糊化玉米淀粉各层级结构变化。结果表明，热处理后的淀粉会出现“内糊化”和“外糊化”，伴有更多的塌陷和崩解，而高静压糊化只会引起“内糊化”。高静压淀粉的远程和近程结构比热处理淀粉更有序。此外，当糊化度达到70%时，热处理淀粉中无定形片层厚度的增加更为明显。热处理比高静压更易于破坏淀粉的片层结构。玉米淀粉的半晶片层结构比晶体结构更易被破坏。热处理和高静压导致淀粉多尺度结构变化趋势相似，但变化程度不同。研究内容（2）比较相同糊化度下高静压和热处理对大米淀粉有序结构的影响。结果表明，与热糊化相比，高静压糊化大米淀粉相对结晶度更高，双螺旋结构和V型单螺旋结构更多。研究内容（3）揭示高静压对大米淀粉溶胀行为的影响。结果表明，高静压糊化淀粉平均粒径从6 μm增至 572 μm，而热糊化淀粉粒径则从6 μm增至877 μm。然而两种糊化淀粉的吸附-解吸等温线均为IV型，孔结构由中孔膨胀为大孔。高静压糊化淀粉的比表面积由1.165 m2/g下降到0.138 m2/g，而热糊化淀粉则下降到0.260 m2/g, 高静压糊化淀粉的膨胀不是瞬时的，高静压糊化包含压缩和膨胀两个过程。相较于热处理，高静压处理能更好的保持淀粉结构的稳定性，因此将其应用于谷物和豆类加工, 对于我国粮食资源的高效利用具有重要的意义。