Abstract
The present study was carried out to improve the method of removing astringency from persimmon fruits by ethanol. Experiments to remove astringency on a large scale within a short period were performed by packing the fruits into well-ventilated plastic containers, stacking the containers in the de-astringency room and heating the room to about 30°C while adding ethanol.
1. It was necessary to insulate the de-astringency room using insulations such as urethane foam 25mm or more in thickness.
2. The addition of ethanol was accomplished by introducing an ethanolic solution into the de-astringency room at a given rate of flow and vaporizing the ethanol with a sufficient amount of air passed. The amount of ethanol penetrating into fruits reached about 80% of the added ethanol.
3. The room was heated by a composite unit of blower and heater, which had a surface temperature of lower than 200°C. Fruit temperature was increased to around 30°C within 1 day after heating started. In order to prevent the development of peel discoloration, the differences in heating rates throughout the load needed to be kept as slight as possible.
4. Ethylene treatment had a strong effect on hastening the ripening of fruits which became non-astringent within a short time. Fruits treated with ethylene produced good marketing qualities such as a melting flesh texture and a sweet taste.
5. The fruits receiving the 3-day de-astringency and ripening treatment using a manufactured equipment were graded, packed and shipped to market. There was no significant difference in market value between these treated fruits and those which became non-astringent after about 2 weeks using a conventional method.
