POSTHARVEST QUALITY OF GA-TREATED FLORIDA GRAPEFRUIT AFTER GAMMA-IRRADIATION WITH TBZ AND STORAGE

Grapefruit, Citrus paradisi (Macf.), harvested from gibberellic acid ( GA) treated trees were irradiated at 0.3 or 0.6 kGy, and evaluated for quality after treatment and simulated commercial storage, The peel of GA-treated fruit retained green color and the fruit were firmer than control fruit after treatment, A condition, not observed before with g rapefruit, was described and termed 'spongy fruit', which increased as irradiation dosage increased. The incidence of fruit peel pitting aft er five weeks' storage increased from <2% to 11% and 25% as irradiatio n dose increased from 0 to 0.3 and 0.6 kGy. The majority of pitting at 0.3 kGy was slight and would not have an affect on U.S. #1 Grade for grapefruit. Incidence of decay (mostly green mold) was reduced with th iabendazole (TBZ), and mean decay among all treatments was <1%. Total soluble solids, titratable acidity and the resulting ratio was not aff ected by GA or irradiation. There was a general decline in the sensory preference for juice flavor, and pulp flavor and texture as irradiati on dose increased. We conclude that GA-treated grapefruit will tolerat e irradiation dosage of 0.3 kGy without serious damage; however, at do sage of 0.6 kGy, serious peel damage detrimental to fruit quality will likely develop during storage.