Essential Oils & Perfumes Part I - A Definition of an Essential Oil and a Brief History

A Brief History

Essential oils have been used by man for thousands of years in one form or another. Their effectiveness has been well documented by healers and shamans throughout history in all cultures. Herbs, which contain essential oils are added to our cooking and impart valuable medicinal properties. Making our Christmas cake or pudding just wouldn’t be the same without the peel of lemon & orange, which contain essential oils that help to preserve, flavour and add aroma.

The Egyptians had a highly advanced civilisation that recognised the importance of these extracts for health and beauty. They used them in everyday life and placed great value on them. They also used them to keep their skin supple in the hot, dry environment by adding base oils such as sweet almond and olive oil. In the reign of Rameses, the monument builders even went on strike because, as they wrote, "we have no ointment".

Hippocrates, the father of medicine, said that "the way to health is to have an aromatic bath and scented massage every day". Why is it that our doctors of today have very little or no knowledge of Hippocrates’ thoughts on the use of essential oils?

Famous for his prophecies is Michel de Nostredame (Nostradamus). But did you know that he spent most of his young years from the year 1521 to the year 1529 constantly on the move across various lands and countries to hear and find out the source and origin of plants? His book The Cosmetics Manual was written in 1555 in which he says of observing various women "during my stays in many countries, even those where the women because of the swiftly passing years contrived secretly and by means of a subtle skill to hide and conceal the principal part of the body, namely the head, in order to show clear evidence that substances applied to the face have succeeded in deceiving the eyes of onlookers."

The word "aromatherapy" comes from the title of a book, Aromatherapie, written by a French chemist and perfumer, Rene Maurice Gattefosse, and published in 1937. His story is often relayed, and began in July 1910 with an accident at work: "In my personal experience, after a laboratory explosion covered me with burning substances which I extinguished by rolling on a grassy lawn, both my hands were covered with a rapidly developing gas gangrene. Just one rinse with lavender essence stopped "the gasification of the tissue".

Gattefosse was so impressed by the fact that lavender essential oil could effectively deal with this very serious condition, he started to investigate the chemical and healing properties of essential oils. He also drew on the experience of doctors using essential oils at the time, including those who had great success in healing soldiers’ wounds during the First World War. He found they also had a significant role in the field of dermatology, and after carrying out research in his own laboratory in the therapeutic action of essential oils on the skin, he published Beauty Products in 1936, and Physiological Aethetics in 1938.

Another pioneer of using essential oils for beauty was Marguerite Maury, a French women who specialised in her salons with using essential oils for rejuvenation and revitalisation, combining them with beauty therapy techniques.

An essential oil is any concentrated, hydrophobic liquid containing volatile aroma compounds from plants. They are also known as volatile or ethereal oils, or simply as the "oil of" the plant material from which they were extracted, such as oil of clove. The term essential indicates that the oil carries distinctive scent (essence) of the plant, not that it is an especially important or fundamental substance. essential oils do not as a group need to have any specific chemical properties in common, beyond conveying characteristic fragrances. They may not necessarily all have strong odours and are not to be confused with essential fatty acids.

Essential oils are generally extracted by distillation. Other processes include expression, or solvent extraction. They are used in perfumes and cosmetics, for flavouring food and drink, and for scenting incense and household cleaning products.

Various essential oils have been used medicinally at different periods in history. Medical applications proposed by those who sell medicinal oils vary from skin treatments to remedies for cancer, and are often based on historical use of these oils for these purposes. Such claims are now subject to regulation in most countries, and have grown correspondingly more vague, to stay within these regulations.

Interest in essential oils has revived in recent decades, with the popularity of aromatherapy, a branch of medicine that has been used for thousands of years, which claims that the specific aromas carried by essential oils have curative effects. Oils are volatilized or diluted in carrier oil and used in massage, or burned as incense.

