Essential Oil Extraction Methods 101

By : Aayush Gupta

Last updated on: June 19, 2021

Table on Contents

Production of essential oils
Steam Distillation
Solvent Extraction
CO2 Extraction
Maceration
Enfleurage
Cold-Press Extraction
Water Distillation
Water and Steam Distillation

Ever wondered how essential oils land up in the products you use in your everyday life? There are different extraction methods used for producing them, each considerably different than the other. Various industries like pharmaceuticals, health and nutrition, beauty and cosmetics, perfume employ these techniques to get the desired oils necessary for making their product. Let’s explore the extraction methods in brief.

Production of essential oils

Essential oils aren’t produced or assembled at a molecular level. They’re extracted from plant materials. They can be synthetically manufactured in the lab as well, but the plant extraction method seems to be the better way of availing them.

A plant is made up of hundreds of molecules that the essential oils are a part of. They serve as its vital “life force” and help the plant to function as a living being. These oils are essentially liquids that are isolated from other plant materials via the removal process.

To extract these oils, there are various extraction methods. The most common way is by dissolving the required plant parts in a solvent medium. This solvent is also a type of liquid that can be water, saltwater, or acidified water. These help the essential oil to get separated from the plant by infusing it with them. This is referred to as the “extract” which can either be in liquid or non-liquid state. Other methods include heating and steaming.

The method applied for extraction is crucial since it affects the molecular structure of the compound, thereby affecting the quality. Steam and high heating are harsher on the isolated compounds while solvents have minimal altering effects.

With that said, let’s have a brief overview of major essential oil extraction techniques.

Steam Distillation

This is the most popular method employed for essential oil extraction. Steam is used for vaporizing the volatile compounds of the plant which is then condensed and collected as a liquid once it is cooled. The temperature at which this extraction method takes place gives it a significant advantage over other methods. It is easy, quick, and cost-effective. Here’s the process involved:

Plant materials are taken in a stainless steel container called “Still” and covered with a lid, thus creating a closed environment.
Steam is injected into the Still through an inlet. This causes the plant to release the volatile essential oils in the form of vapor.
These vaporized oils travel through a condensation flask (also known as the Condenser) and exit the container.
The condenser has two separate pipes. One is for the hot water to exit the Still, and the second for the cold water to enter the condenser.
The hot vapor cools down when it comes in contact with cold water. It is then collected inside a receptacle, also called a Separator.
Since oil and water do not mix, oil is separated from the water and you get essential oil as the final product.
Some essential oils (cloves, for example) are composed of heavier molecules. So they get deposited at the bottom. They need to be siphoned off carefully.

Solvent Extraction

In solvent extraction method, a medium (which is the solvent) is used to extract volatile oils from the plants. This solvent can be hexane, ethanol, or any organic compound. This method is preferred when the compounds are fragile to withstand the rigidity of steam and are present in a low amount inside the plant material. This method is also preferred when you need finer fragrance from the plants. Therefore, the perfume industry makes use of this technique for oil extraction. Since this is a cheaper process, non-volatile plant materials like pigments and waxes are also extracted and removed.

The first plant material is dipped in the solvent.
This causes the essential oils to get separated from the material after undergoing a multi-phase chemical process. The oils are in a waxy stated called “concrete” which needs further separation.
The concrete is then treated with alcohol and heated.
The oil particles get separated and get collected via a condenser.
The chemicals used in the process remain in the oil and the entire product is used in the perfume by perfume manufacturers.

CO2 Extraction

CO2 extraction process generally yields higher quality oils that are less altered structurally. Because of this, the CO2 extraction method is also known as supercritical extraction. This is very much similar to the distillation process and the product is used in aromatherapy and perfume making. Moreover, none of the constituents get damaged by heat or other chemicals that are employed in other extraction methods.

Even though this is similar to the water distillation method, the subtle difference is that C02 is used as a solvent in place of water. There’s also a difference in temperature in which each process operates.

The water distillation process takes place between 140 to 212 degrees F, while supercritical extraction takes place between 95 to 100 degrees F range. CO2 extraction is preferred when the extracts need to be more concentrated and thicker. Concurrently, they give off a more authentic and strong aroma of the compound.

