Drying grain residual annatto by sun combined with drying in dryer with heat accumulator

Abstract

The process of extraction of the pigment bixin results in a large amount of residual grain annatto. Most of this material is discarded, but you can enjoy it by incorporating it into animal feed and human food. This study aimed to dry grain residual annatto using solar energy. The beans were divided into two batches, one with oil, reproducing conditions of the grains after extraction of bixin oil, and other oil-free. The drying was performed during the day in the concrete base covered with black polythene bag with samples in trays and exposed to the sun; overnight half of the samples was placed in a dryer to dry heat accumulator and the other half was in bench laboratory for control. The grains showed levels of initial and final moisture of about 18% wb and 5% wb, respectively. Use the dryer heat accumulator at night allowed the collection of samples with the moisture ratio below 0.1 in the evening of the first day of drying, while the control samples absorbed water during the night. All models studied showed good fit to experimental data, with values of determination coefficients above 0.95 and average values of the squared deviations of less than 0.1. The diffusivity coefficients were of the order of 10-9 m2 s-1 for all treatments, with the grain samples without oil showing the greatest value.