It is well known that essential oils can be extracted from plants by steam distillation. This includes commonly encountered fragrant oils from pine, eucalyptus and lavender, as well as more exotic examples like lemongrass, parsley, mint, etc. Most of these oils tend to contain one major ingredient that makes up 70% or more of the mixture.
Major ingredients in essential oils
I recently had a discussion with one of my associates where we postulated that microwaving the leaves would make the distillation occur quicker and with less energy. I did a literature search later that day and found that microwave extraction of essential oils has been published. A group of Hungarian researchers in 1986 described extracting oils from a variety of plants into methanol, methanol/water and hexane [1]. In 2005 a Malaysian group described their process for microwave assisted extraction of eucalyptus oil into ethanol [2]. In 2015 a group from India described a similar extraction of lemongrass oil into water [3].
Microwave extraction kit sold by OilExTech Microwave ‘dry’ distillation (without a solvent) has also been described in the Journal of Chromatography A in 2004 [4] and in the International Journal of Aromatherapy in 2006 [5]. More recently this process has been capitalized upon by OilExTech, who now sell a home microwave distillation kit for $150 that can be used to extract essential oils from plants and herbs grown in home gardens. Their product has been demonstrated on YouTube using lavender and orange rind.
Cleaning spray product from the Australian Eucalyptus Oil Company I recently encountered the owner of 'The Australian eucalyptus oil company' at a Trash'n'treasure market. As well as the oil itself they also sell laundry power laced with their oil and a spray and wipe product, which is 85% methylated spirits:15% eucalyptus oil (I purchased this product, see left).
I asked the gentleman what batch size they use and how they distill their oil. He said that they collect the offshoots from eucalypt stumps and then carry out a steam distillation on about 100 Kg of plant matter to get about 1 Kg of essential oil. It was claimed that they have been using this same process on Blue Mallee eucalyptus in Arnold, Victoria since 1895.
It will take some time but eventually, microwave systems will be used to extract most essential oils.
I asked the gentleman what batch size they use and how they distill their oil. He said that they collect the offshoots from eucalypt stumps and then carry out a steam distillation on about 100 Kg of plant matter to get about 1 Kg of essential oil. It was claimed that they have been using this same process on Blue Mallee eucalyptus in Arnold, Victoria since 1895.
It will take some time but eventually, microwave systems will be used to extract most essential oils.
References:
- K. Ganzler, A. Salgó and K Valkó. Microwave extraction. A novel sample preparation method for chromatography. Journal of chromatography, vol 371, p299–306, 1986.
- A.A. Saoud, R.M. Yunus, R.A. Aziz and A.R. Rahmat. Study of Eucalyptus Essential Oil Acquired by Microwave Extraction. Proc. WOCMAP III, Vol. 5: Quality, Efficacy, Safety, Processing & Trade in MAPs, 2005.
- M. A. Desai and J. Parikh. Extraction of essential oil from leaves of lemongrass using microwave radiation: Optimization, comparative, kinetic, and biological studies. ACS sustainable chemistry & engineering, DOI: 10.1021/sc500562a, published online Jan 2015.
- M. E. Lucchesi, F. Chemat and J. Smadja. Solvent‑free microwave extraction of essential oil from aromatic herbs: comparison with conventional hydro‑distillation. Journal of Chromatography A, vol 1043, issue 2, p323–327, 2004.
- N. Tigrine-Kordjania, B.Y. Meklatib and F. Chematc. Microwave ‘dry’ distillation as an useful tool for extraction of edible essential oils. International Journal of Aromatherapy, vol 16, issues 3–4, p141–147, 2006.