A COMPREHENSIVE GUIDE TO ESSENTIAL OIL EXTRACTION METHODS
- Rather than being synthetically manufactured in labs, essential oils are extracted from plant materials through removal methods that are suited to the specific plant part containing the oils.
- Essential oils are the liquids that are isolated from plants when introduced to solvents – they are liquefied versions of the plants!
- Popular extraction methods include: Steam Distillation, Solvent Extraction, CO2 Extraction, Maceration, Enfleurage, Cold Press Extraction, and Water Distillation.
- The method of extraction affects essential oil quality by way of pressure and temperatures applied.
- Some extraction methods are best suited to particular plant types and parts; for example, Cold Press extraction is better than Enfleurage for obtaining oils from citrus fruit peels, because the peels need to be pierced and squeezed, which is not achievable through Enfleurage.
PRODUCTION OF ESSENTIAL OILS
Have you ever wondered about how to make essential oils? Let us explain that Essential Oils are not made, but instead, they are extracted from plant materials. Extractions are used to obtain a plant’s active botanical constituents that function as its “life force.” They are essentially the liquefied version of a plant, and they effectively allow its beneficial compounds to reach the blood stream faster than they would by simply consuming the plant.
An herbal extract is produced when a botanical material is introduced to a solvent in which some of the plant material components dissolve. Ultimately, the solvent becomes infused with the botanical materials that it has pulled from the source plant, and this is what is referred to as the “extract.” The solution that remains at the end of the process can be liquid, or the liquid can be removed to turn the remnants of the botanical into a solid. The solvents can act as preservatives or as agents that help plant cells to break down and release their contents.
Steam Distillation is the most popular method used to extract and isolate essential oils from plants for use in natural products. This happens when the steam vaporizes the plant material’s volatile compounds, which eventually go through a condensation and collection process.
STEAM DISTILLATION PROCESS
A large container called a Still, which is usually made of stainless steel, containing the plant material has steam added to it.
Through an inlet, steam is injected through the plant material containing the desired oils, releasing the plant’s aromatic molecules and turning them into vapor.
The vaporized plant compounds travel to the condensation flask or the Condenser. Here, two separate pipes make it possible for hot water to exit and for cold water to enter the Condenser. This makes the vapor cool back into liquid form.
The aromatic liquid by-product drops from the Condenser and collects inside a receptacle underneath it, which is called a Separator. Because water and oil do not mix, the essential oil floats on top of the water. From here, it is siphoned off. (Some essential oils are heavier than water, such as clove essential oil, so they are found at the bottom of the Separator.)
This method employs food grade solvents like hexane and ethanol to isolate essential oils from plant material. It is best suited for plant materials that yield low amounts of essential oil, that are largely resinous, or that are delicate aromatics unable to withstand the pressure and distress of steam distillation. This method also produces a finer fragrance than any type of distillation method.
Through this process, the non-volatile plant material such as waxes and pigments, are also extracted and sometimes removed through other processes.
Once the plant material has been treated with the solvent, it produces a waxy aromatic compound called a "concrete." When this concrete substance is mixed with alcohol, the oil particles are released. The aforementioned chemicals used in the process then remain in the oil and the oil is used in perfumes by the perfume industry or for aromatherapy purposes.
Solvent Extraction encompasses the following methods: Hypercritical CO2 (Carbon Dioxide), Maceration, Enfleurage.
Essential oils derived from the supercritical CO2 extraction of herbs are similar to the oils produced through distillation in that they can be used in aromatherapy and natural perfumery.
Oils derived from steam distillation vary in their qualities depending on the temperatures, pressures, and length of time applied for the process. The CO2 extraction process might thus produce higher quality oils that have not been altered by the application of high heat, unlike the steam distillation process. In CO2 extraction, none of the constituents of the oil are damaged by heat.
Thus, the difference between traditional distillation and supercritical extraction is that instead of heated water or steam, CO2 is used as a solvent in the latter method. The supercritical extraction process operates at temperatures between 95 to 100 degrees F whereas steam distillation operates at temperatures between 140 to 212 degrees F.
In steam distillation, the molecular composition of both the plant matter and the essential oil are changed due to the temperature applied. On the other hand, a CO2 extract is closer in chemical composition to the original plant from which it is derived, as it contains a wider range of the plant’s constituents.
For example, CO2 Extraction of German Chamomile flowers yields a green extract, because the absence of heat means it was not altered from its natural state or “denatured.” The resulting extract is thus more similar in composition to the original flower than the distilled essential oils is.
