Gelatinization kinetics of amaranth starch

The influence of the water:starch ratio and heating rate on the gelatinization of amaranth starch was investigated using differential scanning calorimetry. Onset and peak temperatures did not vary significantly with increase of water content, whereas the completion temperature decreased by more than 14 degreesC when the water content was in excess. A linear relationship was found between moisture content and gelatinization enthalpy for water:starch ratios between 0.81:1 and 2.1. From this relationship the minimum level of water necessary to initiate gelatinization was calculated. For water::starch ratios over 3:1, the enthalpy of gelatinization reached a maximum value. More rapid heating resulted in an increase of the peak and completion temperatures, as well as the gelatinization energy. Heating rates above 10 degreesC min(-1) gave the maximum energy requirements for the completion of gelatinization in an excess of water. The kinetics of gelatinization of amaranth starch was analysed from the DSC traces. A simple mathematical model was tested to evaluate the kinetic parameters. It was shown that in an excess of water and for heating rates above 10 degreesC min(-1), gelatinization followed first-order kinetics with n varying from 0.91 to 0.93. The activation energy was in the range of 157-185 kJ mol(-1). However, the present analysis did not allow for the determination of the kinetic parameter values over the whole gelatinization range.