Here how the CO2 extraction process works:

Plant material is placed inside a chamber.
Carbon dioxide is pressurized which turns it into liquid. Now this “supercritical” carbon dioxide is pumped into this chamber.
CO2 functions as a solvent in a liquid state and help the volatile oils to escape the plant material. These then dissolve with the liquid CO2.
CO2 inside the chamber is then depressurized and evaporated back into gaseous stated to be finally taken out of the chamber.
What remains is the essential oils that are less tampered.

Since CO2 is colorless and odorless, it is easily handled in these procedures. Lastly, there are no harmful substances used in this method. So both humans and environment stay safe.

Maceration

In this extraction method, another type of oil known as “carrier oils” are used as solvents. Oils obtained by this technique are called infused oils. Generally heavier molecules that are known to have therapeutic properties are targeted for extraction. Before employing this method, the plant material is completely dried and grounded. This allows for better and easier extraction. Moreover, the essence of the plant’s valuable offering is retained. In other words, it is pure. That’s why pharmaceutical companies prefer this method over something like steam distillation or solvent extraction.

Grounded plant material is taken in a closed vessel.
A solvent like Menstruum is added to it to soak out the essential compounds.
It is then left undisturbed for 1 week with occasional shaking.
Now, the liquid is strained from the vessel and the solid residue is discarded.
The strained liquid is mixed with expressed liquid.
This mixture is clarified via filtration or subsidence process. Finally, the essential oil is obtained.

The final product will undergo color changes. It is then poured in an airtight container and kept aside for 12 months period. When rancid, this will emit a strong foul smell. 5-10% of this macerated oil is used as an “active botanical” component in cosmetics.

Enfleurage

This is among the archaic essential oil extraction methods that are rarely employed these days. In the Enfleurage method, fat is used as a separation agent instead of a solvent or steam. The fat can be obtained from either plants or animals but has to be colorless at room temperature.

Lard (vegetable or animal fat in pure form) is taken and spread over a chassis.
Fresh flower petals are placed on top of the layer.
This is set aside for 1-3 days. The scent of the flower seeps into the fat.
The petals are replaced and the process is repeated with other flower petals.
This is washed with alcohol and then dried.

There are two types of Enfleurage process. Hot and Cold. Both processes follow the same procedure detailed above. The difference is in Hot process, the fat used is heated to accelerate the action. In either case, the fat that is saturated with a fragrance called “enfleurage pornade” to have it smell better.

Cold-press Extraction

As the name indicated, pressing technique is used for initial separation followed by cold water treatment. This method is particularly used for citrus peels. It is also known as the Expression or Scarification extraction method.

A machine is used to pierce open whole citrus fruits.
This opens up the essential oil sacs and lets the oil and pigments flow down into a collection area.
The fruits are further pressed to squeeze out juice and oil.
The solids the come with it are removed by the centrifuged process.
The oil is now separated from the juice and siphoned off to be collected in another flask.

Water Distillation

The water distillation extraction method is used for extracting oil from delicate flowers like rose and fruits like orange. In this method, boiling water is employed instead of steam which is less damaging to the compounds.

The process is simple. Petals and the required plant parts which contain the majority of the essential oil is taken in a flask. Water is added to it and boiled moderately till boiling point. The water protects the delicate and fragile compounds from overheating and breaking down. The liquid is allowed to cool down. This results in oils getting separated from the water. The oil layer is removed from the flask and used for further processing. The water that remains after separation sometimes may be fragrant. This fragrant water goes by various names like hydrosol, hydrolate, essential water, floral water, etc.

Water and Steam Distillation

This method is used particularly for materials like herb and leaf. In this method, the plant material is taken in stainless steel and submerged in water. Heat is applied from the outside. This is followed by steam being fed into the system. The process remains the same as in the case of water distillation or steam distillation. It’s just a mixture of both methods. The water in the Still restricts the separated oil from overheating.

In conclusion, some methods are better suited only to certain types of plants and parts. Cold press extraction goes hand in hand with Enfleurage, while. It’s all about understanding your specifications and then narrowing down your options, ultimately choosing a particular one.