Effect of cultivation conditions on retrogradation of sweetpotato starch

摘要

Sweetpotatoes were grown under four cultivation conditions, i. e. early planting and early harvesting (I, E-E), standard (II, STD), early planting and late harvesting (III, E-L), and late planting and late harvesting (IV, L-L). Retrogradation of the starch isolated from fresh roots was estimated by the hardness and syneresis rate after two weeks of storage at 5 degreesC. A significant difference in retrogradation among the cultivation conditions and cultivars was observed. The starch tended to exhibit slower retrogradation in late harvesting, where the temperature was low. The differences in amylose content and the proportion of short unit-chains (DP 9-11) of amylopectin among cultivation conditions were also significant. Starch retrogradation was positively correlated with the proportion of chains with DP 12-14 but negatively correlated with the proportion of DP 9-11. Moreover, there was no significant correlation between amylose content and retrogradation. These results indicate that the main factor for retrogradation under any cultivation condition is the proportion of short unit-chains of amylopectin. The best performance of sweetpotato starch as a food ingredient would be achieved by selecting both the proper cultivar and cultivation conditions.