Aromatic Sources - Plant Sources

Plants have long been used in perfumery as a source of essential oils and aroma compounds. These aromatics are usually secondary metabolites produced by plants as protection against herbivores, infections, as well as to attract pollinators. Plants are by far the largest source of fragrant compounds used in perfumery. The sources of these compounds may be derived from various parts of a plant. A plant can offer more than one source of aromatics, for instance the aerial portions and seeds of coriander have remarkably different odors from each other. Orange leaves, blossoms, and fruit zest are the respective sources of petitgrain, neroli, and orange oils.

Bark:

Commonly used barks includes cinnamon and cascarilla. The fragrant oil in sassafras root bark is also used either directly or purified for its main constituent, safrole, which is used in the synthesis of other fragrant compounds such as helional.

Flowers and Blossoms:

Undoubtedly the largest source of aromatics. Includes the flowers of several species of rose and jasmine, as well as osmanthus, mimosa, tuberose, as well as the blossoms of citrus and ylang-ylang trees. Although not traditionally thought of as a flower, the unopened flower buds of the clove are also commonly used. Orchid flowers are not commercially used to produce essential oils or absolutes, except in the case of vanilla, an orchid, which must be pollinated first and made into seed pods before use in perfumery.

Fruits:

Fresh fruits such as apples, strawberries and cherries unfortunately do not yield the expected odors when extracted; if such fragrance notes are found in a perfume, they are synthetic. Notable exceptions include litsea cubeba, vanilla and juniperberry. The most commonly used fruits yield their aromatics from the rind; they include citrus such as oranges, lemons, limes and grapefruit.

Leaves and Twigs:

Commonly used for perfumery are eucalyptus, tea tree, lavender leaf, patchouli, sage, violets, rosemary and citrus leaves. Sometimes leaves are valued for the "green" smell they bring to perfumes, examples of this include hay and tomato leaf.

Resins:

Valued since antiquity, resins have been widely used in incense and perfumery. Highly fragrant and antiseptic resins and resin-containing perfumes have been used by many cultures as medicines for a large variety of ailments. Commonly used resins in perfumery include labdanum, frankincense/olibanum, myrrh, Peru Balsam, Gum Benzoin. Pine and fir resins are a particularly valued source of terpenes used in theorganic synthesis of many other synthetic or naturally occurring aromatic compounds. Some of what is called amber and copal in perfumery today is the resinous secretion of fossil conifers.

Roots, Rhizomes and Bulbs:

Commonly used terrestrial portions in perfumery include iris rhizomes, vertiver roots, various rhizomes of the ginger family.

Seeds:

Commonly used seeds include pepper, tonka bean, coriander, caraway, cocoa, nutmeg, mace, cardamon and anise.

Woods:

Highly important in providing the base notes to a perfume, wood oils and distillates are indispensable in perfumery. Commonly used woods include sandalwood, rosewood, agarwood, birch, cedar, juniper and pine.

Obtaining Natural Odourants

Before perfumes can be composed, the odorants used in various perfume compositions must first be obtained. Synthetic odorants are produced through organic synthesis and purified. Odorants from natural sources require the use of various methods to extract the aromatics from the raw materials. The results of the extraction are either essential oils, absolutes, concretes, or butters, depending on the amount of waxes in the extracted product.

All these techniques will, to a certain extent, distort the odor of the aromatic compounds obtained from the raw materials. This is due to the use of heat, harsh solvents, or through exposure to oxygen in the extraction process which will denature the aromatic compounds, which either change their odor character or renders them odorless.

Maceration / Solvent Extraction:

The most used and economically important technique for extracting aromatics in the modern perfume industry. Raw materials are submerged in a solvent that can dissolve the desired aromatic compounds. Maceration lasts anywhere from hours to months. Fragrant compounds for woody and fibrous plant materials are often obtained in this manner as are all aromatics from animal sources. The technique can also be used to extract odorants that are too volatile for distillation or easily denatured by heat. Commonly used solvents for maceration/solvent extraction include water, hexane, and dimethyl ether. The product of this process is called a "concrete". Also used are;

Supercritical Fluid Extraction:

A relatively new technique for extracting fragrant compounds from a raw material, which often employs Supercritical CO2. Due to the low heat of process and the relatively nonreactive solvent used in the extraction, the fragrant compounds derived often closely resemble the original odor of the raw material.

