Changes in respiration and ethylene production of low-chill subtropical peaches harvested at different maturities

Abstract

Low-chill, non-melting fl esh (NMF) peaches have immense potential as a unique specialty crop for Florida due to their “tree-ripened” fl avor characteristics and slow softening process. The fi rm texture of NMF  peaches is benefi cial for longer shelf life due to reduced susceptibility to mechanical injuries during commercial handling as well as prolonged maintenance of tissue integrity. However, little is known about harvesting and handling NMF peaches for fresh market, or peaches grown in humid tropical and subtropical climates. The objective of this study was to investigate the physiological changes during ripening of low-chill subtropical peaches harvested at different maturities. Two melting fl esh (MF) cultivars, ‘Flordaprince’ and ‘Tropic Beauty’, and two NMF cultivars, ‘UFSun’ and ‘Gulfking’, were chosen. Samples of 12 fruit that represented the mean ground color (GC) CIE L*a*b* a*-value of 100 tagged fruit (±1 standard deviation) were harvested when GC break occurred on 50% of the tagged fruit for each cultivar (i.e., commercial harvest maturity). The samples were ripened at 20 °C for 5 days with respiration and ethylene production being measured each day. Respiration and ethylene production of both MF cultivars increased dramatically after harvest and reached a plateau around day 3 or 4 for more advanced fruit. For NMF peaches, ethylene production rose before respiration increased for ‘Gulfking’ peaches and peaked on day 2. Interestingly, most of the ‘UFSun’ peaches were already at the postclimacteric stage as demonstrated by low ethylene production and constant respiration throughout storage. The results indicate that the NMF cultivars can be harvested when further along on the climacteric phase on the tree than MF cultivars since the NMF fruit were on the climacteric rise or beyond when picked at commercial harvest stage based on ground color development.