 |
The Many Methods of Essential Oil Production
by Misty Rae Cech, Nd
http://www.anandaapothecary.com
Modern methods of essential oil extraction are entering
mainstream aromatherapy, offering new choices in oils never
before available. Labels of CO2 and SCO2 are now found along
with the traditional Steam- and Hydro-distillations,
solvent-extracted Absolutes, and Cold pressing. Is one
process better than another? Does one produce a nicer
smelling oil, or one with greater aromatherapeutic value?
Well, essential oil production, like winemaking, is an art
form as well as a science. The value of any processing
method depends greatly on the experience of the distiller,
as well as the intended application of the final product.
Each method is important, and has it's place in the making
of fine, aromatherapy-grade essential oils.
Steam and Hydro Distillation Methods
Steam-distillation, the most common method of essential oil
extraction, involves the flow of steam into a chamber
holding the plant material. Steam causes small sacs holding
aromatic oils to burst. The essential oil is carried by the
steam into a chilling condenser, where the steam again
becomes water. Hydro-distillation is a similar - plant
material is boiled, with the resultant steam being captured
and condensed. In both methods, the essential oil and water
are then separated; the water, referred to as a hydrosol,
can be retained as it will have some of the plant essence.
Several factors determine the quality of a steam distilled
essential oil. Aside from the plant material itself, most
important elements are time, temperature and pressure, and
the efficiency of the distillation equipment. Essential oils
are very complex products - each is made up of possibly
hundreds of different molecules which come together to form
the aroma and therapeutic properties. Some of these
molecules are delicate structures which can be destroyed by
extreme environmental conditions.
The temperature of the distillation chamber must not be too
high, lest some components of the oil be altered or
destroyed; The same is true of the chamber's pressure.
Lavender oil, for example, should not be distilled at over
245 degrees F and 3 psi. Higher temperatures and pressures
result in a sharp and unplesant aroma, more chemical than
floral, and can lessen the essential oil's therapeutic
results. Further, the extraction period must be allowed to
continue for a certain amount of time in order to flush all
the aromatic components from the plant, as some are released
more slowly than others.
Even with these drawbacks, high temperatures and pressures
are often used to produces large quantities of oil in a
short period of time. These oils are usually destined for
use in cosmetic and processed food manufacturing, but are
sometimes sold to consumers as essential oils for
aromatherapy. These oils will be less expensive, but are of
limited therapeutic and aromatic value.
Absolutes from Delicate Plants
Some flowers do not lend themselves to steam distilling.
They are too delicate, or their fragrance and therapeutic
essences cannot be completely released by water alone. These
oils are instead produced as Absolutes; While not
technically considered essential oils, they can still be of
therapeutic value. Jasmine oil in particular has delicate
flowers who's oils are only found in absolute form (though
CO2 extracted products are just now entering the market).
Making an absolute first involves solvent extraction of a
concrete from the plant material - this is a semi-solid
mixture of around 1:1 wax and oil. The concrete is again
processed using ethyl alcohol - the same alcohol found in
beer, wine, etc. - in which the wax is only slightly
soluble. The volatile plant oil dissolves in the alcohol and
this mixture removed. The alcohol is then evaporated and
the result is an almost pure plant extract. The use of
solvents in the extraction process notwithstanding,
absolutes can have very deep and complex aromas.
CO2's and SCO2's - Cold Extraction with Carbon Dioxide
The most modern technologies involve Carbon Dioxide and
Supercritical Carbon Dioxide extraction. Both methods use
carbon dioxide as the solvent which carries the essential
oil away from the plant material. The lower pressure CO2
extraction involves cooling carbon dioxide to 35-55 deg. F,
and pumping it through the plant material at about one
thousand psi. The carbon dioxide in this condition is
condensed to a liquid. Supercritical CO2 extraction, or
SCO2, involves carbon dioxide heated to 87 degrees F and
pumped through the plant material at around eight thousand
psi; under these conditions, the carbon dioxide is likened
to a thick fog. With release of the pressure in either
process, the carbon dioxide escapes in its gaseous form,
leaving the essential oil behind.
These cold methods have a couple of advantages - As with
steam distillation, there is no solvent ever left behind,
and the product is quite pure. Like absolutes, there is no
heat applied to the plant material or aromatic oil to alter
it. The oil produced reflects the original state of the
plant. The carbon dioxide methods also are the most
efficient, producing the most oil per amount of plant. The
efficiency of CO2 extraction is particularly important when
rare or endangered plant species are involved, such as
Indian Sandalwood oil.
Cold Pressing of Citrus Oils
Finally, there is the cold pressing of citrus oils from the
peels of fruit, as is done with Bitter Orange, Sweet Orange,
Lemon, Grapefruit and the like. This method involves the
simple pressing of the rind at about 120 degrees F to
release the oil. Little alteration from the aromatic oil's
original state occurs - these citrus oils retain their
bright, fresh, uplifting aromas like that of smelling a
wonderfully ripe fruit.
Which is the best method?
CO2 distillation, with it's obvious advantages, is not
always the best choice for a particular aromatherapeutic
need. These oils are still the most expensive, despite the
higher yields. The resultant product differs slightly
compared to one produced another way - the oils produced by
steam distillation of some plants may sometimes be found to
have a more agreeable aroma. Patchouli oil, for example,
seems to benefit from the steam distillation process by
becoming a little warmer and richer. The blue color in
German Blue Chamomile, with it's great anti-inflamatory
properties, only results from steam processing. Many other
essential oils are quite effectively produced via steam
distillation, with little alteration from the original plant
state. Oils from other plant species, however, do seem more
'complete' with CO2 processing - Frankincense oil and most
of the 'spice' oils being good examples where a little
something special is present in the aroma.
Producing essential oils of aromatherapeutic grade is skill
requiring years of experience. It takes the work of a
dedicated artesian at every step, from growing and
harvesting to fine-tuning the distillation process, to
produce a truly fine oil. The making of a fine essential oil
relies far more on knowledge and experience than it does on
the particular extraction method. There are, however,
legitimate reasons to select one distillation method over
another - some plants simply require a particular process to
produce a fine oil, and the oil needed for a particular
application may only be made by one process. In the end, as
is often the case in aromatherapy, your own sense of smell
can tell you which oil will work best for you.
Submit An Article
|
|  |
