Essential Oil Extraction Techniques
Content
Patel P N et al. / Pharmacie Globale (IJCP) 2011, 9 (02)
Available online at www.pharmacie-globale.info
ISSN 0976-8157
Review Article
PHARMACIE GLOBALE
INTERNATIONAL JOURNAL OF COMPREHENSIVE PHARMACY
EXTRACTION OF HERBAL AROMA OILS FROM SOLID SURFACE
Parth N Patel*, Krupa M Patel, Dhaval S Chaudhary, Khushboo G Parmar, Henil A Patel,
Chandni D Kansagra and Dhrubo Jyoti Sen
Shri Sarvajanik Pharmacy College, Gujarat Technological University, Arvind Baug, Mehsana, Gujarat, India.
Received: 12 April 2011; Revised: 20 August 2011; Accepted: 25 August 2011; Available online: 5 September 2011
ABSTRACT
Fragrance extraction refers to the extraction of aromatic compounds from raw materials, using methods such as
distillation, solvent extraction, expression or enfleurage. The results of the extracts are either essential oils,
absolutes, concretes or butters, depending on the amount of waxes in the extracted product. To a certain extent,
all of these techniques tend to distort the odour of the aromatic compounds obtained from the raw materials.
Heat, chemical solvents or exposure to oxygen in the extraction process denature the aromatic compounds,
either changing their odour character or rendering them odourless. This technique is very costly and is rarely
used today. It reached its peak in 1860 and made the reputation of Grasse. It is a labour-intensive process that
yields the highest quality of absolutes because it does not involve heat. Heat always alters the fragrance. It is
used on delicate flowers that cannot stand up to the high heat and that continue to release essential oils after
they have been picked. Examples of these flowers are Jasmine, Violet, Tuberose and Rose. Enfleurage goes back
thousands of years to the ancient Egyptians. It works on the principle that fats absorb smells. Petals or other
fragrant parts of a plant are steeped in fat or non-evaporating oil which will absorb their fragrance. A mixture of
pork, lard and beef suet is smeared on to a glass plate in a wooden frame called a chassis. The flowers are placed
on the fat and left to release their oils for several days. This process was repeated several times with fresh
flower heads until the fat was totally absorbed with essential oil, the resultant substance being known as
'pomade', the oil was then retrieved from the fat by dissolving in an alcoholic solvent. This is mechanically mixed
with alcohol for up to one week, and is chilled to 68°F. The essential oils dissolve in the alcohol and the fat does
not. The mixture is chilled and filtered several times to remove all the fat. The alcohol is then evaporated to leave
the pure absolute. Sometimes enfleurage is now carried out with cloth soaked in olive oil or liquid paraffin,
which is laid over the frames instead of fat, the resultant perfumed oil being then known as 'huile antique'.
Keywords: Essential oil, enfleurage, pomade, supercritical fluid extraction, cohobation, sponge expression, cold
pressed method, machine abrasion, maceration, hypercritical carbon dioxide, Florasols/Phytols Method.
INTRODUCTION
Essential oils are volatile and liquid aroma compounds
from natural sources, usually plants. Essential oils are not
oils in a strict sense, but often share with oils a poor
solubility in water. Essential oils often have an odor and
are therefore used in food flavoring and perfumery.
Essential oils are usually prepared by fragrance extraction
techniques such as distillation including steam
distillation), cold pressing, or extraction (maceration).
Essential oils are distinguished from aroma oils (essential
oils and aroma compounds in an oily solvent), infusions in
a vegetable oil, absolutes and concretes. Typically,
essential oils are highly complex mixtures of often
hundreds of individual aroma compounds.1 (Figure 1)
An essential oil is a concentrated hydrophobic liquid
containing volatile aroma compounds from plants.
Essential oils are also known as volatile oils, ethereal
oils or aetherolea, or simply as the “oil” of the plant from
*Corresponding Author:
Parth N Patel
Shri Sarvajanik Pharmacy College, Gujarat Technological University,
Arvind Baug, Mehsana, Gujarat, India.
Contact no: +91-2762-247711; Email: [email protected]
1
Figure 1. Essences from floral unit
which they were extracted, such as oil of clove. An oil is
"essential" in the sense that it carries a distinctive scent, or
essence, of the plant. Essential oils do not form a
distinctive category for any medical, pharmacological, or
culinary purpose. Essential oils are generally extracted by
distillation. Other processes include expression, or solvent
extraction. They are used in perfumes, cosmetics, soaps
and other products, for flavoring food and drink, and for
adding scents to incense and household cleaning products.
Various essential oils have been used medicinally at
different periods in history. Medical application proposed
by those who sell medicinal oils range from skin
treatments to remedies for cancer, and often are based on
nothing better than historical accounts of use of essential
oils for these purposes. Claims for the efficacy of medical
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treatments and treatment of cancers in particular, are now
Table 1. Essential oils from plants
subject to regulation in most countries. (Table 1)
Agar
oil
distilled
from
Agarwood
(Aquilaria
malaccensis). Highly prized for
its fragrance.
Asafoetida, used medicinally
and to flavor food.
Ajwain oil, distilled from the leaves
of Bishop’s weed (Carum copticum).
Oil contains 35-65% thymol.
Angelica root oil, distilled from the
Angelica archangelica.
Anise oil, from the Pimpinella
anisum, rich odor of licorice, used
medicinally.
Balsam oil, from the Myroxylon
pereirae.
Basil oil is used in making perfumes,
as well as in aromatherapy.
Bay is used in perfumery;
Aromatherapeutic for sprains,
colds, flu, insomnia, rheumatism.
Bergamot
oil,
used
in
aromatherapy and in perfumes.
Black Pepper essential oil is
distilled from the berries of Piper
nigrum. The warm, soothing effect
makes it ideal for treating muscle
aches, pains and strains.
Buchu oil, made from the buchu
shrub. Considered toxic and no
longer widely used. Formerly used
medicinally.
Birch is aromatheapeutic for gout,
Rheumatism, Eczema, Ulcers.
Camphor is used for cold, cough,
fever, rheumatism, arthritis.
Cannabis flower essential oil, used
as a flavoring in foods, primarily
candy and beverages. Also used as a
scent in perfumes, cosmetics, soaps,
and candles.
Caraway oil, used a flavoring in
foods. Also used in mouthwashes,
toothpastes, etc. as a flavoring
agent.
Carrot seed oil (essential oil),
used in aromatherapy.
Cedarwood oil, primarily used in
perfumes and fragrances.
Cinnamon oil, used for flavoring
and medicinally.
Citronella oil, from a plant related to
lemon grass is used as an insect
repellent, as well as medicinally.
Chamomile oil, There are many
varieties of chamomile but only two
are used in aromatherapy- Roman
and German. Both have similar
healing properties but German
chamomile contains a higher level
of azulin (an anti-inflammatory
agent).
Clove leaf oil, used as a topical
anesthetic to relieve dental pain.
Cardamom seed oil, used in
aromatherapy and other medicinal
applications. Extracted from seeds
of subspecies of Zingiberaceae
(ginger). Also used as a fragrance
in soaps, perfumes, etc.
Calamus Root, used medicinally.
Coriander
Costmary oil (bible leaf oil), from
the Tanacetum balsamita.
Costus Root, used medicinally.
Cubeb, used medicinally and to
flavor foods.
Cumin oil/Black seed oil, used as a
flavor,
particularly
in
meat
products. Also used in veterinary
medicine.
Eucalyptus oil, historically used as a
germicide. Commonly used in cough
medicine, among other medicinal
uses.
Curry leaf, used medicinally and to
flavor food.
Fennel seed oil, used medicinally,
particularly for treating colic in
infants.
Fenugreek oil, used medicinally
and for cosmetics from ancient
times.
Frankincense oil, used for
aromatherapy and in perfumes.
Galangal, used medicinally and to
flavor food.
Geranium oil, used in aroma
therapy, used for hormonalimbalance. Geranium oil is often
known as "female" oil.
Ginger oil, used medicinally in
many cultures.
Grapefruit oil, extracted from
the peel of the fruit. Used in
aromatherapy. Contains 90%
limonene.
Henna oil, used medicinally.
Jasmine oil, used for its flowery
fragrance.
Juniper berry oil, used as a flavor.
Also included in traditional
medicine.
Lavender oil, used primarily as
a
fragrance.
Also
used
medicinally.
Lemon oil, similar in fragrance to
the fruit. Unlike other essential oils,
lemon oil is usually cold pressed.
Used medicinally, as an antiseptic,
and in cosmetics.
Lemongrass. Lemongrass is a highly
fragrant grass from India. In India, it
is used to help treat fevers and
infections. The oil is very useful for
insect repellent.
Lime,
antiseptic,
antiviral,
astringent, aperitif, bactericidal,
disinfectant,
febrifuge,
haemostatic, restorative and tonic.
Litsea cubeba oil, lemon-like
scent, often used in perfumes
and aromatherapy.
Melissa oil (Lemon balm), sweet
smelling
oil
used
primarily
medicinally,
particularly
in
aromatherapy.
Mentha arvensis oil/Mint oil, used in
flavoring toothpastes, mouthwashes
and pharmaceuticals, as well as in
aromatherapy and other medicinal
applications.
Mugwort oil, used in ancient times
for
medicinal
and
magical
purposes. Currently considered to
be a neurotoxin.
Mustard oil (essential oil),
containing a high percentage of
allyl isothiocyanate or other
isothiocyanate, depending on
the species of mustard.
Myrrh oil, warm, slightly musty
smell. Used medicinally.
Neem oil or Neem Tree Oil. Used
medicinally.
Neroli is produced from the
blossom of the bitter orange tree.
Nutmeg
Orange oil, like lemon oil, cold
pressed rather than distilled.
Consists of 90% d-Limonene. Used
as a fragrance, in cleaning products
and in flavoring foods.
Oregano oil, contains thymol and
carvacrol, making it a useful
fungicide. Also used to treat
digestive problems.
Orris oil is extracted from the
roots of the Florentine iris (Iris
florentina) and used as a
flavouring agent, in perfume and
medicinally.
Parsley oil, used in soaps,
detergents, colognes, cosmetics
and perfumes, especially men’s
fragrances.
Patchouli
oil,
very
ingredient in perfumes.
common
Perilla essential oil, extracted from
the leaves of the perilla plant.
Contains
about
50-60%
perillaldehyde.
Pennyroyal oil, highly toxic. It is
abortifacient and can even in small
quantities cause acute liver and
lung damage.
Peppermint oil, used in a wide
variety
of
medicinal
applications.
Pine oil, used as a disinfectant, and
in aromatherapy.
Rose oil, distilled from rose petals,
Used primarily as a fragrance.
Rosehip oil, distilled from the
seeds of the Rosa rubiginosa or
Rosa mosqueta. Used medicinally.
Dill oil, chemically almost
identical to caraway seed oil.
High carvone content.
2
Coffee, used to flavor food.
Cranberry seed oil, equally high in
omega-3 omega-6 fatty acids,
primarily used in the cosmetic
industry.
Davana oil, from the Artemisia
pallens, used as a perfume
ingredient and as a germicide.
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Rosemary oil, distilled from the
flowers
of
Rosmarinus
officinalis.
Used
in
aromatherapy, topically to
sooth muscles, and medicinal
for
its
antibacterial
and
antifungal properties.
Sassafras oil, from sassafras
root
bark.
Used
in
aromatherapy,
soap-making,
perfumes,
and
the
like.
Formerly used as a spice, and as
the primary flavoring of root
beer, inter alia.
Spikenard, used medicinally.
Rosewood oil, used primarily for
skin care applications. Also used
medicinally.
Sage oil, used medicinally.
Sandalwood oil, used primarily as
a fragrance, for its pleasant, woody
fragrance.
Savory oil, from Satureja species.
Used in aromatherapy, cosmetic and
soap-making applications.
