Distillation of Essential Oils, Part Two
Hydrosols: A By-product of Distillation
Hydrosols (also known as hydrolats, floral waters, distillates, or “water of _____”) are the by-product or product (depending on the distiller’s purpose) of the distillation process.
Hydrosols are fragrant waters that contain the essence of a plant in a milder, more accessible, and easier to use form than essential oils. They are suitable for all manner of applications for which essential oils are too strong – for example, they are clothing safe, non-comedogenic, hypoallergenic, and pet safe (provided they are the hydrosols of plants that are non-toxic and poisonous to pets, for example, lily hydrosol would be dangerous to cats, but most medical grade essential oils are dangerous to pets due to chemical burn concerns.)
They are quite like essential oils, but are far less concentrated. During distillation, the water-soluble constituents of the aromatic plant and the essence of a plant is released as steam, which condenses into two products – the essential oils, also offered through Haven Craft, and the hydrosols.
Hydrosols also retain a small amount of essential oil. Every liter of hydrosol contains between 0.05 and 0.2 milliliter of dissolved essential oil, depending on the water solubility of the plant’s components and the distillation parameters.
*Please Note: The addition of essential oils to water is not at all the same as true hydrosols, and it is recommended that you read the ingredients label on products to ascertain whether or not you are getting a true hydrosol. When water and essential oils are mixed together with or without a dispersant, this is called a “spritzer” or “aromatic spritzer,” and this product should not be confused with a true hydrosol.
Hydrosols do not need to be shaken before use.
Expression, also referred to as cold pressing, is a method of extraction specific to citrus essential oils, such as tangerine, lemon, bergamot, sweet orange, and lime. In ancient times, expression was done in the form of sponge pressing, accomplished by hand. The zest or rind of the citrus would first be soaked in warm water to make the rind more malleable in the pressing process. A sponge would then be used to press the rind, thus breaking the essential oil cavities. The sponde would then absorb the released essential oil.
Once the sponge was filled, it would then be pressed over a collecting container. The expression would then stand to allow for separation of the essential oil from any released water or juice. The essential oil would then be siphoned off.
A more modern method of extraction, much less labor-intensive, has been termed the “ecuelle a piquer” process. It involves a prodding, pricking, sticking action to release the essential oil.
During the ecuelle a piquer process, the rind of the fruit is placed in a container with spikes that punctures the peel while the device is rotated.
The puncturing of the rind releases essential oils that are then collected in a small area below the container. The end process is the same as above.
The majority of modern expression techniques are accomplished by using machines using centrifugal force. The spinning centrifuge separates the majority of essential oil from the fruit juice and water.
Some aromatherapy and therapeutic oil companies sell both a distilled and an expressed citrus essential oil from the same species. The main differences between a distilled and an expressed citrus essential oil are their toxicity, volatility, and aroma.
Distilled citrus oils deteriorate more quickly and are considerably more unstable than the expressed oils. Distilled citrus oils are not recommended for aromatherapy use.
The one exception would be for distilled lime essential oil, which is considered to be superior in aroma to its expressed counterpart.
Both the expressed and distilled essential oil of bergamot contains the phototoxic furanocoumarin, bergaptene. The aroma of distilled oil is considered to be of lower quality than the expressed oil.
Expressed lemon oil contains the phototoxic furanocoumarin, bergaptene, where as the distilled lemon oil is considered to be non-phototoxic. And like bergamot, the aroma of the distilled oil is considered to be of lower quality.
Expressed lime oil contains the phototoxic furanocoumarin, bergaptene, whereas the distilled oil is not considered to be phototoxic. The main difference with lime is that the distilled essential oil is considered to have the superior aroma. The distilled lime is considered the superior of the lime oils because it has greater similarity to the natural lime scent.
Extraction Techniques for Absolutes (Extracted Oils) & CO2 Extracts
Flowers were being processed via enfleurage in the Grasse region of Southern France long before the modern method of solvent extraction was in widespread use. In the antique perfume trade of France, many flower scents were extracted via enfleurage.
Enfleurage is now considered an ancient art that is passed down through family lines, from generation to generation.
Enfleurage is a cold-fat extraction process that is based upon the principles that fat possesses a high power of absorption, particularly animal fat. The fat used must be relatively stable against rancidity. It is a method used for flowers that continue developing and giving off their aroma even after harvesting (e.g., jasmine and tuberose).
This technique involves placing the flower petals on a layer of glass that is first spread with a thin layer of fat, called “chassis”. The volatile oil diffuses into the fat, then the fat is collected and the oil is extracted from the fat using alcohol.
Once the alcohol evaporates what is left behind is called the absolute.
Today, Grasse continues to be one of the few areas in the world that continues to employ enfleurage as a method of extraction, although it is rare in the aromatherapy market due to the expense. If one finds a jasmine enfleurage on the market, this would typically be considered an absolute.
Some of the therapeutic grade absolutes (extracted oils) carried by Haven Craft were created using enfleurage.
Some plant material is too fragile to be distilled – the heat will break down the material to unusability long before oils are released – and so an alternative method must be used. Solvent extraction is the use of solvents, such as petroleum ether, methanol, ethanol, or hexane, to extract the odiferous lipophilic material from botanicals.
The solvent will also pull out the chlorophyll and other plant tissue, resulting in a highly colored and thick, viscous extract.
