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].