Determination of a suitable thin layer drying curve model for saffron (Crocus sativus L) stigmas in an infrared dryer

Abstract

The drying of saffron stigma was investigated in a laboratory infrared dryer. The effect of temperature on the drying rate of samples at various temperatures (60,70…110 °C) was studied. The drying time decreased with an increase in drying air temperature. The constant-rate period is absent from the drying curve. The drying of saffron occurred in the falling rate period. Four, thin-layer drying models, namely, Lewis, Handerson and Pabis, Page, and Midilli and Kucuk, were fitted to drying data. The performance of these models was investigated by comparing the determination of coefficient (R2) and Root Mean Square Error (RMSE) between the observed and predicted moisture ratios. Among these models, in each of six drying temperatures, the Midilli and Kucuk model gave the best results and showed good agreement with the experimental data obtained from the experiments, including the thin layer drying process. In all drying temperatures, the amounts of R2 were higher than 0.999, and the amounts of RMSE were less than 0.012. According to results, it can be said that the Midilli and Kucuk model adequately described the drying behavior of saffron stigmas at a controlled temperature range 60–110 °C in an infrared dryer.