On mechanisms of removing astringency in persimmon fruits by carbon dioxide treatment I. Some properties of the two processes in the de-astringency

Abstract

Carbon dioxide treatment of persimmon fruit (Diospyros Kaki L., cv. “Hiratanenashi” astringent type) at 20°C for 24 hr, at 30°C for 12 hr, or at 40°C for 6 hr followed by storage in air at 30°C for 3 days produced de-astringent fruit of excellent quality without abnormal softening. The induction process in the anaerobic atmosphere had a Q10 of ca. 2.0 and the subsequent de-astringency process, which proceeded either in air or carbon dioxide, had Q10 of ca. 1.4. During the short gas treatment (at 40°C for 6 hr) the ethanol content increased rapidly and reached a maximum of 28.0 mg and the acetaldehyde content gradually reached 0.443 mg per fruit, whereas the soluble tannin(s) content decreased rapidly to two-thirds of its initial level. There was a lag period of 3 hr in the decrease of soluble tannin(s). Dimedon and sodium bisulfite, as well as sodium fluoride, inhibited de-astringency. The mechanisms of removing astringency in this fruit are discussed.