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Title: Variability of sugars in staple-type sweetpotato (Ipomoea batatas) cultivars: The effects of harvest time and storage

Author
item ADU-KWARTENG, EVELYN - Crop Research Institute - Ghana
item SAKYI-DAWSON, ESTHER - University Of Ghana
item AYERNOR, GEORGE - University Of Ghana
item Truong, Van Den
item Shih, Frederick
item Daigle, Kim

Submitted to: International Journal of Food Properties
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/9/2011
Publication Date: 2/1/2014
Citation: Adu-Kwarteng, E., Sakyi-Dawson, E.O., Ayernor, G.S., Truong, V.D., Shih, F.F., Daigle, K.W. 2014. Variability of sugars in staple-type sweetpotato (Ipomoea batatas) cultivars: The effects of harvest time and storage. International Journal of Food Properties. 17(2):410-420.

Interpretive Summary: Sugar content in sweetpotato which varies among cultivars, agricultural conditions and postharvest handling practices is an important aspect of sweetpotato eating quality and processing characteristics. For fresh root markets, sweetness are usually preferred by consumers but the high level of sugars in sweetpotatoes is a drawback in processed products such as fries. Unlike potatoes, limited information is available on the effects of harvesting dates and storage on sugar content in sweetpotato roots. This study aimed to assess free sugar contents in sweetpotato roots at different levels of maturity and after 3 week storage under tropical conditions. The results indicated that harvest timing significantly affected soluble sugar contents measured at harvest and after short-term storage. Further evaluation on commercial cultivars in the U.S. needs to carry out in order to establish maturity index of sweetpotatoes that are grown for table stocks and processing industry.

Technical Abstract: Total soluble sugar content and composition was studied by high performance liquid chromatography in four high dry-matter sweet potato cultivars at 3, 4, and 5 months maturity. Total soluble sugar consisted of sucrose, glucose, and fructose, ranging from 4.10–10.82 g/100 g (dry-weight basis). At harvest, there were significant differences in total soluble sugar due to maturity (p < 0.001) and cultivar (p < 0.05). The highest total soluble sugar contents were in 5-month samples at harvest (7.36–10.34 g/100 g) and 4-month samples after short-term storage under tropical ambient conditions (8.66–10.82 g/100 g). Estimated amylase enzyme activity varied significantly with harvest age (p < 0.05). Although reducing sugar contents were low, fructose levels in 5-month samples increased considerably after storage.