Kinetics of Phase Transition of Native, Cross‐linked, and Hydroxypropylated Rice Starches

Kinetics of the phase transition of native and chemically modified rice starches have been investigated by using differential scanning calorimetry (DSC) after isothermal treatment. At the experimental conditions, the phase transition of these starches followed pseudo‐first order kinetics. The kinetic order was not affected by the two chemical modifications used, hydroxypropylation and cross‐linking, while the rate constants were altered. From the Arrhenius plot, peak temperature (Tp) from DSC thermogram appeared to be the turning point for the two steps, swelling and disruption/dissolution, associated in the phase transition of starch granules. When the temperature was below Tp high activation energy was obtained and fell in the range of 61 to 75kcal/mol. Once the temperature was above Tp, the activation energy dropped to be in the range of 10 to 30kcal/mol and the starch became less temperature sensitive.