Effect of Temperature on the Physiological Changes of Kabosu (Citrus sphaerocarpa hort. ex Tanaka) Fruit during Storage

Abstract

Green Kabosu fruit (Citrus sphaerocarpa hort. ex Tanaka), a sour orange, tends to lose easily the external green colour and become poor in flavour during storage at room temperature. Therefore, it is important to keep green colour during storage of the fruit. In this study, physiological changes during storage at different temperatures ranging 1°C to 30°C were investigated to elucidate the optimum storage temperature for the fruit.
1. The most rapid degreening of the peel colour was found in the fruit held at 15°C and 20°C, while degreening of the fruit ceased within 1 month at 30°C. At 1°C, degreening was inhibited markedly and the fruit kept good green colour during storage for 4 months.
2. Fruit held at high temperatures tended to show a high rate of respiration during storage. Respiratory rate continued to increase gradually during storage at low temperatures (1°C-10°C).
3. A sudden rise of ethylene production was observed in the fruit stored for 15 days at 1°C, followed by a high rate of production. While the fruit continued to emit low rate of ethylene at temperature within the range 5°C to 20°C.
4. Break points were observed in the Arrhenius plots of respiratory rate of the fruit at 16°C and 4°C.
5. High rate of occurrence of chilling injury was observed in the fruit stored at 1°C for 4 to 6 months. On the other hand, occurrence of chilling injury was seldom in the fruit stored at 5°C and 10°C. Judging from the above results, it may be concluded that green Kabosu fruit is chilling sensitive and that shelf life of Kabosu fruit is less than 4 months at 1°C.
If the fruit has to be stored for more than 4 months, the optimum temperature must be 4°C which is safe temperature from chilling injury.