Schisandra oil, from Schisandra
chinensis, used medicinally.
Spearmint oil, often used in
flavoring mouthwash and chewing
gum, among other applications.
Star anise oil, highly fragrant oil
using in cooking. Also used in
perfumery and soaps, has been used
in toothpastes, mouthwashes, and
skin creams. 90% of the world's star
anise crop is used in the
manufacture of Tami flu, a drug
used to treat influenza, and is hoped
to be useful for avian flu.
Tarragon
oil,
distilled
Artemisia
dracunculus,
medicinally.
Tea tree oil, distilled from
Melaleuca
alternifolia,
used
medicinally. Being a powerful
antiseptic,
antibacterial
and
antiviral agent, tea tree's ability to
fight infection is second to none.
Thyme oil, used medicinally.
Turmeric, used medicinally and to
flavor food.
Valerian, used medicinally.
Wintergreen and Yarrow oil is
used medicinally, to relieve
joint pain
Ylang-ylang from Cananga odorata
used in aromatherapy.
Zedoary, used medicinally and to
flavor food.
As the use of essential oils has declined in evidence-based
medicine, one must consult older textbooks for much
information on their use. Modern works are less inclined
to generalize; rather than refer to "essential oils" as a class
at all, they prefer to discuss specific compounds, such as
methyl salicylate, rather than "oil of wintergreen". Interest
in essential oils has revived in recent decades with the
popularity of aromatherapy, a branch of alternative
Table 2. Various types of essential oils
Chamomile Essential Oil
Eucalyptus Essential Oil
Geranium Essential Oil
Lavender Essential Oil
Lemon Essential Oil
Peppermint Essential Oil
Enfleurage
Enfleurage is a process that uses odorless fats that are
semisolid at room temperature to capture the fragrant
compounds exuded by plants. It is also known as Cold Fat
Extraction. The process can be "cold" enfleurage or "hot"
enfleurage.
Cold enfleurage: A large framed plate of glass, called a
chassis, is smeared with a layer of animal fat, usually 2
part of lard & 1 part of tallow (from pork or beef,
respectively) and allowed to set. Botanical matter, usually
petals or whole flowers, is then placed on the fat and its
scent is allowed to diffuse into the fat over the course of 13 days. The process is then repeated by replacing the
spent botanicals with fresh ones until the fat has reached a
desired degree of fragrance saturation. This procedure
was developed in southern France in the 18th century for
the production of high-grade concentrates. The technique
is yet extensively used in France for the bulk production of
absolute of specific flowers.
Hot enfleurage: Solid fats are heated and botanical matter
is stirred into the fat. Spent botanicals are repeatedly
strained from the fat and replaced with fresh material
until the fat is saturated with fragrance. This method is
considered the oldest known procedure for preserving
3
Vetiver oil (khus oil) a thick,
amber oil, primarily from India.
Used as a fixative in perfumery,
and in aromatherapy.
medicine that claims that essential oils and other aromatic
compounds have curative effects. Oils are volatilized or
diluted in carrier oil and used in massage, diffused in the
air by a nebulizer, heated over a candle flame, or burned
as incense.2 The techniques and methods first used to
produce essential oils was first mentioned by Ibn al-Baitar
(1188–1248), an Andalusian physician, pharmacist and
chemist. (Table 2).
Aromatherapy Essential Oils
Bergamot Essential Oil
Dill Essential Oil
Fennel Essential Oil
Jasmine Essential Oil
Angelica Essential Oil
Aniseed Essential Oil
ISOLATION METHODS
from
used
Ylang-ylang Essential Oil
Frankincense Essential Oil
Tea-tree Essential Oil
Sandalwood Essential Oil
Basil Essential Oil
Rosemary Essential Oil
plant fragrance substances.
In both instances, once the fat is saturated with fragrance,
which is known as “Enfleurage Pomade” is then taken
separately (Defleuraged). The enfleurage pomade was
either sold as it was, or it could be further washed or
soaked in ethyl alcohol to draw the fragrant molecules into
the alcohol. The alcohol is then separated from the fat and
allowed to evaporate in an instrument called as
“Batteuses” which uses vacuum for evaporation purpose &
leaves behind the absolute of the botanical matter. The
spent fat is usually used to make soaps since it is still
relatively fragrant. (Figure 2)
Figure 2. Process of enfleurage
Significance: The enfleurage fragrance extraction method
is by far one of the oldest. It is also costly but is the sole
method of extracting the fragrant oil in delicate floral
botanical such as Jasmine, Lily, Rose, Tuberose, which
would be destroyed or denatured by the high
temperatures required by methods of fragrance extraction
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such as steam distillation. The method can’t supersede by
more efficient techniques such as solvent extraction or
supercritical fluid extraction using liquid carbon dioxide
(CO2) or similar compressed gases because they interfere
with the genuine fragrance of the essential oils.3
Advantages: Heat sensitive essential oils can be separated
in pure & unaltered form; Heating/Electricity is not
required; Eco-friendly technique; No Waste products
while used wax is used in soap production.
Pomade
Pomade is a greasy or waxy substance that is used to style
hair. Pomade makes hair look slick and shiny. Unlike hair
spray and hair gel, pomade does not dry and often takes
several washes to remove. It can be easily removed using a
high-detergent shampoo or other de-greasers such as olive
oil, dish washing liquid and lemon juice. Most pomades
contain petroleum jelly (in fact, petroleum jelly can be
used alone as a pomade) and mineral oil and many also
contain some sort of wax. They may be anhydrous or
emulsified with an aqueous carrier, which makes them
easier to remove. They may also contain perfume and
coloring agents. A wide range of pomades are in
production today and vary in factors such as weight, shine
and scent. The stiffest will have a higher proportion of
waxes such as beeswax while the lightest may have a
higher proportion of oils. (Figure 3)
Figure-3: Pomade containing Fragrance
Steam distillation
Steam distillation is a special type of distillation (a
separation process) for temperature sensitive materials
like natural aromatic compounds. Many organic
compounds tend to decompose at high sustained
temperatures. Separation by normal distillation would
then not be an option, so water or steam is introduced into
the distillation apparatus. By adding water or steam, the
boiling points of the compounds are depressed, allowing
them to evaporate at lower temperatures, preferably
below the temperatures at which the deterioration of the
material becomes appreciable. If the substances to be
distilled are very sensitive to heat, steam distillation can
also be combined with vacuum distillation. After
distillation the vapors are condensed as usual, usually
yielding a two-phase system of water and the organic
compounds, allowing for simple separation. (Figure 4)
Figure 4. Steam distillation (a) unit & (b) Process (c)
Clevenger apparatus
Principle: When a mixture of two practically immiscible
liquids is heated while being agitated to expose the
surfaces of both the liquids to the vapor phase, each
constituent independently exerts its own vapor pressure
as a function of temperature as if the other constituent
were not present. Consequently, the vapor pressure of the
4
whole system increases. Boiling begins when the sum of
the partial pressures of the two immiscible liquids just
exceeds the atmospheric pressure (approximately 101 kPa
at sea level). In this way, many organic compounds
insoluble in water can be purified at a temperature well
below the point at which decomposition occurs. For
example, the boiling point of bromobenzene is 156°C and
the boiling point of water is 100°C, but a mixture of the
two boils at 95°C. Thus, bromobenzene can be easily
distilled at a temperature 61°C below its normal boiling
point.
Applications: Steam distillation is employed in the
manufacture of essential oils, for instance, perfumes. In
this method, steam is passed through the plant material
containing the desired oils. Eucalyptus oil and orange oil
are obtained by this method on the industrial scale. Steam
distillation is also sometimes used to separate
intermediate or final products during the synthesis of
complex organic compounds. Steam distillation is also
widely used in petroleum refineries and petrochemical
plants where it is commonly referred to as "steam
stripping".
Equipment: On a lab-scale steam distillations are carried
out using steam generated outside the system and piped
through macerated biomass or steam generation in-situ
using a Clevenger-type apparatus.4 (Figure 4c)
Supercritical Fluid Extraction (SFE)
SFE is the process of separating one component (the
extractant) from another (the matrix) using supercritical
fluids as the extracting solvent. Extraction is usually from
a solid matrix, but can also be from liquids. SFE can be
used as a sample preparation step for analytical purposes,
or on a larger scale to either strip unwanted material from
a product (e.g. decaffeination) or collect a desired product
(e.g. essential oils). Carbon dioxide (CO2) is the most used
supercritical fluid, sometimes modified by co-solvents
such as ethanol or methanol. Extraction conditions for
supercritical CO2 are above the critical temperature of
31°C and critical pressure of 74 bar. Addition of modifiers
may slightly alter this. The discussion below will mainly
refer to extraction with CO2, except where specified.
(Figure 5)
Figure 5. Supercritical Fluid Extraction; SFE Plant
Procedure: The system must contain a pump for the CO2,
a pressure cell to contain the sample, a means of
maintaining pressure in the system and a collecting vessel.
The liquid is pumped to a heating zone, where it is heated
to supercritical conditions. It then passes into the
extraction vessel, where it rapidly diffuses into the solid
matrix and dissolves the material to be extracted. The
dissolved material is swept from the extraction cell into a
separator at lower pressure and the extracted material
settles out. The CO2 can then be cooled, re-compressed and
recycled, or discharged to atmosphere.
Pumps: Carbon dioxide (CO2) is usually pumped as a
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liquid, usually below 5°C and a pressure of about 50 bars.
The solvent is pumped as a liquid as it is then almost
incompressible; if it was pumped as a supercritical fluid,
much of the pump stroke would be "used up" in
compressing the fluid, rather than pumping it. For small
scale extractions (up to a few grams/minute),
reciprocating CO2 pumps or syringe pumps are often used.
For larger scale extractions, diaphragm pumps are most
common. The pump heads will usually require cooling and
the CO2 will also be cooled before entering the pump.
such as desorption from an active site are sometimes
significant, but not dealt with in detail here. Figure 5
shows the stages during extraction from a spherical
particle where at the start of the extraction the level of
extractant is equal across the whole sphere. As extraction
commences, material is initially extracted from the edge of
the sphere, and the concentration in the center is
unchanged. As the extraction progresses, the
concentration in the center of the sphere drops as the
extractant diffuses towards the edge of the sphere.
Pressure vessels: It can range from simple tubing to more
sophisticated purpose built vessels with quick release
fittings. The pressure requirement is at least 74 bars and
most extractions are conducted at less than 350 bars.
However, sometimes higher pressures will be needed,
such as extraction of vegetable oils, where pressures of
800 bars are sometimes required for complete miscibility
of the two phases. The vessel must be equipped with a
means of heating. It can be placed inside an oven for small
vessels or an oil or electrically heated jacket for larger
vessels. Care must be taken if rubber seals are used on the
vessel, as the CO2 may dissolve in the rubber, causing
swelling and the rubber will rupture on depressurization.
The relative rates of diffusion and dissolution are
illustrated by two extreme cases in Figure 5 which shows
a case where dissolution is fast relative to diffusion. The
material is carried away from the edge faster than it can
diffuse from the center, so the concentration at the edge
drops to zero. The material is carried away as fast as it
arrives at the surface and the extraction is completely
diffusion limited. Here the rate of extraction can be
increased by increasing diffusion rate, for example raising
the temperature, but not by increasing the flow rate of the
solvent. Figure 5 shows a case where solubility is low
relative to diffusion. The extractant is able to diffuse to the
edge faster than it can be carried away by the solvent, and
the concentration profile is flat. In this case, the extraction
rate can be increased by increasing the rate of dissolution,
for example by increasing flow rate of the solvent. The
extraction curve of % recovery against time can be used to
elucidate the type of extraction occurring. Figure-5 shows
a typical diffusion controlled curve. The extraction is
initially rapid, until the concentration at the surface drops
to zero and the rate then becomes much slower. The %
extracted eventually approaches 100%. Figure 5 shows a
curve for a solubility limited extraction. The extraction
rate is almost constant, and only flattens off towards the
end of the extraction. Figure-5 shows a curve where there
are significant matrix effects, where there is reversible
interaction with the matrix, such as desorption from an
active site. The recovery flattens off, and if the 100% value
is not known, then it is hard to tell that extraction is less
than complete.
