Kimia minyak atsiri
TEKNIK PRODUKSI MINYAK ATSIRI
PRODUCTION OF ESSENTIAL OILS
Essential oils may be produced
i.
By steam
- Simple steam distillation
- Saturated steam distillation
- Hydrodiffusion
Ii
Iii
Iv
By expression
By solvent extraction
By Enfleurage
ENFLEURAGE
These procedures take advantage
of the liposolubility of the
fragrant components of plants
in fats.
“Enfleurage” – the plant material
is placed in contact with the
surface of the fat. Extraction is
achieved by
- Cold diffusion into the fat
- Digestion – carried out with
heat, by immersing the plant
in melted fat (also known as
hot enfleurage).
The final product is known as a
floral pomade.
• One of the oldest techniques
• Advantages :
Flowers continue to produce aroma
compounds for several days after day have
been picked.
Ex: jasmine produces 4-5 times essential oils
than is present at any time in the fresh
flower.
Disadvantage : very high labour cost involved
Enfluerage Tehniques
• Cold Enfluerage:
• a single layer flowers is placed on a tray covered beforehand
with a thin layer of grease, which absorbs the volatile
compounds from the flowers.
• The absorption take several days (ex 1-3 days), after which
theflowers replaced with fresh ones until the grease is
saturated.
• The resulting product is called pomades and was either used
directly in cosmetics, or wased wit alcohol. The resulting
solution known as an extrait or absolute de pomade
• Hot Enfluerage:
• Flowers are placed in linen bag, which are then dipped in melted
fat, vegetable oil or mineral oil heated to about 50-60oC. After
maximum 12 hours the bags removes and replaced with fresh
ones.
SOLVENT EXTRACTION
This methods gradually replaces te metods of
enfleurage
Garnier obtained a patent for novel type of
extractior that became widely used first in
France.
Extraction is generally preceded by a process of:
bruising the fresh, wilted or semi-desiccated
organs, chopping herbaceous drugs, pounding
roots & rhizomes or turning wood into chips or
shavings.
The procedure is conducted in specialized facilities
e.g. Soxhlet-type extractor.
SOLVENT EXTRACTION
The solvent selection is influenced by technical & economical
factors
- Selectivity (being a good solvent for the specific
constituents).
- Stability (chemical inertness)
- Boiling point should not be so high that the solvent can be
completely eliminated; nor too low, to limit losses & control
cost
- Handling safety
Solvents most used are aliphatic HC’s – petroleum ether,
hexane, propane & liquid butane.
Although benzene is a good solvent, its toxicity increasingly
limits is use.
SOLVENT EXTRACTION
At the end of the procedure, the solvent contained
in the plant material is recovered by steam
injection or vacum evaporation.
Main disadvantages of solvent extraction
- Lack of selectivity, many lipophilic substances may
end up in the concretes & render further
purification necessary.
- The toxicity of solvents  leads to the restrictive
regulations regarding their use
- Residues in the final product.
EXTRACTION BY SUPERCRITICAL GASSES
Beyond its critical point, a fluid can have the density of a
liquid & the viscosity of a gas  therefore diffuses well
through solids, resulting in a good solvent.
CO2 is the main gas used
Advantages of CO2
- It is a natural product
- chemically inert, non-flammable
- non-toxic
- easy to completely eliminate
- selective
- readily available
- Inexpensive
EXTRACTION BY SUPERCRITICAL GASSES
DISADVANTAGE: Technical constraints
- High cost of initial investment
ADVANTAGES:
- obtain extracts which are very close in
composition to the natural product.
- It is possible to adjust the selectivity & viscosity,
etc by fine tuning the temperature & pressure
- All result in the increase of popularity of this type
of method
EXTRACTION BY SUPERCRITICAL GASSES
USES
Initially developed to decaffeinate coffees, prepare
hops extracts or to remove nicotine from tobacco,
the method is now used to
- Prepare spice extracts (ginger, paprika, celery)
- Specific flavours (black tea, oak wood smoke)
- Plant oils
- To produce specified types of a certain product,
e.g. thujoneless wormwood oil.
EXPRESSION
(E.G.OF CITRUS EPICARPS)
The rind is lacerated, and the contents of the
ruptured secretory cavities are recovered.
CLASSIC PROCESS: an abrasive action is applied on
the surface of the fruit in a flow of water. The
solid waste is eliminated, and the essential oil
separated from the aqueous phase by
centrifugation.
OTHER machines break the cavities by depression,
and collect the essential oil directly  prevents
the degradation linked to the action of water.
EXPRESSION
• Many component of essential oils from citrus fruits are delicate
and suffer significantly from heat degradation when exposed to
steam distillation
• In cold expression, the fruit peel is compressed, lacerated to
rupture the oil cells in the exocarp and release the essential oils.
• 2 methods cold expression :
• Spugma or sponge methods: fruits were halved , and juicy pulp
was removed with a spoon-shaped knife. The peel was placed in
warm water and pressing against a sponge with sufficient force.
The sponge was periodically squeezed over a collecting vessel.
• Scodella or spoon methods: used a funnel-shaped bowl, fruits
turned and pressed. The mixture of essential oils released
together with cell contents was collected in the bottom of
funnel.
EXPRESSION OF CITRUS EPICARPS
Most facilities allow for the simultaneous or
sequential recovery of the fruit juice and of the
essential oil, by collecting the oil with a spray of
water after the abrasion (scarification – puncture
by pins) before or during the expression of the
fruit juice.
Enzymatic treatment of the residual water allows
recycling, and markedly increases the final yield of
essential oil.
Citrus oils are also obtained directly from the fruit
juices (by vacuum de-oiling)
DISTILLATION
a.
