稻米三种淀粉成分的分离及其蒸煮前后的结构差异

分离稻米粉得到4种成分：非淀粉成分、直链淀粉、支链淀粉及中间成分，分别为淡黄色致密粉末、白色疏松粉末、玻璃状和薄膜状物质。扫描电镜下观察非淀粉成分为较大的不规则致密团块；直链淀粉为质地疏松的颗粒：支链淀粉由极细的微粒组成，切面有分层产生的窄裂缝；中间成分处于直链淀粉和支链淀粉间的过渡态，但不是两者的简单混合，颗粒较支链淀粉粗糙，切面分层产生的裂缝较大。无论垩白区还是非垩白区，米质较优的稻米其淀粉体内的淀粉粒均比米质较差的稻米结合紧密，结晶度高；蒸煮后米质较优的稻米的背、中、腹部均比米质较差稻米的相应部位糊化好。品种间背部糊化的差异比中、腹部小，品种内米质优的稻米的背、中、腹部的差异比米质差的稻米小。

Separation of three types of starch fractions in rice and the microstructures of endosperms before and after gelatinization

The rice ( Oryza sativa L. ) powder can be separated into four components: non starch component, amylose, amylopectin and intermediary fraction. The four components were light yellow dense powder, white loose powder, vitrescence and pellicular materials respectively. Scanning electron microscopic images showed that the non starch component as large dense blocks, amylose as small loose granules, and amylopectin was made up of fine particles with narrow cracks on its cross section. The structure of intermediary fraction was between that of the amylose and amylopectin rather than their simple mixture. The intermediary fraction was made up of coarser particles with broader cracks on its cross section as compared with the structure of amylopectin. Starch granules were more compactly arranged and intensively crystallized in both chalkiness and non chalkiness areas of the superior variety than in the inferior variety. Gelatinization was more complete in both dorsal and ventral sides as well as middle part of the superior variety than the corresponding parts of the inferior variety. Varietal difference in gelatinization of dorsal sides was less distinct than that of middle parts and ventral sides. Superior grains showed smaller variations between its different parts in gelatinization than the inferior ones.