Ethanol extraction: A type of solvent extraction used to extract fragrant compounds directly from dry raw materials, as well as the impure oily compounds materials resulting from solvent extraction or enfleurage. Ethanol extraction is not used to extract fragrance from fresh plant materials since these contain large quantities of water, which will also be extracted into the ethanol. Glycols or Glycerine may be substituted for Ethanol.

The problem is that the dry extract is not strictly an extract but a chopped tea or powdered, micronised or ground powder from the actual plant part. The liquid extracts are where you take the powder and extract the active components by various techniques. However this is not simple as the solvent used not only affects the concentration of the extract but also the extent of the extract achieved. That is; by increasing organic solvents you will achieve a different extract than if you only use water or put another way - the solvent type determines what component you will extract - that is, the more polar solvent will extract mainly polar components while the non-polar solvents will mainly extract non-polar components, so you have to determine what active component of the powder you want before you select the solvent to use. Also if you use more solvent then you will extract more than if you use a small amount of solvent.

My suggestion is that you start with a simple maceration technique where he allows the powder to be in contact with the solvent (probably a mixture of 50% Water and 50% Glycerine (a Hydroglyceric extract) or 33% Water ; 33% Ethanol and 33% Glycerine) for at least 48 hours (stirring occasionally) and then filtering the mixture, using the filtrate as the active in the product. Once you have filtered the mixture a further extraction of the original powder by the solvent mix will tell if there is still more to be extracted, hence the procedure should be repeated, until the filtrate is clear. If the amount of filtrate is too much then this can be concentrated down by evaporation.

Another technique is to use a concentrated solvent/powder mixture directly in the product but this depends on if the formulation can withstand particulate matter (sedimentation or flocculation may occur) and if the stability of the formulation can withstand the amount of solvent used. The advantage of this technique is that it provides a "holistic" approach in that all the actives will be transferred to the finished product.

Distillation:

A common technique for obtaining aromatic compounds from plants, such as eucalyptus leaves, orange blossoms and roses. The raw material is heated and the fragrant compounds are re-collected through condensation of the distilled vapour.

Steam Distillation:

Steam from boiling water is passed through the raw material, which drives out their volatile fragrant compounds. The condensate from distillation are settled in a Florentine Flask. This allows for the easy separation of the fragrant oils from the water. The water collected from the condensate, which retains some of the fragrant compounds and oils from the raw material is called hydrosol and sometimes sold. Note; a hydrosol should not be confused with a floral water which is an essential oil dissolved into water by using a solubiliser.

This is most commonly used for fresh plant materials such as flowers, leaves and stems.

Dry/destructive distillation: The raw materials are directly heated in a still without a carrier solvent such as water. Fragrant compounds that are released from the raw material by the high heat often undergo anhydrous pyrolysis, which results in the formation of different fragrant compounds, and thus different fragrant notes. This method is used to obtain fragrant compounds from fossil amber and fragrant woods where an intentional "burned" or "toasted" odor is desired.

Expression (sometimes called Cold Pressing):

Raw material is squeezed or compressed and the oils are collected. Of all raw materials, only the fragrant oils from the peels of fruits in the citrus family are extracted in this manner since the oil is present in large enough quantities as to make this extraction method economically feasible.

Enfleurage:

Absorption of aroma materials into wax and then extracting the odorous oil with ethyl alcohol. Extraction by enfleurage was commonly used when distillation was not possible due to the fact that some fragrant compounds denature through high heat. This technique is not commonly used in the present day industry due to its prohibitive cost and the existence of more efficient and effective extraction methods.

