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Essential oil

2007 Schools Wikipedia Selection. Related subjects: General Biology

     Plant oils
           Types
   Vegetable fats  (list)
   Essential oil   (list)
   Macerated      ( list)
           Uses
   Drying oil - Oil paint
   Cooking oil
   Fuel - Biodiesel
   Aromatherapy
        Components
   Saturated fat
   Monounsaturated fat
   Polyunsaturated fat
   Trans fat

   An essential oil is a concentrated, hydrophobic liquid containing
   volatile aromatic compounds from plants. It is produced by
   distillation. Other extraction processes to obtain aromatic plant
   compounds include expression, or solvent extraction. Essential oils are
   used in perfumery, aromatherapy, cosmetics, incense, for flavoring food
   and drink, and to a lesser extent, in medicine and household cleaning
   products. They are valuable commodities to the fragrance and flavorant
   industries.

   Essential oil is also known as volatile oil and ethereal oil. It may
   also be referred to as "oil of" the raw plant material from which it
   was extracted, such as oil of clove. The term essential is intended to
   indicate that the oil is the fragrant essence of the plant from which
   it is extracted and not in the more common sense of being
   indispensable. It is not to be confused with essential fatty acids.

   Medical use of vegetable oils has a long and distinguished history.
   Many oils that are use medicinally are essential oils, which are
   distilled rather than pressed or otherwise extracted. Medical
   properties claimed by those who sell medicinal oils vary 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 correspondingly more
   vague, to stay within these regulations.

   Interest in such uses of essential oils has enjoyed a revival in recent
   decades, with the popularity of aromatherapy, in which oils are heated
   and volatilized.

Production

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 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 smells and are therefore not sold.

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-products of the commercial citrus industry
   are even cheaper.

   Prior to the discovery of distillation, essential oils (EO) were
   extracted by pressing.

Solvent extraction

   Most flowers contain very little volatile oil to undergo expression and
   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. Extracts
   from hexane and other hydrophobic solvent are called concretes, which
   is mixture of essential oil, waxes, resins, and other lipophilic (oil
   soluble) plant material.

   Although highly fragrant, concretes contain large quantities of
   non-fragrant waxes and resins. As such another solvent, often 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.

   In supercritical fluid extraction, supercritical carbon dioxide is used
   as a solvent. This method has many benefits, including avoiding
   petrochemical residues in the product. It does not obtain 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

   Estimates of total production of essential oils are difficult to
   obtain. One estimate, compiled from data in 1989. 1990 and 1994 from
   various sources gives the following total production, in tonnes, of
   essential oils for which more than 1,000 tonnes were produced.

                  Oil         Tonnes
          Sweet orange        12,000
          Mentha arvensis      4,800
          Peppermint           3,200
          Cedarwood            2,600
          Lemon                2,300
          Eucalyptus globulus  2,070
          Litsea cubeba        2,000
          Clove (leaf)         2,000
          Spearmint            1,300

Essential oil use in aromatherapy

   Aromatherapy is a form of herbal medicine, in which healing effects are
   ascribed to the aromatic compounds in essential oils and other plant
   extracts. Many common essential oils have medicinal properties that
   have been applied in folk medicine since ancient times and are still
   widely used today. For example, many essential oils have antiseptic
   properties, though some are stronger than others. In addition, many
   have an uplifting effect on the mind, though different essential oils
   have different properties.

Solvents

   Essential oils are usually lipophilic compounds. It thus has been found
   that alcohols, such as methanol and ethanol (primarily 100%
   concentrations), or organic solvents, such as acetone, are the best
   diluents to be used for dilution. Water is not recommended as water and
   fats do not dissolve in one another, although oil dilution in water can
   be achieved at extremely low concentrations of oil, and depending on
   the viscosity of the oil.

Raw Materials

   Essential oils are derived from various parts of plants. Some, like
   orange oil, are derived from any of several parts of the plant.

          Berries
                 + Allspice
                 + Juniper

          Seeds
                 + Almond
                 + Anise
                 + Celery
                 + Cumin
                 + Nutmeg oil

          Bark
                 + Cassia
                 + Cinnamon

          Wood
                 + Camphor
                 + Cedar
                 + Rosewood
                 + Sandalwood

          Rhizome
                 + Ginger

                             Leaves
                                    + Basil
                                    + Bay leaf
                                    + Cinnamon
                                    + Common sage
                                    + Eucalyptus
                                    + Lemon grass
                                    + Melaleuca
                                    + Oregano
                                    + Patchouli
                                    + Peppermint
                                    + Pine
                                    + Rosemary
                                    + Spearmint
                                    + Tea tree
                                    + Thyme
                                    + Wintergreen

                             Resin
                                    + Frankincense
                                    + Myrrh

                                             Flowers
                                                    + Chamomile
                                                    + Clary sage
                                                    + Clove
                                                    + Geranium
                                                    + Hyssop
                                                    + Jasmine
                                                    + Lavender
                                                    + Manuka
                                                    + Marjoram
                                                    + Orange
                                                    + Rose
                                                    + Ylang-ylang

                                             Peel
                                                    + Bergamot
                                                    + Grapefruit
                                                    + Lemon
                                                    + Lime
                                                    + Orange
                                                    + Tangerine

                                             Root
                                                    + Valerian

Rose oil

   The most well-known essential oil is probably Rose oil, produced from
   Rosa damascena and Rosa centifolia. Steam-distilled rose oil is known
   as "rose otto" or "attar of roses" while oil which is solvent-extracted
   is known as "rose absolute".

Dangers

   Because of their concentrated nature, EO's generally should not be
   applied directly to the skin in their undiluted or "neat" form. Some
   can cause severe irritation or provoke an allergic reaction. Instead,
   essential oil should be applied with a plants oils or other fats
   (carrier oil), such as olive, hazelnut, or any other "soft" oil. Common
   ratio of essential oil disbursed in a carrier oil is 0.5–3% (most less
   than 10%) and depends on its purpose. Some EO's including many of the
   citrus peel oils, are photosensitizers, increasing the skin's reaction
   to sunlight and making it more likely to burn.

   Industrial users of essential oils should consult the material safety
   data sheets (MSDS) to determine the hazards and handling requirements
   of particular oils.

   Pesticide residues

   There is some concern about pesticide residues in EO's, particularly
   those used therapeutically. For this reason, many practitioners of
   aromatherapy choose to buy organically produced oils.

   Ingestion

   While some advocate the ingestion of essential oils for therapeutic
   purposes, this should never be done except under the supervision of a
   professional who is licensed to prescribe such treatment. Some very
   common EO's such as Eucalyptus are extremely toxic internally.
   Pharmacopoeia standards for medicinal oils should be heeded. EO's
   should always be kept out of the reach of children. Some oils can be
   toxic to some domestic animals, cats in particular. Owners must ensure
   that their pets do not come into contact with potentially harmful
   essential oils.

   Smoke

   The smoke from burning essential oils may contain potential
   carcinogens, such as polycyclic aromatic hydrocarbons (PAHs). Essential
   oils are naturally high in volatile organic compounds (VOCs). The
   internal use of essential oils should be fully avoided during pregnancy
   without consulting with a licensed professional, as some can be
   abortifacients in dose 0.5–10 ml.

   Toxicology

   LD50 of most EO or their main components are 0.5-10 g/kg (orally or
   skin test).
   Retrieved from " http://en.wikipedia.org/wiki/Essential_oil"
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   with only minor checks and changes (see www.wikipedia.org for details
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