Studies on the quality of agricultural products in storage and processing and on the production of juicy foods from agricultural products using bioreactors

"To increase the consumption of agricultural products in a tendency of supply over demand, the quality of kiwifruit was examined in growing, storing and ripening stages, and the continuous production of new juicy foods mainly from kiwifruit using different kinds of bioreactors was executed. The results of the study are summarized as follows. 1. Quality of kiwifruit under different conditions of harvest, storage and ripening Compositional changes of 'Hayward' kiwifruit in the growing stage and in the ripening stage after harvest were examined during October and December. The total sugar content increased abruptly due to a rapid decrease in starch from the biginning of October. Citric acid as titratable acidity slightly increased in December. Kiwifruit harvested at the biginning of December was evaluated to be in the best quality after ripening. The effects of temperature during storage on the quality of kiwifruit were clarified. The low temperature prevented kiwifruit from ripening during storage. The effects of ethylene concentration, temperature and duration of exposure to ethylene, and temperature after removal of ethylene on the ripening of kiwifruit were investigated. Exposure to ethylene accelerated softening of fruits. Ripening at the temperature over20degC brought about rotting and decay of kiwifruit by microorganisms on the fruit surface, but it did not occur at the temperature of 15degC. The best quality of the ripened kiwifruit was obtained when the fruits were exposed to ethylene at the concentration over 50 ppm at 20degC for 24 h followed by standing in air at 15degC after removal of ethlene. 2. Continuous production of wine using bioreactor with immobilized yeast cell. The alcohol fermentation of kiwifruit-and persimmon-juice was studied under the continuous production. Immobilized cells of Saccharomyces cerevisiae kyokai No.9 were entrapped in the sterilized condition using calcium alginate. When the kiwifruit-juice was provided into the reactor at residence times of 12 and 6 h, the ethanol concentration and the productivity were 11 and 10%, and 7.5 and 13.4 g/1/ h, respectively. The same values were obtained for persimmon-juice. Fermentation of both fruit-juices were continued for 50 days without microbial contamination. The sweet type gave the higher sensory scores for both kiwifruit-and persimmon-wine."