Steam DistillationThe
majority of essential oils available today are extracted using a steam
distillation process. It's the oldest form of essential oil extraction
and
is believed by many to be the only way oils should be extracted. The
process really is quite simple and as long as this extraction process
is closely monitored, the steam will remain at a temperature that won't
damage the plants.
The desired plant
material is placed onto a still. A still is a specialized piece of
equipment that is used in the distillation process. It consists of a
vessel into which heat is added and a device that is used for cooling.
The plant is first placed into the vessel. Next steam is added and
passed through the plant. The heat from the steam helps to open the
pockets of the plant that contain the plant's aromatic molecules or
oils. Once open, the plant releases these aromatic molecules and in
this state, the fragrant molecules are able to rise along with the
steam.
The vapors carrying these molecules travel
within a closed system towards the cooling device. Cold water is used
to cool the vapors. As they cool, they condense and transform into a
liquid state. The liquid is collected in a container and as with any
type of oil/water mixture, it separates. The oils float towards the top
while the water settles below. From there, it's a simple matter of
removing the oils that have been separated. These are the highly
condensed, aromatic oils used in aromatherapy.
The
water is not discarded, however. The water, which also contains the
plant's aroma along with the other parts of the plant that are water
soluble, are the hydrosols - a milder form of the essential oils.
These, too are also used in aromatherapy.
When
steam is used, it's created at a pressure higher than that of the
atmosphere. The boiling point is above 100 degrees Celsius and creates
an extraction process that is safe and fast. If the temperature is
allowed to become too hot, however, the plant material as well as its
essential oils can easily become damaged.
Water DistillationWater
distillation involves placing the desired plant material in a still and
then submerging it in water. The water is then brought to a boil. The
heat helps open the pockets containing the plant's aromatic molecules
so they can be extracted. The vapors cool and condense, the essential
oils separate from the water and they're collected.
The
water in this case provides protection for the plant because it acts as
a barrier. Less pressure is used as well as a lower temperature than
that which is used in the steam distillation method. This extraction
method works well with plants that cannot tolerate high heat.
Other Distillation
MethodsHydro distillation is similar to steam
distillation. The only difference is that instead of introducing the
heat from the bottom and up through the still, as happens in steam
distillation, the heat passes into the still from the top. It's cooled
from below, which makes collection of the essential oils easier. This
method actually results in a higher yield of essential oils because
less steam and consequently less processing time are involved.
In
a water/steam combination distillation method, plant material is
submerged into heated water and steam is forced through the water,
opening the pockets containing the aroma molecules. When cooled, the
essential oils condense and are collected as described above.
Essential Oil Extraction
Processes - ExpressionIt's true that essential
oils are an essential part of aromatherapy. But contrary to what some
people think, the term 'essential' doesn't mean essential as in 'being
a necessary part of'. Instead, essential oils are the oils extracted
from the 'essence' of a plant - those parts that contain the plant's
aroma molecules.
Using different methods of
extraction guarantees that the highest concentrations of oils can be
extracted. Essential oils are gathered from many different types of
plants and many different parts of those plants. Flowers, fruits,
herbs, stems, roots, leaves, buds, blossoms, seeds, nuts and even tree
bark produce some of the most aromatic and therapeutic essential oils.
Essential oil extraction methods fall under three main categories:
expression, solvent extraction and distillation. The following is an
overview of these extraction processes and methods.
ExpressionThe
expression form of essential oil extraction does not involve the use of
a heat source. This is the method commonly used to extract oils from
the rinds of citrus. In earlier times, rinds were squeezed by hand and
a sponge was used to collect the essential oils. The fruit would be
removed and then the rinds along with the pith would be soaked in water
to make them easier to work with. They'd then be turned upside-down.
Turning them upside-down caused the cells containing the oils to break
apart. Once broken, the oils would drip out and soak into a nearby
sponge. When the sponge became saturated, the oils were squeezed into a
container so they could be decanted.
Ecuelle a PicuerAnother
expression method involved sticking pins into the skins of fruit for
the purpose of damaging the cells that contain the essential oils. The
apparatus used had a built-in container for collecting the oils and the
other parts of the fruit that ended up in the collection area. The
final steps involved separating the essential oils and decanting them.
This is called the ecuelle a picuer method.
Machine AbrasionThose
were quite laborious processes, and thankfully, technological advances
led to the invention of machines to do this type of tedious work.
Nowadays, oils from rinds are extracted using centrifugal force. This
rapid process is called Machine Abrasion.
Cold PressedThis
form of expression extraction is also used to extract essential oils
from nuts and seeds and from the rinds of citrus. Mechanical pressure
is used to force the oils out. The oils extracted contain water, but
this water will, in time, evaporate, leaving just the essential oils.
The downside of using this extraction method is that the cold pressed
oils spoil more quickly than those extracted using other methods.
That's why, to eliminate waste, it's important to purchase these
essential oils in small quantities.
Essential Oil Extraction Processes
- Solvent ExtractionSome plant material cannot
tolerate the heated forms of extraction such as steam distillation.
High heat damages these plants and once damaged, their essential oils
too are damaged and are no longer able to be extracted. For these
plants, as well as 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, those true to aromatherapy refuse to use them.
As
mentioned above, there are times when solvent extraction makes sense.
This process involves a lot of chemistry and is somewhat confusing to
understand but in general it is as follows.
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. 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 used in the manufacturing of perfumes and
fragrances, not in aromatherapy or skin care products.
Super Critical
Carbon Dioxide (CO2) ExtractionThe end result
of super critical carbon dioxide (CO2) extraction - one of the newest
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.
It's an inert solvent meaning that it's 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 not yet widely used. The equipment needed
for this extraction process is very expensive, which keeps production
costs high. And because production costs are high, so too are the costs
of the essential oils that are produced via carbon dioxide extraction.
MacerationWith
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 they 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.
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