Although steam distillation is the most well-known technique for extracting essential oil from plants, there are several other methods that are used to remove and concentrate the aromatic constituents from plant materials. Here is a brief description of each method and their influence on the aromatherapeutic properties and fragrance of the oil.
Essential Oils: Distillation & Expression
Essential oils are produced in the cells of aromatic plants and are held in specialized glands. They are released from the plant and collected (concentrated) most often through steam distillation (and sometimes hydro or water distillation or a combination thereof). Distillation is a method of separating components based on differences in volatile constituents in a heated mixture. Steam distillation involves bubbling steam through the plant material. The temperature of steam is easy to control, making it ideal for heat-sensitive essential oils. The essential oils contained in plants are immiscible in water and have a higher boiling point, allowing the essential oil to vaporize at a lower temperature than it normally would on its own. Other methods used to create pure essential oils are dry or vacuum distillation, dry/destructive distillation, and expression (for citrus peels). Expression, also referred to as “cold pressed”, is a method where oil is obtained by using high mechanical pressure to literally squeeze the oil from the plant material.
Click here for a list of available Essential Oils.
Concretes & Absolutes: Solvent Extraction
Concretes and Absolutes are highly concentrated aromatic materials extracted from plants. The multi-step process includes first extracting the aromatic oil from the plant material with a solvent such as hexane. After the hexane is removed what is left behind is a waxy substance called a concrete. This semi-solid to solid highly fragrant material contains a large amount of pigments and waxes. Due to their waxy texture, concretes are perfect for making solid perfumes. They have a somewhat delicate, yet long lasting aroma and are soluble in both carrier oil and alcohol, though often it is necessary to filter any insoluble waxes and solid material that remains.
From the concrete the aromatic oils are then extracted and separated from most of the plant waxes and non-aromatic material with ethyl alcohol. After the ethyl alcohol is removed, the remaining substance is called an absolute. An absolute is the most concentrated form of natural fragrance, with an aroma close to the plant from which it came, and is highly regarded in natural perfumery. Absolutes still contain some waxes and pigments along with other constituents from the plant, but are mostly comprised of the concentrated aromatic oil. In addition, they usually contain a small percentage of alcohol remaining from the second phase of the extraction process (typically up to 2 or 3 percent).
Absolutes differ from essential oils in that essential oils do not contain waxes, are much lighter in color or have no color, and have a lighter aroma. Essential oils are typically used in skincare and for therapeutic purposes, while absolute and concretes are for natural perfumery.
Click here for a list of available Absolutes.
CO2 Extracts: Solvent Extraction
CO2 extracts display some of the characteristics of both essential oils and absolutes. Like essential oils, they contain many beneficial therapeutic properties. But unlike absolutes, they are not solvent extracted. Instead of using a solvent like hexane, they are extracted using CO2 (carbon dioxide) gas under pressure at ambient temperature. Under normal atmospheric conditions CO2 is a gas, but when highly compressed it becomes supercritical – neither a gas nor a liquid. Supercritical CO2 is an excellent organic solvent that can be used to extract aromatic oils from plants. The beauty of CO2 extraction is that once the oil is extracted from the plant material, the CO2 returns to its gaseous state by lowering its pressure, allowing the gas to quickly and completely dissipate.
Depending on the pressure used, a “select” or “total” extract will result. Select extracts are created at lower pressures, and are more similar to essential oils in that they are usually fully mobile liquids, and essential oil constituents make up the vast majority of the extract. Total extracts are created using higher pressures and contain more constituents of the plant, can be thicker or waxier, and more closely resemble the constituents of the whole plant rather than just the essential oil fraction of the plant.
Because of the purity of CO2 extracts and since they display some very favorable characteristics not found in essential oils, CO2 extracts are primarily used by the food, body care, and herbal industries, yet CO2 extracts are also excellent for aromatherapy and natural perfumery. This extraction technique (more accurately called supercritical CO2 extraction) is a relatively new and expensive technology that is more efficient in some ways than steam distillation, because the process has the ability to capture a broader spectrum of the plant components, giving a fragrance more true to the original plant material without the use of chemical solvents. Other benefits are that the extraction process happens at lower temperatures than steam distillation and that carbon dioxide is nontoxic, odorless, and is easily removed from the extracted oil at the end of the process.
Click here for a list of available CO2 Extracts.
Eden Botanicals also specializes in bringing you some of the finest organic extracts available. Our organic extracts are made using modernized technology similar to the ancient method of enfleurage (gentle extraction of oil from precious flowers by soaking them first in vegetable fat, then using alcohol as a solvent to separate the oils from the fat). The extraction process uses only certified organic solvents such as fixed oils and alcohol to coax the aromatic essence out of the plant material. The resulting bio-available essence, extracted without added heat, captures the intricate aroma of the original plant material. We are one of a select few in North America who carry the organic extracts made from Rose, Jasmine, Carnation, Orange Blossom, and Tuberose. These oils are best used for body care and aromatherapy due to the ‘aliveness’ of the essences. However, natural perfumers who wish to create organic perfumes will also love these oils. This new technology, for the first time allows Jasmine oil to be used for true aromatherapy purposes, whereas previously it had only been available as an absolute and therefore had not been recommended for therapeutic applications.
Resins & Other Types of “Oils”
We carry a few other types of natural aromatic oils that have been extracted using other processes. These include natural exudates and resins (or resinoids). These aromatic essences are collected from the resin that oozes out of the bark of trees when the trees are tapped (like rubber trees or maple trees [for maple syrup]). Another type of aromatic oil we offer comes from the traditional destructive distillation method that gives rise to Fossilized Amber Oil. In destructive distillation, the starting material (such as Benzoin resin) is super-heated and cooked until an oil substance is obtained from the solid starting material. Thus, oil can be obtained from something that didn’t really have oil in it in the first place.
We also offer 10% dilutions which are pure essential oils or absolutes diluted in Fractionated Coconut Oil. Our 10% dilutions are inexpensive ways to experience some of the more rare and precious oils that we offer. They contain 10% of the essential oil or absolute in a 90% Fractionated Coconut Oil base. Fractionated Coconut oil has an extremely long shelf life, is clear and odorless, holds the fragrance of aromatic oils well, and is beneficial for the skin.