Reconsideration of the mechanism of astringency loss on persimnon fruit.

为了进一步探讨荔枝脱涩的机理和研究单宁细胞的性质，我们进行了以下研究：1.采后在树上或干燥器中用乙醇蒸汽进行脱涩处理。去涩果实中的凝固单宁在果肉的布朗宁反应完成之前，可在HCl-MeOH中再溶解。然而，尽管没有布朗宁反应，但在干燥器中去除涩味的果实中，凝固的单宁不能再溶解。这些结果表明，凝固单宁在反应过程中存在多种状态。2.与未处理涩果的甲醇提取单宁相比，乙醇处理涩果的HCl-MeOH再溶解单宁的凝胶色谱显示出较小的分子尺寸。从未经处理的涩味水果中用HCl-MeOH提取的单宁也显示出比从同一水果中用MeOH提取的单宁更小的分子尺寸。这一结果表明非共价键参与了凝固过程。3.我们建立了一种从完整细胞中收集和分析细胞汁液的方法。将成熟果实的果肉薄片置于玻璃侧，并将微量移液管插入细胞中以提取其内容物。4.对所收集的细胞液中单宁含量和糖组分进行了测定，单宁细胞中单宁含量为10 ~ 12%，可溶性糖含量为10 ~ 13%，而薄壁细胞中单宁含量为微量，可溶性糖含量为20%左右。有趣的是，单宁细胞只含有少量的蔗糖，而薄壁细胞中蔗糖的比例相对较高。

In order to reconsider the mechanism of astringency removal and to study the nature of tannin cells, we carried out the following studies :1.Astringency of the fruit was removed by ethanol vapor on the tree or in a desiccator after harvesting. Coagulated tannins from the fruit whose astringency was removed on the tree could be resolubilized in HCl-MeOH unless browning reaction of the flesh was completed. However, coagulated tannins could not be resolubilized in the fruit whose astringency was removed in a desiccator, despite of the absence of browning reaction. These results indicate that coagulated tannins have several states in reactions.2.Gel chromatography of tannins resolubilized with HCl-MeOH from ethanol-treated fruit showed smaller molecular size when compared with tannins extracted with MeOH from untreated astringent fruit. Tannins extracted with HCl-MeOH from untreated astringent fruit also showed smaller molecular size than tannins extracted with MeOH from the same fruit. This result shows an involvement of noncovalent bonds in coagulation.3.We developed a method for collecting and analyzing cell saps from intact cells. Thin section of fruit flesh of mature fruit was put on a glass side, and a micropipette was inserted into a cell to withdraw its contents. By this method, we could collect about 5 or 7nl of cell sap per tannin cell, while about 2nl per parenchymatous.4.When tannin content and sugar constituents in collected cell saps were determined, tannin cells contained 10 to 12% of tannins and 10 to 13% of soluble sugars, while parenchymatous cells contained trace amounts of tannins and about 20% of soluble sugars. It was interesting that tannin cells contained only slight amount of sucrose, in contrast with relatively high ratio of sucrose in parenchymatous cells.