CONVECTIVE HOT AIR DRYING KINETICS OF RED BEETROOT IN THIN LAYERS

The effect of air temperature on drying kinetics of red beetroot slices was investigated experimentally in a cabinet tray dryer. Drying was carried out at 70, 75, 80, and 85 °C with an air velocity 2 m/s and relative humidity 30 %. The drying data thus obtained were analyzed to get effective diffusivity values by applying the Fick’s diffusion model. Effective diffusivity increased with increasing temperature. An Arrhenius relation with an activation energy value of 35.59 kJ/mol expressed the effect of temperature on the diffusivity. Also, within the given operating range, the average heat transfer coefficient at the air-product interface is estimated. Experimental data were fitted to ten mathematical models available in the literature. The Midilli et al. and Wang & Singh models are given better prediction than the other models and satisfactorily described drying characteristics of red beetroot slices.