RIPENESS AND TISSUE DEPTH EFFECTS ON HEAT INACTIVATION OF PAPAYA ETHYLENE-FORMING ENZYME

Heat inactivation studies were conducted on the ethylene-forming enzyme system (EFE) in papayas of different maturities, and at three tissue depths. D-values showed EFE in the mesocarp and endocarp were more heat sensitive than EFE in the exocarp. Within the mesocarp and endocarp, EFE in 1/4- and 1/2-ripe papayas were more heat labile than in mature green and color break fruits. Ion leakage increased concomitantly with increased mesocarp and endocarp ripeness confirming that papayas ripen differentially from the innermost tissues outwards. Membrane integrity as determined by ion leakage may explain the increase in heat sensitivity of EFE in riper tissues.