Effect of Temperature and Reaction Time on the Swelling Power and Solubility of Gadung (Dioscorea hispidaDennst ) Tuber Starch during Heat Moisture Treatment Process

The starch from Gadung (Dioscorea hispida Dennst) has been underutilized in food and industrial applications due to its instability under harsh processing conditions, especially with high temperature. Gadung starch has a low setback viscosity, retrogrades less and therefore unable to form strong gels. Heat moisture treatment (HMT) may be one of alternatives to improve thermal stability and result in unique properties desired by various end users. In this research, Gadung starch was modified using hydrothermal treatment employing moisture content (MC) of 16 g water/100 g starch (wb) at various temperature (80, 90, 100 and 110°C) and reaction times (2, 4, 6, 8, 10, 12 and 16 h). In general, an increase in temperature from 80 °C up to 100 °C and time during HMT caused a decrease in swelling power (SP) and water solubility (WS) of the starch. However, unique phenomena were observed when the HMT of the starch was carried out at 110 °C as the swelling power and water solubility of the starch were higher than that obtained from HMT at 100 °C. Under this condition, both swelling power and water solubility of the starch increased when HMT was conducted from 2 up to 6 hours. Beyond 6 hours, the swelling power and water solubility of the starch gradually decreased.