QUALITY OF STORED MARSH AND RUBY RED GRAPEFRUIT AFTER HIGH-TEMPERATURE, FORCED-AIR TREATMENT

'Marsh' and 'Ruby Red' grapefruit (Citrus paradisi Macf.) tolerated a high-temperature, forced-air, vapor heat treatment of 43.5C for 260 minutes, a treatment applied for security against the Caribbean fruit fly [Anastrepha suspensa (Loew)]. Fruit did not develop symptoms of quality deterioration during subsequent storage. With 'Marsh' fruit, 99% and 96% were sound, whereas with 'Ruby Red' 98% and 94% were sound after storage at 10C for 28 days or 10C for 28 days plus 7 days at 21C, respectively. Differences in means for percentage of sound fruit were not significant for cultivar or vapor heat treatment. After the final storage period, there was significantly more (2.4-fold, P less-than-or-equal-to 0.05) aging observed on 'Ruby Red' fruit than on 'Marsh', averaged over all treatments. Vapor heat did not affect aging of 'Ruby Red' but increased aging of 'Marsh' fruit. Decay was reduced to almost-equal-to 2.0% in vapor heat-treated fruit from 5.0% for nontreated fruit. The efficacy of thiabendazole to control stem end rot was increased on vapor heat-treated fruit compared with nontreated fruit. After the final inspection, the appearance of 'Marsh' fruit was fresher (index 2.0) than that of 'Ruby Red' fruit (index 2.3), but the appearance of vapor heat-treated and nontreated fruit was similar. Peel color of 'Ruby Red' fruit was not affected by the vapor heat treatment, but, after 4 weeks at 10C plus 1 week at 21C, 'Marsh' fruit that were not treated were greener than those treated with vapor heat. The vapor heat treatment tested is a potentially viable quarantine procedure for Florida grapefruit that can be applied without adversely affecting fruit quality during normal storage.