CO2 extracts are usually thicker than their essential oil counterparts and often give off more of the aroma of the natural herb, spice, or plant than a distilled essential oil. CO2 extracts have been said to contain more plant constituents than the amount extracted from the same plant using steam distillation.
THE CO2 EXTRACTION PROCESS
Pressurized carbon dioxide becomes liquid while remaining in a gaseous state, which means it is now "supercritical." In this state, it is pumped into a chamber filled with plant matter.
Because of the liquid properties of the gas, the CO2 functions as a solvent on the natural plant matter, pulling the oils and other substances such as pigment and resin from the plant matter. The essential oil content then dissolves into the liquid CO2.
The CO2 is brought back to natural pressure and evaporates back into its gaseous state, while what is left is the resulting oil.
C02 is colorless, odorless, and can be easily and completely removed by releasing the pressure in the extraction chamber. It is what we exhale and is needed by plants in order for them to thrive, which illustrates its harmlessness when employed in the extraction process. This absence of potentially harmful solvents in C02 extraction means neither the human body nor the environment is polluted.
Macerated oils are also referred to as infused oils. They are created when carrier oils are used as solvents to extract therapeutic properties from plant material. The benefit of a macerated oil above a distilled oil is that more of a plant’s essence is captured in the oil, because it captures heavier, larger plant molecules than the ones captured in the distillation process. This keeps the product closer to retaining more of the plant’s valuable offerings.
The ideal plant material to be infused will be harvested so that it is as dry as possible, as any plant moisture will cause the oil to become rancid and will encourage microbial growth. Adding 5% of Vitamin E oil or Wheatgerm oil (which is high in Vitamin E) will prevent rancidity.
Plant material is finely cut, crushed, or ground into moderately coarse powder.
Plant material is placed in a closed vessel.
Solvent (Menstruum) is added.
The mixture is allowed to stand for 1 week and is shaken occasionally.
The liquid is strained.
Solid residue (Marc) is pressed to recover any remaining liquid.
Strained and expressed liquids are mixed.
Liquids are clarified through filtration or subsidence.
When the maceration process is complete, the base oil will likely have changed color. The final maceration should be filtered of its plant material and poured into an airtight container to be stored in a cool, dry place for up to 12 months. A macerated oil will go cloudy or will smell bad when rancid.
5-10% of a macerated oil can be used as an ‘active botanical’ in a cosmetic formula. Used in a larger quantity, it can also replace a plain base oil.
Enfleurage is not commonly used today, but it is one of the oldest methods of essential oil extraction that implements the use of fat. By the end of this process, either vegetable fat or animal fat becomes infused with the flower’s fragrance compounds. The fats that are used are odorless and solid at room temperature. The enfleurage process can be done either “hot” or “cold.” In both instances, the fat that is saturated with fragrance is called "enfleurage pomade."
Highly purified and odorless vegetable or animal fat, usually lard or tallow, is spread out over glass plates in a frame called a chassis and is allowed to set.
Fresh flower petals or fresh whole flowers are then placed on top of the layer of fat and pressed in. They are allowed to set for 1-3 days or for a couple of weeks depending on the flowers that are used. During this time, their scent seeps into the fat.
The depleted petals are replaced and the process is repeated until the fat reaches the desired saturation.
The final product is the enfleurage pomade: the fat and the fragrant oil. This is washed with alcohol to separate the botanical extract from the remaining fat, which is used to make soap. When the alcohol evaporates from this mixture, the “absolute” is what is left over.
The only difference in this process is that the fats are heated.
This method is also called Expression or Scarification and is used for citrus peels in particular.
The whole fruit is placed in a device that mechanically pierces it to rupture the essential oil sacs, which are located on the underside of the rind. The essential oil and pigments run down into the device’s collection area.
The whole fruit is pressed to squeeze out the juice and the oil.
The oil and juice that are produced still contain solids from the fruits, such as the peel, and must be centrifuged to filter the solids from the liquids.
The oil separates from the juice layer and is siphoned off into another receptacle.
Delicate flowers such as roses and orange blossoms would clump together when introduced to steam in the distillation process, so the most effective method of extraction in this situation is to submerge fragile plant material in pure boiling water instead. The water protects the extracted oil from overheating. The condensed liquids cool down and separate from each other. The remaining water, which can sometimes be fragrant, is referred to by several names including hydrolate, hydrosol, herbal water, essential water, floral water, or herbal distillate.
WATER AND STEAM DISTILLATION
In this method that can be employed with herb and leaf material, the plant material is immersed in water in a Still to which heat is applied. Steam is fed into the main Still from outside.
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