Senescent spots which developed on the yellow banana peel at later shelf storage occur as physiological denature. The initiation and development of the spotting were investigated by microscopic observations and change of phenolic content. Several layers of cells from the surface of banana peels showed browning from the vertical view, and brown particles in the cells were observed from the horizontal view by light microscopy. Scanning electron microscopy (SEM) revealed that the browning part of spots are sunken like craters from normal cell area and stomata were located in their center. Dopamine content of outmost peel was more abundant than the other parts of peel and pulp. However the content of dopamine in the area decreased during ripening, particularly in the area of senescent spots.

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The effect of 1-methylcyclopropene (1-MCP) treatment on the postharvest quality of sudachis (Citrus sudachi hort. ex Shirai) was investigated with the aim of prolonging their storage period. Sudachis were treated with 1-MCP at various concentrations of 0, 0.01, 0.1, 0.5 and 1.0μl·l^-1 for 6, 12 or 24hr at 20°C and then stored in the dark at 20°C. The treatment with 0.1μl·l^-1 1-MCP for 24hr was the most effective in delaying the degreening of sudachis. This treatment with 0.1μl·l^-1 1-MCP did not induce peel browning, weight loss and internal quality degradation in sudachis. On the other hand, at higher concentrations (ie., 0.5 and 1.0μl·l^-1), 1-MCP had little effect on the delay of degreening and induced undesirable responses, such as peel browning and weight loss. We suggest that appropriate 1-MCP treatment as postharvest treatment could be applied for commercial use to the maintenance of the marketable green color of sudachi.

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Three cultivars (Norin-1, Toyoshiro and Snowden) of Japanese processing potatoes were stored at 5 and 12°C for 90 days. The sugar contents, and invertase, sucrose-6-phosphate synthase (SPS) and UDP-glucose pyrophosphorylase (UGPase) activities of these three cultivars were measured at intervals during storage. The aim of this study was to determine whether storage temperature affects the three enzyme levels in potatoes. The low-temperature storage (5°C) increased reducing sugar contents during storage compared with the high-temperature storage (12°C). In addition, the low-temperature storage increased the invertase and SPS activities of the three cultivars. These results suggest that invertase and SPS play an important role in the accumulation of reducing sugars in Japanese processing potatoes stored at low temperatures.

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Acetyl-CoA synthetase (ACS) activity in fully ripened bananas was determined by HPLC. The ACS activity was higher for acetate as a substrate than for butyrate. The higher substrate specificity for acetate than for butyrate evidences that banana produces a great amount of acetate esters and a less amount of butyrate esters. The K_m for MgCl₂ for butyryl-CoA formation was 5-fold higher than that for acetyl-CoA formation. ACS activity was assayed in mitochondrial, microsomal, and cytosol fractions isolated from ripened banana pulp and the highest total enzyme activity was detected in the cytosol fraction. This is the first report on the presence of this enzyme, ACS, in fruit pulp.

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