Tropical Crop Quality After Quarantine Treatment Using Irradiation

Many horticultural commodities intended for export must receive an approved quarantine treatment before shipment. Irradiation is becoming an acceptable option for meeting phytosanitary requirements of fresh produce traded internationally. Irradiation at doses up to 1000 Gy have been approved by the FDA for the preservation and disinfestation of fresh fruits and vegetables. Use of the technology is accelerating with the approval of low dose generic treatments for insect disinfestation and the availability of irradiation facilities. However, commercial adoption of irradiation treatment requires an understanding of the radiotolerance limits for individual commodities, as well as the multiple factors that may mediate phytotoxicity. Careful attention to dosimetry and fruit physiology is needed to accurately determine phytotoxic thresholds. Research on the irradiation tolerance of tropical crops is presented, including the effects of cultivar, maturity, and storage period on the quality of treated sweet potatoes, bananas, and dragon fruit. Two purple-fleshed sweet potato cultivars retained good quality following irradiation and storage for 12 weeks at 15 °C, but a white-fleshed cultivar developed postharvest decay that decreased overall root quality. The purple-fleshed roots tolerated 600 Gy irradiation without quality loss and were sweeter than non-irradiated roots. For specialty bananas, doses between 600–800 Gy did not compromise visual quality, composition, or ripening behavior, depending on fruit maturity and harvest season. Irradiation did not extend banana shelf-life, but there was an acceleration of sucrose hydrolysis in treated fruit. Three clones of non-climacteric dragon fruit tolerated 800 Gy irradiation, with minimal effects on visual quality after 12 d storage at 10 °C. Currently, Hawaii-grown papayas, sweet potatoes, bananas, longans, and rambutans are being irradiated and marketed successfully, but the state has approvals to export 18 fruits and 6 vegetables with irradiation.