Product temperature is the critical factor to be controlled in the postharvest storage of fruits and vegetables. Temperature has the sin- gle greatest effect on respiration rate and thus deterioration rate of the product. Rapid product cooling after harvest is essential in the preservation of most fresh commodities. Though there are a number of precooling methods, care should be taken when selecting a method for a specific commodity. Product properties differ from commodity to commodity. Factors that must be taken into account when selecting a precooling method include; product deterioration rate, sensitivity to water contact, temperature of freezing, temperature of chilling, sensitivity to water loss, economics, and the expected storage duration. Due to the combination of these factors, some precooling methods are not suited for certain products. Optimum storage of commodities is necessary to prolong their fresh quality. Storage temperature vary from product to product, depending on chilling sensitivity. Other factors that can be controlled to maximise storage duration include relative humidity and gas concentrations. The recommended relative humidities is commodity-specific, depending on the nature of the product. Proper relative humidity levels will decrease the moisture loss of the product, preventing shrivelling or wilting. Controlling or modifying the gas compositions of O_2, CO_2, and C_2H_4 can also be useful in prolonging the storage-life. Though these changes can increase the storage-life of a commodity, they are best used in conjunction with low temperature management as this factor still remains the most critical. When modifying the gas composition care must be taken not to allow the O_2 levels to reach anaerobic conditions or for CO_2 levels to become harmful to the product. Reducing C_2H_4 levels can retard the ripening process in many fruits. The recommended levels of these gases vary from product to product, and some produce may not benefit from such changes. The decision of using modified or controlled gas compositions also depends on the economics involved. These systems require well sealed storage rooms and the necessary equipment to produce the desired levels. Hence, for short-term storage it may not be economical.
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