糯玉米胚乳淀粉粒的粒度分布特征

Size distribution of waxy corn endosperm starch granules

以7个糯玉米品种为材料,采用激光衍射粒度分析仪测定其胚乳淀粉粒粒径以及体积、表面积和数目的分布,明确糯玉米胚乳淀粉粒的粒度分布特征。结果表明:糯玉米胚乳淀粉粒的粒径为0.375—30.07μm,其上限为22.73—30.07μm,平均粒径为12.33-14.60μm。淀粉粒的体积和表面积分布呈现三峰曲线,数目分布呈现单峰曲线。以体积分布曲线凹处为界线将糯玉米淀粉粒分为小型(<3.519μm)、中型(3.519—7.422μm)和大型(>7.422μm)。7个糯玉米品种小型、中型和大型淀粉粒体积分别占总体积的11.25%—12.46%、1.79%—6.98%和80.77%—86.96%,表面积分别占总表面积的54.28%—57.13%、2.50%—8.26%和35.97%—40.38%,数目分别占总数目的98.71%—99.39%、0.20%—0.76%和0.39%—0.53%。可见,糯玉米胚乳淀粉主要由小型淀粉粒组成,其对表面积的贡献最大,而大型淀粉粒对体积的贡献最大。品种间比较,小型淀粉粒的粒度分布差异不显著,中型和大型淀粉粒的粒度分布存在显著差异。

Seven waxy corn varieties were used as test materials and their endosperm starch granules＇ diam- eters, volumes, surface areas and quantity distributions were measured by a laser diffraction particle size analyzer so as to clarify the size distribution of waxy corn endosperm starch granules. The results showed that the starch granule sizes were 0. 375--30.07 μm, the upper limit was 22.73--30.07 μm, and the mean was 12.33-- 14.60 μm. Both starch granule volume and surface area distributions presented a triple humped curve, and the quantity distribution a unimodal curve. According to the concave point of volume distribution curve, the starch granules could be divided into small size （ 〈 3. 519 μm） , medium size （3. 519--7. 422 μm） and large size （ 〉 7. 422μm）. Among the 7 varieties the ratios of small-, medium- and large-sized granules＇ volumes to the total volume were respectively ll. 25%--12.46%, 1.79%--6.98% and 80.77%--86.96%, the ratios of small-,medium- and large-sized granules＇ surface areas to the total surface area were respectively 54.28%-- 57.13% ,2.50%--8.26% and 35.97%---40.38% , and the ratios of small-, medium- and large-sized granules＇ quantities to the total quantity were respectively 98.71% --99.39% ,0.20% ---0.76% and 0.39% --0.53%. It was clear that the waxy corn endosperm starch was mainly composed of small starch granules which had the largest contribution to surface area, and the large starch granules had the largest contribution to volume. The intervarietal comparison indicated that among the 7 varieties the size distributions of small starch granules were not significantly different but those of medium and large starch granules were significantly different.