What Are Essential Oils?
Essential oils are natural aromatic extracts from plant material including grasses, leaves, flowers, needles, twigs, peels of fruit, seeds, bark, and roots. For example, rose essential oil comes from the flowers, basil from the leaves, lime from the rind, anise from the seeds, sandalwood from the wood, frankincense from the resin of its tree, and so on.
The aromatic essential oil compounds are stored in tiny pockets in plant material and must be extracted to be released. The type of plant material (leaves, flowers, roots) being used determines which method of extraction will produce the best results.
For more information please read our blog, "What Are Essential Oils."
Methods of Extraction
"True essential oils" are only extracted either by steam distillation or, in the case of citrus oils, expressed.
Steam distillation is the most popular method to extract essential oils.
During this process the botanicals are placed in a still and pressurized steam is forced through the plant material. The hot steam forces open pockets aromatic compounds. The compounds escape from the plant material and evaporate into the steam.
The steam must be hot enough to allow the release of the essential oil while not damaging the plant material The steam with essential oil then passes through a cooling system where the steam condenses into a liquid consisting of essential oil and water. The essential oil, being lighter than the water, will float to the top and can then be separated from the water. The water by-product of distillation is called a floral water.
Anyone who has peeled a fresh citrus fruit knows the refreshing, energizing aroma. But citrus oils do not hold up well when heat is used in extraction. Expression is called a "cold pressed" method of extraction since no heat is needed to extract the essential oil. It is mostly used to extract citrus essential oils. In this process, the oil is forced from the material under high mechanical pressure. Many base oils are extracted in the same way.
Absolutes are similar to essential oils since they are highly-aromatic, concentrated extracts from plants. However, while essential oils must be produced by steam distillation or expression, absolutes require the use of a solvent for extraction and therefore cannot be called essential oils.
Some plant materials, like vanilla, which is difficult to extract, or jasmine flowers or rose petals, which are too delicate to survive the process of distillation, use another method to extract their aromatic essence, a process called solvent extraction.
This process utilizes petroleum solvents such as petroleum ether, hexane or toluene; alcohol solvents such as methanol or ethanol; or carbon dioxide. As the solvent is added to the botanical it is absorbed and allows the release of the aromatic compounds.
These solvent extracted compounds are called "absolutes" and are very concentrated. Technically they should not be called essential oils. They are either extracted using:
- petroleum solvents
- ethanol solvents
- supercritical CO2 extraction process. This method helps to maintain the integrity of the base constituents of the oil and produces a highly concentrated finished product without using petroleum solvents.
Petroleum Solvent: Years ago almost all absolutes were extracted in this manner. However, since residues of the petroleum solvent, like hexane, may remain in the aromatic oil, solvent extraction was not recommended for essential oils used for aromatherapy. These residues may also cause allergic reactions and skin irritation.
Ethanol Solvent: While the petroleum solvents can be very dangerous, ethanol (food grade drinking alcohol) is a rather benign solvent. The plant material is steeped in ethanol. The alcohol is evaporated out and a highly concentrated oil known as an absolute is left behind. Sometimes people will list an absolute, like vanilla, as an essential oil, but absolutes are not technically essential oils.
Supercritical Carbon Dioxide Extraction: Carbon dioxide extraction is a fairly new way and natural method to extract the essential oil from botanical material. It produces great essential oils but at this time is also very expensive. Under pressure, the temperature of the carbon dioxide is increased to about 92 degrees Fahrenheit (33 degrees Celsius). At this temperature carbon dioxide enters a phase that is part liquid and part gas. Carbon Dioxide is an excellent solvent to extract pure essential oils since carbon dioxide does not chemically interact with the essential oil extracted. To remove the carbon dioxide solvent, simply decrease the pressure and the carbon dioxide returns to a gaseous state leaving the pure essential oil with no residues.
The Rosemary Oil Extract we use as an antioxidant in some of our products is extracted using this Carbon Dioxide method. It is a method that can be used to obtain a USDA Certified Organic extraction.
The most important consideration when purchasing essential oils is to buy from a reputable supplier that lists the method of extraction and tests their oils for the presence of adulterated additives.
When purchasing an essential oil or a product containing essential oils, be sure to ask about the extraction method!
The essential oils used in Chagrin Valley products are steam distilled except for the citrus oils which are cold pressed.
If we use any absolutes they are either Carbon Dioxide extracted (if available) or Ethanol extracted.