|Baldwin, Elizabeth - Liz|
Submitted to: Proceedings of Florida State Horticultural Society
Publication Type: Abstract Only
Publication Acceptance Date: 4/5/2003
Publication Date: N/A
Technical Abstract: Heat-treatments have been evaluated and utilized commercially to reduce postharvest decay, chilling sensitivity, and maintain quality of perishable horticultural products. Recent studies exposing grapefruit to short-duration, high temperature water (e.g., 62 °C for 20 seconds) have shown promise at reducing subsequent development of mold (Penicillium) and increasing resistance to chilling injury. Among the most prevalent citrus decay organisms in Florida are the stem0end rots (Diplodia natalensis and Phomopsis citri). Whereas Penicillium species invade citrus tissue through wounds, the stem-end rot organisms develop latent infections within the button tissue that are more protected from physical and chemical treatments. Here we report on efforts to identify heat-treatments that do not result in visible grapefruit peel injury, while reducing subsequent postharvest decay from natural infections. `Marsh' white or `Ruby' red grapefruit were exposed to a range of heat treatments for 0 to 120 seconds at water or vapor temperatures ranging from 50 to 65 °C (122-149 °F). Treatments were administered before or after washing. Fruit were usually not waxed, except for one test where fruit were washed and waxed immediately after heat treatments to simulate potential commercial packinghouse application. Fruit tolerance to heat injury followed a time x temperature relationship that was relatively consistent between experiments, even when vapor heat was used. In general, grapefruit could tolerate 10 seconds of 59 °C heat, but extending exposure time to 120 seconds required lowering the temperatures to 53 °C to prevent peel injury. Some time x temperature combinations were identified that reduced postharvest decay without causing peel injury. Injurious treatments were often associated with elevated fruit respiration. Simulated commercial degreening conditions before or after the heat-treatments had no affect on the development of peel injury.