Enzymatically modified starch with low digestibility produced from amylopectin by sequential amylosucrase and pullulanase treatments

Enzymatically modified starch with controllable digestibility may find unique applications. In the present study, side chains of amylopectin were elongated by amylosucrase, followed by debranching with pullulanase to produce linear chains that self-assembled to form microparticles containing aggregated nanoparticles. Amylosucrase treatment for a longer time resulted in longer branches that were not changed after the subsequent modification by pullulanase. The A-type crystalline structure of native amylopectin was changed to the B-type and the percentage of crystallinity progressively increased after amylosucrase and subsequent pullulanase treatments. Elongation of branch chains favored the formation of thermal stable double helices, which decreased the contents of slowly digestible and rapidly digestible starches and increased the content of resistant starch from 9.1% of native amylopectin to be as much as 67.2% of microparticles. This study may provide an efficient and environmentally benign technology to produce modified starch with controllable physical and digestion properties enabling novel applications.