Effects of Hot Air Drying and Vacuum Drying on Thin-Layer Drying Kinetics and Quality Changes of Essential Oil of the Fruits of Evodia rutaecarpa (Juss.) Benth

In the present study, thin-layer drying has been applied to improve drying efficiency and perfume production from E. rutaecarpa. Thus, the effects of the drying kinetics and temperature on the quality of E. rutaecarpa for essential oil production were studied. Seven kinds of mathematical models, such as Midilli et al., Overhults et al. and Lewis et al., were applied to model and verify the relationship between moisture ratio and time in the drying process. The Midilli et al. model could simulate the drying process very well. The essential oils obtained before and after different drying process were extracted via steam distillation, and the extracted essential oil components were identified with GC-MS. The moisture diffusion of E. rutaecarpa under hot air drying and vacuum drying at 35 degrees C, 45 degrees C and 55 degrees C are 8.39x10(-9), 1.07x10(-8), 1.37x10(-8), and 1.02x10(-8), 1.16x10(-8), 1.19x10(-8), respectively, and the activation energy is 20.51 kJ/mol and 6.63 kJ/mol. Based on the quality of the essential oil of the E. rutaecarpa leaves obtained at different temperatures, the proposed approximate drying temperature of E. rutaecarpa for application was 45-55 degrees C. During the drying process, the moisture of E. rutaecarpa in this temperature range may drop below the safe moisture within 7-5.5 h for storage with 12.1-9.7 % essential oil loss. This study showed the oil quality and quantity of the essential oil of E. rutaecarpa as well as the fresh sample in different drying methods and drying temperatures were compared, while the drying quality of E. rutaecarpa was further compared.