There are various methods being employed to extract essential oils. The following gives a description of the commonly used extraction methods.
This is the most popular and least expensive way of extracting essential oils. For some plants, distillation can be done immediately after gathering them. Other plants need to be dried first before extraction.
Distillation requires a lot of skill. If the person doing it is not skilled enough, the essential oil could be lost or its composition could be altered. The process begins by heating the plant material using either of these two methods putting the plant in water and then allowing the water to boil or making the plant pass through steam.
Heat causes the plants cells to collapse, thereby releasing the essential oils, which then evaporate. The essential oils in the form of vapor are transported through a pipe that passes through a cooling tank. This is where the steam condenses back to liquid form.
The liquid, which is actually a combination of oil and water, is collected in a container.
What follows is the simple step of separating oil and water. Essential oils will float on the surface because they are lighter than water, and they can be siphoned off.
There are plants that cant withstand distillation so the solvent extraction method is used to obtain their essential oils. In this method, the plant parts are placed in an extracting unit where they are washed with a solvent again and again. The solvent causes the extractable composition of the plant to dissolve.
The extract is then gathered and filtered, and the filtrate goes through low-pressure distillation. A waxy material, called concrete, remains. This concrete contains volatile oil.
The concrete undergoes a further purification process to eliminate the waxy material. This is done by warming the concrete and stirring it with alcohol. In this stage, the concrete breaks down into smaller particles.
The concrete is separated from the aromatic molecules, which are soluble in alcohol. However, at this stage, there is still some concrete that dissolves along with the aromatic molecules, meaning the product is not yet pure.
The next procedure involves agitating the solution and then freezing at a very low temperature. This process precipitates the remaining wax. Finally, the solution obtained is cold filtered to obtain a pure product, called the absolute. Thats where the essential oil comes from.
Carbon Dioxide Extraction
This extraction method, which was created for the production of perfume, was first introduced in the 1980s. This is an expensive method because it uses high-end equipment. The oils extracted through this method are purer, of higher quality, and are in almost the same form as the essential oil that exists naturally in the plant.
Carbon dioxide (CO2) undergoes high pressure, making the gas convert into liquid form. The liquid CO2 is then used as a liquid solvent to extract the aromatic molecules. The process used for doing this is the same as that used to obtain the absolute (as previously described) except that there are no solvent residues because CO2 converts back to gas at normal temperature.
This method is used for plants belonging to the citrus family, such as orange, lemon, lime, and grapefruit. In effect, the essential oil is extracted by cold pressing the rind. The essential oil found in small sacs beneath the rinds surface is then released. A sponge is used to collect it, and after the sponge is soaked, it is squeezed into a container.
Originally, this method was done by simply exerting hand pressure on the rind of the citrus fruit, but there are now machines used for doing this. Because citrus fruits yield large amounts of oil and the extraction process is cheaper than for others, the essential oils from these plants generally cost less.
In this method, the plants are put in a container of warm vegetable oil in order to break down the cells and release the essential oils. The vat, which contains the essential oils, is agitated for a few days, and the end product is filtered.
After this, the oil can be bottled and used in massage. Calendula and hypericum are examples of oils that are extracted through maceration. This method yields infused oil instead of essential oil.
Hydrofusion or Percolation
This is a modern extraction method and is perhaps the newest one being used today. Hydrofusion uses simpler equipment that yields oil faster than distillation and in a less complicated process than carbon dioxide extraction.
The plant, suspended on a grid, is subjected to steam spray. This process releases a liquid consisting of oil and condensed steam. The resulting liquid is cooled, after which the oil is separated from the water.
This method makes use of a new kind of benign, gaseous solvents called florasols. The role of these solvents in extracting essential oils was first described by Dr. Peter Wilde in the 1980s.
The process is done below ambient temperature, which does not allow the plant products to undergo thermal degradation. It yields a clear and free-flowing oil devoid of waxes.