Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2003
Publication Date: 12/31/2003
Citation: Follett, P.A., Sanxter, S.S. 2003. Lychee quality after hot water immersion and x-ray irradiation quarantine treatments. Hortscience 38 (6): 1159-1162. 2003.
Interpretive Summary: Lychee is a host for pest fruit flies in Hawaii and therefore must undergo a quarantine treatment before export to the U.S. mainland. A direct comparison of two quarantine treatments for lychee was made. Hot water immersion treatment was more detrimental to fruit quality than x-ray irradiation treatment, and irradiated fruits did not differ significantly from untreated control fruits. On the basis of fruit quality maintenance, irradiation is a better choice of quarantine treatment than hot water immersion for lychee.
Technical Abstract: 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 a) hot water immersion at 49.0 degrees C for 20 min, b) irradiation treatment at a minimum absorbed dose of 400 Gy, or c) left untreated as controls. Fruit were then stored at 2 or 5 degrees 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. 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 degrees C for 20 min. or 2) irradiation at 400 Gy, or c) left untreated as controls. Fruit were then stored at 4 degrees 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.