Pressure maintenance: The pressure in the system must
be maintained from the pump right through the pressure
vessel. In smaller systems (up to about 10 mL/min) a
simple restrictor can be used. This can be either a capillary
tube cut to length or a needle valve which can be adjusted
to maintain pressure at different flow rates. In larger
systems a back pressure regulator will be used, which
maintains pressure upstream of the regulator by means of
a spring, compressed air or electronically driven valve.
Whichever is used, heating must be supplied, as the
adiabatic expansion of the CO2 results in significant
cooling. This is problematic if water or other extracted
material is present in the sample, as this may freeze in the
restrictor or valve and cause blockages.
Collection: The supercritical solvent is passed into a
vessel at lower pressure than the extraction vessel. The
density and hence dissolving power, of supercritical fluids
varies sharply with pressure and hence the solubility in
the lower density CO2 is much lower, and the material
precipitates for collection. It is possible to fractionate the
dissolved material using a series of vessels at reducing
pressure. The CO2 can be recycled or depressurized to
atmospheric pressure and vented. For analytical SFE, the
pressure is usually dropped to atmospheric and the now
gaseous carbon dioxide bubbled through a solvent to trap
the precipitated components.5
Heating and cooling: This is an important aspect. The
fluid is cooled before pumping to maintain liquid
conditions and then heated after pressurization. As the
fluid is expanded into the separator, heat must be
provided to prevent excessive cooling. For small scale
extractions, such as for analytical purposes, it is usually
sufficient to pre-heat the fluid in a length of tubing inside
the oven containing the extraction cell. The restrictor can
be electrically heated, or even heated with a hairdryer. For
larger systems, the energy required during each stage of
the process can be calculated using the thermodynamic
properties of the supercritical fluid. There are two
essential steps to SFE, transport (by diffusion or
otherwise) from with the solid particles to the surface, and
dissolution in the supercritical fluid. Other factors, such as
diffusion into the particle by the SF and reversible release
5
Optimization: The optimum will depend on the purpose
of the extraction. For an analytical extraction to determine,
say, antioxidant content of a polymer, then the essential
factor is complete extraction in the shortest time.
However, for production of an essential oil extract from a
plant, then quantity of CO2 used will be a significant cost,
and "complete" extraction not required, a yield of 70-80%
perhaps being sufficient to provide economic returns. In
another case, the selectivity may be more important, and a
reduced rate of extraction will be preferable if it provides
greater discrimination. Therefore few comments can be
made which are universally applicable.
Maximizing diffusion: This can be achieved by increasing
the temperature, swelling the matrix, or reducing the
particle size. Matrix swelling can sometimes be increased
by increasing the pressure of the solvent, and by adding
modifiers to the solvent. Some polymers and elastomers in
particular are swelled dramatically by CO2, with diffusion
being increased by several orders of magnitude in some
cases.
Maximizing solubility: Generally, higher pressure will
increase solubility. The effect of temperature is less
certain, as close to the critical point, increasing the
temperature causes decreases in density, and hence
dissolving power. At pressures well above the critical
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pressure, solubility is likely to increase with temperature.
Addition of low levels of modifiers (sometimes called
entrainers), such as methanol and ethanol, can also
significantly increase solubility, particularly of more polar
compounds.
Optimizing flow rate: The flow rate of CO2 should be
measured in terms of mass flow rather than by volume
because the density of the CO2 changes according to the
temperature both before entering the pump heads and
during compression. Coriolis flow meters are best used to
achieve such flow confirmation. To maximize the rate of
extraction, the flow rate should be high enough for the
extraction to be completely diffusion limited (but this will
be very wasteful of solvent). However, to minimize the
amount of solvent used, the extraction should be
completely solubility limited (which will take a very long
time). Flow rate must therefore be determined depending
on the competing factors of time and solvent costs and
also capital costs of pumps, heaters and heat exchangers.
The optimum flow rate will probably be somewhere in the
region where both solubility and diffusion are significant
factors.6
Advantages:
Environmental improvement and reduced product
contamination: SFE is an alternative to liquid extraction
using solvents such as hexane or dichloromethane. There
will always be some residual solvent left in the extract and
matrix and there is always some level of environmental
contamination from their use. In contrast, carbon dioxide
is easy to remove simply by reducing the pressure, leaving
almost no trace, purchased CO2 has almost always been
reclaimed, which reduces the total carbon foot-print. The
use of SFE with CO2 is approved by the Soil Association for
organic products. The CO2 used is largely a byproduct of
industrial processes or brewing and its use in SFE does not
cause any extra emissions.
Selectivity: The properties of a supercritical fluid can be
altered by varying the pressure and temperature, allowing
selective extraction. For example, volatile oils can be
extracted from a plant with low pressures (100 bar),
whereas liquid extraction would also remove lipids. Lipids
can be removed using pure CO2 at higher pressures and
then phospholipids can be removed by adding ethanol to
the solvent.
Speed: Extraction is a diffusion-based process, with the
solvent required to diffuse into the matrix and the
extracted material to diffuse out of the matrix into the
solvent. Diffusivities are much faster in supercritical fluids
than in liquids and therefore extraction can occur faster.
Also, there is no surface tension and viscosities are much
lower than in liquids, so the solvent can penetrate into
small pores within the matrix inaccessible to liquids. Both
the higher diffusivity and lower viscosity significantly
increase the speed of the extraction: An extraction using
an organic liquid may take several hours, whereas
supercritical fluid extraction can be completed in 10-60
minutes.
Limitations: The requirement for high pressures
increases the cost compared to conventional liquid
extraction, so SFE will only be used where there are
significant advantages. Carbon dioxide itself is non-polar,
and has somewhat limited dissolving power, so cannot
always be used as a solvent on its own, particularly for
polar solutes. The use of modifiers increases the range of
materials which can be extracted. Food grade modifiers
6
such as ethanol can often be used, and can also help in the
collection of the extracted material, but reduces some of
the benefits of using a solvent which is gaseous at room
temperature.7
Water Distillation Method
In water distillation, the botanical material is completely
immersed in water and then is boiled. This method
protects the oil to be extracted till a certain degree since
surrounding water prevents it from overheating. Then it is
condensed and cooled down. The oil is then separated out,
as it layers on the top of the water. The water separated
out in this process is termed as floral waters (also called
hydrosol or sweet water) such as rose water, orange water
and lavender water. Water distillation can be operated at
low pressures to reduce boiling temperature. This helps in
protecting the botanical material and essential oil as well.
This method is used for extraction of oils that are sensitive
to heat. If a lot of exposure to hot water is not mentioned
for a particular plant such as lavender, it is best to find an
extraction method better suited. Any botanical material
that contains high amounts of esters does not take well to
this extraction method, since the exposure to hot water
will break down the esters into alcohols and carboxylic
acids.
Steam Distillation Method
Steam distillation is the most common method of
extracting essential oils. Steam distillation is done in a still
(The still is all with a head and a well-insulated swan's
neck proceeded by a mechanism to prevent fumes and
impurities passing through). Fresh, or sometimes dried,
botanical material is placed in a closed container of the
still, and pressurized steam is generated which enters the
container and circulates through the plant material. The
heat of the steam forces the intercellular pockets that hold
the essential oils to open and release them. The
temperature of the steam should not be very high as it can
damage the botanical material but should be high enough
to open the pockets which hold the essential oil. Tiny
droplets of essential oil evaporate and attach to the steam.
The steam which then contains the essential oil, is passed
through a cooling system to condense the steam, which
forms a liquid from which the essential oil and water is
then separated by decantation. The oil forms a layer on the
water surface as it does not dissolves in water and hence
is separated easily. This method is not used for extraction
of oils that are sensitive to heat. (Figure 6)
Figure 6. Steam distillation unit
Hydro Diffusion Method
Hydro Diffusion method for extraction of oils is a type of
steam distillation and is only different in the way in which
steam is enters the container of the still. In hydro
diffusion, steam is fed in from the top onto the botanical
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material while in the case of steam distillation; steam is
fed from the bottom. In this way the steam can saturate
the plants more evenly and in less time than with steam
distillation. The condensation of the oil containing steam
mixture occurs below the area in which the botanical
material is held. The main advantage of this method over
steam distillation is that less steam is used hence shorter
processing time and therefore a higher oil yield. This
method is also less harsh on the botanical material.
fruit absorbed the water. After the fruit has absorbed the
water and become more elastic, it was inverted which
helped to rupture the oil cells and a sponge placed next to
the rind. It was then squeezed to release the volatile oil,
which was then collected directly into the sponge. As soon
as the sponge became saturated with oil, it was squeezed
and the essential oil collected in a vessel and then
decanted.9 (Figure 9)
Figure 9. Sponge expression method
Fractional Distillation Method
When we say fractional distillation, it only refers to
normal distillation process. In this only difference is that
the oil is not collected continuously, but is collected in
parts i.e. fractions and oil normally so extracted is “YlangYlang oil”. (Figure 7)
Figure 7. Fractional distillation unit
Rectification Method
When an essential oil contains any impurities, it can be
purified by re-distillation; either in steam or in vacuum
and this purification of oil by re-distillation is referred to
as rectification. This process is used to make oils of
standard quality. An example of rectification is eucalyptus
oil. (Figure 8)
Figure 8. Rectification unit
Cohobation Method
In some essential oil extractions, some chemical or part of
the essential oil gets dissolved in water and therefore gets
removed from the oil. So to get the whole oil, we add the
deficient chemical to the deficient oil and re-distillation is
done until we get the complete oil. An example of this is
rose oil.8
Sponge Expression Method
Most citrus essences are extracted by means of expression,
and in the past were done by hand where the fruit pulp
was removed, with the rind and pith then soaked in warm
water to make the rind more pliable, since the pith of the
7
Cold Pressed Method
Another expression method of extracting essential oils is
coldpressed expression, or scarification method. It is used
to obtain citrus fruit oils such as bergamot, grapefruit,
lemon, lime, mandarin, orange, and tangerine oils. In this
process, fruit rolls over a trough with sharp projections
that penetrate the peel. This pierces the tiny pouches
containing the essential oil. Then the whole fruit is pressed
to squeeze the juice from the pulp and to release the
essential oil from the pouches. The essential oil rises to the
surface of the juice and is separated from the juice by
centrifugation. 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.10 (Figure 10)
Figure 10. Cold pressed method
Machine Abrasion Method
Machine Abrasion is very much same as cold pressed
expression method and is mainly used in extraction of
citrus essential oils. In machine abrasion, a machine strips
off the outer peel of the botanical material, which is then
removed by running water and left over is then fed into a
centrifugal separator. The centrifugal separation is done
extremely fast. But, it should be noted that due to the fact
that the essential oil is combined with other cell content
for some time, some alteration could occur in the oil due to
enzymatic action.11 (Figure 11)
Figure 11. Machine abrasion method
Solvent Extraction Method
Very delicate aromatics, Jasmine, Linden Blossom, etc.
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cannot survive the process of distillation. To capture their
magical aromas, a process of solvent extraction is used. A
hydrocarbon solvent (usually hexane) is added to the
botanical material to help dissolve the extractable matter
from the botanical material which includes non-aromatic
waxes, pigments and highly volatile aromatic molecules.
