Essential oils: Difference between revisions
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An '''essential oil''' - [[liquid]] [[extraction|extracts]] from [[plant]]s, which are called aromatic herbs or aromatic [[plant]]s and from some other materials (as lichens, honey etc.). This pressed, [[Distillation|distilled]] or extracted substances containing volatile [[aroma compound]]s, mainly [[hydrophobic]] ([[terpene]]s, [[terpeniod]]s, [[benzene]] derivates (aromatic compounds), [[aldehyde]]s, [[organic acids]] etc.). | An '''essential oil''' - [[liquid]] [[extraction|extracts]] from [[plant]]s, which are called aromatic herbs or aromatic [[plant]]s and from some other materials (as lichens, honey etc.). This pressed, [[Distillation|distilled]] or extracted substances containing volatile [[aroma compound]]s, mainly [[hydrophobic]] ([[terpene]]s, [[terpeniod]]s, [[benzene]] derivates (aromatic compounds), [[aldehyde]]s, [[organic acids]] etc.). | ||
*Essential oils also known as '''volatile''' or '''ethereal''' oils, or simply as the "oil of" the plant material from which they were extracted, such as ''oil of clove''. The | *Essential oils also known as '''volatile''' or '''ethereal''' oils, or simply as the "oil of" the plant material from which they were extracted, such as ''oil of clove''. The traditional name '''essential oil''' indicates that the oil carries distinctive [[scent]] (essence) of the [[plant]], not that it is an especially important or fundamental substance. | ||
<!--Essential oils do not as a group need to have any specific chemical properties in common, beyond conveying characteristic fragrances. They are not to be confused with [[essential fatty acid]]s. | <!--Essential oils do not as a group need to have any specific chemical properties in common, beyond conveying characteristic fragrances. They are not to be confused with [[essential fatty acid]]s. | ||
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===Distillation=== | ===Distillation=== | ||
{{see also|distillation}} | {{see also|distillation}} | ||
Some common essential oils, such as [[lavender]], [[peppermint]], [[tea-tree]] and [[eucalyptus]], are distilled. Raw plant material, consisting of the [[flower]]s, [[leaf|leaves]], [[wood]], [[bark]], [[root]]s, [[seed]]s, or [[peel (fruit)|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. | |||
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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 | fractional distillation]]. | 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 | fractional distillation]]. | ||
The water recondensed from the distillation process is referred to as a hydrosol, hydrolat, [[herbal distillate]] or plant water essence, which may be sold as another fragrant product. Popular hydrosols are [[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 | The water recondensed from the distillation process is referred to as a [[hydrosol]], hydrolat, [[herbal distillate]] or plant water essence, which may be sold as another fragrant product. Popular hydrosols are [[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 [[smell]]s and are therefore not sold. | ||
===Expression=== | ===Expression=== | ||
Most citrus peel oils are usually expressed mechanically, or ''[[cold-pressed]]''. Due to the large quantities of oil in citrus peel and the relatively low cost to grow and harvest the raw materials, citrus-fruit oils are cheaper than most other essential oils. Lemon or sweet orange oils that are obtained as [[by-product]]s of the commercial citrus industry are even cheaper. | Most citrus peel oils are usually expressed mechanically, or ''[[cold-pressed]]''. Due to the large quantities of oil in citrus peel and the relatively low cost to grow and harvest the raw materials, citrus-fruit oils are cheaper than most other essential oils. Lemon or sweet orange oils that are obtained as [[by-product]]s of the commercial citrus industry are even cheaper. | ||
Prior to the discovery of [[distillation]], essential oils (EO) were extracted by pressing. | Prior to the discovery of [[distillation]], some essential oils (EO) were extracted by pressing. | ||
===Solvent extraction=== | ===Solvent extraction=== | ||
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Although highly fragrant, concretes contain large quantities of non-fragrant waxes and resins. As such another solvent, often [[ethanol|ethyl alcohol]], which only dissolves the fragrant low-molecular weight compounds, is used to extract the fragrant oil from the concrete. The alcohol is removed by a second distillation, leaving behind the ''[[Absolute (substance)|absolute]]''. | Although highly fragrant, concretes contain large quantities of non-fragrant waxes and resins. As such another solvent, often [[ethanol|ethyl alcohol]], which only dissolves the fragrant low-molecular weight compounds, is used to extract the fragrant oil from the concrete. The alcohol is removed by a second distillation, leaving behind the ''[[Absolute (substance)|absolute]]''. | ||
Supercritical carbon dioxide is used as a solvent in supercritical fluid extraction. This method has many benefits, including avoiding [[petrochemical]] residues in the product. It does not yield an absolute directly. The supercritical carbon dioxide will extract both the waxes and the essential oils that make up the concrete. Subsequent processing with liquid carbon dioxide, achieved in the same extractor by merely lowering the extraction temperature, will separate the waxes from the essential oils. This lower temperature process prevents the decomposition and denaturing of compounds and provides for a superior product. When the extraction is complete, the pressure is reduced to ambient and the carbon dioxide reverts back to a gas, leaving no residue. Although supercritical carbon dioxide is also used for making [[decaffeinated]] [[coffee]], the actual process is different. | [[Supercritical carbon dioxide]] is used as a solvent in supercritical fluid extraction. This method has many benefits, including avoiding [[petrochemical]] residues in the product. It does not yield an absolute directly. The supercritical carbon dioxide will extract both the waxes and the essential oils that make up the concrete. Subsequent processing with liquid carbon dioxide, achieved in the same extractor by merely lowering the extraction temperature, will separate the waxes from the essential oils. This lower temperature process prevents the decomposition and denaturing of compounds and provides for a superior product. When the extraction is complete, the pressure is reduced to ambient and the carbon dioxide reverts back to a gas, leaving no residue. Although supercritical carbon dioxide is also used for making [[decaffeinated]] [[coffee]], the actual process is different. | ||
===Production quantities=== | ===Production quantities=== | ||
Revision as of 09:54, 1 August 2008
An essential oil - liquid extracts from plants, which are called aromatic herbs or aromatic plants and from some other materials (as lichens, honey etc.). This pressed, distilled or extracted substances containing volatile aroma compounds, mainly hydrophobic (terpenes, terpeniods, benzene derivates (aromatic compounds), aldehydes, organic acids etc.).
- Essential oils also known as volatile or ethereal oils, or simply as the "oil of" the plant material from which they were extracted, such as oil of clove. The traditional name essential oil indicates that the oil carries distinctive scent (essence) of the plant, not that it is an especially important or fundamental substance.
Production
Distillation
- See also: distillation
Some common essential oils, such as lavender, peppermint, tea-tree 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.
Aromatherapy
Raw Materials