Modelling and Optimization of Drying Variables in Desiccant Air Drying of Aloe vera (Aloe barbadensis Miller) Gel

Abstract

Desiccant air drying characteristics of Aloe vera (Aloe barbadensis Miller) gel were investigated at temperature range of 40 to 70°C, relative humidity range of 15 to 30% and air velocity range of 0.5 to 2.0 m/s. The drying time varied from 330 to 900 minutes. The specific energy consumption during drying was found in the range of 201.60 to 415.17 MJ/kg. The diffusivity coefficient increased with the temperature from 4.93 to 16.38 x 10-10 m2/s. Aloin, a major anthroquinone responsible for therapeutic properties was quantified by High Performance Liquid Chromatography (HPLC) and found within acceptable limits for applications in foods. Response surface methodology (RSM) was applied to optimize the desiccant air drying process to produce best quality Aloe vera gel powder. The optimized process parameters were temperature 64°C, relative humidity 18% and air velocity 0.8 m/s. Three mathematical models namely, Newton, Page and Henderson-Pabis models were evaluated in the kinetics research. The fit quality of the proposed models was evaluated by using the linear regression coefficient (r2), sum square error (SSE), root mean square error (RMSE) and Chi-square statistic (). The drying behaviour of Aloe vera gel was well predicted by Page model within the limits of the experiment.