Improving resistance of crystallized starch by narrowing molecular weight distribution

Crystallized debranched waxy rice starch had higher resistant starch (RS) content and crystallinity than crystallized debranched normal rice starch. Thus, debranched waxy rice starch (Unf) with molecular-weight dispersity (DM) at 2.161 was fractionated into F1, F2 and F3 with the DM at 1.604, 1.466 and 1.658, respectively. Moreover, the peak molecular weight of Unf, F1, F2 and F3 was 3.146e + 03, 2.906e + 03, 3.585e + 03, and 4.178e + 03 Da, respectively. Obviously, Unf had higher molecular weight but wider distribution than F1. After crystallization, Unf and F1 had similar RS content and crystallinity. Similar phenomenon occurred to F2 and F3. These results suggested that narrowing molecular weight distribution promoted crystallization of starch and improved its resistance. To further improve efficiency of preparing RS by crystallization, crystallization of F3 was optimized. Under the optimal conditions, the yield and RS content of crystallized F3 reached 81.2% and 80.6%, respectively.