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.
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