See also: Distillation
Today, most common essential oils, such as lavender, peppermint, and eucalyptus, are distilled. Raw plant material, consisting of the flowers, leaves, wood, bark, roots, seeds, or peel, is put into an alembic (distillation apparatus) over water. As the water is heated the steam passes through the plant material, vaporizing the volatile compounds. The vapors flow through a coil where they condense back to liquid, which is then collected in the receiving vessel.
Most oils are distilled in a single process. One exception is Ylang-ylang (Cananga odorata), which takes 22 hours to complete through a fractional distillation.
The recondensed water is referred to as a hydrosol, hydrolat, herbal distillate or plant water essence, which may be sold as another fragrant product. Popular hydrosols include rose water, lavender water, lemon balm, clary sage and orange blossom water. The use of herbal distillates in cosmetics is increasing. Some plant hydrosols have unpleasant smells and are therefore not sold.
Saturday, April 17, 2010
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An essential oil is a concentrated, hydrophobic liquid containing volatile aroma compounds from plants. Essential oils are also known as volatile, ethereal oils or aetherolea, or simply as the "oil of" the plant from 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 as a group need to have any specific chemical properties in common, beyond conveying characteristic fragrances.
Essential oils are generally extracted by distillation. Other processes include expression, or solvent extraction. They are used in perfumes, cosmetics, soap and other products, for flavoring food and drink, and for scenting 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 are often based on historical use of these oils for these purposes. Such claims are now subject to regulation in most countries, and have grown more vague to stay within these regulations.
Interest in essential oils has revived in recent decades with the popularity of aromatherapy, a branch of alternative medicine which claims that the specific aromas carried by essential oils have curative effects. Oils are volatilized or diluted in a carrier oil and used in massage, diffused in the air by a nebulizer or by heating over a candle flame, or burned as incense, for example.
Essential oils are generally extracted by distillation. Other processes include expression, or solvent extraction. They are used in perfumes, cosmetics, soap and other products, for flavoring food and drink, and for scenting 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 are often based on historical use of these oils for these purposes. Such claims are now subject to regulation in most countries, and have grown more vague to stay within these regulations.
Interest in essential oils has revived in recent decades with the popularity of aromatherapy, a branch of alternative medicine which claims that the specific aromas carried by essential oils have curative effects. Oils are volatilized or diluted in a carrier oil and used in massage, diffused in the air by a nebulizer or by heating over a candle flame, or burned as incense, for example.
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Absolutes are usually more concentrated than essential oils. Also, the efficiency and low temperature of the extraction process helps prevent damage to the fragrant compounds. With a good understanding of the solvent they are using, extractors can produce absolutes with aromas closer to the original plant product than is possible with essential oils produced through distillation. Examples of this are rose otto (steam distilled rose oil), as opposed to rose absolute, and neroli (steam distilled oil from the blossom of the bitter orange tree), as opposed to orange blossom absolute. Also, some botanicals are too delicate to be steam distilled and can only yield their aroma through other methods, such as solvent extraction or lipid absorption. Examples of these are jasmine, tuberose, and mimosa.
This production method leaves trace amounts of solvents in the absolutes. Therefore, absolutes are considered undesirable for aromatherapy, since it is believed that they could cause allergies and affect the immune system. However, absolutes are used extensively in perfumery because the aromatic compounds in absolutes have not undergone processes involving high temperatures. This makes them smell fresher, brighter, and jam-like. Although the solvent traces produce off-notes in the final product, this is not a problem if the absolute is of a decent quality.
This production method leaves trace amounts of solvents in the absolutes. Therefore, absolutes are considered undesirable for aromatherapy, since it is believed that they could cause allergies and affect the immune system. However, absolutes are used extensively in perfumery because the aromatic compounds in absolutes have not undergone processes involving high temperatures. This makes them smell fresher, brighter, and jam-like. Although the solvent traces produce off-notes in the final product, this is not a problem if the absolute is of a decent quality.
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Used in perfumery and aromatherapy, absolutes are similar to essential oils. They are concentrated, highly-aromatic, oily mixtures extracted from plants. Whereas essential oils can typically be produced through steam distillation, absolutes require the use of solvent extraction techniques or more traditionally, through enfleurage.