When this solution is filtered and then the filtrate is
subjected to distillation at low pressure, a substance
containing resin (resinoid), or a combination of wax and
essential oil (known as concrete) is left. The concrete is
further processed to remove the waxy materials which
dilute the pure essential oil. To prepare the absolute from
the concrete, the waxy concrete is warmed and stirred
with alcohol (usually ethanol). When we heat and stir the
concrete, it breaks up into minute globules, and separation
takes place as aromatic oil is more soluble in alcohol than
that in wax. But along with the aromatic molecules a
certain amount of wax is also dissolved and this can be
removed only by agitating and freezing the solution at
very low temperatures (around minus -35°C). In this way
most of the wax precipitates out. As a final precaution the
purified solution is cold filtered leaving only the wax-free
material (the absolute) i.e. the essential oil. This solvent
extraction actually yields three usable products; first the
concrete (as in rose concrete, my favorite solid perfume),
the precious absolutes i.e. the oils, and the floral waxes, for
addition to candles, thickening creams and lotions as a
softly floral scented alternative to beeswax. Although
more cost-efficient than enfleurage, solvent extraction is
more expensive than steam distillation so it is reserved for
costly oils which cannot be distilled. This is not considered
the best method for extraction of essential oils, as the
solvents can leave a residue behind which could cause
allergies and effect the immune system, but it's great for
making resins for this very reason.12
Maceration Method
Maceration actually creates more of infused oil rather than
an essential oil and is most often used for creating extracts
and resins. The botanical material is soaked in vegetable
oil, water, or another solvent. If it's soaked in vegetable oil,
and then heated and strained, it can be used for massage
and if soaked in water or another solvent such as alcohol,
will create a much thicker extract or resin.13 (Figure-12)
Figure 12. Maceration method
as other solvent extraction methods. To remove the
carbon dioxide solvent, you simply need to remove the
pressure applied. This process has to take place in a closed
chamber since the hypercritical pressure required for
carbon dioxide is 200 atmospheres. To achieve this
pressure specific equipment is required which is very
expensive. The advantage of this method, of course, is that
no solvent residue remains, since at normal pressure and
temperature, the carbon dioxide simply reverts to a gas
and evaporates. Hypercritical carbon dioxide extraction
has given us essences of some aromatics that don't yield
essential oils, for example Rose Hip Seed and Calendula.
Many carbon dioxide extractions have fresher, cleaner,
and crisper aromas than steam-distilled essential oils, and
they smell more similar to the living plants. Scientific
studies show that carbon dioxide extraction produces
essential oils that are very potent and have great
therapeutic benefits.14 (Figure 13)
Figure 13. Hypercritical CO2 method
Florasols/Phytols Method
This extraction method uses a new type of benign gaseous
solvents. The unique properties of these solvents are used
for the extraction of aromatic oils and biologically active
components from botanical materials. Florasol is the
solvent upon which the process is based. Extraction occurs
at or below ambient temperatures; hence there is no
thermal degradation of the products. The extraction
process utilizes the selectivity of the solvent and produces
free flowing clear oil free of waxes. (Figure 14)
Figure 14. Florasol method
Hypercritical Carbon dioxide (CO2) Method
The use of hypercritical carbon dioxide extraction is a
fairly new way to extract essential oils from botanical
material and although a bit on the expensive side, does
yield good quality oils. Carbon dioxide becomes
hypercritical at 33 degrees celsius, which is a state in
which it is not really gas or liquid, but has qualities of both,
and is an excellent solvent to use in the extraction of
essential oils since low temperature is required and the
fact that the process is near to instantaneous.
‘Florasols’ Are NOT ‘Essential Oils’! Why? ‘Essential’ oils
are made by steam or water distillation. The plant material
is boiled for several hours in a kettle with lots of water
(typically three times its weight). Some of the water turns
to steam which carries the fragrant oil with it. The steam is
condensed back to water by cooling it in condensers. The
‘essential’ oil floats on the surface of the condensed water
and is skimmed off. So, ‘essential oil’ has all been cooked.
Heat will have damaged and changed many of the fragile,
naturally occurring substances. Much of the most delicate,
fragrant, light, volatile components will have been lost
during the condensation. Much of the fragrant is also lost –
dissolved in the condensed waters (rose water is a
fragrant!), this loss have been at the expense of the oil.
This process uses huge amounts of fossil fuel to boil the
plant/water mix, pollutes, and also produces vast
quantities of boiling hot liquid waste.
The carbon dioxide is inert and therefore does not
chemically react with the essence that is being extracted
and hence, essential oils can be extracted in a similar way
‘Florasols’ Are NOT ‘Absolutes’! Why?
‘Absolutes’ are made from ‘concretes’ by milling them with
98% alcohol. Strong alcohol dissolves the ‘absolutes’ out of
8
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Patel P N et al. / Pharmacie Globale (IJCP) 2011, 9 (02)
the buttery mass of ‘concretes’. This alcohol solution is
frozen to – minus 10°C (14°F), which precipitates the
waxes. This cold solution is filtered and the
filtrate/solution concentrated by rigorously boiling off of
the alcohol under vacuum. The ‘absolutes’ is the oil which
is left after the alcohol has been boiled away. Alcohol boils
at 78°C. So “absolutes’ have been through TWO ‘boilingoff’ processes (the first from hexane, the second from
alcohol), Volatile fragrant components will have been
stripped out and lost and damage will have been done to
the delicate heat sensitive components of the oil on both
occasions.
‘Florasols’ Are NOT ‘Concretes’! Why? ‘Concretes’ are
made by stirring up vegetable matter with hexane
(gasoline) or chlorinated solvents (such as methylene
chloride). Hexane dissolves (extracts) many of the plant’s
components. The hexane solution is then evaporated to
dryness at 75°C. The ‘concrete’ is what it’s left, after the
hexane has been driven off/boiled away. So, ‘concretes’
have also been heated. They also contain residual hexane.
They contain about 50% of the plant’s waxes, pigments,
resins, fats, (triglycerides and fatty acids) and sterols and
their esters. Heating will have caused damage to the fragile
components and the loss of their delicate ‘volatiles,
particularly if the hexane has been removed under high
vacuum (which is usual practice) hexane is lost into the
atmosphere where it is a serious ‘Volatile Organic
Compound’ – VOC pollutant, contributing to toxic.
Needless to say, the process is also extremely hazardous as
hydrocarbons are all flammable. We can however extract
from Concretes using our HFC Process and, in this case, we
first coat the Concrete onto a carrier medium and then
extract using the normal ‘FLORASOLS’ process. The
extraction time will be longer than a standard extraction,
but the yield will of cause be proportionally higher as the
concentration of the oil in the Concrete is higher also. As
an example; 1kg of Rose Concrete may produce 500 gms of
oil whereas 1 kg of Rose will provide 1 gm of oil.
‘Florasols’ Are NOT ‘SCFE Oil’! Why? Warm carbon
dioxide gas at exceeding high pressure can be used to
dissolve fragrant/flavour oils from some plant materials.
The acidic gas, carbon dioxide, is passed through the warm
REFERENCES
1. Handa S S, Khanuja S P S, Longo G, Rakesh D D;
Extraction Technologies for Medicinal and Aromatic
Plants. International Center for Science & High
Technology. Trieste. 2008.
2. Alfred G, Goodman L S. Goodman and Gilman's The
pharmacological basis of therapeutics. New York:
Pergamon Press. 1990.
3. Prabuseenivasan S, Manickkam J and Ignacimuthu S;
In-vitro antibacterial activity of some plant essential
oils. BMC Complement Altern Med. 2006; 6:39.
4. Henley D V, Lipson N, Korach K S, Bloch C A;
Prepubertal gynecomastia linked to lavender and tea
tree oils. New England Journal of Medicine. 2007;
356(5):479-85.
5. Bischoff K, Guale F; Australian tea tree (Melaleuca
alternifolia) oil poisoning in three purebred cats. J Vet
Diagn Invest. 1998; 10(2):208-10.
6. Perfume connoisseurs speak of a fragrance's "sillage",
or the discernible trail it leaves in the air when applied.
Fortineau Anne-Dominique. "Chemistry Perfumes Your
Daily Life". Journal of Chemical Education. 2004;
81(1):2345-2358.
9
plant material at 300 – 500 times the pressure of the
atmosphere (pressure such as those found in the nature at
the bottom of the Pacific Ocean, three miles down!) - don’t
try this at home! This ‘fluid’ dissolves oil, resins and waxes
out of the plant material. When the pressure is allowed to
fall to only 100 ‘Bar’ (=100 time atmospheric pressure, the
oil form into a mist and can be collected. Needless to say,
the equipment needed for this process is massive in the
extreme and very costly and uses huge quantities of
electricity to drive it. This is why products are so
expensive. The effect of the high degree (all low as pH 2.0)
at these temperatures on the ‘naturalness’ of SCFE
products, will reward further study.15
Commonly used Techniques for Aroma Oil Extraction
(Table 3)
Table 3. Different types of extraction
Water Distillation
Steam Distillation
Hydro Diffusion
Fractional Distillation
Rectification
Cohobation
Sponge Expression
Methods
Cold pressed Expression
Machine Abrasion
Solvent Extraction
Maceration
Enfleurage
Hypercritical Carbon Dioxide (CO2)
Florasol
Use of essential oils with aromatherapy (Table 4)
Table 4. Use of essential oils with aromatherapy
Use of essential oils
Aromatherapy Recipes
Air
reshening
Compresses
Emotional
Balance
Acne
Physical
Balance
Sun Screen
Massage
Bubble Baths
Cleansers &
Toners
Shower gels
Face oils
Moisturizers
Bathing
Hair care
Foot and
baths
Jacuzzis
hand
Massage
Saunas
Showers
Skin care
Sitz bath
Steam inhalations,
Vaporization
Shampoos
Perfumes and
Colognes
CONCLUSION
Nature produces essential oils in flowers which are
extracted by several processes to make perfumes or
essences from ancient period. All the fragrances are well
accepted for various purposes in our daily routine for
making natural harmony with nature.
7. Calkin R R and Jellinek J S; Perfumery: practice and
principles. John Wiley & Sons, Inc. 1994; ISBN 0-47158934-9.
8. Kumar P, Caradonna-Graham V M, Gupta S, Cai X, Rao P
N, Thompson J. "Inhalation challenge effects of perfume
scent strips in patients with asthma". Ann Allergy
Asthma Immunol. 1995; 75(5):429-433.
9. Frosch P J, Rastogi S C, Pirker C et al. Patch testing with
a new fragrance mix - reactivity to the individual
constituents and chemical detection in relevant
cosmetic products. Contact Derm. 2005; 52(4):216-225.
10. Apostolidis S, Chandra T, Demirhan I, Cinatl J, Doerr H
W, Chandra A; Evaluation of carcinogenic potential of
two nitro-musk derivatives, musk xylene and musk
tibetene in a host-mediated in-vivo/in-vitro assay
system. Anticancer Res. 2002; 22(5):2657-2662.
11. Schmeiser H H, Gminski R, Mersch-Sundermann V;
Evaluation of health risks caused by musk ketone. Int J
Hyg Environ Health. 2001; 203(4):293-299.
12. Schreurs R H, Legler J, Artola-Garicano E et al. In-vitro
and in-vivo antiestrogenic effects of polycyclic musks in
zebrafish. Environ Sci Technol. 2004; 38(4):997-1002.
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13. Rastogi S C, Bossi R, Johansen J D et al. Content of oak
moss allergens atranol and chloroatranol in perfumes
and similar products. Contact Derm. 2004; 50(6):367370.
14. Duedahl-Olesen L, Cederberg T, Pedersen K H, Højgård
A; Synthetic musk fragrances in trout from Danish fish
10
farms and human milk. Chemosphere. 2005; 61(3):422431.
15. Peck A M, Linebaugh E K, Hornbuckle K C; Synthetic
musk fragrances in Lake Erie and Lake Ontario
sediment cores. Environ Sci Technol. 2006;
40(18):5629-5235.
