Integration of microwave assisted pretreatment for ameliorating the extraction of lemongrass essential oil by steam distillation and follow up with phenolic extraction: Improvising traditional processes through a green approach

Abstract

This article revolves around pioneering the use of microwave as a contact less one step biomass pretreatment process designed to improve the performance of traditional steam distillation both in terms of yield and oil quality. Pretreatment was performed by exposing the fresh biomass to three different power levels (170 W, 425vW and 765vW). Pretreatment at 425 W for 10 min followed by SD successfully reduced the SD time by 50 % and the yield of lemongrass essential oil was found to increase by 2.7 times when compared to non-pretreated control. The Oil obtained through such biomass pretreatment was also found to be 12.3 % richer in citral content with increased presence of isoeugenol, eucalyptol, caryophyllene and limonene. Thermogravimetric analysis and antioxidant activity check for the oil obtained from pretreated biomass was performed and compared to control to ascertain that microwaves did not have any detrimental effect on the chemical and biological property of the oil. Mechanism behind accelerated extraction was explained with the support of micrographs obtained from scanning electron microscopy. The biomass (which had undergone pretreatment) remaining after essential oil extraction was found suitable for reuse and it yielded 6.9 % more phenolic content when compared to non-pretreated control. The costing of per g oil production from SD was found to be Rs. 31.5 whereas for SD with pretreated sample it was Rs. 6.0 per g of oil. Thus a simple innovation can bring huge relief to small scale producers dependent on traditional distillation.