Kinetics and mathematical modeling of thin layer drying of osmo-treated aloe vera (aloe barbadensis) gel slices

Abstract

In the present work, the drying kinetics of osmo-pretreated Aloe vera gel slices (AVGS) was investigated. AVGS with an initial moisture content of 98.29% (wet basis) were subjected to 5 hr of osmosis process (10% NaCl solution, at 40 degrees C, NaCl solution to A. vera ratio = 5:1), prior to atmospheric thin layer drying at air temperatures of 55, 70, and 85 degrees C and air volumetric air flow rates of 0.015, 0.036, and 0.054 m(3)/s for the duration of 160 min. Results showed the mean values of the moisture ratio in air temperatures of 55, 70, and 85 degrees C were categorized into three levels (p < .01) of 0.551, 0.429, and 0.336, respectively, while the corresponding values for the osmo-convective method were 0.561, 0.418, and 0.321, respectively. Similarly, the mean values of the moisture ratio in air flow rates of 0.015, 0.036, and 0.054 m(3)/s for the convective and osmo-convective method assigned to different levels (p < .01) of 0.511, 0.417, 0.385 and 0.510, 0.416, 0.372, respectively. Superposition technique was utilized to propose a new model for each drying method. The predicted moisture ratios evaluated by the superposition technique were in a good agreement with experimental values of moisture ratio