Some plant material cannot
tolerate the heated forms of extraction such as steam
distillation. The high of these
processes damages these plants and once damaged, their essential
oils too are damaged and are no
longer able to be extracted.
In these instances, as
well as a few others, solvents such as ether, ethanol, methanol,
hexane, alcohol and petroleum are used instead.
The problem with using
solvents to extract essential oils is that most of the time, residual
solvents or impurities remain in the end product. Because they're
impure, aromatherapy purists generally refuse to use them.
As mentioned above, there are times when solvent extraction makes
sense. This process, however, involves a lot of chemistry and is
somewhat confusing to understand but in general it is as follows.
The plant material is first washed in a bath of hydrocarbon solvents.
This process dissolves the necessary plant materials including the
aromatic molecules, waxy matter and pigment and the dissolved matter
mixes in with the solvent.
The solvent mixture is
then filtered and distilled using low pressure. After distillation and
further processing, either a resin or a concentrated concrete remain.
Additional processing using alcohol helps extract the essential oils.
This is a very fast and cost-effective method of essential oil
extraction, but there is a downside to it. With solvent extraction,
residual solvents remain and their presence can cause problems if used
by individuals with allergies or sensitive skin. That's another reason
why essential oils extracted using solvents are commonly used in the
manufacturing of perfumes and fragrances, not in aromatherapy or skin
care products.
Super
Critical Carbon Dioxide (CO2) Extraction
The end result of super critical carbon dioxide (CO2) extraction - one
of the newest of the essential oil extraction technologies - is a
super-concentrated, high-quality version of essential oil. This rapid
extraction method uses lower temperatures and higher pressure to
transform carbon dioxide, a gas, into a liquid. The carbon dixoide is
an inert solvent. This means that it is non-reactive and
therefore cannot form another chemical compound. When the extraction
process is complete, the carbon dioxide is returned back to a gaseous
state therefore, no residual remains.
All that is left is pure
essential oil.
Although this technology produces one of the purest forms of essential
oil, it is still not yet widely used. The equipment needed for this
extraction process is very expensive, which tends to keep production
costs high. As production costs are high, so too are the costs of the
finished product, the essential oils that are produced via
carbon dioxide extraction.
Maceration
With this essential oil extraction method, hot oil is used as a way to
rip apart cell membranes. The plant material is first saturated with
hot oil and allowed to soak until the cell membranes rupture. As these
break apart, essential oils are released into the oil in which the
plant material is soaking. When the release period is complete, the
plant material is removed from the oil. The oil that remains then gets
decanted.
