Microwave ‘dry’ distillation as an useful tool for extraction of edible essential oils

Abstract

Microwave “Dry” Distillation or microwave accelerated distillation (MAD) is proposed as a method for “green” extraction of edible essential oils extensively used in the fragrance, flavour, and pharmaceutical industries and also in aromatherapy. It is a combination of microwave heating and dry distillation, performed at atmospheric pressure without adding any solvent or water. Isolation and concentration of volatile compounds is performed by a single stage. Rosemary was extracted with MAD at atmospheric pressure and 100 °C for 30 min. The extracted compounds were removed from the aqueous extract by simple decantation, determined by gas chromatography-flame ionisation (GC-FID) and identified by gas chromatography–mass spectrometry (GC/MS). Hydrodistillation of rosemary was performed with 2 L of water for 3 h for comparison of the results with those provided by the proposed method: extraction time, yields, chemical composition and quality of the essential oil, efficiency and costs of the process. Extraction of essential oils from rosemary with MAD was better in terms of energy saving, extraction time (30 min versus 3 h), oxygenated fraction (59% versus 46%), exact product yield (0.6% versus 0.6%) and product quality. MAD is a green technology and appears as a good alternative for the extraction of edible essential oils from aromatic plants used in aromatherapy and the food industry.