Relationship between fruit softening and the change of pectic or hemicellulosic compounds in cell wall of Japanese persimmon 'Hiratanenashi' and 'Fuyu'

Abstract

'Hiratanenashi' 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 after removed astringency. 'Tuyu' fruit is also popular persimmon fruit which is the non-astringency cultivar. The present study was conducted to investigate the relationship between the changes in fruit firmness and cell wall composition (pectic and hemicellulosic composition) and 'Eliratanenashi' and 'Tuyu' cultivars. (1) Sugar of phenol-acetic acid-water (PAW) fraction from 'Tuyu' fruits were increased, but the content of 'Hiratanenashi' fruit did not change during storage. Soluble polyuronide contents increased both cultivars during storage. (2) The contents of cyclohexane-trans-1, 2-diamine tetra-acetate (CDTA) soluble polyuronide and sugar contents of 'Fuyu' fruit was decreased markedly during from 10 day to 15 day in storage. 'Hiratanenashi' fruit was not change during storage.The contents of Na2CO3 soluble polyuronide and sugar contents of both cultivars were similar pattern of CDTA soluble fraction. (3) The contents of guanidium-thiocyanate (GTC) -soluble and KOH-soluble sugar from hemicellulosic components did not change in 'Hiratanenashi' and 'Tuyu' fruit during storage. These results indicated that the fruit softening of 'Hiratanenashi' and 'Tuyu' are attributable to increase of water-soluble polyuronide and decrease of water-insoluble polyuronide contents. Pectic component in 'Fuyu' fruit is much quantity comparison with 'Hiratanenashi' fruit, and polyuronide and sugar contents in pectic component of both cultivars have a similar tendency to fruit firmness.