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Peter A. Follett and Suzanne S. Sanxter

Hot-water immersion and irradiation quarantine treatments are used to disinfest lychee (Litchi chinensis Sonn.) of fruit flies and other pests before export from Hawaii to the U.S. mainland. In the first experiment, one day after harvest, `Kaimana' lychee fruit were subjected to 1) hot-water immersion at 49.0 °C for 20 minutes, 2) irradiation treatment at a minimum absorbed dose of 400 Gy, or 3) left untreated as controls. Fruit were then stored at 2 or 5 °C in perforated plastic bags, and quality attributes were evaluated after 8 days. Lychee fruit treated with hot-water immersion were darker (lower lightness) and less intensely colored (lower chroma) than irradiated or untreated fruits at both storage temperatures. Fruit stored at 2 °C were darker (lower lightness) than fruit stored at 5 °C, but fruit held at 5 °C had greater weight loss. External appearance of fruit treated with hot-water immersion was rated as unacceptable, whereas irradiated and nontreated fruit were rated as acceptable. Taste of fruit was rated as acceptable in all treatments. In the second experiment, lychee fruit were subjected to 1) hot-water immersion at 48, 48.5, or 49 °C for 20 minutes or 2) irradiation at 400 Gy, or 3) left untreated as controls. Fruit were then stored at 4 °C in perforated plastic bags, and external appearance of the pericarp was evaluated after 1, 2, 5, 7, 8, and 9 days. Pericarp darkening was more rapid for lychee fruit treated with hot-water immersion than irradiated or control fruit, and the degree of quality loss increased with increasing hot-water immersion temperature. Overall, under these experimental conditions, irradiation was superior to hot-water immersion as a quarantine treatment on the basis of fruit quality maintenance.

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Peter A. Follett and Suzanne S. Sanxter

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.

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Peter A. Follett and Suzanne S. Sanxter

Hot-water immersion and irradiation quarantine treatments are used to disinfest longan [Dimocarpus longan (Lour.) Steud.] of fruit flies and other pests before export from Hawaii to the U.S. mainland. One day after harvest, longan fruit (cvs. Chompoo and Biew Kiew) were subjected to hot-water immersion at 49 °C for 20 minutes, irradiation treatment at a minimum absorbed dose of 400 Gy, or left untreated as controls. Fruit were then stored at 10 °C in perforated plastic bags, and quality attributes were evaluated after 7, 14, and 21 days. `Chompoo' and `Biew Kiew' fruit treated by hot-water immersion were darker (lower L*) and less intensely colored (lower C*) than irradiated or untreated fruits after 14 days of posttreatment storage. For both cultivars, external appearance of fruit treated by hot-water immersion was rated as unacceptable after 14 and 21 days of posttreatment storage, whereas irradiated and nontreated fruit were rated as acceptable on all days. Penicillium mold contributed to the unacceptable external appearance ratings after 21 days for fruit that were treated by hot-water immersion. With both cultivars, taste of fruit treated with hot-water immersion was rated as unacceptable after 21 days of storage, whereas irradiated fruit remained acceptable. Overall, under these experimental conditions, irradiation was superior to hot-water immersion as a quarantine treatment based upon the maintenance of fruit quality.