Abstract
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