Reconsideration of the mechanism of astringency loss on persimnon fruit.

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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.