ETHYLENE BIOSYNTHESIS AND PHYSICOCHEMICAL CHANGES DURING FRUIT RIPENING OF CHERIMOYA (ANNONA-CHERIMOLA, MILL)

This work indicates that cherimoya behaves like a climacteric fruit after harvesting, because it shows respiration and ethylene crises connected with its ripening. The increase in ethylene production is caused by an increase in the activities of ACC-synthase and ethylene-forming enzyme (EFE), which are very low in the freshly picked fruit, but increase rapidly over the second day, reaching a maximum on the third day. During the climacteric there is also a low amount of 1-aminocyclopropane-1-carboxylic acid (ACC) in its conjugated form. Skin browning increases after harvesting, but this is not related to a decrease of chlorophyll, since the chlorophyll level remains stable throughout the entire post-harvest period. The level of browning shows a good correlation (r=0.947) with the L parameter of colour of reflection. There is a temporal coincidence between the onset of ethylene production, the degradation of starch, the loss of firmness and the build up of total sugars.