Studies on Tannins of Fruits and Vegetables

It was usually explained that the removal of astringency resulted from the condensation of tannin with acetoaldehyde produced by alcholdehydrogenase and so the distinction between astringent and non-astringent persimmon fruits was mainly under the control of alcholdehydrogenase activity. But it also expected that tannin of non-astringent persimmon was different from that of astringent one. Therefore, the components of tannin in the fruits of many varieties of persimmon, were studied. Unknown polyphenolic compound isolated from astringent fruits was identified with β-D-glucogallin (β-1-O-galloyl-D-glucose). From the patterns of the distribution of low molecular polyphenolics, paper chromatograms were divided into three classes, i.e. astringent, non-astringent, and intermediate type. High molecular tannin of non-astringent varieties contained more leucoanthocyanin and leucocyanidin than that of astringent varieties. These results were just as expected. Morecover, the quantitative and qualitative changes of polyphenolic compounds during the ripening. of fruits were studied.