KINETIC STUDY OF HYDRATED RED RICE USING A NON-ISOTHERMAL METHOD

Abstract

The objective of this research was to evaluate through thermogravimetric analysis and its derivative (TG and DTG), the decomposition kinetics of the starch present on red paddy rice submitted to the hydration process at temperatures of 45°C, 55°C, 65° C and 75°C. The analysis of the experimental data of TG in the decomposition region was performed by obtaining the function g (α) for the kinetic mechanisms of the Coats – Redfern (CR) model called unidimensional contraction (R1 model), one-dimensional diffusion (D1 model), random nucleation and growth, Avrami Erofe’ve Equation (A2 model), Random nucleation and growth, Avrami Erofe’s Equation (A3 model) and First-order (random nucleation with one nucleus on the individual particle (F1 model). The results obtained show that in the kinetics of starch decomposition evaluated for red paddy rice, there was a loss of mass corresponding to 51.92- 57.07%, in the temperature range of thermal decomposition of starch of 240.16°C- 356.43°C. As well as the calculation of the function g (α) showed that the first-order kinetic model (F1 model) fitted well to the experimental data, with a coefficient of determination above 99%, confirming that the mechanism that described the decomposition of the starch present in hydrated red rice is of first-order (n=1). With pre-exponential factor (ln A) that reduced the values with increasing hydration temperature. Activation energy and enthalpy values were reduced through the hydration process from 45°C to 75°C.