Characterization of carbohydrate metabolism in relation to quality of root tuber in edible sweetpotato

Chinese. 【目的】探讨食用型品种块根碳水化合物代谢特性及与品质的关系。【方法】以淀粉型品种为对照,选用典型的食用型品种于2004～2005年2个生长季在山东农业大学试验农场进行试验研究。试验采用块根膨大过程中定期取样的方法,观察块根膨大过程中可溶性糖、淀粉及淀粉组分含量的变化、淀粉酶活性变化及其与甘薯收获期块根品质的关系。【结果】与淀粉型品种比较,食用型品种块根总淀粉含量、直链淀粉含量以及支链淀粉含量均较低,可溶性总糖和β-胡萝卜素含量较高;块根粉的高峰黏度和崩解值等较高、糊化温度较低;块根蒸煮食味较好。栽秧100d以后,食用型甘薯块根总淀粉含量和β-淀粉酶活性下降,可溶性总糖含量提高,其变化趋势与淀粉型品种相反。【结论】食用型品种块根膨大后期,由于淀粉酶的作用导致淀粉分解是其总淀粉含量较低、可溶性总糖含量较高的一个重要原因。

English. [Objective] The objective of this study is to clarify the carbohydrate metabolism and its relation to quality in root tuber of edible sweetpotato. [Method] The typical varieties of edible sweetpotato and the varieties of starchy sweetpotato as a control were grown in a replicated field experiment at agricultural experiment station of Shandong Agricultural University in 2 summer crop seasons of 2004 and 2005. The changes of starch content, soluble sugar content and amylase activity during root tuber development, and the storage root quality at the harvest were determined by using periodic sampling during storage root development. [ Result ]The total starch content, the amylose content and the amylopectin content in root tuber of edible sweetpotato were all lower than that in storage root of starchy sweetpotato; but the contents of total soluble sugar and beta-carotene in storage root of edible sweetpotato were higher than that in root tuber of starchy sweetpotato. The peak visco and breakdown et al. of root tuber flour were higher, and the pasting temperature of root tuber flour was lower in edible sweetpotato than in starchy sweetpotato. The eating quality of root tuber was better in edible sweetpotato than in starchy sweetpotato. The total starch content and the β-amylase activity were decreased, the total soluble sugar was increased 100 days after planting in edible sweetpotato, the direction of changes were in opposite to starchy sweetpotato. [ Conclusion ] In short, the important reason that the total starch content was lower, and the total soluble sugar content was higher in root tuber of edible sweetpotato than in root tuber of starchy sweetpotato was that the starch was decomposed with the action of the amylase during the later-stage of root tuber development in edible sweetpotato.