COMPARATIVE RESPONSES OF PREHARVEST GA-TREATED GRAPEFRUIT TO VAPOR HEAT AND HOT-WATER TREATMENT

'Marsh' grapefruit (Citrus paradisi Macf.) produced in Florida must be certified for security against unwanted pests before entry into some domestic and export markets. Application of heat by hot water (HW) has been shown to cause severe injury to grapefruit; however, direct comp arisons between forced vapor heat (VH) and HW have been lacking. Grape fruit preharvest-treated with gibberellic acid (GA) or not treated, we re postharvest-treated with VH or HW such that the surfaces of fruit w ere exposed to the same rate of temperature increases and treatment du rations. Condition and quality attributes were then compared with ambi ent air (AA) and ambient mater (AW) controls after storage. After 4 we eks' storage at 10 degrees C plus 1 week at 20 degrees C, scald affect ed 5% of HW and 20% of VH-treated fruit. No scald developed on control fruit. At the end of storage, mass loss for HW and VH fruit was appro ximate to 5%. HW-treated fruit had a 5-fold higher incidence of aging than VH fruit; however, control fruit showed significantly more aging than all heat-treated fruit. Gibberellic acid (GA) and the heat treatm ents reduced decay relative to the control. GA-treated fruit remained greener during storage than control fruit. These findings indicate tha t VH and HW treatments at the temperatures and durations to control th e Caribbean fruit fly (Anastrepha suspensa, Loew) will likely cause pe el injury to 'Marsh' grapefruit produced in Florida, regardless of tre atment with GA.