Comparison of Rambutan Quality after Hot Forced-air and Irradiation Quarantine Treatments

Abstract

Insect disinfestation treatments are required for many of Hawaii's tropical fruits before export to the U.S. mainland. For rambutan, Nephelium lappaceum L., irradiation at 250 Gy is an Animal Plant Health Inspection Service (APHIS)-approved quarantine treatment, but a hot forced-air treatment has also been proposed for eliminating fruit fly pests. Two days after harvest, rambutan fruit (cultivars R134 and R167) were subjected to: 1) hot forced-air at a seed surface temperature of 47.2 °C, 2) irradiation treatment at 250 Gy, or 3) left untreated as controls. Fruit were then stored at 10 °C in perforated plastic bags, and quality attributes were evaluated after 4, 8, and 12 days. `R134' fruit treated with hot forced-air were significantly darker (lower L*) and less intensely colored (lower C*) than irradiated or nontreated fruits after 4 and 8 days of posttreatment storage; the external appearance was unacceptable after 4 days of storage, whereas irradiated fruit remained acceptable through 8 days of storage. Differences between treatments were less pronounced for `R167'. `R167' fruit treated with hot forced-air had lower L* and C* values and less acceptable external appearance ratings than did irradiated fruit at 4, 8, and 12 days posttreatment, but differences were not statistically significant. For both cultivars, external appearance of fruit in all treatments was unacceptable after 12 days of storage, whereas taste was rated as acceptable for all treatments on each day. Overall, under these experimental conditions, irradiation was superior to hot forced-air as a quarantine treatment on the basis of fruit quality maintenance.