Submitted to: HortScience
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/11/2004
Publication Date: 4/20/2005
Citation: Wall, M.M. 2005. Storage quality and composition of sweetpotato roots after quarantine treatment using low doses of x-ray irradiation. Hortscience 40:424-427. Interpretive Summary: Hawaii-grown sweetpotatoes cannot be shipped to mainland U.S. or international markets without being treated for quarantine security against insect pests. In 2004, the U.S. Dept. of Agriculture, Animal and Plant Health Inspection Service (USDA-APHIS) approved the movement of irradiated sweetpotatoes from Hawaii. However, irradiation may shorten the storage life of sweetpotato roots. Therefore, three cultivars were evaluated for storage quality and composition following low dose irradiation and 3 months of storage. Any reduction in quality was attributed to softening and postharvest disease, and these effects were cultivar and dose dependent. For a white-fleshed cultivar, postharvest decay adversely impacted the internal color, firmness, and overall quality of irradiated roots that were stored for 3 months. Two purple-fleshed cultivars retained good quality following irradiation and storage, and these are the primary export cultivars from Hawaii.
Technical Abstract: Sweetpotato [Ipomoea batatas (L.) Lam.] roots of three Hawaii-grown cultivars ('Mokuau', 'Okinawan', and 'Yoshida') were treated with 0, 200, or 400 Gy x-ray irradiation and stored for 12 weeks at 15 EC. The storage quality of nonirradiated and irradiated roots was compared for weight loss, sprouting, firmness, color, postharvest decay, and carbohydrate concentrations. Nonirradiated roots lost 3 to 4% weight during storage, whereas roots treated with 400 Gy lost 4.7 to 8.6% weight. Sprouting was negligible for all treatments. Storage tended to increase root firmness, while irradiation tended to decrease firmness. The starch contents of 'Mokuau' and 'Okinawan' roots were not affected by irradiation or storage. Irradiation tended to decrease the starch content of 'Yoshida' roots. Glucose and fructose concentrations were not affected by irradiation, but these sugars increased during storage. Sucrose concentrations of roots irradiated with 400 Gy were double those of nontreated roots after 12 weeks storage. The purple-fleshed cultivars, 'Mokuau' and 'Okinawan', retained good quality following irradiation and storage, but firmness decreased somewhat for roots treated with 400 Gy. These purple sweetpotatoes are the primary export cultivars from Hawaii. For the white-fleshed cultivar, 'Yoshida', postharvest decay adversely impacted the internal color, firmness, and overall quality of roots treated with 400 Gy and stored for 12 weeks.