Comparison of rambutan quality after hot forced-air and irradiation quarantine treatments

Insect disinfestation treatments are required for many of Hawaii's tropical fruits before export to the U.S. mainland. For rambutan, Nephelium lappace um L., irradiation at 250 Gy is an Animal plant Health Inspection Service ( APHIS)-approved quarantine treatment, but a hot forced-air treatment has al so been proposed for eliminating fruit fly pests. Two days after harvest, r ambutan fruit (cultivars R134 and R167) were subjected to: 1) hot forced-ai r at a seed surface temperature of 47.2 degreesC, 2) irradiation treatment at 250 Gy, or 3) left untreated as controls. Fruit were then stored at 10 d egreesC in perforated plastic bags, and quality attributes were evaluated a fter 4, 8, and 12 days. 'R134' fruit treated with hot forced-air were signi ficantly darker (lower L*) and less intensely colored (lower C*) than irrad iated or nontreated fruits after 4 and 8 days of posttreatment storage; the external appearance was unacceptable after 4 days of storage, whereas irra diated fruit remained acceptable through 8 days of storage. Differences bet ween treatments were less pronounced for 'R167'. 'R167' fruit treated with hot forced-air had lower L* and C* values and less acceptable external appe arance ratings than did irradiated fruit at 4, 8, and 12 days posttreatment , but differences were not statistically significant. For both cultivars, e xternal appearance of fruit in all treatments was unacceptable after 12 day s of storage, whereas taste was rated as acceptable for all treatments on e ach day. Overall, under these experimental conditions, irradiation was supe rior to hot forced-air as a quarantine treatment on the basis of fruit qual ity maintenance.