Essential Oils are concentrated, aromatic volatile compounds that can sometimes seem magical to those of us who love and use them. The term “essential oil” is actually short for quintessential oil from the Aristotelian idea that matter is composed of four elements, namely, fire, air, earth, and water. The fifth element, or quintessence, was then considered to be spirit or life force. Before we understood the science of extraction, it was believed that by extracting essential oils you were capturing the spirit or life force of the plant. Even ancient people understood the power and beauty of essential oils! While there are many topics to cover with essential oils, our goal in this blog is to unveil some of the mystery of essential oils by discussing how they are made.
Distillation
Distillation is the most common and oldest method (5000 years old!) of extracting essential oils. The advantage of distillation is that the volatile components can be distilled at temperatures lower than the boiling points of each constituent and are easily separated from the condensed water. During distillation, the plant material is placed inside the still. The still is then sealed and depending on the distillation method, steam or water/steam is forced through the plant material removing its volatile constituents. The volatile constituents move through a connecting pipe into a condenser. The condenser then cools the volatile constituents back into liquid form. The liquid is then collected.
Because water and oil, including essential oil, don’t mix, the essential oil can be found floating on the surface of the water. It is then easily siphoned off. Some essential oils are heavier than water and are found below the water instead of floating on top, such as with clove essential oil. The remaining water is what is commonly called a hydrosol or distillate. The most common types of distillation include:
- Steam Distillation: By far the most common method of extraction. During this process, steam is introduced into the still at a high pressure and high temperature.
- Water Distillation: In this method, the plant material is in direct contact with the water. Most commonly used for extraction of flower petals like Rose and Orange Blossom as steam causes this delicate plant material to clump together making it difficult for the steam to force its way through.
- Water & Steam Distillation: This starts the same as water distillation, except the plant material is placed on a grid above the water and steam is introduced from outside the main still compartment.
- Fractional Distillation: This is a fairly new method of extracting different constituents from the plant by halting the distillation process at precise points. The separate constituents are collected and combined with other constituents from other plant materials also using fractional distillation. The result is complex scent profiles that often don’t resemble the original plant materials at all. In fact, some fragrances previously unattainable naturally are able to be made using this method such as Mango, Pear, and Lingonberry!
Cold Press
Cold Press or Expeller Press is a purely mechanical process for removing essential oils. It’s generally limited to citrus such as orange, grapefruit, lime, and lemon as the essential oils are contained in the peel of the fruit. This is a fun method you can even do at home!
- Simply soak the rind of your citrus in warm water until warm and soft.
- Remove from water and place on cutting board or in a large mixing bowl with a nice flat bottom.
- Take a sponge or clean cloth and press down on the outside of the rind allowing the sponge/cloth to soak up all of the liquid.
- Squeeze your sponge into a clean bowl and wait for the water and oils to separate. siphon off the oil and voila! You have a citrus essential oil – home made! This is not a very sanitary method and if you siphon any water into your oil you could potentially be growing bacteria and mold so I would suggest you use your oil immediately, or add it to a skin or hair care recipe with proper preservation.
While this method is fun to try at home, in larger scale extraction a much less labor-intensive and much more modern method is used. The fruit is placed in a machine where rind of the fruit is pierced with spikes while being rotated. The punctured rind releases its oil which is then collected, usually by using centrifugal force. This is much simpler and faster but the end process is the same as both of these methods involve a strictly mechanical process producing an essential oil that smells almost exactly like the fresh fruit it’s extracted from. These oils tend to be more fragile and generally require refrigeration.
Solvent
Solvents such as petroleum ether, methanol, ethanol, or hexane, are used to extract essential oils from plant materials too delicate for the processes mentioned above. The solvent will also pull out the chlorophyll and other plant tissue, resulting in a highly colored or thick/viscous extract which is then mixed with alcohol to produce what is commonly known as an absolute. Absolutes can also be obtained through a process called enfleurage, which involves extraction through a fat or oil, but this method is not commonly practiced. These absolutes are highly aromatic and are usually more viscous (some are very resinous and hard to work with) and darkly colored compared to essential oils obtained through cold press or distillation. The most common absolutes are Rose and Jasmine as these flowers are very delicate. Absolutes, even though extracted through some harsh chemicals, have a very low concentration of solvent residue of only about 5-10 PPM (parts per million).
CO2 Hypercritical Extraction
CO2 extraction is pretty exciting from a science perspective. CO2 under pressure turns into a liquid with is then used as a solvent to extract the essential oils. The best part, the CO2 is completely inert and will not leave a residue. Often CO2 extracts retain more of the plant’s original properties which are often not present compared to other extraction methods. The downside is that if there is pesticide or herbicide present on the plant material, it will also be present in the essential oil at higher concentrations compared to other extraction methods. This is easily remedied by using only organic plant material.
Here’s the list of our own Essential Oils so you can see how each one is made.
