Effects of Postharvest Heat Treatments on Chilling Injury, Diseases, and Quality of Tuscan Melons

The cultivars of the so-called Tuscan or Italian cantaloups (Cucumis melo Group cantalupensis) have shown different response to low temperatures during storage. Heat treatments previous to storage at low temperatures have been shown to reduce chilling injury. Two cultivars expressing low and moderate sensitivity to the disorder, Diva and Venezia, respectively, were harvested at slip initiation and subjected to heat treatments by immersion in water at 60 ºC for 0, 1, 2, 4, and 6 minutes. After drying and cooling, fruits were stored for 18 days at 0 ºC, plus 3 additional days at 20 ºC. Results after the storage period showed that, although slightly, heat treatments significantly decreased chilling injury in Diva, but had no significant effect on Venezia; heat treatments over 2 or 4 minutes induced heat injury in the fruits of Venezia and Diva, respectively.  The effect of heat treatments on disease development was significant, with all treatments showing lower growth of pathogens than the control; the predominant diseases in both cultivars were fungi (Alternaria spp., Cladosporium spp., and Rhizopus spp.). Visual quality was higher in fruits heat treated for 1 or 2 minutes, mainly due to null or low disease development; internally, there were no significant changes in color or soluble solids, however, a significant reduction of firmness occurred in all treatments during storage, and most fruits heat treated for 4 or 6 minutes presented off flavors.