Farmers Review Africa May/June 2017 Farmers Review Africa | Page 45
Supplement
temperature requirements. e time until harvest. Temperature must also be stable as quality of fresh horticultural commodities
cooling, temperature stability and its duration changes may affect respiration and marketable markedly depends upon the quality attained at the
need to be considered. quality. time of harvest.
Relative humidity Despite decades of educational efforts, the most
By lowering produce temperature as soon as
possible aer harvest — generally within four
hours — the following effects are achieved:
·
Respiration rate is decreased.
Maintaining high humidity around harvested common causes of posthar vest losses in
produce reduces water loss, which would result developing countries continue to be rough
· Water loss is reduced. in decreased returns through poor quality (for handling and inadequate cooling and
· Ethylene production is suppressed. example, wilting, shrivelling) and loss of temperature maintenance. e lack of sorting to
· Sensitivity to ethylene is reduced. saleable weight. eliminate defects before storage and the use of
· Microbial development is slowed. High humidity should be used with low inadequate packaging materials further add to the
Most leafy vegetables and 'temperate' fruit — temperature storage because humidity and problem.
including pome and citrus fruits — are not chill- warmth combined favour the growth of fungi In general, minimizing rough handling, sorting to
sensitive and can be stored between 0°C and 2°C and bacteria. Although the relative humidity of remove damaged and diseased produce and
for long periods without signi cant loss of visual air increases when it is cooled, it is still necessary effective temperature management will help
quality. Tropical and subtropical fruit and some to check the relative humidity in a coolroom is considerably toward maintaining a quality
root vegetables are chill-sensitive and may be satisfactory. product and reducing storage losses. Storage life
damaged at low temperatures. ey are generally Preharvest factors greatly in uence both the will be enhanced if the temperature during the
stored at 13°C or above, although some may be condition of the crop at harvest and the crop's postharvest period is kept as close to the optimum
stored safely as low as 5°C if cooled soon aer storage and nutritive potential. e postharvest as feasible for a given commodity.
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FARMERS
REVIEW AFRICA
May - June 2017