Thin layer drying kinetics of lemon verbena leaves: A quality assessment and mathematical modeling

The thin-layer drying kinetics of lemon verbena leaves were studied by using a solar cabinet dryer at air temperature (at three levels of 30, 40, and 50 degrees C), air velocity (at three levels of 2, 2.5, and 3 m/s), and mesh tray size (3, 6, and 10 mm). A completely randomized factorial design was used to analyze the effect of independent factors on drying time and essential oil yield. Results showed that all experiments have shorter drying time and higher essential oil content than the shade-drying method. Also, the best drying conditions that led to an optimal essential oil yield (1.73 mL/g DM) involved a lower temperature (30 degrees C) and velocity (2 m/s) and a mesh size of 10 mm. A good adaptation between the experimental and the predicted moisture content was observed, whereby the statistical criteria of R-2, root mean square error, and le were calculated as 0.99, 0.08, and 0.01, respectively.