Extraction Methods

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: Steam Distillation, Hydrodistillation, Cohobation and Molecular Distillation

Essential oils are biologically important substances produced by aromatic plants that are stored in specialized glands, roots and leaf hairs. Among their many functions they can act as insect deterrents and pollinator attractants or serve as protective agents when under attack – but to most humans, they simply smell good. Essential oils may be released from the plant and collected (concentrated) under the conditions of high-pressure steam distillation and sometimes hydro- or water/steam distillation, or a combination thereof.

Distillation is a method of separating components based on differences in evaporation rate of volatile constituents through temperature, pressure and subsequent condensation taking place within the still. The essential oils contained in plants are insoluble in – and have a higher boiling point – than water, allowing the essential oil to vaporize at a lower temperature than it normally would on its own.

Water/Steam Distillation is a high-yield process and is used for most aromatic plants yet, due to low pressure, requires a longer distillation time to extract all the volatiles. Direct steam distillation involves bubbling steam through the plant material and is suitable for aromatic plants with lower temperature needs. Hydrodistillation involves covering the plant material in water prior to longer distillation times and is useful for some resins, spice powders and chopped roots or bark.

Cohobation describes a process of re-distillation, or an extra evaporation/condensation of previously distilled, aromatic distillate water, and is exclusively used to maximize the yield of rose ottos and to fortify their hydrosols. In addition to enriching the yield of essential oil, the dissolved, more hydrophilic volatiles are also concentrated in the hydrosol as a result of cohobation, making it more stable, extra fragrant and maximally therapeutic.

Molecular Distillation is a process using only extremely low vacuum pressure, and for this reason it is also called ‘vacuum distillation’. Molecular distillation lowers the boiling point of liquids in a molecular still and is used to separate and remove undesirable molecules such as colorants, or to concentrate heat-sensitive molecules such as fatty acids. Molecular distillation also eliminates the low-boiling, ‘dirty’ top notes, resulting in a refined, super suave aroma.

Click here for a list of available Essential Oils.

Cold Pressed Extraction: Citrus Peel Essential Oils and Carrier Oils

Cold Pressed Extraction, also referred to as Cold Expression, is a method used primarily for heat-sensitive Citrus Peel Essential Oils. In this process the essential oil is obtained first by abrasion or laceration of citrus peels that are subsequently centrifuged to separate the volatile, aromatic molecules from the juice, peel solids and heavier compounds such as waxes and flavonoids. Cold Pressing should be performed quickly to avoid oxidation, hydrolysis or resinification of the essential oil which can occur upon contact with air or water.

While the term ‘Cold Pressed’ can also apply to the process used to extract Carrier Oils (aka ‘fixed’ oils), it is more accurate in this case to refer to the process as Expeller Pressed Extraction. At this time there are no formal legal standards that define what it means to ‘Cold Press’ a fatty oil. Expeller Pressed Extraction is a low-heat process utilized for Carrier Oils that is especially important for preserving vulnerable fats, flavors and nourishing components that are susceptible to degradation if exposed to high temperatures. It is a physical process that effectively utilizes a screw press and compression to squeeze oil from the raw material with no added heat. Many sources say that the temperature for this method does not exceed 49˚C (120˚F), but pressure and friction can sometimes raise temperatures from 60˚C up to 99˚C (140˚F - 210˚F).

Click here for a list of available Citrus Peel Oils and Carrier Oils.

Concrètes & Absolutes: Solvent Extraction

Concrètes and Absolutes are concentrated aromatic materials extracted from plants in a multi- phase process. The first phase is extraction of the aromatic constituents from the plant material using a solvent such as hexane. When the hexane is vacuum-removed, it leaves behind a semi-solid to solid and highly fragrant material called a concrète that is comprised of a large amount of pigments and waxes. Due to their waxy texture, concrètes are perfect for making solid perfumes. They have somewhat delicate, yet long lasting aromas and are soluble usually in both carrier oils and alcohol, though often it is necessary to filter out any insoluble waxes and/or solid materials that remain.

In the second phase, aromatic oils are extracted and separated from most of the plant waxes and non-aromatic materials as the concrète is washed in ethyl alcohol, followed by filtration and/or centrifuging; the alcohol is recovered by gentle vacuum. The remaining aromatic material is called an absolute. Absolutes are the most concentrated form of botanical fragrance, highly regarded in natural perfumery, with an aroma close to that of the living plant material. Absolutes still contain some waxes and pigments along with other constituents from the plant, but are mostly comprised of the concentrated aromatic material that can range in consistency from mobile to quite viscous and even solid. 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, tend to be much lighter in color or have no color, and have comparatively lighter aromas. While essential oils are excellent choices for skincare and for aromatherapy applications, absolutes and concrètes are reserved for use in 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 properties. But unlike absolutes, they are not extracted with petrochemical solvents such as hexane. Instead, they are extracted with 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 is used to extract aromatic oils from plants. The procedure is fast and gentle and is completely enclosed to prevent the presence of oxygen, thus preserving the composition of the chemical constituents. Highly volatile top notes are not lost, and the bottom notes of less volatile and sensitive oxygenated sesquiterpenes are fully preserved as well. Hydrolysis of monoterpene esters or the loss of monoterpene alcohols in the heart notes is also largely avoided during extraction. Another impressive benefit of CO₂ extraction is that once the oil is extracted from the plant material, the supercritical CO₂ is returned to its gaseous state at normal air pressure, quickly and completely dissipating and without generating toxic waste.

