Effects of Electrolyte Concentration and Ultrasound Pretreatment on Ohmic-Assisted Hydrodistillation of Essential Oils from Mentha piperita L.

In this study, the effects of salt concentration (1, 3 and 6% w/v) and ultrasound pretreatment (50 W for 5, 10 and 15 minutes) on extraction parameters and extracted essential oil from peppermint by ohmic-assisted hydrodistillation (OAHD), a recently innovated extraction technique, have been studied. The results showed that salt concentration significantly affected the extraction parameters of OAHD, while ultrasound pretreatment had negligible effect. Sudden eruption of essential oil glands was observed in scanning electron micrographs of all OAHDs mint leaves. GC-MS analysis did not indicate any noticeable change in the compounds of all the extracted essential oils. The results of this study showed that increase of electrolyte concentration could speed up OAHD process without any adverse effect on essential oil quality, while ultrasound pretreatment neither reduced process time nor increased extraction yield of OAHD.