Digestibility and pasting properties of rice starch heat-moisture treated at the meltin temperature (Tm)

Non-waxy and waxy rice starches adjusted to 20% moisture (wet based, w.b.) were heated in a differential scanning calorimeter to determine the optimum parameters for producing slowly digestible starch (SDS). Starches heated to the temperature of melting (T-m) and held for 60 min in the calorimeter showed a slow digestibility compared to unheated samples. Digestibility decreased by 25 and 10%, respectively, for non-waxy and waxy rice starches relative to non-treated starches. Heat-moisture treatment of waxy corn, non-waxy corn and wheat starches at the T-m determined for non-waxy rice starch did not result in significant decreases in digestibility. For waxy rice starches heat-treated in microwave or conventional ovens at the T-m, there were slight but significant increases in digestibility of the treated starches compared to non-treated starches at all incubation times. Digestibility was higher for starches heated for 30 min than for 60 min. Non-waxy rice starches did not show any significant changes in digestibility. Heat-moisture treatment at the T-m and the holding time of sample at that temperature in a differential scanning calorimeter were found to be significant to the formation of slowly digestible heat-moisture treated starch.