The first product created during solvent extraction is known as a concrete. A concrete is the concentrated extract that contains the waxes and the fats of the botanical material, as well as the odoriferous oils from the plant.
The concrete is then mixed with alcohol, which serves to extract the aromatic principle of the material.
The final product is known as an absolute or as an extracted oil.
Solvent extraction is used for jasmine, tuberose, carnation, gardenia, jonquil, violet leaf, narcissus, mimosa, and other delicate flowers.
Neroli (orange blossom) and rose can be distilled or solvent-extracted.
The name neroli typically implies the essential oil, whereas the name orange blossom is commonly used for the absolute or hydrosol of neroli. The name rose is used to describe either the essential oil or the absolute.
Companies selling essential oils should rightfully clarify whether the product you are purchasing is an essential oil or absolute. This information should be on the label and in the product catalog. It often isn’t, though, so reflect upon the price – if it seems too good to be true, it probably is.
After the solvent extraction process has been completed, the resulting absolute will have an extremely low concentration of solvent residue, approximately 5 to 10ppm (parts per million). The current European Union standards are for less than 10 parts per million solvent residues in a finished absolute.
This does not interfere in their use as therapeutic oils – some believe it does, but my teacher did not.
It may interfere in their use as medical grade essential oils. Even with such a potentially small residue (less than .0001%), many holistic herbalists disagree with the use of absolutes for individuals with a compromised immune system, due to the potential effect of the residual pesticide.
However, absolutes do have therapeutic value and are often used for psychological purposes and for animals, particularly horses. Many therapists incorporate absolutes, such as rose, jasmine, and tuberose absolutes, as a valuable part of their therapeutic applications of aromatherapy. Ultimately the decision to use absolutes is up to the practitioner and personal preferences.
Absolutes are used extensively in the cosmetic and perfume industries due to their strong aromas – they often smell more like the botanical material than essential oils do.
There are also different grades of absolutes.
The top grade is the uncut, which can be a thick or semisolid substance, making them difficult to work with.
Less expensive grades are diluted with alcohol or a carrier oil, called a “filler”, to make them more user friendly, although often the strength of aroma is slightly diminished.
If the absolute pours very easily and is thin or runny, it has likely been “cut” or “filled”.
Most bath oils and gels, candles, shampoos, toothpaste, fly spray, aromatherapy suppliers, and air fresheners (somewhere around 98 percent), use absolutes rather than medical grade essential oils.
CO2 Hypercritical Extraction
Hypercritical carbon dioxide (CO2) extraction is a relatively new process, developed for for the extraction of aromatic products.
CO2 under pressure will turn from a gas into a liquid, which can then be used as an inert liquid solvent.
This liquid solvent is able to diffuse throughout the botanical material, thus extracting its aromatic constituents.
CO2 extracts contain most of the same constituents as their essential oil counterparts, although they can contain some elements not found in essential oils. For instance, the essential oil of ginger (Zingiber officinale) does not contain the bitter principles, however the CO2 extract does. Also, the CO2 extract of frankincense (Boswellia carterii) has immune enhancing and anti-inflammatory activity not found in the essential oil.
CO2 extracts are known for their strong similarity in aroma to the actual plant aroma, sometimes stronger than the abolutes produced from pressure extraction.
Other common CO2 extracts on the market include German chamomile (Matricaria recutita) and Calendula (Calendula officinalis).
The three main disadvantages for this process are cost, potential pesticide residue, and the lack of information regarding their safety, therapeutic benefits, and medical benefits.
With regard to pesticide residue, carbon dioxide extraction has been demonstrated to concentrate from 7 to 53 times more pesticide residues in the final extract. Therefore, it seems pertinent to only use organic plant material for CO2 extraction.
Perhaps as more CO2 extracts become available and more practitioners use them, further details regarding their applications will become apparent.
Two of the most common essential oils available via CO2 extraction include frankincense and ginger.
The Phytonic process is a one of the newest methods of extracting essential oils using non-CFCs (non-chlorofluorocarbons). It is also called Florasol Extraction. The oils produced are called phytols.
The oils are promising and are very close to nature; however, it does use fluoro-hydrocarbons which can be potentially harmful. The process also has some potentially negative environmental effects that need to be addressed.
More research needs to be done into phytol oils and the process itself before Haven Craft will carry phytol oils.
Warm Oil Infusion
It is possible to extract the volatile oils from plants into warm carrier oil by gently macerating the botanical materials and placing them in a carrier oil and slowly bringing that oil up to heat. These are not considered essential oils or absolutes, but they are good for home therapeutic when a great deal of oil is called for, such as in producing a salve or balm to be used all over the body.
There is a method of solvent extraction that can be done at home to obtain a kind of extracted oil. It would not be considered a therapeutic or medical grade essential oil or absolute, but it is considered an alchemic oil and suitable for use in magick.
The process generally uses undenatured ethyl alcohol or very high proof grain alcohol. It does not use rubbing alcohol.
The plant material is macerated in alcohol for some time, then the plant material is strained out. The alcohol is then placed into an environment below the freezing point. The oil will congeal on top of the alcohol, which will not freeze, and can then be extracted. This method is very good for delicate materials that will burn before steam distillation releases the oils, such as jasmine.