The Journal of Nutrition. Unter bestimmten geologischen Bedingungen können sich aus Ölschiefern im Laufe der Erdgeschichte durch zunehmende Überlagerung und Temperaturerhöhung Erdölmuttergesteine bilden. Although highly fragrant, concretes contain large quantities of non-fragrant waxes and resins. Zur Überwachung der tiefliegenden Grundwasserleiter werden im Umfeld Monitoring -Bohrungen niedergebracht. Always consult a doctor before use.
Sie wird dabei besonders von Licht, Wärme oder gelösten Metall ionen gefördert und verläuft hauptsächlich über radikalische Reaktionsmechanismen. Weiter können Hydroperoxide zu Ketonen zerfallen und, falls es auch zu einer Spaltung der einfachen C—C-Bindung kommt, auch zu Aldehyden oder Carbonsäuren. Daneben werden für die Nahrung relevante ungesättigte Fettsäuren zusätzlich mit einem Lipidnamen versehen, hier Der Nachweis und die Gehaltsbestimmung von Ölsäure wie auch anderer Fettsäuren in Fetten wird in der Regel durch Gaschromatographie der Methylester durchgeführt; ergänzend kann eine Trennung der ungesättigten Isomere mit Silbernitrat-Dünnschichtchromatographie erfolgen.
Als Resultat hat man ein Verschwinden der Braunfärbung. Ölsäure wird als Bestandteil von Mischungen mit anderen Fettsäuren in veränderlichen Anteilen vor allem zur Herstellung von Seifen und Metallseifen sowie für die Tensidproduktion verwendet. Wenn nicht anders vermerkt, gelten die angegebenen Daten bei Standardbedingungen. Ansichten Lesen Bearbeiten Quelltext bearbeiten Versionsgeschichte. Navigation Hauptseite Themenportale Zufälliger Artikel.
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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 is purifed 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.
Hydrosols include rose water , lavender water, lemon balm , clary sage , and orange blossom water. The use of herbal distillates in cosmetics is increasing. Most citrus peel oils are expressed mechanically or cold-pressed similar to olive oil extraction. Lemon or sweet orange oils are obtained as byproducts of the citrus industry. Before the discovery of distillation, all essential oils were extracted by pressing.
Most flowers contain too little volatile oil to undergo expression, but their chemical components are too delicate and easily denatured by the high heat used in steam distillation. Instead, a solvent such as hexane or supercritical carbon dioxide is used to extract the oils. Although highly fragrant, concretes contain large quantities of non-fragrant waxes and resins.
Often, another solvent, such as ethyl alcohol , is used to extract the fragrant oil from the concrete.
The precipitates are then filtered out and the ethanol is removed from the remaining solution by evaporation, vacuum purge, or both, leaving behind the absolute. Supercritical carbon dioxide is used as a solvent in supercritical fluid extraction. This method can avoid petrochemical residues in the product and the loss of some "top notes" when steam distillation is used. 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. When the extraction is complete, the pressure is reduced to ambient and the carbon dioxide reverts to a gas, leaving no residue.
Florasol is another solvent used to obtain essential oils. It was originally developed as a refrigerant to replace Freon. The essential oils are mostly pure and contain little to no foreign substances.
Estimates of total production of essential oils are difficult to obtain. One estimate, compiled from data in , , and from various sources, gives the following total production, in tonnes, of essential oils for which more than 1, tonnes were produced. The medical value of essential oils is the subject of ongoing research, and varies among species, presence or absence of active compound s , route of administration, potency, and dosage. Some may be inappropriate for persons with certain medical conditions or who take certain prescriptions or over-the-counter OTC medications.
Taken by mouth, many essential oils can be dangerous in high concentrations. Typical effects begin with a burning feeling, followed by salivation. In the stomach, the effect is carminative , relaxing the gastric sphincter and encouraging eructation belching. Further down the gut, the effect typically is antispasmodic. Different essential oils may have drastically different pharmacology. Some act as locally anesthetic counterirritants and, thereby, exert an antitussive effect. Some essential oils, such as those of juniper and agathosma , are valued for their diuretic effects.
Many essential oils affect the skin and mucous membranes in ways that are valuable or harmful. Many essential oils, particularly tea tree oil , may cause contact dermatitis. Typically, they produce rubefacient irritation at first and then counterirritant numbness.
