Drying Kinetics of American Ginseng Slices in Thin-layer Air Impingement Dryer

Thin-layer air impingement drying kinetics of American ginseng slices were investigated under different drying temperatures (35, 40, 45, 50, 55, 60, and 65°C), air velocities (3, 6, 9, and 12 m/s), and sample thicknesses (1, 2, 3, and 4 mm). Results indicated that the drying time is more significantly affected by drying temperature followed by sample thickness and air velocity. Drying rate curves illustrated that the whole drying process happened in the falling rate period. Additionally, from initial drying to the moisture content of about 0.5 kg/kg, the drying rate increased with the increase of drying temperature and air velocity or decreased with the increase of sample thickness. The moisture effective diffusivity (D eff) was determined both neglecting shrinkage and considering shrinkage. The drying activation energy of American ginseng slices was 46.64 kJ/mol determined by Arrhenius relationship. The moisture effective diffusivity and drying activation energy of American ginseng slices were compared to other biomaterials and related issues were also discussed. The current work is useful for designing air impingement drying system, evaluating and saving energy consumption of American ginseng slices.