[edit] Production
First, an organic solvent, such as hexane, is added to the plant material to help extract the hydrophobic compounds. This solution is filtered and concentrated by distillation to produce a waxy mass called concrete. The lower molecular weight, fragrant compounds are extracted from the concrete into ethanol. When the ethanol evaporates, an oil—the absolute—is left behind.
[edit] Production
First, an organic solvent, such as hexane, is added to the plant material to help extract the hydrophobic compounds. This solution is filtered and concentrated by distillation to produce a waxy mass called concrete. The lower molecular weight, fragrant compounds are extracted from the concrete into ethanol. When the ethanol evaporates, an oil—the absolute—is left behind.
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In addition, there are potential safety concerns. Because essential oils are highly concentrated they can irritate the skin when used neat, that is undiluted.[citation needed]. Therefore, they are normally diluted with a carrier oil for topical application. Phototoxic reactions may occur with citrus peel oils such as lemon or lime.[23] Also, many essential oils have chemical components that are sensitisers (meaning that they will after a number of uses cause reactions on the skin, and more so in the rest of the body). Some of the chemical allergies could even be caused by pesticides, if the original plants are cultivated [24], [25]. Some oils can be toxic to some domestic animals, with cats being particularly prone.[26][27]
Two common oils, lavender and tea tree, have been implicated in causing gynaecomastia, an abnormal breast tissue growth, in prepubescent boys, although the report which cites this potential issue is based on observations of only three boys (and so is not a scientific study), and two of those boys were significantly above average in weight for their age, thus already prone to gynaecomastia.[28] A child hormone specialist at the University of Cambridge claimed "... these oils can mimic estrogens" and "people should be a little bit careful about using these products."[29]
As with any bioactive substance, an essential oil that may be safe for the general public could still pose hazards for pregnant and lactating women.
While some advocate the ingestion of essential oils for therapeutic purposes, licensed aromatherapy professionals do not recommend self prescription due the highly toxic nature of some essential oil. Some very common oils like Eucalyptus are extremely toxic when taken internally. Doses as low as one teaspoon has been reported to cause clinically significant symptoms and severe poisoning can occur after ingestion of 4 to 5 ml.[30] A few reported cases of toxic reactions like liver damage and seizures have occurred after ingestion of sage, hyssop, thuja, and cedar.[31] Accidental ingestion may happen when oils are not kept out of reach of children.
Oils both ingested and applied to the skin can potentially have negative interaction with conventional medicine. For example, the topical use of methyl salicylate heavy oils like Sweet Birch and Wintergreen may cause hemorrhaging in users taking the anticoagulant Warfarin.
Adulterated oils may also pose problems depending on the type of substance used
Two common oils, lavender and tea tree, have been implicated in causing gynaecomastia, an abnormal breast tissue growth, in prepubescent boys, although the report which cites this potential issue is based on observations of only three boys (and so is not a scientific study), and two of those boys were significantly above average in weight for their age, thus already prone to gynaecomastia.[28] A child hormone specialist at the University of Cambridge claimed "... these oils can mimic estrogens" and "people should be a little bit careful about using these products."[29]
As with any bioactive substance, an essential oil that may be safe for the general public could still pose hazards for pregnant and lactating women.
While some advocate the ingestion of essential oils for therapeutic purposes, licensed aromatherapy professionals do not recommend self prescription due the highly toxic nature of some essential oil. Some very common oils like Eucalyptus are extremely toxic when taken internally. Doses as low as one teaspoon has been reported to cause clinically significant symptoms and severe poisoning can occur after ingestion of 4 to 5 ml.[30] A few reported cases of toxic reactions like liver damage and seizures have occurred after ingestion of sage, hyssop, thuja, and cedar.[31] Accidental ingestion may happen when oils are not kept out of reach of children.
Oils both ingested and applied to the skin can potentially have negative interaction with conventional medicine. For example, the topical use of methyl salicylate heavy oils like Sweet Birch and Wintergreen may cause hemorrhaging in users taking the anticoagulant Warfarin.
