Effects of heat-moisture treatment on the multiscale structure and digestibility of sweet potato starch

The effects of water content on the multi-scale structure and digestibility of sweet potato starch (SPS) during heat-moisture treatment (HMT) were studied, and the relationship between water content, starch structure and starch digestibility was analysed. The results showed that the surface of SPS granules changed after HMT, mainly in the form of depression, rupture and adhesion, and the change was more obvious with the increase of water content, and the crystalline structure changed from the original A-type to A + V-type. The relative crystallinity and double helix content decreased, the thickness of semi-crystalline layered structure increased, and the peak intensity decreased. The molecular weight of SPS after HMT tended to be distributed in the low molecular weight range of 4 x 10(4) g mol(-1) < M-w <4 x 10(5) g mol(-1). These structural changes promoted the rearrangement of the intermolecular structure of SPS, which made amylase shield the original action site when acting on SPS, and converted part of rapidly digestible starch (RDS) content into slow digestible starch (SDS) and resistant starch (RS) content, resulting in the increase of SDS and RS content. Especially in HMT-25, the RS content of SPS was the highest, which was 28.60%. The experimental data can provide theoretical support for broadening the application of SPS.