A unique model of gravity assisted solvent free microwave based extraction of essential oil from mentha leaves ensuring biorefinery of leftover waste biomass for extraction of nutraceuticals: Towards cleaner and greener technology

The rising discourse over concerns on climate change due to non environmental compatibility of traditional industrial processes have fuelled the development of digitized, high performing, ecofriendly technologies which are in tandem with environment In the context of extraction of essential oil, drawbacks of classical hydrodistillation such as thermal degradation, high energy consumption, time consuming, low yield have made way for more greener approach. The novelty in the proposed work lies in the development of a rapid, solvent free, gravity assisted microwave based extraction model. The model ensures complete bio-refinery of the residual biomass for extraction of other non-volatile principles with special emphasis to nutraceuticals. The developed working protocol is based on a novel approach of delivering a high power microwave surge concept. An initial high power microwave surge at 60% power level was applied for 2 min, followed by a surge at 40% power level for 2 min and finally followed by sustained microwave firing at 20% power level for 6 min. The above conditions resulted in extraction of 10 mL (dehydrated) of oil from 60 g fresh mentha leaves. The yield of oil was 5 times higher than conventional hydrodistillation method for 6 h. The results of extraction yield were found to be in tandem with the oil quality (volatile principles and biological activity). The biomass obtained after extraction of oil retained the phenolics, flavonoids and other nutraceutical principles thus making it suitable for re-extraction. (C) 2019 Elsevier Ltd. All rights reserved.