挤压对糙米中淀粉理化性质的影响

挤压对糙米中淀粉理化性质的影响

林雅丽，张晖，王立，钱海峰，齐希光

（江南大学食品学院，江苏无锡 214122）

摘要：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。

关键词：挤压；糙米；淀粉；晶体结构；分子结构

文章篇号：1673-9078(2016)12-254-259 DOI: 10.13982/j.mfst.1673-9078.2016.12.039 Effect of Extrusion on the Physicochemical Properties of Starch in Brown

Rice

LIN Y a-li, ZHANG Hui, W ANG Li, QIAN Hai-feng, QI Xi-guang

(School of Food Science and Technology, Jiangnan University, Wuxi 214122, China) Abstract: 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.

Key words: extrusion; brown rice; starch; crystalline structure; molecular structure

糙米是稻谷脱壳后不经碾磨的米粒。由于皮层被保留，糙米富含维生素、矿物质、谷维素及γ-氨基丁酸等成分，营养丰富，长期食用糙米可以有效控制高血压和高血脂。虽然糙米的营养保健价值日渐引起人们重视，但其直接蒸煮食用却一直受到限制，这主要收稿日期：2015-12-21

基金项目：国家“十二五”科技支撑计划课题（2012BAD37B08）

作者简介：林雅丽（1989-），女，硕士研究生，主要从事粮食深加工方面的研究

通讯作者：张晖（1966-），女，博士，教授，主要从事粮食深加工方面的研究 因为糙米作为主食直接食用存在米饭较硬，饭粒松散不黏连，且蒸煮时间长的缺点。因此，近年来改善糙米食用品质及开发糙米主食食品已成为研究热点[1]。

食品挤压加工技术是集混合、熟化、破碎、杀菌、预干燥和成型等工艺为一体的新型加工技术。通过挤压技术重新造粒生产的重组米，不仅营养损失较少，而且可以克服谷物因皮层的存在而口感粗糙的缺点。挤压食品的主要成分是淀粉，所以挤压过程中淀粉的变化对产品品质有重要影响。淀粉在挤压过程中会发生低水分状态下的糊化，并且挤压机腔体内高温、高压和高剪切的环境，会使淀粉部分降解，导致淀粉含

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