Santacruz Stalin, Koch Kristine, Andersson Roger, Aman Per
Department of Food Science, Swedish University of Agricultural Sciences, P.O. Box 7051, SE-750 07 Uppsala, Sweden.
J Agric Food Chem. 2004 Apr 7;52(7):1985-9. doi: 10.1021/jf030601k.
The starch accumulation-degradation process as well as the structure of leaf starch are not completely understood. To study this, starch was isolated from potato leaves collected in the early morning and late afternoon in July and August, representing different starch accumulation rates. The starch content of potato leaves varied between 2.9 and 12.9% (dry matter basis) over the night and day in the middle of July and between 0.6 and 1.5% in August. Scanning electron microscopy analyses of the four isolated starch samples showed that the granules had either an oval or a round shape and did not exceed 5 microm in size. Starch was extracted by successive washing steps with dimethyl sulfoxide and precipitated with ethanol. An elution profile on Sepharose CL-6B of debranched starch showed the presence of a material with a chain length distribution between that generally found for amylose and amylopectin. Amylopectin unit chains of low molecular size were present in a higher amount in the afternoon than in the morning samples. What remains at the end of the night is depleted in specific chain lengths, mainly between DP 15 and 24 and above DP 35, relative to the end of the day.
淀粉的积累-降解过程以及叶片淀粉的结构尚未完全明晰。为研究此问题，从7月和8月清晨及傍晚采集的马铃薯叶片中分离出淀粉，这两个时段代表了不同的淀粉积累速率。7月中旬，马铃薯叶片的淀粉含量在夜间和白天之间变化于2.9%至12.9%（以干物质计），8月则在0.6%至1.5%之间。对四个分离出的淀粉样品进行扫描电子显微镜分析表明，淀粉颗粒呈椭圆形或圆形，尺寸不超过5微米。通过用二甲基亚砜连续洗涤步骤提取淀粉，并用乙醇沉淀。脱支淀粉在琼脂糖CL-6B上的洗脱图谱显示存在一种物质，其链长分布介于直链淀粉和支链淀粉通常的分布之间。下午样品中低分子尺寸的支链淀粉单位链含量高于上午样品。相对于一天结束时，夜间结束时剩余的物质在特定链长上减少，主要在DP 15至24以及DP 35以上。
