Towards more rational techniques for the isolation of valuable essential oils from plants

Attention is drawn to the use of new and clean alternative methods for the isolation of essential oils from plants. A critical overview is presented o f conventional methods (based on either organic solvent extraction or disti llation) and new alternatives (including microwave-assisted extraction (MAE ) as well as supercritical CO2 (SC-CO2) extraction and subcritical water ex traction), The advantages and disadvantages of each technique are reported and special emphasis is given to the use of continuous subcritical water ex traction which emerges as clearly advantageous over conventional techniques (by avoiding the use of organic solvents and considerably shortening the e xtraction time, as well as increasing the efficiency) and recent techniques , such as MAE (by increasing the efficiency) and SC-CO2 extraction (by avoi ding the co-extraction of cuticular waxes and lipids and the need for a sam ple drying stage prior to extraction). (C) 1999 Published by Elsevier Scien ce B.V. All rights reserved.