本文研究了挤压对糙米淀粉糊化和热力学性质、结晶结构、支链淀粉分支链长等的影响。结果表明，挤压处理使糙米淀粉的峰值粘度、回生值和热焓值分别由1811 cP、1677 cP和9.41 J/g降低至107 cP、53 cP和0.97 J/g，淀粉发生糊化。糙米淀粉X-射线衍射峰的强度和位置在挤压后均发生变化，淀粉结晶结构由A型转变为V型，相对结晶度由31.33%降至20.95%。傅立叶变换红外光谱图中1047 cm-1/1022 cm-1的比率由挤压前的0.811下降为挤压后的0.732，表明挤压使淀粉结晶区比例降低。同时，挤压后淀粉-碘复合物吸收光谱强度增加，说明挤压使直链淀粉比例增加。阴离子交换色谱结果显示，挤压后支链淀粉A链（DP6-12）比例增加，B1链（DP13-24）和B2链（DP25-36）比例减少，证明支链淀粉发生降解。此外，扫描电子显微镜结果表明，挤压产物中淀粉颗粒变大，淀粉表面变得粗糙且有褶皱和裂痕。

The effects of extrusion on the gelatinization, thermal properties, crystalline structure, and the branch length of amylopectin chain of brown rice starch were studied. The results showed that the peak viscosity, setback, and enthalpy of starch all declined from 1811 cP, 1677 cP, and 9.41 J/g to 107 cP, 53 cP, and 0.97 J/g, respectively after extrusion, leading to gelatinization. Extrusion also changed the X-ray diffraction peaks and locations, and transformed the crystalline structure from A type to V type. Additionally, the relative crystallinity of brown rice starch decreased from 31.33% to 20.95% upon extrusion. The ratio of 1047 cm-1/1022 cm-1 in the Fourier transform infrared absorption spectra was also reduced from 0.811 to 0.732, which indicated that the proportion of crystalline regions in starch was reduced after extrusion. In addition, the absorption intensity of starch-iodine compounds increased after extrusion, which indicated that the proportion of amylose had also increased. The results of high-performance anion-exchange chromatography pulsed amperometric detection showed that the proportion of A chains (DP6-12) increased, while the proportion of B1 chains (DP13-24) and B2 chains (DP25-36) both decreased after extrusion, which indicated that amylopectin had been degraded. Moreover, the results of scanning electron microscopy showed that the starch granules of the extrudate were bigger; the starch surface was also rougher, and had more wrinkles and cracks after extrusion.

国家“十二五”科技支撑计划课题（2012BAD37B08）