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

This work indicates that cherimoya behaves like a climacteric fruit af ter harvesting, because it shows respiration and ethylene crises conne cted 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 incr ease rapidly over the second day, reaching a maximum on the third day. During the climacteric there is also a low amount of 1-aminocycloprop ane-1-carboxylic acid (ACC) in its conjugated form. Skin browning incr eases after harvesting, but this is not related to a decrease of chlor ophyll, since the chlorophyll level remains stable throughout the enti re 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 te mporal coincidence between the onset of ethylene production, the degra dation of starch, the loss of firmness and the build up of total sugar s.