Effects of Curing, Constant-Temperature Storage, and Baking on Sweet Potato Sweetness

Abstract

　In this study, changes in the amount of sweetness components in four varieties of commercially available sweet potatoes (Ipomoea batatas L.) were measured after curing, constant-temperature storage, and baking. The relationship between the amount of sweetness components after baking and the degree of sweetness was then examined. The following results were obtained:(1) The total amount of sweetness components after curing treatment increased by 1.13-1.91-fold in all four sweet potato varieties relative to the control. The amount of sucrose increased significantly in "Beniazuma" and "Himeayaka". The amounts of sucrose also increased in "Beniharuka" and "Quick Sweet", but no significant difference was observed. The amount of glucose increased significantly only in "Beniharuka". (2) The total amount of sweetness components after constant-temperature storage increased by 1.20-fold in "Beniazuma" and 1.36-fold in "Beniharuka" relative to the control. By contrast, no change in the glucose contents of "Himeayaka" and "Quick Sweet" were noted. The increase in the amount of sucrose did not differ significantly among all four varieties. However, the amount of sucrose significantly increased in all four varieties after constant-temperature storage relative to the control. (3) The total amount of sweetness components in "Yakiimo" after baking was 15.44-19.33 g / 100 g FW. The amount of maltose, which is the main sweetening ingredient of sweet potato, was 10.47-14.56 g. The degree of sweetness relative to the total amount of sweet ingredients was as follows : "Beniharuka"＝9.8, "Beniazuma"＝9.5, "Himeayaka"＝9.1, and "Quick Sweet"＝8.1. Maltose contributed 46%-57% of the total sweetness components, while sucrose contributed 40%-46%. Therefore, sucrose, similar to maltose, is an important sweetening ingredient in "Yakiimo".