Pharmacie Globale© (IJCP), Vol. 02, Issue 08
Available online at www.pharmacie-globale.info
ISSN 0976-8157
Review Article
PHARMACIE GLOBALE
INTERNATIONAL JOURNAL OF COMPREHENSIVE PHARMACY
EXTRACTION OF HERBAL AROMA OILS FROM SOLID SURFACE
Parth N Patel*, Krupa M Patel, Dhaval S Chaudhary, Khushboo G Parmar, Henil A Patel,
Chandni D Kansagra and Dhrubo Jyoti Sen
Shri Sarvajanik Pharmacy College, Gujarat Technological University, Arvind Baug, Mehsana, Gujarat, India.
Received: 12 April 2011; Revised: 20 August 2011; Accepted: 25 August 2011; Available online: 5 September 2011
ABSTRACT
Fragrance extraction refers to the extraction of aromatic compounds from raw materials, using methods such as
distillation, solvent extraction, expression or enfleurage. The results of the extracts are either essential oils,
absolutes, concretes or butters, depending on the amount of waxes in the extracted product. To a certain extent,
all of these techniques tend to distort the odour of the aromatic compounds obtained from the raw materials.
Heat, chemical solvents or exposure to oxygen in the extraction process denature the aromatic compounds,
either changing their odour character or rendering them odourless. This technique is very costly and is rarely
used today. It reached its peak in 1860 and made the reputation of Grasse. It is a labour-intensive process that
yields the highest quality of absolutes because it does not involve heat. Heat always alters the fragrance. It is
used on delicate flowers that cannot stand up to the high heat and that continue to release essential oils after
they have been picked. Examples of these flowers are Jasmine, Violet, Tuberose and Rose. Enfleurage goes back
thousands of years to the ancient Egyptians. It works on the principle that fats absorb smells. Petals or other
fragrant parts of a plant are steeped in fat or non-evaporating oil which will absorb their fragrance. A mixture of
pork, lard and beef suet is smeared on to a glass plate in a wooden frame called a chassis. The flowers are placed
on the fat and left to release their oils for several days. This process was repeated several times with fresh
flower heads until the fat was totally absorbed with essential oil, the resultant substance being known as
'pomade', the oil was then retrieved from the fat by dissolving in an alcoholic solvent. This is mechanically mixed
with alcohol for up to one week, and is chilled to 68°F. The essential oils dissolve in the alcohol and the fat does
not. The mixture is chilled and filtered several times to remove all the fat. The alcohol is then evaporated to leave
the pure absolute. Sometimes enfleurage is now carried out with cloth soaked in olive oil or liquid paraffin,
which is laid over the frames instead of fat, the resultant perfumed oil being then known as 'huile antique'.
Keywords: Essential oil, enfleurage, pomade, supercritical fluid extraction, cohobation, sponge expression, cold
pressed method, machine abrasion, maceration, hypercritical carbon dioxide, Florasols/Phytols Method.
INTRODUCTION
Essential oils are volatile and liquid aroma compounds
from natural sources, usually plants. Essential oils are not
oils in a strict sense, but often share with oils a poor
solubility in water. Essential oils often have an odor and
are therefore used in food flavoring and perfumery.
Essential oils are usually prepared by fragrance extraction
techniques such as distillation including steam
distillation), cold pressing, or extraction (maceration).
Essential oils are distinguished from aroma oils (essential
oils and aroma compounds in an oily solvent), infusions in
a vegetable oil, absolutes and concretes. Typically,
essential oils are highly complex mixtures of often
hundreds of individual aroma compounds.1 (Figure 1)
An essential oil is a concentrated hydrophobic liquid
containing volatile aroma compounds from plants.
Essential oils are also known as volatile oils, ethereal
oils or aetherolea, or simply as the “oil” of the plant from
*Corresponding Author:
Parth N Patel
Shri Sarvajanik Pharmacy College, Gujarat Technological University,
Arvind Baug, Mehsana, Gujarat, India.
Contact no: +91-2762-247711; Email: [email protected]
1
Figure 1. Essences from floral unit
which they were extracted, such as oil of clove. An oil is
"essential" in the sense that it carries a distinctive scent, or
essence, of the plant. Essential oils do not form a
distinctive category for any medical, pharmacological, or
culinary purpose. Essential oils are generally extracted by
distillation. Other processes include expression, or solvent
extraction. They are used in perfumes, cosmetics, soaps
and other products, for flavoring food and drink, and for
adding scents to incense and household cleaning products.
Various essential oils have been used medicinally at
different periods in history. Medical application proposed
by those who sell medicinal oils range from skin
treatments to remedies for cancer, and often are based on
nothing better than historical accounts of use of essential
oils for these purposes. Claims for the efficacy of medical
Pharmacie Globale© (IJCP), Vol. 02, Issue 08
Patel P N et al. / Pharmacie Globale (IJCP) 2011, 9 (02)
treatments and treatment of cancers in particular, are now
Table 1. Essential oils from plants
subject to regulation in most countries. (Table 1)
Agar
oil
distilled
from
Agarwood
(Aquilaria
malaccensis). Highly prized for
its fragrance.
Asafoetida, used medicinally
and to flavor food.
Ajwain oil, distilled from the leaves
of Bishop’s weed (Carum copticum).
Oil contains 35-65% thymol.
Angelica root oil, distilled from the
Angelica archangelica.
Anise oil, from the Pimpinella
anisum, rich odor of licorice, used
medicinally.
Balsam oil, from the Myroxylon
pereirae.
Basil oil is used in making perfumes,
as well as in aromatherapy.
Bay is used in perfumery;
Aromatherapeutic for sprains,
colds, flu, insomnia, rheumatism.
Bergamot
oil,
used
in
aromatherapy and in perfumes.
Black Pepper essential oil is
distilled from the berries of Piper
nigrum. The warm, soothing effect
makes it ideal for treating muscle
aches, pains and strains.
Buchu oil, made from the buchu
shrub. Considered toxic and no
longer widely used. Formerly used
medicinally.
Birch is aromatheapeutic for gout,
Rheumatism, Eczema, Ulcers.
Camphor is used for cold, cough,
fever, rheumatism, arthritis.
Cannabis flower essential oil, used
as a flavoring in foods, primarily
candy and beverages. Also used as a
scent in perfumes, cosmetics, soaps,
and candles.
Caraway oil, used a flavoring in
foods. Also used in mouthwashes,
toothpastes, etc. as a flavoring
agent.
Carrot seed oil (essential oil),
used in aromatherapy.
Cedarwood oil, primarily used in
perfumes and fragrances.
Cinnamon oil, used for flavoring
and medicinally.
Citronella oil, from a plant related to
lemon grass is used as an insect
repellent, as well as medicinally.
Chamomile oil, There are many
varieties of chamomile but only two
are used in aromatherapy- Roman
and German. Both have similar
healing properties but German
chamomile contains a higher level
of azulin (an anti-inflammatory
agent).
Clove leaf oil, used as a topical
anesthetic to relieve dental pain.
Cardamom seed oil, used in
aromatherapy and other medicinal
applications. Extracted from seeds
of subspecies of Zingiberaceae
(ginger). Also used as a fragrance
in soaps, perfumes, etc.
Calamus Root, used medicinally.
Coriander
Costmary oil (bible leaf oil), from
the Tanacetum balsamita.
Costus Root, used medicinally.
Cubeb, used medicinally and to
flavor foods.
Cumin oil/Black seed oil, used as a
flavor,
particularly
in
meat
products. Also used in veterinary
medicine.
Eucalyptus oil, historically used as a
germicide. Commonly used in cough
medicine, among other medicinal
uses.
Curry leaf, used medicinally and to
flavor food.
Fennel seed oil, used medicinally,
particularly for treating colic in
infants.
Fenugreek oil, used medicinally
and for cosmetics from ancient
times.
Frankincense oil, used for
aromatherapy and in perfumes.
Galangal, used medicinally and to
flavor food.
Geranium oil, used in aroma
therapy, used for hormonalimbalance. Geranium oil is often
known as "female" oil.
Ginger oil, used medicinally in
many cultures.
Grapefruit oil, extracted from
the peel of the fruit. Used in
aromatherapy. Contains 90%
limonene.
Henna oil, used medicinally.
Jasmine oil, used for its flowery
fragrance.
Juniper berry oil, used as a flavor.
Also included in traditional
medicine.
Lavender oil, used primarily as
a
fragrance.
Also
used
medicinally.
Lemon oil, similar in fragrance to
the fruit. Unlike other essential oils,
lemon oil is usually cold pressed.
Used medicinally, as an antiseptic,
and in cosmetics.
Lemongrass. Lemongrass is a highly
fragrant grass from India. In India, it
is used to help treat fevers and
infections. The oil is very useful for
insect repellent.
Lime,
antiseptic,
antiviral,
astringent, aperitif, bactericidal,
disinfectant,
febrifuge,
haemostatic, restorative and tonic.
Litsea cubeba oil, lemon-like
scent, often used in perfumes
and aromatherapy.
Melissa oil (Lemon balm), sweet
smelling
oil
used
primarily
medicinally,
particularly
in
aromatherapy.
Mentha arvensis oil/Mint oil, used in
flavoring toothpastes, mouthwashes
and pharmaceuticals, as well as in
aromatherapy and other medicinal
applications.
Mugwort oil, used in ancient times
for
medicinal
and
magical
purposes. Currently considered to
be a neurotoxin.
Mustard oil (essential oil),
containing a high percentage of
allyl isothiocyanate or other
isothiocyanate, depending on
the species of mustard.
Myrrh oil, warm, slightly musty
smell. Used medicinally.
Neem oil or Neem Tree Oil. Used
medicinally.
Neroli is produced from the
blossom of the bitter orange tree.
Nutmeg
Orange oil, like lemon oil, cold
pressed rather than distilled.
Consists of 90% d-Limonene. Used
as a fragrance, in cleaning products
and in flavoring foods.
Oregano oil, contains thymol and
carvacrol, making it a useful
fungicide. Also used to treat
digestive problems.
Orris oil is extracted from the
roots of the Florentine iris (Iris
florentina) and used as a
flavouring agent, in perfume and
medicinally.
Parsley oil, used in soaps,
detergents, colognes, cosmetics
and perfumes, especially men’s
fragrances.
Patchouli
oil,
very
ingredient in perfumes.
common
Perilla essential oil, extracted from
the leaves of the perilla plant.
Contains
about
50-60%
perillaldehyde.
Pennyroyal oil, highly toxic. It is
abortifacient and can even in small
quantities cause acute liver and
lung damage.
Peppermint oil, used in a wide
variety
of
medicinal
applications.
Pine oil, used as a disinfectant, and
in aromatherapy.
Rose oil, distilled from rose petals,
Used primarily as a fragrance.
Rosehip oil, distilled from the
seeds of the Rosa rubiginosa or
Rosa mosqueta. Used medicinally.
Dill oil, chemically almost
identical to caraway seed oil.
High carvone content.
2
Coffee, used to flavor food.
Cranberry seed oil, equally high in
omega-3 omega-6 fatty acids,
primarily used in the cosmetic
industry.
Davana oil, from the Artemisia
pallens, used as a perfume
ingredient and as a germicide.
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Rosemary oil, distilled from the
flowers
of
Rosmarinus
officinalis.
Used
in
aromatherapy, topically to
sooth muscles, and medicinal
for
its
antibacterial
and
antifungal properties.
Sassafras oil, from sassafras
root
bark.
Used
in
aromatherapy,
soap-making,
perfumes,
and
the
like.
Formerly used as a spice, and as
the primary flavoring of root
beer, inter alia.
Spikenard, used medicinally.
Rosewood oil, used primarily for
skin care applications. Also used
medicinally.
Sage oil, used medicinally.
Sandalwood oil, used primarily as
a fragrance, for its pleasant, woody
fragrance.
Savory oil, from Satureja species.
Used in aromatherapy, cosmetic and
soap-making applications.
Schisandra oil, from Schisandra
chinensis, used medicinally.
