Storage Quality and Composition of Sweetpotato Roots after Quarantine Treatment Using Low Doses of X-ray Irradiation

Abstract

<jats:p>Sweetpotato [<jats:italic>Ipomoea batatas</jats:italic> (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 °C. 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. When all cultivars were averaged, sweetpotatoes treated with 400 Gy and stored for 12 weeks had the lowest starch concentrations and highest total sugar concentrations. 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. The `Okinawan' sweetpotato is the primary export cultivar 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.</jats:p>

Effect of Cutting Styles on Quality and Antioxidant Activity of Stored Fresh-Cut Sweet Potato (Ipomoea batatas L.) Cultivars

“…As shown in Table 1, the firmness of both sweet potato cultivar decreased with storage time, and similar results were also found in the research of Wall et al [13]. Besides, the increased of wounding intensity accelerated the decrease of firmness in sweet potatoes and shred cutting sweet potatoes presented the lowest firmness in both cultivars during storage.…”

“…The color was evaluated by measuring L*, a*, and b* values (L* indicates Lightness, a* red/green coordinate, and b* is the yellow/blue coordinate). The firmness was measured according to the method described by Wall et al [13] with some modifications. The firmness was measured on two paired sides using a TA-XT2i texture analyzer (Stable Micro System Ltd., London, UK) with a 3 mm diameter probe at a speed of 60 mm/min for slice and pie style while 5 mm diameter probe at a speed of 1 mm/s was used for shred style.…”

Sweetpotato Cultivar Trials on Hawai‘i Island

“…Similarly, 'Okinawan', PI 531094, 'Murasaki-29', and 'Picadito' roots had the highest starch content. The range of values for soluble sugars and starch contents generally agrees with other reports for sweetpotato cultivars (LaBonte et al, 2000;Picha, 1985;Van Den et al, 1986;Wall, 2005). The dry matter content exceeded 30% for most of the white-fleshed cultivars and for 'Okinawan'.…”

Generic Radiation Quarantine Treatments: The Next Steps

“…Hawaii grows several unique varieties of sweet potato, including a purple-ßeshed type (Wall 2005). Hawaii was unable to export its sweet potatoes without quarantine treatment against Euscepes postfaciatus (Fairmaire) (Coleoptera: Curculionidae) and sweetpotato vine borer (federal quarantine pests), and sweetpotato weevil, Cylas formicarius elegantulus (Summers) (a quarantine pest for California and much of the southwestern United States) (Follett 2006a).…”