The 2010 ASHS Annual Conference

Heat treatment involves non-lethal stress that stimulates defense reactions in plants that protect them from subsequent stresses and is also known to inhibit ripening. Non-melting flesh (NMF) peaches were used in this study due to their reduced textural changes during ripening, which contributes to extended postharvest life and reduced postharvest mechanical injuries compared with traditional melting flesh (MF) peaches. The decreased capacity of NMF peaches to degrade cell walls (i.e., soften) could be related to a deletion of endo-polygalacturonase (endo-PG) gene or a truncation of the mRNA.The NMF peach cultivars ‘UFSun’ and ‘Delta’ were immersed in 46 °C (HT) or 20 °C (NT) water for 30 min before being placed at 20 °C for 5 days to allow ripening. The HT ‘UFSun’ fruit retained their initial flesh firmness throughout storage while this effect was observed only through Day 3 for ‘Delta’ fruit. Exo-PG activity was similar in both control and HT fruit, but endo-PG activity was significantly higher in HT fruit for both cultivars. Furthermore, the endo-PG activity of HT peaches was significantly higher in ‘UFSun’ than ‘Delta’, but exo-PG activity did not differ between the cultivars. The enhanced endo-PG activity in HT fruit of both cultivars did not parallel firmness changes since endo-PG activity was stimulated while the initial flesh firmness was retained. Soluble solids content, titratable acidity, and pH were also measured but there were no significant differences between the control and HT fruit for either cultivar. Hence, hot water treatment could be a potentially useful postharvest handling method to delay peach fruit softening without affecting their appealing flavor.