Impact of annealing on the hierarchical structure and physicochemical properties of waxy starches of different botanical origins

The effect of annealing on structure and physicochemical properties of four different waxy starches were investigated to understand the mechanism of annealing in the absence of amylose. Granule morphology, X-ray pattern, molecular order, and gelatinization enthalpy remained unchanged upon annealing. Relative crystallinity of waxy corn starch increased from 42.4 to 46.1% on annealing, while it remained unchanged in other starches. Annealing increased the gelatinization temperatures, while it decreased the temperature range. Waxy potato starch showed the highest increase in T_o, where it was 8.1 °C after 72 h of annealing. Viscosity profiles were only slightly affected by the annealing treatment. Susceptibility towards amylolysis increased in waxy corn and waxy barley, while it decreased in waxy potato and waxy rice. This study demonstrated that even in the absence of amylose, annealing caused changes in the structure and properties, however, the extents of these changes varied depending on the botanical origin.