Structure and functional properties of taro starch modified by dry heat treatment.

ABSTRACT

Taro starch (TS) was modified by dry heat treatment (DHT) for different periods (1, 3, 5, and 7 h at 130 °C) and temperatures (90, 110, 130, and 150 °C for 5 h) to expand its applications in food and other industries. The structure and functional properties of DHT-modified TS were characterized. It was found that TS granules became agglomerated after DHT, and the particle size, amylose content, solubility, and retrogradation enthalpy change of TS increased with increasing dry heating time and temperature, whereas the relative crystallinity, molecular weight, swelling power, gelatinization temperature, and enthalpy change decreased. The absorbance ratio of 1047 cm-1/1022 cm-1 for DHT-modified TS (except at 7 h) was higher than that of native TS. DHT increased the contact angle of TS in a time- and temperature-dependent manner. At a moderate strength, DHT increased the pasting viscosity, relative setback value, and storage modulus but decreased the relative breakdown value. Moreover, DHT (except at 150 °C) caused a decrease in the rapid digestive starch content and estimated glycemic index of TS. These results suggested that DHT-modified TS could be used in foods with high viscosity requirements, gel foods, and low-glycemic index starch-based foods.