粳米分层淀粉的理化性质

目的:提高粳米淀粉的高值化利用和粳米分层淀粉的综合应用。方法:分别采用碱法和酶法提取粳米淀粉，对离心后3层淀粉的基础成分、溶解度、膨润力和糊化特性等理化指标进行分析，并采用扫描电镜、红外光谱分析其结构特性。结果:碱法和酶法提取的各层淀粉的淀粉含量为91%～99%,其中中层淀粉的相对比例最高，碱法和酶法提取的中层淀粉的淀粉含量高于上层和下层，而上层和下层淀粉的蛋白质含量和直链淀粉含量均高于中层淀粉的。碱法和酶法提取的各层淀粉的溶解度和膨润力均随温度的上升而增加，且碱法和酶法提取的上层和下层淀粉的热稳定性优于中层淀粉的。扫描电镜结果显示碱法和酶法提取的各层淀粉颗粒均较为完整，酶法提取的各层淀粉颗粒分布相对稀疏；红外光谱图中，碱法和酶法提取的各层淀粉具有相似的主要特征吸收峰，中层淀粉的短程有序性高于上层和下层淀粉。结论:可进一步开发利用粳米上层和下层淀粉，提高粳米资源的综合利用。

Physicochemical properties of layered starch of japonica rice

Objective: This study aimed to improve the high-value utilization of japonica starch and the comprehensive application of japonica layered starch. Methods: Japonica starch was extracted by alkaline and enzymatic methods, and the physicochemical indexes such as basic composition, solubility, swelling power and pasting characteristics of the 3 layers of starch after centrifugation were analyzed, and the structural characteristics were studied by scanning electron microscopy and infrared spectroscopy. Results: The contents of the three starch layers extracted by alkali and enzymatic methods ranged from 91% to 99%, with the highest relative proportion of the middle layer starch. The amylose content of the middle layer starch extracted by alkali and enzymatic methods was higher than that of the upper and lower layers, while the protein content and straight chain amylose content of the upper and lower layers starch were higher than that of the middle layer. The solubility and bulking power of all layers of starch extracted by alkali and enzymatic methods increased with the increase of temperature, and the thermal stability of the upper and lower layers of starch extracted by alkali and enzymatic methods was better than that of the middle layer of starch. The results of scanning electron microscopy showed that the starch granules of all layers extracted by alkaline and enzymatic methods were more complete, and the distribution of starch granules of all layers extracted by the enzymatic method was relatively sparse. In the infrared spectra, the main characteristic absorption peaks of all layers extracted by alkaline and enzymatic methods were similar, and the short-range orderliness of the middle layer was higher than that of the upper and lower layers of starch. Conclusion: The upper and lower starch layers of japonica rice can be further exploited to improve the comprehensive utilization of japonica rice resources.