Removal of the out-shell for lotus root starch improved the effect of heat-moisture modification on multi-structure, physicochemical and digestibility properties

In this paper, the surface gelatinization method was used to remove the outer shell of lotus root starch granules, and then it was treated with heat-moist treatment (HMT). The results showed that the gelatinization pattern was gradually gelatinized towards the umbilical point and formed a transparent gelatinization layer. The integrity of the granules was maintained, but the surface of lotus root starch became rough and appeared as holes. Heat-moist treatment significantly increases the gelatinization temperature and solubility. Removing the starch shell was more conducive to the interactions between starch and water molecules. Under the same conditions of heat-moist treatment, compared with the ungelatinized starch, the proportion of A chains and peak viscosity was significantly lower. At the same time, crystallinity, solubility and digestibility were significantly higher. The intermolecular cross-linking during the treatment led to an increase and then a decrease in the 1047/1022 cm−1 ratio and a more stable molecule structure. These results may provide new insight into the structural arrangement within starch granules and expand the application of heat-moist treatment. [Display omitted] •Heat-moist and dehulling treatment maintained starch's growth rings and crystal type.•The gelatinization pattern was gradually gelatinized towards the umbilical point.•The dehulling treatment facilitated the interaction between starch and water molecules.•The resistant starch content varied depending on treatment conditions.•Heat-moist treatment after dehulling was more favorable for starch solubility.