Essential oils are volatile essences extracted from aromatic plants. Among all the species found in the plant kingdom, only 4,000 contain aromatic essences. However, only a few hundred contain enough for us to extract essential oils with a significant yield. Essential oils are complex mixtures combining different compounds (terpenes, alcohols, ketones, aldehydes) that provide numerous benefits, whether ingested, inhaled, or applied topically. Let's explore together the different methods of extracting essential oils.
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How are essential oils obtained?
Summary
- Steam distillation or the process of obtaining an essential oil is the most common method
- Mechanical pressure, the method of obtaining citrus essences
- Solvent extraction, a process often considered environmentally unfriendly
- Supercritical CO2 extraction, a modern and eco-friendly method
- Sources
Published April 11, 2022,
updated on October 2, 2024,
by
Maylis, Chemical Engineer
—
4 min read
Steam distillation or the process of obtaining an essential oil is the most common method.
Even though there are several methods of extracting essential oils from aromatic plants, the low-pressure steam distillation is the most common technique used to extract essential oils from plants. Invented in the 11th century, it involves several steps.
The water is brought to a boil within aboilerto capture the steam produced.
The plant material to be distilled (flowers, leaves, roots, seeds...) is placed in a copper or stainless steel container known as a still.
Under low pressure, steam is sent into the still and passes through the plant material to be distilled. This causes the aromatic sacs of the plant to burst and isolates the compounds.
Aromatic molecules are driven up the distiller by steam until they reach the swan neck. This steam, laden with essence, passes through a conduit called a coil which is immersed in a bath of cold water.
The steam cools and condenses back into a liquid state, which is collected in adecantation vessel, also known as a Florentine flask or essencier. Floating on the surface of the collected liquid is theessential oil, which is lighter than the water used for its extraction, and is none other than thehydrosol.
Note: Thehydrodistillation process is almost similar with one difference: initially, the plant material and water are not separated but heated together, directly in the same container (still).
Mechanical pressure, the method of obtaining citrus essences.
This refers to the simplest method of obtaining an essential oil. It simply involves a cold mechanical pressure to manually burst the aroma sacs. The essence and water are then simply separated by a cold decantation. This process is primarily used to extract essential oils from citrus fruits such as lemon, the yellow mandarin and green, lime, bergamot, or orange.
Solvent extraction, a process often considered environmentally unfriendly.
This technique is particularly prevalent in perfumery as it allows for the extraction of compounds with a very pronounced scent. It involves mixing plant material with a solvent in a tank and heating the mixture. The solvents can range in their environmental impact (petroleum ether, methanol, ethanol, hexane...). This extraction technique is somewhat controversial due to its lack of environmental friendliness. Moreover, traces of the solvent can potentially be found in the resulting substance.
Supercritical CO2 extraction, a modern and eco-friendly method.
Even though this extraction method is very costly, it provides essential oils of very high quality (biochemical composition almost similar to the original essence of the plant). The principle is simple: the plant material is traversed by a flow of carbon dioxide (CO2) which increases the pressure and allows the aromatic sacs to "naturally" burst.
In addition to being clean and cost-effective, one of the added values of this technique is that the essential oil recovered can retain its designation as"organic"in future skincare products.
Sources
Zarith Asyikin Abdul Aziz & others, Essential Oils: Extraction Techniques, Pharmaceutical And Therapeutic Potential - A Review, Current Drug Metabolism, (2018).
Hesham H. A. & al., Techniques for Extracting Essential Oils from Plants: A Review, Australian Journal of Basic and Applied Sciences, (2016).
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