脱渋方法の異なるハウスカキ‘刀根早生’果実のβ-D-galactosidase活性の変化と軟化の関係

Tonewase'fruit is the most popular Japanese persimmon (Diospyros kaki Thunb.) in Japan. It has fine flesh and good taste after its astringency was removed. But the fruit has very short shelf life, because of rapid softening. There are two ways for removing astringency; 1) treatment with alcohol on tree and 2) treatment with carbon dioxide (CO2). The present study was conducted to investigate the relationship between the changes in fruit firmness and β-D-galactosidase activity which was hydrolyzed hemicellulosic components. (1) The loosing of fruit firmness was not different between treatments of alcohol on tree and CO2 at 20°C for 24 hours (CTSD method) for removing astringency until 4 days after storage at 20°C, however, the former showed slow softening during storage for 8 days but the latter was rapid softening at 6 days (5 days after treatment). The respiration and ethylene production of fruits treated with carbon dioxide and non-treatment were similar pattern and increased at the end of storage period. However, the fruit of alcohol treatment on tree maintained low level which was comparison with non-treatment and carbon dioxide fruit. (2) The activity of β-D-galactosidase which was non-treatment and CTSD treatment for removal astringency increased during storage. The fruit of alcohol treatment on tree maintained low activity during storage. Finally, the activity of non-treatment and CTSD treatment fruit was higher than alcohol treatment on tree one during storage. These results indicated that the fruit softening of 'Tonewase' is attributable to increase of ethylene production and attended to increased, β-D-galactosidase activity. It was suggested that the fruit softening of alcohol treatment on tree, CTSD treatment, and non-treatment fruits were depend on a degree of hydrolyzed hemicellulosic components during storage or postharvest.