Progressive alterations in crystalline structure of starches during heat-moisture treatment with varying iterations and holding times.
Corn, tapioca and potato starches after heat-moisture treatment (HMT) at 95-96 °C for 0-60 min with 1-6 iterations were characterized for their gelatinization properties to elucidate the HMT-generated differences in crystalline structure of the starches. The enthalpy changes (ΔH) of all HMT starches were decreased, and the decreases in ΔH of the whole and of the fraction corresponding to well-ordered region of crystalline structure were both in the order of corn < tapioca < potato. With increasing HMT iteration and holding time, the same order was also observed for the shifting extent of pasting properties of HMT starches to that of restricted-swelling granules. The findings demonstrate the crystalline structure of starch consists of less- and well-ordered regions, and suggest that the extent of intermingling of these regions might be in the order of corn < tapioca < potato starches.