A new allomorph distribution of C-type starch from root tuber of Apios fortunei

Starch was isolated from root tuber of Apios fortunei. Its morphology, thermal properties, and crystalline structure were investigated in this study. The results showed that the starch had spherical, polygonal, and ellipsoidal granule shapes with central hila, showed two separate gelatinization peaks, and exhibited C-type crystallinity. Hot stage microscope observation showed that starch could be divided into two groups of granules with low and high gelatinization temperatures, and the Group 1 and 2 granules accounted for 45.5% and 54.5% of the total granule number, respectively. The gelatinization peak temperatures of Group 1 and 2 starch granules changed from 68.3 to 66.6 degrees C and from 75.4 to 82.7 degrees C with the increase of KCl concentration in water from 0 to 2 M. The Group 2 starch granules were further separated from starch through gelatinizing Group 1 granules at 78 degrees C in 2 M KCl, and displayed intact granular shape, A-type crystallinity, and single gelatinization peak. The Group 1 and 2 starch granules corresponded to B- and A-type starches, respectively, but had no differences in morphology, size, and amylose content. The above results showed that the A- and B-type allomorphs of C-type starch from A. fortunei were distributed in the different starch granules. (C) 2015 Elsevier Ltd. All rights reserved.