TOLERANCE OF RED-FLESHED GRAPEFRUIT TO A CONSTANT OR STEPPED TEMPERATURE, FORCED-AIR QUARANTINE HEAT-TREATMENT

The quality of red-fleshed grapefruit after exposure to a constant (46 degrees C for 300 min), or stepped (40 degrees C for 120 min, 50 degr ees C for 90 min, and 52 degrees C until the fruit center temperature is 48 degrees C) temperature, forced-air quarantine heat treatment was evaluated. Grapefruit exposed to either heat treatment had lower titr atable acidity and slightly better flavor ratings than fruit not expos ed to a heat treatment. Neither of the heat treatments resulted in ext ernal or internal damage to the fruit nor an increased incidence of de cay during storage. The average center temperature of fruit exposed to the stepped temperature heat treatment reached 48 degrees C after 240 min of treatment, and exceeded that of fruit exposed to the constant temperature treatment by 2 degrees C for about 80 min. Though both hea t treatments provide quarantine security against the Mexican fruit fly , the constant temperature heat treatment is preferred over the steppe d temperature heat treatment because fruit are not exposed to high tem peratures that, given sufficient duration of exposure, could potential ly lower market quality.