Solvent-free microwave extraction of essential oil from oregano
Applicability of solvent-free microwave extraction (SFME) in the extraction of essential oil from Origanum vulgare L. was examined and the effects of microwave power and extraction time on the yield and composition of the product were investigated. Specific gravity and refractive index of the essential oil and its solubility in alcohol were also examined. Hydrodistillation was performed as control. GC–MS/FID was used for the determination and quantification of aroma compounds in the essential oils. SFME offered significantly higher essential oil yields (0.054 mL/g) as compared to hydrodistillation (0.048 mL/g). When 622 W microwave power was used in SFME, conventional process time was reduced by 80%. The main aroma compound of oregano essential oil was found to be thymol (650–750 mg/mL). No significant differences were obtained in the compositions and physical properties of oregano essential oils obtained by SFME and hydrodistillation.