mathematical modeling for the annatto (bixa orellana l.) seed drying process

The pigment extraction process using annatto (Bixa orellana L.) seed produces a large amount of seed waste. Although most of these seeds are discarded, a number of studies report promising results with their use in animal feed. The good fiber content also suggests human nutrition applications, with possible incorporation in dietary foods. In the present study, annatto seeds derived from color extraction were dried, with and without the layer of oil left over from the process. Seeds were dried at 40, 50, 60 and 70 °C. Drying data were fitted to the Diffusion Approximation, Two Term, Midilli, Page and Thompson models. Drying was carried out up to a moisture content of approximately 5% wet basis. All the models studied exhibited adequate fit to the drying kinetics data of the annatto seeds, with coefficients of determination above 0.98 and root mean squared error (RMSE) below 1.0. Seeds with oil had longer drying times at 40 and 50 °C and shorter times at 60 and 70 °C. The coefficients of diffusion showed values between 2.67 x 10-11 and 9.50 x 10-11 m² s-1 and between 2.7 x 10-11 and 6.21 x 10-11 m² s-1, while activation energies for liquid diffusions were 38.04 and 23.52 kJ mol-1, for residual seed drying with and without oil, respectively.