カキ果実のアルコール脱渋時におけるタンニン•糖の抽出条件, タンニン含量と渋み及びアルコールの挙動

Abstract

Experiments were conducted during the de-astringency in persimmon fruits by ethanol treatment to determine the optimum conditions of ethanol extraction for the quantitative analysis of tannin and sugar contents, the relatiouship between the decrease in tannin concentration and loss in astringency, and the behaviour of ethanol during the penetration into fruits.1. The tannin concentration was greatest when fruit tissue was homogenized and extracted with 70% ethanol. In astringent fruits on the course of de-astringency, a small increase in tannin concentration was observed when the 70% ethanolic extract was heated to boiling.2. When fruit tissue was homogenized and extracted with a decreasing concentration of ethanol, there were a decrease in non-reducing sugar and a corresponding increase in reducing sugar, indicating the conversion of non-reducing to reducing sugar. The total sugar concentration did not change significantly. The accurate determination of sugar content was achieved by homogenizing and extracting fruit tissue with 70% ethanol and immediately heating these extracts to boiling.3. There was a relatively high correlation between the degree of astringency and tannin concentration when fruit tissue was homogenized and extracted with 70% ethanol and then heated. Fruits containing about 0.2% of tannin were slightly astringent, and fruits containing less than about 0.1% of tannin were almost non-astringent.4. The penetration of ethanol gas into fruits occurred mainly through the peel surface. The rate of ethanol penetration into fruits increased proportionally to ethanol gas concentration in the surrounding atmosphere. There was little effect of either cultivar or holding temperature on the penetration rate.