SIMPLE STEAM DISTILLATION/ WATER DISTILLATION
The principle is to boil and vaporize a suspension of aromatic plant
material and water in a vat so that its vapours can be
condensed and collected. The essential oils is separated by
gravity.
Plant material is immersed directly in a still filled with water. This is
then brought to a boil.
Heterogeneous vapours are condensed on a cold surface.
Essential oil separates based on difference in density and
immiscibility.
In the 11th cemtury, Abu Sina added the frame to the vat, fixed above
the level of water, on which the material to be distillated was
placed.
b. SATURATED STEAM
Plant does not come into contact
with the water  steam is
injected through the plant
material placed on perforated
trays.
It is possible to operate under
moderate pressure.
Advantages: Limits the alteration of
the constituents of the oil
It shortens the duration of the
treatment
It conserves energy
It can also be conducted on on-line
in automated set ups.
c. HYDRODIFFUSION
Pulses of steam is sent through the plant
material at very low pressure from (top to
bottom).
ADVANTAGE: Normally produces a product of
high quality.
Saves time and energy.
iii. OTHER METHODS
- Steam distillation by microwaves under vacuum. In
this procedure, the plant is heated selectively by
microwave radiation in a chamber inside which the
pressure is reduced sequentially.
- fresh plants require no added water.
- ADVANTAGE: This method is fast, consumes little
energy and yields a product which is most often of a
higher quality than the traditional steam distillation
product.
Distillations:
Steam Distillation
1.
Steam distillation arises from an interesting curiosity of immiscible
systems
2.
The distillation of liquids that are fully miscible is governed by Raoult’s
Law
PT = NAP˚A +NBP˚B + NCP˚C + …
(1)
•
•
3.
The mixture will have its own unique boiling point
The contribution of each component to the vapor phase is
related to its partial vapor pressure and mole fraction
In the distillation of immiscible liquids, the two act as two separate
liquids
A
B
Distillations:
Steam Distillation
4.
The total vapor pressure above an immiscible system is equal to the
sum of the vapor pressures independent of their relative amounts
PT = P˚A + P˚B + P˚C + … (2)
5. The mixture will boil at a temperature
typically lower than either liquid
6. Consider a mixture of iodobenzene and water:
At 98 IoC the value of each vapor pressure is:
H
H
O
46 torr + 714 torr
= 760 torr Mixture boils!
Distillations:
Steam Distillation
7. The mole fraction of each component (nA and nB) in the vapor
phase is
given by the ratio of its partial pressure over the total
pressure: nA =
P˚A/PT (3) and nB = P˚B/PT (4)
8. If the vapor is condensed, the resulting distillate has the same
composition. The ratio of the mole fractions for A and B in the
distillate is then given by Equation 5, which results from dividing
equation 3 by equation 4:
nA/nB = P˚A/P˚B (5)
•
Thus in the case of the steam distillation of iodobenzene and water, the
vapor phase, iodobenzene would only have a mole fraction of 0.064 (46
torr/714 torr)
•
But because it has a larger molecular weight (204 vs. 18 grams per mole)
about 0.7 grams of iodobenzene are
collected for every gram of
water
•
In the gas phase the two are fully miscible, but once the vapor condenses –
the two are no longer miscible – and can be physically separated
Distillations:
Steam Distillation
B. Uses/Apparatus
•
This method is typically used
to extract the volatile
components of plants for use
in perfumery, flavors or
aromatherapy products.
•
Steam distillation is used in
the industries that produce
these products as well as
amateur set-ups like this one
Isolation of Natural Products
• This isolation of a “natural product” from its native matrix is one of the oldest examples
of applied organic chemistry – medicines and herbal remedies prepared by early human
civilizations are good examples of this
• This field undergoing explosive growth as we attempt to find interesting molecules in
nature that can be used for medicinal purposes as well as for flavorings, dyes and
cosmetics from a natural rather than synthetic source
• The American Chemical Society (ACS) publishes
a Journal that covers recent developments in this
highly interesting and important field
• Papers start with the isolation of the
animal or plant from it’s native environment
followed by the various separation and identification
techniques used to identify each component
• Recently, the initial assays of the anti-microbial,
anti-carcinogenic and toxicity behavior of each
component are also reported
When these isolations are for medicinal purposes, the field is known as Pharmacognosy
"Pharmacognosy" derives from two Greek words, "pharmakon" or drug, and
"gnosis" or knowledge. Like many contemporary fields of science, pharma-cognosy has
undergone significant change in recent years and today represents a highly interdisciplinary
science which is one of five major areas of pharmaceutical education.
Its scope includes the study of the physical, chemical, biochemical and biological properties
of drugs, drug substances, or potential drugs or drug substances of natural origin as well as
the search for new drugs from natural sources.
Research problems in pharmacognosy include studies in the areas of phytochemistry,
microbial chemistry, biosynthesis, biotransformation, chemotaxonomy, and other biological
and chemical sciences.
TREATMENTS OF THE OILS
Occasionally it is necessary to decolourize, neutralize
or rectify the oils obtained.
i. Steam jet under vacuum
Allows for the elimination of smelly or irritating
products, and to obtain a final product of
desired “profile”.
ii. Chromatrographic techniques
This permits a good separation of the essential oil
from non-volatile lipophilic compounds.
iii. OTHER METHODS
- Steam distillation by microwaves under vacuum. In
this procedure, the plant is heated selectively by
microwave radiation in a chamber inside which the
pressure is reduced sequentially.
- fresh plants require no added water.
- ADVANTAGE: This method is fast, consumes little
energy and yields a product which is most often of a
higher quality than the traditional steam distillation
product.