The structure and digestibility of sequential enzyme modified starch from Coix lachryma-jobi L

Sequential enzyme modification is a new method of starch modification. In this study, sequential enzyme (α-amylase (AA), β-amylase (BA), transglucosidase (TG) and pullulanase (Pull)) modification method was used to modify Coix lachryma-jobi L. starch, and the effects of TG treatment time on the physicochemical properties of starch were investigated. The results indicate that the morphology of sequentially enzyme-modified starch granules was altered, showing fissures, indentations on the granule surface, hollow regions, or fragmented structures. Compared with native starch, the amylose content, solubility, expansion potential and transparency increased, the relative crystallinity of Pull-S and TG-0 h starch decreased. With the extension of TG modification time, the relative crystallinity of starch granules, slow-digestible starch (SDS) content and peak gelatinization temperature (Tp) first increased and then decreased, while resistant starch (RS) first decreased and then increased. TG 12 h, RS content (40.65 %) was the lowest and SDS content (55.93 %) was the highest. Despite these changes, the difference in chain length distribution between native starch and enzyme-modified starch was comparable.