Turpentine oil and camphor are two typical examples of oils that cause such effects. Menthol and some others produce a feeling of cold followed by a sense of burning.
This is caused by its effect on heat-sensing nerve endings. Some essential oils, such as clove oil or eugenol, were popular for many hundred years in dentistry as antiseptics and local anesthetics. Aromatherapy is a form of alternative medicine in which healing effects are ascribed to the aromatic compounds in essential oils and other plant extracts.
In a systemic review of published studies on essential oils as alternative medicines, only 10 were found to be of acceptable methodological quality, and even these 10 were still weak in reference to scientific standards. Research has shown that essential oils have potential as a natural pesticide.
In case studies, certain oils have been shown to have a variety of deterring effects on pests, specifically insects and select arthropods. However, the molecules within the oils that cause these effects are normally non-toxic for mammals. These specific actions of the molecules allow for widespread use of these green pesticides without harmful effects to anything other than pests.
Although they may not be the perfect replacement for all synthetic pesticides, essential oils have prospects for crop or indoor plant protection, urban pest control,  and marketed insect repellants, such as bug spray. Certain essential oils have been shown in studies to be comparable, if not exceeding, in effectiveness to DEET , which is currently marketed as the most effective mosquito repellent.
Although essential oils are effective as pesticides when first applied in uses such as mosquito repellent applied to the skin, it is only effective in the vapor stage. Since this stage is relatively short-lived, creams and polymer mixtures are used in order to elongate the vapor period of effective repellency. In any form, using essential oils as green pesticides rather than synthetic pesticides has ecological benefits such as decreased residual actions.
Essential oils are usually lipophilic literally: They can be diluted in solvents like pure ethanol and polyethylene glycol. The most common way to safely dilute essential oils for topical use is in a carrier oil. This can be any vegetable oil readily available, the most popular for skin care being jojoba, coconut, wheat germ, olive and avocado.
Essential oils are derived from sections of plants. Some plants, like the bitter orange , are sources of several types of essential oil. Balsam of Peru , an essential oil derived from the Myroxylon , is used in food and drink for flavoring, in perfumes and toiletries for fragrance, and in medicine and pharmaceutical items for healing properties.
Garlic oil is an essential oil derived from garlic. Most eucalyptus oil on the market is produced from the leaves of Eucalyptus globulus. Not only do the products of different species differ greatly in characteristics and effects, but also the products of the very same tree can vary grossly.
Lavender oil has long been used in the production of perfume. Rose oil is produced from the petals of Rosa damascena and Rosa centifolia. Steam-distilled rose oil is known as "rose otto", while the solvent extracted product is known as "rose absolute". The potential danger of an essential oil is sometimes relative to its level or grade of purity, and sometimes related to the toxicity of specific chemical components of the oil.
Many essential oils are designed exclusively for their aroma-therapeutic quality; these essential oils generally should not be applied directly to the skin in their undiluted or "neat" form. Some can cause severe irritation, provoke an allergic reaction and, over time, prove hepatotoxic. Some essential oils, including many of the citrus peel oils, are photosensitizers , increasing the skin's vulnerability to sunlight.
Industrial users of essential oils should consult the safety data sheets SDS to determine the hazards and handling requirements of particular oils. Even certain therapeutic grade oils can pose potential threats to individuals with epilepsy or pregnant women.
Essential Oil use in children can pose a danger when misused because of their thin skin and immature livers. This might cause them to be more susceptible to toxic effects than adults. The flash point of each essential oil is different. Estrogenic and antiandrogenic activity have been reported by in vitro study of tea tree oil and lavender essential oils. Two published sets of case reports suggest the lavender oil may be implicated in some cases of gynecomastia , an abnormal breast tissue growth in prepubescent boys.
Some of the substances are found in "at least 65 other essential oils". The study did not include animal or human testing. Exposure to essential oils may cause a contact dermatitis. Glass syringes are often used, but have coarse volumetric graduations. Chemistry syringes are ideal, as they resist essential oils, are long enough to enter deep vessels, and have fine graduations, facilitating quality control. Unlike traditional pipettes, which have difficulty handling viscous fluids, the chemistry syringe, also known as a positive displacement pipette, has a seal and piston arrangement which slides inside the pipette, wiping the essential oil off the pipette wall.
Some oils can be toxic to some domestic animals, cats in particular.
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