Fragrant Extracts

Although fragrant extracts are known to the general public as the generic term "essential oils", a more specific language is used in the fragrance industry to describe the source, purity, and technique used to obtain a particular fragrant extract.

Of these extracts, only absolutes, essential oils, and tinctures are directly used to formulate perfumes.

Absolute:

A highly concentrated viscous semi-solid or solid perfume material, usually purified from a pomade or concrete by soaking them in ethanol. By using a slightly hydrophilic compound such as ethanol, most of the fragrant compounds from the waxy source materials can be extracted without dissolving any of the fragrant less waxy molecules. Absolutes are usually found in the form of an oily liquid.

Concrete:

Fragrant materials that have been extracted from raw materials through solvent extraction using volatile hydrocarbons. Concretes usually contain a large amount of wax due to the ease in which the solvents dissolve various hydrophobic compounds. As such concretes are usually further purified through distillation or ethanol based solvent extraction. Concretes are typically either waxy or resinous solids or thick oily liquids.

Essential Oil:

Fragrant materials that have been extracted from a source material directly through distillation or expression and obtained in the form of an oily liquid. An essential oil is a volatile and aromatic liquid which generally constitutes the odorous principles of the plant. It is obtained by a process of expression or distillation from a single botanical form or species, even from a specific part of the herb (eg flower, bark, root or whole plant).Oils extracted through expression are sometimes called expression oil.

Pomade:

A fragrant mass of solid fat created from the enfleurage process, in which odorous compounds in raw materials are adsorbed into animal fats. Pomades are found in the form of an oily and sticky solid.

Tincture:

Fragrant materials produced by directly soaking and infusing raw materials in ethanol. Tinctures are typically thin liquids.

Hydrosol:

The hydrosol is produced from the distillation process and is the water distilled fraction containing volatile water soluble components from the herb or plant.

Floral Water:

Contain a very small amount of essential oil and water soluble extracts from the plant dissolved into water. A floral water usually also contains a solubiliser to aid in clarification.

Linen Water:usually contain a very small amount of essential oil but no water soluble extracts from the plant. The floral water is produced from the distillation process and then further treatment to remove tannins and other components which may stain cloth.

Decoction:

A herbal preparation where the plant material (usually hard or woody) is boiled in water and reduced to make a concentrated extract.

Infusion:

A herbal remedy prepared by steeping the plant material in Water.

Rectification:

The process of redistilling applied to essential oils to rid them of certain constituents.

Oleoresin:

A less volatile but aromatic liquid which generally constitutes the odorous principles of the plant. It is obtained by a process of liquid extraction from a single botanical form or species, even from a specific part of the herb, usually the bark, root or whole plant. It is a dark molasses type mass and is often used as a concentrated form (eg as in Vanilla oleoresin) or a fixative (eg as in Benzoin resin). Resinoid crystals are the materials from sap (trees) and extracts (usually from bark) that are solid, substantive to skin and difficult to remove from skin. These properties make them ideal for perfume fixatives (the base that dissolves the fragrance and holds them on skin for extended periods). Ambergris is another type although animal derived (non-harmful in that it is the regurgitation of undigested shell that is from the whale's diet).

1. Some resinoids will dissolve directly into the essential oil, given time. This depends on the type of resinoid and the type of essential oil. Gentle warming will assist but if too hot then the essential oil will lose its effect.
2. Use heat to melt the resinoid, usually in the presence of a small amount of carrier oil (enough to produce a viscous liquid). The essential oil is then dissolved in this mix (preferably when cooler ie below 40°C).
3. Dissolve the Resinoid in Alcohol - add the essential oils - then dry until only the resinoid/perfume mix remains.

Note; if used at high levels in the product they may have a tendency to make the final product thicker and possibly a yellow/amber colour. They might also give the skin a waxy after feel. Hence the level must be carefully determined beforehand.

12 October 2007