Spearmint oil, often used in
flavoring mouthwash and chewing
gum, among other applications.
Star anise oil, highly fragrant oil
using in cooking. Also used in
perfumery and soaps, has been used
in toothpastes, mouthwashes, and
skin creams. 90% of the world's star
anise crop is used in the
manufacture of Tami flu, a drug
used to treat influenza, and is hoped
to be useful for avian flu.
Tarragon
oil,
distilled
Artemisia
dracunculus,
medicinally.
Tea tree oil, distilled from
Melaleuca
alternifolia,
used
medicinally. Being a powerful
antiseptic,
antibacterial
and
antiviral agent, tea tree's ability to
fight infection is second to none.
Thyme oil, used medicinally.
Turmeric, used medicinally and to
flavor food.
Valerian, used medicinally.
Wintergreen and Yarrow oil is
used medicinally, to relieve
joint pain
Ylang-ylang from Cananga odorata
used in aromatherapy.
Zedoary, used medicinally and to
flavor food.
As the use of essential oils has declined in evidence-based
medicine, one must consult older textbooks for much
information on their use. Modern works are less inclined
to generalize; rather than refer to "essential oils" as a class
at all, they prefer to discuss specific compounds, such as
methyl salicylate, rather than "oil of wintergreen". Interest
in essential oils has revived in recent decades with the
popularity of aromatherapy, a branch of alternative
Table 2. Various types of essential oils
Chamomile Essential Oil
Eucalyptus Essential Oil
Geranium Essential Oil
Lavender Essential Oil
Lemon Essential Oil
Peppermint Essential Oil
Enfleurage
Enfleurage is a process that uses odorless fats that are
semisolid at room temperature to capture the fragrant
compounds exuded by plants. It is also known as Cold Fat
Extraction. The process can be "cold" enfleurage or "hot"
enfleurage.
Cold enfleurage: A large framed plate of glass, called a
chassis, is smeared with a layer of animal fat, usually 2
part of lard & 1 part of tallow (from pork or beef,
respectively) and allowed to set. Botanical matter, usually
petals or whole flowers, is then placed on the fat and its
scent is allowed to diffuse into the fat over the course of 13 days. The process is then repeated by replacing the
spent botanicals with fresh ones until the fat has reached a
desired degree of fragrance saturation. This procedure
was developed in southern France in the 18th century for
the production of high-grade concentrates. The technique
is yet extensively used in France for the bulk production of
absolute of specific flowers.
Hot enfleurage: Solid fats are heated and botanical matter
is stirred into the fat. Spent botanicals are repeatedly
strained from the fat and replaced with fresh material
until the fat is saturated with fragrance. This method is
considered the oldest known procedure for preserving
3
Vetiver oil (khus oil) a thick,
amber oil, primarily from India.
Used as a fixative in perfumery,
and in aromatherapy.
medicine that claims that essential oils and other aromatic
compounds have curative effects. Oils are volatilized or
diluted in carrier oil and used in massage, diffused in the
air by a nebulizer, heated over a candle flame, or burned
as incense.2 The techniques and methods first used to
produce essential oils was first mentioned by Ibn al-Baitar
(1188–1248), an Andalusian physician, pharmacist and
chemist. (Table 2).
Aromatherapy Essential Oils
Bergamot Essential Oil
Dill Essential Oil
Fennel Essential Oil
Jasmine Essential Oil
Angelica Essential Oil
Aniseed Essential Oil
ISOLATION METHODS
from
used
Ylang-ylang Essential Oil
Frankincense Essential Oil
Tea-tree Essential Oil
Sandalwood Essential Oil
Basil Essential Oil
Rosemary Essential Oil
plant fragrance substances.
In both instances, once the fat is saturated with fragrance,
which is known as “Enfleurage Pomade” is then taken
separately (Defleuraged). The enfleurage pomade was
either sold as it was, or it could be further washed or
soaked in ethyl alcohol to draw the fragrant molecules into
the alcohol. The alcohol is then separated from the fat and
allowed to evaporate in an instrument called as
“Batteuses” which uses vacuum for evaporation purpose &
leaves behind the absolute of the botanical matter. The
spent fat is usually used to make soaps since it is still
relatively fragrant. (Figure 2)
Figure 2. Process of enfleurage
Significance: The enfleurage fragrance extraction method
is by far one of the oldest. It is also costly but is the sole
method of extracting the fragrant oil in delicate floral
botanical such as Jasmine, Lily, Rose, Tuberose, which
would be destroyed or denatured by the high
temperatures required by methods of fragrance extraction
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such as steam distillation. The method can’t supersede by
more efficient techniques such as solvent extraction or
supercritical fluid extraction using liquid carbon dioxide
(CO2) or similar compressed gases because they interfere
with the genuine fragrance of the essential oils.3
Advantages: Heat sensitive essential oils can be separated
in pure & unaltered form; Heating/Electricity is not
required; Eco-friendly technique; No Waste products
while used wax is used in soap production.
Pomade
Pomade is a greasy or waxy substance that is used to style
hair. Pomade makes hair look slick and shiny. Unlike hair
spray and hair gel, pomade does not dry and often takes
several washes to remove. It can be easily removed using a
high-detergent shampoo or other de-greasers such as olive
oil, dish washing liquid and lemon juice. Most pomades
contain petroleum jelly (in fact, petroleum jelly can be
used alone as a pomade) and mineral oil and many also
contain some sort of wax. They may be anhydrous or
emulsified with an aqueous carrier, which makes them
easier to remove. They may also contain perfume and
coloring agents. A wide range of pomades are in
production today and vary in factors such as weight, shine
and scent. The stiffest will have a higher proportion of
waxes such as beeswax while the lightest may have a
higher proportion of oils. (Figure 3)
Figure-3: Pomade containing Fragrance
Steam distillation
Steam distillation is a special type of distillation (a
separation process) for temperature sensitive materials
like natural aromatic compounds. Many organic
compounds tend to decompose at high sustained
temperatures. Separation by normal distillation would
then not be an option, so water or steam is introduced into
the distillation apparatus. By adding water or steam, the
boiling points of the compounds are depressed, allowing
them to evaporate at lower temperatures, preferably
below the temperatures at which the deterioration of the
material becomes appreciable. If the substances to be
distilled are very sensitive to heat, steam distillation can
also be combined with vacuum distillation. After
distillation the vapors are condensed as usual, usually
yielding a two-phase system of water and the organic
compounds, allowing for simple separation. (Figure 4)
Figure 4. Steam distillation (a) unit & (b) Process (c)
Clevenger apparatus
Principle: When a mixture of two practically immiscible
liquids is heated while being agitated to expose the
surfaces of both the liquids to the vapor phase, each
constituent independently exerts its own vapor pressure
as a function of temperature as if the other constituent
were not present. Consequently, the vapor pressure of the
4
whole system increases. Boiling begins when the sum of
the partial pressures of the two immiscible liquids just
exceeds the atmospheric pressure (approximately 101 kPa
at sea level). In this way, many organic compounds
insoluble in water can be purified at a temperature well
below the point at which decomposition occurs. For
example, the boiling point of bromobenzene is 156°C and
the boiling point of water is 100°C, but a mixture of the
two boils at 95°C. Thus, bromobenzene can be easily
distilled at a temperature 61°C below its normal boiling
point.
Applications: Steam distillation is employed in the
manufacture of essential oils, for instance, perfumes. In
this method, steam is passed through the plant material
containing the desired oils. Eucalyptus oil and orange oil
are obtained by this method on the industrial scale. Steam
distillation is also sometimes used to separate
intermediate or final products during the synthesis of
complex organic compounds. Steam distillation is also
widely used in petroleum refineries and petrochemical
plants where it is commonly referred to as "steam
stripping".
Equipment: On a lab-scale steam distillations are carried
out using steam generated outside the system and piped
through macerated biomass or steam generation in-situ
using a Clevenger-type apparatus.4 (Figure 4c)
Supercritical Fluid Extraction (SFE)
SFE is the process of separating one component (the
extractant) from another (the matrix) using supercritical
fluids as the extracting solvent. Extraction is usually from
a solid matrix, but can also be from liquids. SFE can be
used as a sample preparation step for analytical purposes,
or on a larger scale to either strip unwanted material from
a product (e.g. decaffeination) or collect a desired product
(e.g. essential oils). Carbon dioxide (CO2) is the most used
supercritical fluid, sometimes modified by co-solvents
such as ethanol or methanol. Extraction conditions for
supercritical CO2 are above the critical temperature of
31°C and critical pressure of 74 bar. Addition of modifiers
may slightly alter this. The discussion below will mainly
refer to extraction with CO2, except where specified.
(Figure 5)
Figure 5. Supercritical Fluid Extraction; SFE Plant
Procedure: The system must contain a pump for the CO2,
a pressure cell to contain the sample, a means of
maintaining pressure in the system and a collecting vessel.
The liquid is pumped to a heating zone, where it is heated
to supercritical conditions. It then passes into the
extraction vessel, where it rapidly diffuses into the solid
matrix and dissolves the material to be extracted. The
dissolved material is swept from the extraction cell into a
separator at lower pressure and the extracted material
settles out. The CO2 can then be cooled, re-compressed and
recycled, or discharged to atmosphere.
Pumps: Carbon dioxide (CO2) is usually pumped as a
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liquid, usually below 5°C and a pressure of about 50 bars.
The solvent is pumped as a liquid as it is then almost
incompressible; if it was pumped as a supercritical fluid,
much of the pump stroke would be "used up" in
compressing the fluid, rather than pumping it. For small
scale extractions (up to a few grams/minute),
reciprocating CO2 pumps or syringe pumps are often used.
For larger scale extractions, diaphragm pumps are most
common. The pump heads will usually require cooling and
the CO2 will also be cooled before entering the pump.
such as desorption from an active site are sometimes
significant, but not dealt with in detail here. Figure 5
shows the stages during extraction from a spherical
particle where at the start of the extraction the level of
extractant is equal across the whole sphere. As extraction
commences, material is initially extracted from the edge of
the sphere, and the concentration in the center is
unchanged. As the extraction progresses, the
concentration in the center of the sphere drops as the
extractant diffuses towards the edge of the sphere.
Pressure vessels: It can range from simple tubing to more
sophisticated purpose built vessels with quick release
fittings. The pressure requirement is at least 74 bars and
most extractions are conducted at less than 350 bars.
However, sometimes higher pressures will be needed,
such as extraction of vegetable oils, where pressures of
800 bars are sometimes required for complete miscibility
of the two phases. The vessel must be equipped with a
means of heating. It can be placed inside an oven for small
vessels or an oil or electrically heated jacket for larger
vessels. Care must be taken if rubber seals are used on the
vessel, as the CO2 may dissolve in the rubber, causing
swelling and the rubber will rupture on depressurization.
The relative rates of diffusion and dissolution are
illustrated by two extreme cases in Figure 5 which shows
a case where dissolution is fast relative to diffusion. The
material is carried away from the edge faster than it can
diffuse from the center, so the concentration at the edge
drops to zero. The material is carried away as fast as it
arrives at the surface and the extraction is completely
diffusion limited. Here the rate of extraction can be
increased by increasing diffusion rate, for example raising
the temperature, but not by increasing the flow rate of the
solvent. Figure 5 shows a case where solubility is low
relative to diffusion. The extractant is able to diffuse to the
edge faster than it can be carried away by the solvent, and
the concentration profile is flat. In this case, the extraction
rate can be increased by increasing the rate of dissolution,
for example by increasing flow rate of the solvent. The
extraction curve of % recovery against time can be used to
elucidate the type of extraction occurring. Figure-5 shows
a typical diffusion controlled curve. The extraction is
initially rapid, until the concentration at the surface drops
to zero and the rate then becomes much slower. The %
extracted eventually approaches 100%. Figure 5 shows a
curve for a solubility limited extraction. The extraction
rate is almost constant, and only flattens off towards the
end of the extraction. Figure-5 shows a curve where there
are significant matrix effects, where there is reversible
interaction with the matrix, such as desorption from an
active site. The recovery flattens off, and if the 100% value
is not known, then it is hard to tell that extraction is less
than complete.
