Physicochemical Properties of Root Starches from New Types of Sweetpotato

Abstract

Physicochemical properties of root starches from new types of sweetpotatoes [low amylose variety, Kyukei 89376-12 (K89376-12) ; high sweet variety, Kyushu No. 127 (K127) ; Okinawa variety, Miyano No. 36 (M36)] showing distinct root properties after cooking were determined . The structural properties of K89376-12 starch were similar to those of Koganesengan starch except for the amylose content. The result suggests that a difference in the pasting properties between the two starches was attributable to the difference in their amylose contents. On the other hand, the starches from K127 and M36 showed low pasting temperature and large viscosity on cooling, and also high digestibility by a crude glucoamylase. In terms of the apparent amylose content or chain-length distribution of the debranched whole starch, M36 starch showed an ordinary amylose content . M36 amylopectin, how ever, was found to have a large amount of long chains overlapping with the amylose fraction; thus, a low amylose character of M36 starch was revealed. Furthermore, high-performance anion-exchange chromatography revealed that the amylopectins of K127 and M36 were rich in short chains with DP 6- 11. Thus, it was found that the new types of sweetpotatoes possess the respective characteristic starches.