Seasonal variations had a great influence on the ripening patterns of banana fruit. Normal ripening was enhanced or delayed by the effect of the maturing season on the fruit. Fruit maturing in summer (harvested in autumn) showed an increase in the rate of ripening, while fruit harvested in winter and spring showed a decrease in the rate of ripening. The banana fruit are sensitive to temperatures outside of their acclimated range. Due to ineffective storage and faulty handling procedures, cold and heat stress is a universal problem in bananas. Large amounts of fruit are lost due to heat and cold stress. Chilling injury occurs when bananas experience or are stored at temperatures below 13C, for a few hours to a few days. Temperatures slightly above 30C may cause extensive heat damage. The three main mechanisms suggested for the prevention of chilling and heat injury are the synthesis of small heat shock proteins, changes in the saturation of fatty acids of the membranes and suppression of the ethylene production and respiration rates. The prevention of cold and heat stress is investigated by monitoring the effect of short-term heat treatment and treatment with ethylene inhibitors on the ripening of the fruit. To determine changes in ripening the following eight ripening parameters are monitored: Yellowing, firmness of the pulp, sugar concentration, starch content, ethylene synthesis, respiration rate, rate of moisture loss and ion leakage. It was found that 1-methylcyclopropene (1-MCP) alleviates the symptoms of heat injury up to a point, but the symptoms of chilling injury were not affected. The effects of the three temperatures investigated: 35°C, 40°C and 45°C for different times. A short pre-heat treatment of 35˚C for 20 minutes proved successful to delay the ripening of the banana fruit, but did not protect the fruit against heat or chilling injury. The results of this study clearly indicate that both chilling and heat injury involve the action of ethylene and suggested that longer exposures to 1-MCP may be effective in preventing both types of injury. / Prof. C.S. Whitehead
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:8228 |
| Date | 17 April 2008 |
| Creators | De Villiers, Bernard Johann |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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