Pressure maintenance: The pressure in the system must
be maintained from the pump right through the pressure
vessel. In smaller systems (up to about 10 mL/min) a
simple restrictor can be used. This can be either a capillary
tube cut to length or a needle valve which can be adjusted
to maintain pressure at different flow rates. In larger
systems a back pressure regulator will be used, which
maintains pressure upstream of the regulator by means of
a spring, compressed air or electronically driven valve.
Whichever is used, heating must be supplied, as the
adiabatic expansion of the CO2 results in significant
cooling. This is problematic if water or other extracted
material is present in the sample, as this may freeze in the
restrictor or valve and cause blockages.
Collection: The supercritical solvent is passed into a
vessel at lower pressure than the extraction vessel. The
density and hence dissolving power, of supercritical fluids
varies sharply with pressure and hence the solubility in
the lower density CO2 is much lower, and the material
precipitates for collection. It is possible to fractionate the
dissolved material using a series of vessels at reducing
pressure. The CO2 can be recycled or depressurized to
atmospheric pressure and vented. For analytical SFE, the
pressure is usually dropped to atmospheric and the now
gaseous carbon dioxide bubbled through a solvent to trap
the precipitated components.5
Heating and cooling: This is an important aspect. The
fluid is cooled before pumping to maintain liquid
conditions and then heated after pressurization. As the
fluid is expanded into the separator, heat must be
provided to prevent excessive cooling. For small scale
extractions, such as for analytical purposes, it is usually
sufficient to pre-heat the fluid in a length of tubing inside
the oven containing the extraction cell. The restrictor can
be electrically heated, or even heated with a hairdryer. For
larger systems, the energy required during each stage of
the process can be calculated using the thermodynamic
properties of the supercritical fluid. There are two
essential steps to SFE, transport (by diffusion or
otherwise) from with the solid particles to the surface, and
dissolution in the supercritical fluid. Other factors, such as
diffusion into the particle by the SF and reversible release
5
Optimization: The optimum will depend on the purpose
of the extraction. For an analytical extraction to determine,
say, antioxidant content of a polymer, then the essential
factor is complete extraction in the shortest time.
However, for production of an essential oil extract from a
plant, then quantity of CO2 used will be a significant cost,
and "complete" extraction not required, a yield of 70-80%
perhaps being sufficient to provide economic returns. In
another case, the selectivity may be more important, and a
reduced rate of extraction will be preferable if it provides
greater discrimination. Therefore few comments can be
made which are universally applicable.
Maximizing diffusion: This can be achieved by increasing
the temperature, swelling the matrix, or reducing the
particle size. Matrix swelling can sometimes be increased
by increasing the pressure of the solvent, and by adding
modifiers to the solvent. Some polymers and elastomers in
particular are swelled dramatically by CO2, with diffusion
being increased by several orders of magnitude in some
cases.
Maximizing solubility: Generally, higher pressure will
increase solubility. The effect of temperature is less
certain, as close to the critical point, increasing the
temperature causes decreases in density, and hence
dissolving power. At pressures well above the critical
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pressure, solubility is likely to increase with temperature.
Addition of low levels of modifiers (sometimes called
entrainers), such as methanol and ethanol, can also
significantly increase solubility, particularly of more polar
compounds.
Optimizing flow rate: The flow rate of CO2 should be
measured in terms of mass flow rather than by volume
because the density of the CO2 changes according to the
temperature both before entering the pump heads and
during compression. Coriolis flow meters are best used to
achieve such flow confirmation. To maximize the rate of
extraction, the flow rate should be high enough for the
extraction to be completely diffusion limited (but this will
be very wasteful of solvent). However, to minimize the
amount of solvent used, the extraction should be
completely solubility limited (which will take a very long
time). Flow rate must therefore be determined depending
on the competing factors of time and solvent costs and
also capital costs of pumps, heaters and heat exchangers.
The optimum flow rate will probably be somewhere in the
region where both solubility and diffusion are significant
factors.6
Advantages:
Environmental improvement and reduced product
contamination: SFE is an alternative to liquid extraction
using solvents such as hexane or dichloromethane. There
will always be some residual solvent left in the extract and
matrix and there is always some level of environmental
contamination from their use. In contrast, carbon dioxide
is easy to remove simply by reducing the pressure, leaving
almost no trace, purchased CO2 has almost always been
reclaimed, which reduces the total carbon foot-print. The
use of SFE with CO2 is approved by the Soil Association for
organic products. The CO2 used is largely a byproduct of
industrial processes or brewing and its use in SFE does not
cause any extra emissions.
Selectivity: The properties of a supercritical fluid can be
altered by varying the pressure and temperature, allowing
selective extraction. For example, volatile oils can be
extracted from a plant with low pressures (100 bar),
whereas liquid extraction would also remove lipids. Lipids
can be removed using pure CO2 at higher pressures and
then phospholipids can be removed by adding ethanol to
the solvent.
Speed: Extraction is a diffusion-based process, with the
solvent required to diffuse into the matrix and the
extracted material to diffuse out of the matrix into the
solvent. Diffusivities are much faster in supercritical fluids
than in liquids and therefore extraction can occur faster.
Also, there is no surface tension and viscosities are much
lower than in liquids, so the solvent can penetrate into
small pores within the matrix inaccessible to liquids. Both
the higher diffusivity and lower viscosity significantly
increase the speed of the extraction: An extraction using
an organic liquid may take several hours, whereas
supercritical fluid extraction can be completed in 10-60
minutes.
Limitations: The requirement for high pressures
increases the cost compared to conventional liquid
extraction, so SFE will only be used where there are
significant advantages. Carbon dioxide itself is non-polar,
and has somewhat limited dissolving power, so cannot
always be used as a solvent on its own, particularly for
polar solutes. The use of modifiers increases the range of
materials which can be extracted. Food grade modifiers
6
such as ethanol can often be used, and can also help in the
collection of the extracted material, but reduces some of
the benefits of using a solvent which is gaseous at room
temperature.7
Water Distillation Method
In water distillation, the botanical material is completely
immersed in water and then is boiled. This method
protects the oil to be extracted till a certain degree since
surrounding water prevents it from overheating. Then it is
condensed and cooled down. The oil is then separated out,
as it layers on the top of the water. The water separated
out in this process is termed as floral waters (also called
hydrosol or sweet water) such as rose water, orange water
and lavender water. Water distillation can be operated at
low pressures to reduce boiling temperature. This helps in
protecting the botanical material and essential oil as well.
This method is used for extraction of oils that are sensitive
to heat. If a lot of exposure to hot water is not mentioned
for a particular plant such as lavender, it is best to find an
extraction method better suited. Any botanical material
that contains high amounts of esters does not take well to
this extraction method, since the exposure to hot water
will break down the esters into alcohols and carboxylic
acids.
Steam Distillation Method
Steam distillation is the most common method of
extracting essential oils. Steam distillation is done in a still
(The still is all with a head and a well-insulated swan's
neck proceeded by a mechanism to prevent fumes and
impurities passing through). Fresh, or sometimes dried,
botanical material is placed in a closed container of the
still, and pressurized steam is generated which enters the
container and circulates through the plant material. The
heat of the steam forces the intercellular pockets that hold
the essential oils to open and release them. The
temperature of the steam should not be very high as it can
damage the botanical material but should be high enough
to open the pockets which hold the essential oil. Tiny
droplets of essential oil evaporate and attach to the steam.
The steam which then contains the essential oil, is passed
through a cooling system to condense the steam, which
forms a liquid from which the essential oil and water is
then separated by decantation. The oil forms a layer on the
water surface as it does not dissolves in water and hence
is separated easily. This method is not used for extraction
of oils that are sensitive to heat. (Figure 6)
Figure 6. Steam distillation unit
Hydro Diffusion Method
Hydro Diffusion method for extraction of oils is a type of
steam distillation and is only different in the way in which
steam is enters the container of the still. In hydro
diffusion, steam is fed in from the top onto the botanical
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material while in the case of steam distillation; steam is
fed from the bottom. In this way the steam can saturate
the plants more evenly and in less time than with steam
distillation. The condensation of the oil containing steam
mixture occurs below the area in which the botanical
material is held. The main advantage of this method over
steam distillation is that less steam is used hence shorter
processing time and therefore a higher oil yield. This
method is also less harsh on the botanical material.
fruit absorbed the water. After the fruit has absorbed the
water and become more elastic, it was inverted which
helped to rupture the oil cells and a sponge placed next to
the rind. It was then squeezed to release the volatile oil,
which was then collected directly into the sponge. As soon
as the sponge became saturated with oil, it was squeezed
and the essential oil collected in a vessel and then
decanted.9 (Figure 9)
Figure 9. Sponge expression method
Fractional Distillation Method
When we say fractional distillation, it only refers to
normal distillation process. In this only difference is that
the oil is not collected continuously, but is collected in
parts i.e. fractions and oil normally so extracted is “YlangYlang oil”. (Figure 7)
Figure 7. Fractional distillation unit
Rectification Method
When an essential oil contains any impurities, it can be
purified by re-distillation; either in steam or in vacuum
and this purification of oil by re-distillation is referred to
as rectification. This process is used to make oils of
standard quality. An example of rectification is eucalyptus
oil. (Figure 8)
Figure 8. Rectification unit
Cohobation Method
In some essential oil extractions, some chemical or part of
the essential oil gets dissolved in water and therefore gets
removed from the oil. So to get the whole oil, we add the
deficient chemical to the deficient oil and re-distillation is
done until we get the complete oil. An example of this is
rose oil.8
Sponge Expression Method
Most citrus essences are extracted by means of expression,
and in the past were done by hand where the fruit pulp
was removed, with the rind and pith then soaked in warm
water to make the rind more pliable, since the pith of the
7
Cold Pressed Method
Another expression method of extracting essential oils is
coldpressed expression, or scarification method. It is used
to obtain citrus fruit oils such as bergamot, grapefruit,
lemon, lime, mandarin, orange, and tangerine oils. In this
process, fruit rolls over a trough with sharp projections
that penetrate the peel. This pierces the tiny pouches
containing the essential oil. Then the whole fruit is pressed
to squeeze the juice from the pulp and to release the
essential oil from the pouches. The essential oil rises to the
surface of the juice and is separated from the juice by
centrifugation. 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.10 (Figure 10)
Figure 10. Cold pressed method
Machine Abrasion Method
Machine Abrasion is very much same as cold pressed
expression method and is mainly used in extraction of
citrus essential oils. In machine abrasion, a machine strips
off the outer peel of the botanical material, which is then
removed by running water and left over is then fed into a
centrifugal separator. The centrifugal separation is done
extremely fast. But, it should be noted that due to the fact
that the essential oil is combined with other cell content
for some time, some alteration could occur in the oil due to
enzymatic action.11 (Figure 11)
Figure 11. Machine abrasion method
Solvent Extraction Method
Very delicate aromatics, Jasmine, Linden Blossom, etc.
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Patel P N et al. / Pharmacie Globale (IJCP) 2011, 9 (02)
cannot survive the process of distillation. To capture their
magical aromas, a process of solvent extraction is used. A
hydrocarbon solvent (usually hexane) is added to the
botanical material to help dissolve the extractable matter
from the botanical material which includes non-aromatic
waxes, pigments and highly volatile aromatic molecules.
