So... how do you get the oil out of the plant? There are several types of processes to remove oil from plants. In the future I will even review oils from animals, plants and even eggs. This describes extraction of Carrier Oils.
Filtering:
This is done to remove sediment particles, it removes a negligible amount of flavor and antioxidants (about 5%). It makes a product more visually appealing.
Boiling:
This method is used mostly to remove animal fats, like lard.
Cold Pressed/Cold Expeller Pressed:
The seeds/nuts and/or fruit pulp are crushed then mechanically pressed. The temperature should not exceed 120oF which is cause by friction from the pressing. This method produces less oil, but the oil is of a higher quality. Generally oils produced by this method only require to be filtered once to remove particles (shell pieces or fruit fibers).
The seeds/nuts and/or fruit pulp are crushed then mechanically pressed. The temperature should not exceed 120oF which is cause by friction from the pressing. This method produces less oil, but the oil is of a higher quality. Generally oils produced by this method only require to be filtered once to remove particles (shell pieces or fruit fibers).
Hot Pressed:
Seeds/nuts and fruit pulp are crushed and heated, then the oil is pressed out. This process does produce a large amount of oil than cold pressed. The raw material left behind can be pressed again to obtain more oil. The material is heat to approximately 140oF or more. This method can produce impurities and usually requires the oil to be filtered.
Expeller Pressed:
Expeller pressed oils are mechanically pressed from seeds/nuts and/or fruit pulp at high pressure to obtain maximum yield. The oil is collected and later filtered. High pressure extraction can cause temperatures to rise above 120 degrees. Only if temperature is monitored and kept under 120 degrees, can the oil be called cold pressed. Otherwise it is simply called expeller pressed.
Expeller pressed oils are mechanically pressed from seeds/nuts and/or fruit pulp at high pressure to obtain maximum yield. The oil is collected and later filtered. High pressure extraction can cause temperatures to rise above 120 degrees. Only if temperature is monitored and kept under 120 degrees, can the oil be called cold pressed. Otherwise it is simply called expeller pressed.
Solvent Extracted:
Sometimes it is necessary to use a solvent in order to extract the oil from certain seeds, nuts or kernels in order to make the extraction cost effective. Hexane is usually the solvent of choice. The nuts/seeds are extracted using hexane or similar chemicals typically yield a much higher return rate. The compound causes most organic materials to quickly break down, which boosts yields well into the 90%. Once the oil has been obtained, the solvent is then removed from the oil (and used again), but a trace percentage of the solvent may still be present in the final oil.
Sometimes it is necessary to use a solvent in order to extract the oil from certain seeds, nuts or kernels in order to make the extraction cost effective. Hexane is usually the solvent of choice. The nuts/seeds are extracted using hexane or similar chemicals typically yield a much higher return rate. The compound causes most organic materials to quickly break down, which boosts yields well into the 90%. Once the oil has been obtained, the solvent is then removed from the oil (and used again), but a trace percentage of the solvent may still be present in the final oil.
CO2 Extracted/Supercritical Carbon Dioxide Extraction:
The raw material is finely ground, then the oils is extracted using fluid carbon dioxide as the solvent. Carbon dioxide is converted to liquid using high pressure making it a safe and effective solvent that allows all the desirable active constituents of a plant to be collected without the risk of heat degradation. Once the extraction is complete, the pressure is released allowing the carbon dioxide to return to its natural gaseous state, leaving behind only the extracted essence of the plant. CO2 extracted oils are the closest representation of the natural plant ever. The chemical composition may have different therapeutic and safety properties than oils extracted by other methods. CO2 total extracts include the volatile components as well as the heavier, waxy components that give plants their color, and are therefore thick and waxy in consistency.
The raw material is finely ground, then the oils is extracted using fluid carbon dioxide as the solvent. Carbon dioxide is converted to liquid using high pressure making it a safe and effective solvent that allows all the desirable active constituents of a plant to be collected without the risk of heat degradation. Once the extraction is complete, the pressure is released allowing the carbon dioxide to return to its natural gaseous state, leaving behind only the extracted essence of the plant. CO2 extracted oils are the closest representation of the natural plant ever. The chemical composition may have different therapeutic and safety properties than oils extracted by other methods. CO2 total extracts include the volatile components as well as the heavier, waxy components that give plants their color, and are therefore thick and waxy in consistency.
Infusion/Macerate:
An infused or macerated oil is a vegetable oil that has been "infused" with the fat soluble properties of other botanicals or a base oil. Dried or fresh plant material is macerated by being steeped in a Vegetable Oil and agitated (shaken vigorously) daily for anything from several days to 6 weeks. Botanical material is then removed by filtering the Oil, leaving the Oil with some of the therapeutic properties of the botanical material. The base oil is sometimes gently heated to encourage infusion. The final oil is then well filtered to remove any traces of plant particles. The benefit to using an infused vegetable oil is that the infused oil will contain the therapeutic properties of both the vegetable oil and the botanicals that were infused into the oil.
An infused or macerated oil is a vegetable oil that has been "infused" with the fat soluble properties of other botanicals or a base oil. Dried or fresh plant material is macerated by being steeped in a Vegetable Oil and agitated (shaken vigorously) daily for anything from several days to 6 weeks. Botanical material is then removed by filtering the Oil, leaving the Oil with some of the therapeutic properties of the botanical material. The base oil is sometimes gently heated to encourage infusion. The final oil is then well filtered to remove any traces of plant particles. The benefit to using an infused vegetable oil is that the infused oil will contain the therapeutic properties of both the vegetable oil and the botanicals that were infused into the oil.
