Studies on the Mechanism of the Removal of Astringency in Japanese Persimmons (Diospyros Kaki L.)

(I) On the alcoholdehydrogenase activity of kaki fruits

Abstract

It was shown that the distinction between astringent and non-astringent varieties of kaki resulted partly from the difference of alcoholdehydrogenase activity which might possibly related with the formation of acetaldehyde in the flesh of kaki fruits. But, the varietal difference of the enzyme activity was not studied definitely. Then, the alcoholdehydrogenase activities of astringent and non-astringent kaki fruits were detected by using Thumberg method. In the non-astringent variety, it was found clearly that the alcoholdehydrogenase in the flesh of fruits was very active. In the astringent variety, the enzyme activity was not able to detect because of the inhibition by soluble kaki tannin. But after the removal of soluble tannin in the components of Thumberg tube, such as precipitation with gelatin, the enzyme activity was found slightly. And after the artificial removal of astringency by the treatment of ethanol, very active alcoholdehydrogenase was detected in the flesh of astringent fruits as same as non-astringent one. The results suggested that the alcoholdehydrogenase might be active to the full extent in the astringent kaki fruits, and so the distinction between astringent and non-astringent varieties might be not explained sufficiently by the varietal difference of alcoholdehydrogenase activity.