A Study of the Drying Japanese Persimmons

III. Effects of Drying Temperatures on Astringency Removal of Persimmon Fruits

Abstract

The disappearance of astringency during drying of peeled persimmon fruits (Diospyros Kaki L., Hiratanenashi and Yokono cvs.) was observed at temperatures from 5°C to 50°C. The astringency was removed faster as the temperature rose, and the removal was complete after about 20 days at 5°C and 10°C, 10 days at 30°C, and 3 days at 40°C and 50°C.
In the course of drying, the amount of oxygen intake and carbon dioxide production by drying fruits increased as the temperature rose. In temperatures over 15 °C, respiration pattern similar to that of the fruit with climacteric rise appeared in the drying peeled fruit but not in the non-peeled fruit at any temperature.
During drying, the amount of alcohol and acetaldehyde produced in the fruits increased as the drying temperature rose, and the alcohol content was about eight or more times that of acetaldehyde at all stages. The formation of the two volatiles was parallel at any temperature.
From these results, removal of astringency from persimmon fruits during drying from 5°C to 50°C seemed mainly due to the action of acetaldehyde which was produced by anaerobic respiration.
The same results were obtained using Japanese persimmon fruits harvested in 1976 and 1977.