Abstract
The ripening of bananas is a process that needs to take place in
accurately controlled conditions to ensure synchronization of all
the metabolic processes that are involved with ripening so that the
best quality product can be made available to the consumer. Optimal
ripening requires the correct ambient room temperature and relative
humidity, adequate ventilation and ethylene treatment. Banana
ripening occurs at temperatures between 16º-18ºC, with 95% humidity
and constant ventilation. Ripening is triggered when the bananas are
exposed to ethylene for 24 hours. Fruit that ripens in ideal
circumstances has a bright yellow colour, firm soft pulp and strong
peel, are sweet tasting and have a pungent aroma. The conditions in
the store and ripening rooms, especially temperature, are not always
regulated to the optimum and subtropical fruits such as bananas are
injured at temperatures below 12ºC. Phase transitions in the
membranes, from a liquid-crystalline to a solid gel-like phase, are
responsible for chilling injury. Chilling injury delays ripening,
but does not noticeably influence the eating quality of the fruit.
The bananas are still sweet with a firm soft pulp and strong peel.
The aroma production is however reduced by the cold and undesirable
colour changes occur. The chilling injured bananas are dull greyyellow
in colour with brown or black spots on the peel. The peel
sometimes becomes completely brown or black. The quality of the
bananas is potentially influenced by this colour change since the
consumer judges the fruit on visual appearance. Controlled
atmosphere storage and modified atmosphere packaging reduce chilling
injury and extends the life of the fruit due to delayed ripening.
Chilling injured fruit consequently has less brown or black spots
and sometimes even an improved yellow colour. A better quality
product can be supplied to the consumer and the temperature control
in the storeroom does not need to be 100% accurate. The advantages
of these techniques are attributed to the modified atmospheres,
namely reduced oxygen and increased carbon dioxide concentrations
which influence respiration, ethylene synthesis and action.
Prof. C.S. Whitehead