Figure 14. Mechanism of microwave extraction of essential oils based on dielectric heating [22].
Advances in the microwave extraction method led to the development of other methods of microwave extraction. Including: microwave assisted solvent extraction [91], vacuum microwave hydro-distillation [92] microwave hydro-distillation [93], solvent-free microwave extraction [94], microwave accelerated steam distillation [95], microwave hydro-diffusion and gravity (MHG) [36] and microwave-assisted simultaneous distillation-solvent extraction [96]. Figure 15 gives a schematic description of microwave assisted extraction methods [20]. Extraction essential oil by microwave steam diffusion (MSDF) is performed. 125 g raw material (lavandin) soaked in water during 10 min, 500 W, t:15 min, and the yield was obtained 5.4% [27]. Essential oil of citrus sinensis L. with 5.43% yield was obtained by microwave steam distillation (MSD) [97].