四周柿後熟誘發脫澀可能機制之研究

Studies on the Possible Mechanism of Ripening Process Induced Deastringency in 'Syh Jou' Persimmon (Diospyros kaki L.) Fruit

本試驗的目的為調查四周柿果實經盆收處理後，果實後熟誘導脫澀期間，果實內所發生的生理變化。益收（Ethephon, 2-Chloroethylphosphonic acid）處理後的果實，產生大量的乙烯誘發果官的軟化，並伴隨著澀味的去除，在30°C下處理3日即具商品價值。經盆收處理脫澀後的柿果，可溶性單寧轉變為不可溶性，減少糖度計之折射效果，因而造成由曲折糖度計測定之糖度的下降。＇四周＇柿軟化脫澀時，果實中的乙醇和乙醛含量及酒精去氫酶（alcoholdehydrogenase, EC 1.1. l .1 , ADH）的活性，均於果實脫澀後才有顯著的增加現象，且以含0.1%乙醇及0.01%乙醛之空氣處理柿果，無法去除澀味是頁示乙醛可能非＇四周＇柿後熟誘發脫澀的主要因子。此外，在脫澀前後果肉的榨汁率有顯著下降趨勢，經脫澀處理3日後，榨汁率下降約50%,其變化趨勢和澀味消失之趨勢相符合，因而推測水分變化可能和＇四＇周柿柿果後熟誘發的脫澀有關。

The objectives of this experiment were to investigate the physiological changes of'Syh Jou'persimmon (Diospyros ka如L.) and the effects of deastringent, ripening process. Three days after ethephon treatment (30°C), fruit softening occurred simultaneously with deastringency, and large quantity of ethylene. The result showed that the total solid content of persimmon decreased gradually during the deastringent process. The phenomenon appears to be linked with a reduction in soluble tannin content, which tends to alter the overall result. Deastringency removes soluble tannin by converting it to insoluble polymer thus causes a decline in the refractometer reading. Results also showed that concentration of ethanol, acetaldehyde and activity of alcohol dehydrogenase increased after deastringency. As the objectionable taste could not be succes、fully removed by 0.1 % ethanol and 0.0 I% acetaldehyde, this finding seemed to indicate that acetaldehyde was not the factor responsible for the deastringent process inducing by the after-ripening. The significant decrease in centrifugal water of the fruits about 50% three days after deastringency could implicate the involvement of water in the initiation of the process. Ethephon treatment resulted in high level of ethylene, which triggered fruit ripening and cell wall dehydration. The lowering of osmotic potential in the cellular space leads to cell dehydration, which in turn polymerizes soluble tannin into an insoluble form thus removal astringency of the persimmon fruit.