When this solution is filtered and then the filtrate is
subjected to distillation at low pressure, a substance
containing resin (resinoid), or a combination of wax and
essential oil (known as concrete) is left. The concrete is
further processed to remove the waxy materials which
dilute the pure essential oil. To prepare the absolute from
the concrete, the waxy concrete is warmed and stirred
with alcohol (usually ethanol). When we heat and stir the
concrete, it breaks up into minute globules, and separation
takes place as aromatic oil is more soluble in alcohol than
that in wax. But along with the aromatic molecules a
certain amount of wax is also dissolved and this can be
removed only by agitating and freezing the solution at
very low temperatures (around minus -35°C). In this way
most of the wax precipitates out. As a final precaution the
purified solution is cold filtered leaving only the wax-free
material (the absolute) i.e. the essential oil. This solvent
extraction actually yields three usable products; first the
concrete (as in rose concrete, my favorite solid perfume),
the precious absolutes i.e. the oils, and the floral waxes, for
addition to candles, thickening creams and lotions as a
softly floral scented alternative to beeswax. Although
more cost-efficient than enfleurage, solvent extraction is
more expensive than steam distillation so it is reserved for
costly oils which cannot be distilled. This is not considered
the best method for extraction of essential oils, as the
solvents can leave a residue behind which could cause
allergies and effect the immune system, but it's great for
making resins for this very reason.12
Maceration Method
Maceration actually creates more of infused oil rather than
an essential oil and is most often used for creating extracts
and resins. The botanical material is soaked in vegetable
oil, water, or another solvent. If it's soaked in vegetable oil,
and then heated and strained, it can be used for massage
and if soaked in water or another solvent such as alcohol,
will create a much thicker extract or resin.13 (Figure-12)
Figure 12. Maceration method
as other solvent extraction methods. To remove the
carbon dioxide solvent, you simply need to remove the
pressure applied. This process has to take place in a closed
chamber since the hypercritical pressure required for
carbon dioxide is 200 atmospheres. To achieve this
pressure specific equipment is required which is very
expensive. The advantage of this method, of course, is that
no solvent residue remains, since at normal pressure and
temperature, the carbon dioxide simply reverts to a gas
and evaporates. Hypercritical carbon dioxide extraction
has given us essences of some aromatics that don't yield
essential oils, for example Rose Hip Seed and Calendula.
Many carbon dioxide extractions have fresher, cleaner,
and crisper aromas than steam-distilled essential oils, and
they smell more similar to the living plants. Scientific
studies show that carbon dioxide extraction produces
essential oils that are very potent and have great
therapeutic benefits.14 (Figure 13)
Figure 13. Hypercritical CO2 method
Florasols/Phytols Method
This extraction method uses a new type of benign gaseous
solvents. The unique properties of these solvents are used
for the extraction of aromatic oils and biologically active
components from botanical materials. Florasol is the
solvent upon which the process is based. Extraction occurs
at or below ambient temperatures; hence there is no
thermal degradation of the products. The extraction
process utilizes the selectivity of the solvent and produces
free flowing clear oil free of waxes. (Figure 14)
Figure 14. Florasol method
Hypercritical Carbon dioxide (CO2) Method
The use of hypercritical carbon dioxide extraction is a
fairly new way to extract essential oils from botanical
material and although a bit on the expensive side, does
yield good quality oils. Carbon dioxide becomes
hypercritical at 33 degrees celsius, which is a state in
which it is not really gas or liquid, but has qualities of both,
and is an excellent solvent to use in the extraction of
essential oils since low temperature is required and the
fact that the process is near to instantaneous.
‘Florasols’ Are NOT ‘Essential Oils’! Why? ‘Essential’ oils
are made by steam or water distillation. The plant material
is boiled for several hours in a kettle with lots of water
(typically three times its weight). Some of the water turns
to steam which carries the fragrant oil with it. The steam is
condensed back to water by cooling it in condensers. The
‘essential’ oil floats on the surface of the condensed water
and is skimmed off. So, ‘essential oil’ has all been cooked.
Heat will have damaged and changed many of the fragile,
naturally occurring substances. Much of the most delicate,
fragrant, light, volatile components will have been lost
during the condensation. Much of the fragrant is also lost –
dissolved in the condensed waters (rose water is a
fragrant!), this loss have been at the expense of the oil.
This process uses huge amounts of fossil fuel to boil the
plant/water mix, pollutes, and also produces vast
quantities of boiling hot liquid waste.
The carbon dioxide is inert and therefore does not
chemically react with the essence that is being extracted
and hence, essential oils can be extracted in a similar way
‘Florasols’ Are NOT ‘Absolutes’! Why?
‘Absolutes’ are made from ‘concretes’ by milling them with
98% alcohol. Strong alcohol dissolves the ‘absolutes’ out of
8
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Patel P N et al. / Pharmacie Globale (IJCP) 2011, 9 (02)
the buttery mass of ‘concretes’. This alcohol solution is
frozen to – minus 10°C (14°F), which precipitates the
waxes. This cold solution is filtered and the
filtrate/solution concentrated by rigorously boiling off of
the alcohol under vacuum. The ‘absolutes’ is the oil which
is left after the alcohol has been boiled away. Alcohol boils
at 78°C. So “absolutes’ have been through TWO ‘boilingoff’ processes (the first from hexane, the second from
alcohol), Volatile fragrant components will have been
stripped out and lost and damage will have been done to
the delicate heat sensitive components of the oil on both
occasions.
‘Florasols’ Are NOT ‘Concretes’! Why? ‘Concretes’ are
made by stirring up vegetable matter with hexane
(gasoline) or chlorinated solvents (such as methylene
chloride). Hexane dissolves (extracts) many of the plant’s
components. The hexane solution is then evaporated to
dryness at 75°C. The ‘concrete’ is what it’s left, after the
hexane has been driven off/boiled away. So, ‘concretes’
have also been heated. They also contain residual hexane.
They contain about 50% of the plant’s waxes, pigments,
resins, fats, (triglycerides and fatty acids) and sterols and
their esters. Heating will have caused damage to the fragile
components and the loss of their delicate ‘volatiles,
particularly if the hexane has been removed under high
vacuum (which is usual practice) hexane is lost into the
atmosphere where it is a serious ‘Volatile Organic
Compound’ – VOC pollutant, contributing to toxic.
Needless to say, the process is also extremely hazardous as
hydrocarbons are all flammable. We can however extract
from Concretes using our HFC Process and, in this case, we
first coat the Concrete onto a carrier medium and then
extract using the normal ‘FLORASOLS’ process. The
extraction time will be longer than a standard extraction,
but the yield will of cause be proportionally higher as the
concentration of the oil in the Concrete is higher also. As
an example; 1kg of Rose Concrete may produce 500 gms of
oil whereas 1 kg of Rose will provide 1 gm of oil.
‘Florasols’ Are NOT ‘SCFE Oil’! Why? Warm carbon
dioxide gas at exceeding high pressure can be used to
dissolve fragrant/flavour oils from some plant materials.
The acidic gas, carbon dioxide, is passed through the warm
REFERENCES
1. Handa S S, Khanuja S P S, Longo G, Rakesh D D;
Extraction Technologies for Medicinal and Aromatic
Plants. International Center for Science & High
Technology. Trieste. 2008.
2. Alfred G, Goodman L S. Goodman and Gilman's The
pharmacological basis of therapeutics. New York:
Pergamon Press. 1990.
3. Prabuseenivasan S, Manickkam J and Ignacimuthu S;
In-vitro antibacterial activity of some plant essential
oils. BMC Complement Altern Med. 2006; 6:39.
4. Henley D V, Lipson N, Korach K S, Bloch C A;
Prepubertal gynecomastia linked to lavender and tea
tree oils. New England Journal of Medicine. 2007;
356(5):479-85.
5. Bischoff K, Guale F; Australian tea tree (Melaleuca
alternifolia) oil poisoning in three purebred cats. J Vet
Diagn Invest. 1998; 10(2):208-10.
6. Perfume connoisseurs speak of a fragrance's "sillage",
or the discernible trail it leaves in the air when applied.
Fortineau Anne-Dominique. "Chemistry Perfumes Your
Daily Life". Journal of Chemical Education. 2004;
81(1):2345-2358.
9
plant material at 300 – 500 times the pressure of the
atmosphere (pressure such as those found in the nature at
the bottom of the Pacific Ocean, three miles down!) - don’t
try this at home! This ‘fluid’ dissolves oil, resins and waxes
out of the plant material. When the pressure is allowed to
fall to only 100 ‘Bar’ (=100 time atmospheric pressure, the
oil form into a mist and can be collected. Needless to say,
the equipment needed for this process is massive in the
extreme and very costly and uses huge quantities of
electricity to drive it. This is why products are so
expensive. The effect of the high degree (all low as pH 2.0)
at these temperatures on the ‘naturalness’ of SCFE
products, will reward further study.15
Commonly used Techniques for Aroma Oil Extraction
(Table 3)
Table 3. Different types of extraction
Water Distillation
Steam Distillation
Hydro Diffusion
Fractional Distillation
Rectification
Cohobation
Sponge Expression
Methods
Cold pressed Expression
Machine Abrasion
Solvent Extraction
Maceration
Enfleurage
Hypercritical Carbon Dioxide (CO2)
Florasol
Use of essential oils with aromatherapy (Table 4)
Table 4. Use of essential oils with aromatherapy
Use of essential oils
Aromatherapy Recipes
Air
reshening
Compresses
Emotional
Balance
Acne
Physical
Balance
Sun Screen
Massage
Bubble Baths
Cleansers &
Toners
Shower gels
Face oils
Moisturizers
Bathing
Hair care
Foot and
baths
Jacuzzis
hand
Massage
Saunas
Showers
Skin care
Sitz bath
Steam inhalations,
Vaporization
Shampoos
Perfumes and
Colognes
CONCLUSION
Nature produces essential oils in flowers which are
extracted by several processes to make perfumes or
essences from ancient period. All the fragrances are well
accepted for various purposes in our daily routine for
making natural harmony with nature.
7. Calkin R R and Jellinek J S; Perfumery: practice and
principles. John Wiley & Sons, Inc. 1994; ISBN 0-47158934-9.
8. Kumar P, Caradonna-Graham V M, Gupta S, Cai X, Rao P
N, Thompson J. "Inhalation challenge effects of perfume
scent strips in patients with asthma". Ann Allergy
Asthma Immunol. 1995; 75(5):429-433.
9. Frosch P J, Rastogi S C, Pirker C et al. Patch testing with
a new fragrance mix - reactivity to the individual
constituents and chemical detection in relevant
cosmetic products. Contact Derm. 2005; 52(4):216-225.
10. Apostolidis S, Chandra T, Demirhan I, Cinatl J, Doerr H
W, Chandra A; Evaluation of carcinogenic potential of
two nitro-musk derivatives, musk xylene and musk
tibetene in a host-mediated in-vivo/in-vitro assay
system. Anticancer Res. 2002; 22(5):2657-2662.
11. Schmeiser H H, Gminski R, Mersch-Sundermann V;
Evaluation of health risks caused by musk ketone. Int J
Hyg Environ Health. 2001; 203(4):293-299.
12. Schreurs R H, Legler J, Artola-Garicano E et al. In-vitro
and in-vivo antiestrogenic effects of polycyclic musks in
zebrafish. Environ Sci Technol. 2004; 38(4):997-1002.
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13. Rastogi S C, Bossi R, Johansen J D et al. Content of oak
moss allergens atranol and chloroatranol in perfumes
and similar products. Contact Derm. 2004; 50(6):367370.
14. Duedahl-Olesen L, Cederberg T, Pedersen K H, Højgård
A; Synthetic musk fragrances in trout from Danish fish
10
farms and human milk. Chemosphere. 2005; 61(3):422431.
15. Peck A M, Linebaugh E K, Hornbuckle K C; Synthetic
musk fragrances in Lake Erie and Lake Ontario
sediment cores. Environ Sci Technol. 2006;
40(18):5629-5235.
Pharmacie Globale© (IJCP), Vol. 02, Issue 08
