'La France' European pear fruit undergoes dramatic softening during ripening in an ethylene-dependent manner, whereas 'Yali' Chinese pear does not exhibit softening in spite of its massive ethylene production during ripening. To identify the key factors involved in fruit softening, the two-dimensional gel electrophoresis profiles of cell wall proteins extracted from ripening flesh tissues of 'La France' and 'Yali' pears were compared. The accumulation levels of 19 protein spots changed significantly during the ripening in 'La France' pear. When softening pears of this variety were treated with 1-MCP, a strong ethylene inhibitor, fruit softening was retarded. In parallel with this retardation, the levels of 15 of the 19 protein spots were restored or decreased to those at preclimacteric stages. For 'Yali' pear, the accumulation levels of 8 of the 15 protein spots remained unchanged during ripening, suggesting the involvement of these 8 proteins in the nonsoftening feature of 'Yali' pear. We therefore selected 2 of the 8 protein spots as potential key factors of fruit softening, since their accumulation was up-regulated during the ripening in 'La France' pear.

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This study investigated the postharvest changes in the activities of invertase (EC ; 3. 2. 1. 26), sucrose synthase (SS ; EC 2. 4. 1. 13) and sucrose phosphate synthase (SPS ; EC 4. 4. 1. 14) in cucumber fruits (Cucumis sativus L. cv. Project X) stored at 13 and 25°C for 20 days to understand the changes in fruit quality in relation to firmness and color after harvest. The acid invertase activities in the soluble and cell-wall-bound fractions in the cucumber stored at 25°C were significantly higher than those stored at 13°C from days 4 to 16. The acid invertase activity was 30-35 times higher than the SS activity on day 8 of storage at 25°C. The SS and SPS activities in the cucumber fruits stored at 25°C showed the highest activity on day 8. Low-temperature storage was effective in decreasing invertase activity in both fractions, thereby suppressing sucrose degradation. Low-temperature storage at 13°C caused no chilling injury to the cucumber. It was effective in maintaining sucrose content, color and firmness of cucumber fruits.

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We investigated the effects of harvest date on the storability in cold storage (1°C and 5°C), of on-tree alcohol-treated 'Hiratanenashi' persimmons packed individually in plastic film. The persimmons, treated with ethanol on the tree to remove astringency on Oct. 3 (108 days after full bloom), were harvested on Nov. 2 (the color score near the fruit apex was about 5), Nov. 10 (the color score near the fruit apex was about 6 and the fruit surface was fully colored), and Nov. 16 (the color score near the fruit apex was about 7). These persimmons were packed individually directly after harvesting in plastic film and were stored at 1 °C and 5 °C. The fruit samples from each harvesting date stored at 1 °C had better storability than the fruit samples stored at 5 °C. At either storage temperature, the fruit samples harvested on Nov. 2 had the highest storability. The storability of the fruit samples harvested on Nov. 2 judged by the rate of fruit softening was at least three months under cold storage at 1°C. Peel color index, flesh firmness, and soluble solid concentration of the fruit samples from each harvesting date at both storage temperatures changed very little during storage. The scores for eating quality of all fruit samples decreased slightly as the duration of cold storage was prolonged. Fluctuations in the score of the fruit samples stored at 5°C were larger than that of the fruit samples stored at 1°C. The eating quality of the fruit samples harvested on Nov. 2 was fairly good during the three month storage period.

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Ready-to-drink (RTD) beverages prepared from 18 kinds of fruit juice were packed in 190 g cans. The gamma-aminobutyricacid (GABA) content of the packed beverages was investigated using an amino acid analyzer. The GABA contents of beverages prepared from concentrated citrus juice were 7-40mg/ 100 g. As the representative of RTD beverages, Rio red grapefruit juice in an 800 ml PET bottles, which contained 33mg/100 g GABA, was used to evaluate the shelf-life of the beverages in a storage test. The GABA content of this juice showed no decrease after heating at 80, 90, 97 and 115°C, during storage at 20, 37 and 55°C, or after irradiation with 20, 000lux using fluorescent lamps. These results show that GABA is stable in RDT beverages during storage.

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