Adulterated oils may also pose problems depending on the type of substance used
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Some benefits that have been linked to aromatherapy, such as relaxation and clarity of mind, may arise from the placebo effect rather than from any actual physiological effect. The consensus among most medical professionals is that while some aromas have demonstrated effects on mood and relaxation and may have related benefits for patients, there is currently insufficient evidence to support the claims made for aromatherapy.[16] Scientific research on the cause and effects of aromatherapy is limited, although in vitro testing has revealed some antibacterial and antiviral effects.[17] [18] There is no evidence of any long-term results from an aromatherapy massage other than the pleasure achieved from a pleasant-smelling massage.[19] A few double blind studies in the field of clinical psychology relating to the treatment of severe dementia have been published.[20][21] Essential oils have a demonstrated efficacy in dental mouthwash products.[22]
Skeptical literature suggests that aromatherapy is based on the anecdotal evidence of its benefits rather than proof that aromatherapy can cure diseases. Scientists and medical professionals acknowledge that aromatherapy has limited scientific support, but critics argue that the claims of most aromatherapy practitioners go beyond the data, and/or that the studies are neither adequately controlled nor peer reviewed.
Some proponents[who?] of aromatherapy believe that the claimed effect of each type of oil is not caused by the chemicals in the oil interacting with the senses, but because the oil contains a distillation of the "life force" of the plant from which it is derived that will "balance the energies" of the body and promote healing or well-being by purging negative vibrations from the body's energy field. Arguing that there is no scientific evidence that healing can be achieved, and that the claimed "energies" even exist, many skeptics reject this form of aromatherapy as pseudoscience or even quackery
Skeptical literature suggests that aromatherapy is based on the anecdotal evidence of its benefits rather than proof that aromatherapy can cure diseases. Scientists and medical professionals acknowledge that aromatherapy has limited scientific support, but critics argue that the claims of most aromatherapy practitioners go beyond the data, and/or that the studies are neither adequately controlled nor peer reviewed.
Some proponents[who?] of aromatherapy believe that the claimed effect of each type of oil is not caused by the chemicals in the oil interacting with the senses, but because the oil contains a distillation of the "life force" of the plant from which it is derived that will "balance the energies" of the body and promote healing or well-being by purging negative vibrations from the body's energy field. Arguing that there is no scientific evidence that healing can be achieved, and that the claimed "energies" even exist, many skeptics reject this form of aromatherapy as pseudoscience or even quackery
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Oils with standardized content of components (marked FCC, for Food Chemical Codex) have to contain a specified amount of certain aroma chemicals that normally occur in the oil[citation needed]. But there is no law that the chemicals cannot be added in synthetic form in order to meet the criteria established by the FCC for that oil[citation needed]. For instance, lemongrass essential oil has to contain 75% aldehyde[citation needed] to meet the FCC profile for that oil, but that aldehyde can come from a chemical refinery instead of from lemongrass. To say that FCC oils are "food grade" then makes them seem natural when in fact they are not necessarily so.
Undiluted essential oils suitable for aromatherapy are termed therapeutic grade, but in countries where the industry is not regulated, therapeutic grade is based on industry consensus and is not a regulatory category[citation needed]. Some aromatherapists take advantage of this situation to make misleading claims about the origin and even content of the oils they use. Likewise, claims that an oil's purity is vetted by mass spectrometry or gas chromatography have limited value, since all such testing can do is show that various chemicals occur in the oil[citation needed]. Many[which?] of the chemicals that occur naturally in essential oils are manufactured by the perfume industry and adulterate essential oils because they are cheaper. There is no way to distinguish between these synthetic additives and the naturally occurring chemicals.
The best instrument for determining whether an essential oil is adulterated is an educated nose{[which?]. Many people can distinguish between natural and synthetic scents, but it takes experience
Undiluted essential oils suitable for aromatherapy are termed therapeutic grade, but in countries where the industry is not regulated, therapeutic grade is based on industry consensus and is not a regulatory category[citation needed]. Some aromatherapists take advantage of this situation to make misleading claims about the origin and even content of the oils they use. Likewise, claims that an oil's purity is vetted by mass spectrometry or gas chromatography have limited value, since all such testing can do is show that various chemicals occur in the oil[citation needed]. Many[which?] of the chemicals that occur naturally in essential oils are manufactured by the perfume industry and adulterate essential oils because they are cheaper. There is no way to distinguish between these synthetic additives and the naturally occurring chemicals.
The best instrument for determining whether an essential oil is adulterated is an educated nose{[which?]. Many people can distinguish between natural and synthetic scents, but it takes experience
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