Depending on the pressure used, ‘select’ or ‘total’ extracts will result. Select extracts are created at lower pressures and are more similar to essential oils, being fully mobile liquids with mostly volatile constituents making up the vast majority of the extract. Total extracts are created using higher pressures and contain more higher molecular weight, lipophilic constituents of the plant, can be thicker or waxier, and more closely resemble the whole plant rather than just the essential oil fraction of the plant. Some CO₂ total extracts are, in fact, carrier oils – e.g., Pomegranate Seed CO₂and Rosehip Seed CO₂ .

Because of the stability and versatility of CO₂ extracts, and since they display some very favorable characteristics not found in essential oils, they are enthusiastically used by food, body care, and herbal product manufacturers. The attractiveness of supercritical CO₂ extraction is shown by the already existing industrial applications of natural hop extraction, decaffeination of tea and coffee, defatting of cocoa powder and extraction of herbs and spices, to name a few. But with wider availability these extracts are now finding enthusiasts in aromatherapy and natural perfumery.

Major benefits of CO₂ extracts:

occur at lower temperatures (up to 40˚C / 104˚F) than steam distillation
carbon dioxide, acting as the solvent, is nontoxic, odorless, and is easily removed from the extracted oil at the end of the process
have more stability and a long shelf life
contain no carbohydrates, inorganic salts, proteins/allergens, or germs
meet strict heavy metal requirements

Click here for a list of available CO2 Extracts.

Organic Extracts

Eden Botanicals also specializes in offering some of the finest organic extracts available. Our organic extracts are made using a modernized technology similar to the ancient method of enfleurage – the gentle extraction of oil from precious flowers by soaking them first in vegetal fat, then using alcohol as a solvent to separate the oils from the fat. This 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 de Mai, Jasmine, and Orange Blossom. 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 extraction method for the first time allows Jasmine, Carnation and Tuberose – in the form of organic extracts – to be used for true aromatherapy purposes, whereas previously they had only been available as solvent extracted absolutes that are recommended for perfumery only.

Enfleurage

Enfleurage (French, from enfleurer: to saturate with the perfume of flowers) is an extraction process first developed by the ancient Egyptians for the transfer of aromatic volatiles found in flowers to a fixed oil or fat. Although seldom used today, it was one of several methods perfected by French perfumers in the early days of that country’s perfume industry. Using only flowers that release their scent long after being harvested resulted in successful enfleurage yields.

Jasmine, tuberose, violet, and jonquil flowers, all hand collected, continuously release their scent for many hours after being picked – thus, they are ideally suited to the enfleurage process. In the original method, both sides of large plates of glass in wooden frames (aka châssis) were spread with specially prepared odorless fats (aka corps or corps gras). Freshly picked flowers were placed face-down by hand across the entire surface of fat on the top side; each plate was then placed horizontally in a tall frame that held numerous plates stacked one above the other and spaced a few inches apart. Depending on the flower, they remained in place on the corps from 12 to 72 hours, after which the spent flowers were removed (defleurage), the plate turned over, and fresh flowers were applied to the corps. This process was repeated until the corps was saturated with the aromatic oil from the flowers – until the end of the flower harvest. The saturated fat (aka pommade or pomade) was scraped from the glass with spatulas into a vessel called a batteuse in which the pommade was continuously washed and stirred with ethyl alcohol that was sufficiently warmed to melt the fat. The alcoholic solution (extrait) was then chilled, causing the waxes and fats to precipitate out, followed by removal of the alcohol via vacuum distillation. This process resulted in products known as, for example, jasmine absolute from pommade, jasmine enfleurage or enfleurage of jasmine. In the words of author Ernest Guenther, “The highest quality of floral oils most true to nature resulted from [the enfleurage method].”

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).

Resins augment and help give lasting power to the other ingredients contained in perfume compositions. Plant resins vary greatly in consistency, and may be extracted by means of multiple methods to ensure maximum yield and optimum fragrance quality. Balsams are soft resins containing benzoic or cinnamic acid. Oleoresins are semi-soft resins and are mixtures of oil and resin. Gum-resins are semi-solid resins that are mixtures of gum or mucilaginous substances and resin. Resinous exudates, sometimes referred to as tears, are used as protective elements in plants, a particular necessity when living in harsh, desert terrain. In their natural state, resins could be viewed as a botanical slice of life – the aromatic molecules are frozen in time until they are liberated by various extraction methods.

Another type of aromatic oil we offer comes from the traditional destructive distillation method that gives rise to Fossilized Amber Oil. In Dry or Destructive Distillation, decomposition of an organic (carbon-based) raw material takes place by heating it to high temperatures without the presence of water or steam. The chemical process itself is called “pyrolysis” from the Greek-derived pyro “fire” and lysis “separating.” This process creates a change in chemical composition where completely new volatile compounds are produced that were not present in the original material. Thus, oil can be obtained from something that really didn't contain oil in the first place.

Dilutions

In our collection we also offer 5% and 10% dilutions – 5 or 10% pure essential oils or absolutes diluted in 90-95% Fractionated Coconut Oil - Organic. Our dilutions represent an exceptional value and are a less costly way to experience some of the more rare and precious oils among our offerings. We prefer organic Fractionated Coconut Oil for our dilutions – it is a clear and odorless carrier oil with an extremely long shelf life that also holds the fragrance of aromatic oils well and is non-reactive with and beneficial for the skin.

Click here for a list of available Dilutions.