Effects of cooking methods on starch and sugar composition of sweetpotato storage roots

Sweetpotato has rich nutrition, good ecological adaptability and high yield. There is a lack of knowledge about the effects of cooking methods on starch and sugar components in elite Chinese cultivars. In this study, sweetpotato storage roots from four cultivars "Xinxiang", "Jinyu", "Zimei" and "Yuzishu 263" were treated by baking, boiling and steaming and subsequently analyzed for starch content, amylase activity and sugar contents including glucose, fructose, sucrose and maltose. Results indicated that cooking reduced starch content and final amylase activity and increased reducing sugar content especially maltose content, but did not have significant influence on non-reducing sugar content. These effects were different among the four cultivars and three cooking methods. Baking led to the least starch reduction. Storage roots of "Jinyu" contained the highest amount of sugar content and thus sweetest. Sugar composition analysis suggested that cultivars "Xinxiang" and "Jinyu" belong to high-maltose cultivars. This study may provide useful information for evaluating the cooking quality of sweetpotato cultivars.