異なる地域での甘ガキ‘次郎’の自然脱渋過程の解析

Abstract

When grown in colder northern districts of Japan, pollination constant/non-astringent (PCNA) persimmon fruits often remain astringent at harvest season.Fruit growth and changes in soluble tannin content in flesh of PCNA persimmon cv. Jiro were compared between fruits from Yamagata (colder, northern district) and from Kyoto (warmer, middle district) with reference to changes of mean temperature in both districts in 1983 and from 1985 to 1987.Loss of astringency occurred before early or middle of August in Kyoto. In Yamagata, however, it varied with years; in some years the fruit had an astringent taste even in late September. This is suggested to be mainly due to the difference in mean temperature between the two areas during the period after bloom, especially in late stage of fruit growth. In Yamagata, the high mean temperature accelerated fruit growth in early stage, resulting in faster decrease of soluble tannin content. Larger fruit contained less soluble tannin than smaller fruit harvested on the same day at the same place. In the colder area, a little astringent taste is sometimes retained in the fruit at the later stage, after August. No clear relationship was observed between complete disappearance of the astringency and the mean temperature in the later stage.In Kyoto, fruit growth and soluble tannin content were investigated on several PCNA cultivars. There was no clear relationship between fruit growth and soluble tannin content. Cultivars retaining astringent taste at the late stage tend to contain more tannin substances at the immature stage. The rate of removal of soluble tannin, however, was not different among the cultivars.