Enhanced extraction of wild mint (Mentha longifolia L.) leaf essential oil by ultrasound pre-treatment prior to hydrodistillation

Ultrasound pre-treatment (U) followed by conventional hydrodistillation (HD) was used to extract wild mint leaf essential oil in a short time with high quality compared with the HD. The effects of ultrasound power, ultrasound time, extraction time and essential oil yield were studied. The volatile oil constituents of the essential oil samples were analyzed by GC-MS. Extraction of essential oil with U+HD decreased total extraction time (< 1 h vs. 4 h in HD) with the same essential oil yield (5.4%). Scanning electron microscopy of mint leaves indicated the efficiency of U+HD in the eruption and destruction of oil glands. The oxygenated monoterpenes/monoterpene hydrocarbons (O/H) ratio, as a quality index for the distinct aroma of wild mint essential oil, and sensory analysis indicated the superior quality of the samples obtained by U at 60 W power for 10 min followed by HD for 33 min. These results suggest that ultrasound assisted extraction is an appropriate pretreatment techniqueprior to HD for the extraction of high-quality wild mint essential oil in minutes. The effect of direct incorporation of the investigated essential oil into olive oil on its sensory attributes and oxidative stability was studied