Essential oils can be extracted using a variety of methods,
although some are not commonly used today. Nowadays, a reputable distiller will
try to preserve the original qualities of the plant, but the final therapeutic
result is often not formed until after the extraction process. During
extraction, the qualities of the oil change to give it more value - for
example, chamazulene (characteristic of the pure blue colour of German
Chamomile) is formed during the steam distillation process. Currently, the most
popular method for extraction is steam distillation. Many old-time distillers
favor this method for most oils, and say that none of the newer methods
produces better quality oils. Steam distillation is a special type of
distillation or a separation process for temperature sensitive materials like
oils, resins, hydrocarbons, etc. which are insoluble in water and may decompose
at their boiling point. The fundamental nature of steam distillation is that it
enables a compound or mixture of compounds to be distilled at a temperature
substantially below that of the boiling point(s) of the individual
constituent(s). Essential oils contain substances with boiling points up to 200°C
or higher temperatures. In the presence of steam or boiling water, however,
these substances are volatilized at a temperature close to 100°C at atmospheric
pressure. Fresh, or sometimes dried, botanical material is placed in the plant
chamber of the still and the steam is allows to pass through the herb material
under pressure which softens the cells and allows the essential oil to escape
in vapor form. The temperature of the steam must be high enough to vaporize the
oil present, yet not so high that it destroys the plants or burns the essential
oils. As they are released, the tiny droplets of essential oil evaporate and,
together with the steam molecules, travel through a tube into the still's 18
condensation chamber. As the steam cools, it condenses into water. The
essential oil forms a film on the surface of the water. To separate the
essential oil from the water, the film is then decanted or skimmed off the top.
The remaining water, a byproduct of distillation, is called floral water,
distillate, or hydrosol. It retains many of the therapeutic properties of the
plant, making it valuable in skin care for facial mists and toners. In certain
situations, floral water may be preferable to be pure essential oil, such as
when treating a sensitive individual or a child, or when a more diluted
treatment is required. Rose hydrosol, for example, is commonly used for it's
mild antiseptic and soothing properties, as well as it's pleasing floral aroma.
Essential oil isolated by steam distillation are different in composition to
those naturally occurring in the oil bearing glands of plants, since the steam
distillation conditions cause chemical reactions to occur which result in the
formation of certain artificial chemicals, called artifacts. Some of these are
considered beneficial e.g. the formation of chamazulene during the steam
distillation of Chamomile oil; whilst others may not be e.g. the hydrolysis of
linalyl acetate during the distillation of clary sage. Few, if any, essential
oils are unscathed by the thermal conditions of steam distillation, but some
distillation techniques can, in certain instances, be a measure less damaging
than others (e.g. hydro diffusion – a sort of inverted steam distillation where
steam is introduced at the top of the vegetable material-packed container, and
oil and condensate issue from the bottom – can produce oils with higher ester
contents i.e. less thermally induced hydrolysis). A number of factors determine
the final quality of a steam distilled essential oil. Aside from the plant material
itself, most important are time, temperature and pressure, and the quality of
the distillation equipment. Essential oils are very complex products. Each is
made up of many, sometimes hundreds, of distinct molecules which come together
to form the oil's aroma and therapeutic properties. Some of these molecules are
fairly delicate structures which can be altered or destroyed by adverse
environmental conditions. So, much like a fine meal is more flavorful when made
with patience, most oils benefit from a long, slow 'cooking' process. It is
possible that longer distillation times may give more complete oil. It is also
possible however, that longer distillation time may lead to the accumulation of
more artifacts than normal. This may have a curious effect of 19 appearing to
improving the odour, as sometimes when materials that have a larger number of
components are sniffed, the perception is often of slightly increased
sophistication, added fullness and character, and possibly, and extra
pleasantness.
Cold Pressing
Cold pressing is used to extract the essential oils from citrus
rinds such as orange, lemon, grapefruit and bergamot. This method involves the
simple pressing of the rind at about 120 degrees F to extract the oil. The
rinds are separated from the fruit, are ground or chopped and are then pressed.
The result is a watery mixture of essential oil and liquid which will separate
given time. Little, if any, alteration from the oil's original state occurs –
these citrus oils retain their bright, fresh, uplifting aromas like that of
smelling a wonderfully ripe fruit. It is important to note that oils extracted
using this method have a relatively short shelf life, so make or purchase only
what you will be using within the next six months.
Solvent Extraction
A hydrocarbon solvent is added to the plant material to help
dissolve the essential oil. When the solution is filtered and concentrated by
distillation, a substance containing resin (resinoid), or a combination of wax
and essential oil (known as concrete) remains. From the concentrate, pure
alcohol is used to extract the oil. When the alcohol evaporates, the oil is
left behind. This is not considered the best method for extraction as the
solvents can leave a small amount of residue behind which could cause allergies
and effect the immune system.
CO2 & Super Critical CO2 Extraction
The most modern technologies, Carbon Dioxide and Supercritical
Carbon Dioxide extraction involve the use of carbon dioxide as the 'solvent'
which carries the essential oil away from the raw plant material. The lower
pressure CO2 extraction involves chilling carbon dioxide to between 35 and 55
degrees F, and pumping it through the plant material at about 1000 psi. The
carbon dioxide in this condition is condensed to a liquid. Supercritical CO2
extraction (SCO2) involves carbon dioxide heated to 87 degrees F and pumped
through the plant material at around 8,000 psi – under these conditions; the
carbon dioxide is likened to a 'dense fog' or vapor. With release of the
pressure in either process, the carbon dioxide escapes in its gaseous form,
leaving the essential oil behind. The usual method of extraction is through
steam distillation. After extraction, the properties of a good quality
essential oil should be as close as possible to the "essence" of the
original plant. The key to a 'good' essential oil is through low pressure and
low temperature processing. High temperatures, rapid processing and the use of
solvents alter the molecular structure, will destroy the therapeutic value and
alter the fragrance.
CARRIER OILS
Carrier oils and
essential oils are made from plants. Carrier oils are used to dilute essential
oils and “carry” them to skin. That’s because essential oils are potent and can
cause irritation when applied directly to skin. Most carrier oils are unscented
or lightly scented and don’t interfere with an essential oil’s therapeutic
properties. They may be used alone or with other oils to nourish your skin.
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