The impact of heat-moisture treatment on the molecular structure and physicochemical properties of normal and waxy potato starches

Normal and waxy potato starches were heat-moisture treated (HMT) at 100°C for 16h at a moisture content of 24%. Starch chain interactions, X-ray pattern and intensities, crystallite orientation, molecular order and polymorphic composition changed on HMT. However, birefringence intensity and amylopectin chain length remained unaltered in both starches on HMT. The above structural changes on HMT increased gelatinization temperatures widened the gelatinization temperature range and increased thermal stability in both starches. However, HMT decreased granular swelling, extent of amylose leaching, iodine complexing ability, peak viscosity, extent of set-back, enthalpy of gelatinization, acid susceptibility and the steepness of the adsorption isotherm in both normal and waxy starches. The extent of changes to starch structure and properties on HMT was different in normal and waxy starches due to differences in their amylose content and amylopectin chain mobility.