Fruit and vegetables after harvest remain in a living state; they respire using the reserve carbohydrates and organic acids and are capable of enzyme interconversions of their constituents. Processes like ripening continue after harvest but, because the harvested commodity has only a limited supply of reserve carbohydrate and is removed from its normal source of water, premature senescence and wilting may be promoted. The harvested commodity is susceptible to mechanical damage which can lead to bruising and a combination of senescence and damage can give increased susceptibility to fungal and bacterial rotting. The browning reaction which results when fruits or vegetables are bruised or cut is due to the action of the enzyme polyphenoloxidase on phenolic compounds producing quinones which then polymerise to produce the familiar brown or black pigments. Post‐harvest treatments are designed to minimise these deleterious effects while controlling processes such as ripening so that the commodity can be sold in the optimal condition.
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