Refined, Bleached and Deodorized (RBD):
When ordering oils, you may see RBD listed next to its name or in conjunction with its extraction method. The terms listed below explain this process.
Refined:
Some oils undergo a refinement process in order to remove impurities, improve the color or texture, or stabilize the shelf life of the oil. The oil is reacted with a sodium hydroxide solution to saponify the free fatty acids into soap (which sink to the bottom). Phosphorus may be added to remove mucilage and wax. The oil is then filtered or centrifuged and washed with water until the pure oil remains. The oil may also be degummed to remove the sticky phospholipids, color pigments and odor lending portions.
Bleached:
Some oils are bleached in order to improve the color and clarity of the oil. Bleaching is generally done by passing the oil through fuller's earth, active charcoal, or clay and then filtering the oil to remove the filtrates.
Some oils are bleached in order to improve the color and clarity of the oil. Bleaching is generally done by passing the oil through fuller's earth, active charcoal, or clay and then filtering the oil to remove the filtrates.
Deodorized:
Deodorization process is used to remove compounds that lend an unappealing or overpowering aroma or taste in an oil. This is generally done by blowing high temperature steam through the oil to vaporize the aromatic components. This process is made more effective by heating the oil to high temperatures and performing this process under a vacuum to help remove all of the odorous substances. Due to the high temperatures used, deodorization is clearly the most damaging process of refinement
EDIT: Here is information from another website that perfectly describes extraction methods for Essential oils. www.aromaworld4u.com a great website for people interested in aromatherapy and essential oils. Here is a repost from their website on essential oil extraction:
Cohobation: 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.
Expression
This method is used to extract citrus essential oils. It is basically a cold pressed method of extraction.
EDIT: Here is information from another website that perfectly describes extraction methods for Essential oils. www.aromaworld4u.com a great website for people interested in aromatherapy and essential oils. Here is a repost from their website on essential oil extraction:
Essential Oil Extraction Methods
The term "essential oil" is generally applied to all aromatic products such as essence oils, absolutes, resinoids, and concretes. To get essential oils the aromatic essence molecules of the plant must be captured by technical extraction methods. Essential oils are liquids stored in various places in plants, that can be removed from the plant using extraction methods such as steam distillation, cold pressing, chemicals, or fat-absorption.
Essential oils can be extracted using a variety of methods as mentioned above, although some are not commonly used today. Presently, the most popular method for extraction is steam distillation and the majority of essential oils used in aromatherapy are distilled in this way, but as technology is advancing, more efficient and economical methods are being developed.
The extraction of an oil require large quantity of plant material and the method used to extract the oil is time consuming and requires a high degree of skill and care. Hence, pure essential oils are expensive, but they are also highly effective - only a few drops at a time are required to achieve the desired effect.
Essential oils are usually liquid, but can also be solid, like orris root or semi-solid according to temperature, like the rose. They dissolve in pure alcohol, fats and oils but not in water.
Some of the important methods of extraction are discussed below :
Distillation
In this, water is heated to produce water vapor, which carries the volatile chemical of the aromatic material with it. The water vapor is then condensed using a condenser and the resulting distillate is collected. The essential oil will normally float on top of the hydrosol (the distilled water component) and is separated out.
Water Distillation In water distillation, the botanical material is completely immersed in water and then is boiled. This method protects the oil to be extracted to 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 do 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 Steam distillation is the most common method of extracting essential oils. Steam distillation is done in a still (The still is tall with a head and a well-insulated swan's neck preceded 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
Hydro Diffusion 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 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.
Fractional Distillation 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 Ylang-Ylang oil.
Rectification 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.
Cohobation: 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.
Expression
This method is used to extract citrus essential oils. It is basically a cold pressed method of extraction.
Sponge Expression 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 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.
Cold-pressed Expression 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.
Although many citrus oils are also produced by steam distillation, they seem to lack the vibrancy of the cold pressed oils.
Machine Abrasion 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.
Solvent Extraction
In this extraction method, solvents are used to extract the essential oils from the botanical material.
Solvent Very delicate aromatics, Jasmine, Linden Blossom, etc. can not 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 degree celsius). 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.
Maceration Maceration actually creates more of an "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.
Enfleurage Enfleurage is a very labour-intensive way of extraction and an expensive process. Therefore it is rarely used today. In some cases where flowers, such as jasmine or tuberose, have very low contents of essential oil and are extremely delicate, heating them would destroy them before releasing the essential oils, enfleurage is used to remove the essential oils.
Flower petals are placed on solid sheets of warm fat, which will absorb the essential oil from the flowers. When all the fragrance is transferred from the flowers to the fat they are removed and replaced with fresh ones. This process is repeated several times until the fat becomes saturated with the essential oil.
A solvent, usually alcohol, is then added to the saturated fat which separates the essential oil from the fat. The remaining fat is then used to make soaps.
Enfleurage has the advantage that even the most delicate components of the flower oils are preserved
Hypercritical Carbon Dioxide (CO2) 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.
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 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 a 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.
Florasol/Phytol 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 a free flowing clear oil free of waxes.
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