Different types of essential oils

Essential oils (EO) are obtained by different methods -- distillation being the most familiar. There are four different types of essential oils: absolutes vs. concretes, expressed, solvent-extracted, and steam-distilled.
Absolutes are "essences," rather than "essential" oils. They are generally obtained from the extraction of a concrete with alcohol. A concrete is the solid waxy residue derived from hexane extraction of plant parts(usually the flower petals). This method is used for botanicals where the fragrance and therapeutic parts of the plant can only be unlocked using solvents. These are not to be used internally, as traces of petrochemicals remain in the product. Jasmine and neroli are examples of absolutes.
Expressed oil are pressed from the rind of fruits (usually citrus). Tangerines, grapefruits, lemons and oranges are produced by this method. Technically speaking, these are not EO - they are expressed product, but they are highly regarded for their therapeutic properties, none the less. It is best to use only organically grown crops for this method, since pesticide residues, especially highly toxic, carbamate and chloride-based petrochemicals, can become highly concentrated in this product.
Solvent extration involves the use of oil-soluble solvents, such as hexane, dimethylenechloride, and acetone. There is no guarantee that the finished product will be free of solvent residues. Steam distillation is the oldest and most traditional extraction method. Plant material is inserted into a cooking chamber, and steam is passed through it. After the steam is collected and condensed, it is processed through a separator to collect the product. The amount of pressure used, the amount of time the plant parts is steamed and the material the steam chamber is constructed of contribute a great deal to the quality of the product.
Glossaries related to the different types of essential oils
Absolute : the most concentrated form of fragance obtained when distilling a concrete.
Balsam : water soluble, semi-solid or viscous resinous exudate similar to that gum.
Concrete : a waxy concentrated semi-solid EO extract, made from plant parts, and is used to make absolute.
Essence : the liquid products resulting from the condensation of vapour from puree processing.
Essential oils : volatile aromatic liquid consisting the odorous principles botanical matter
Fixed oil : obtained from plants that are fatty and non-volatile
Flower water : the water resulting from the distillation of essential oils, which still contains some of the properties of the plant parts used in the processing.
Fractionated oil : it have been re-distilled, either to have terpenes removes or remove other substances.
Infused oil : its is produced by steeping the macerated botanical material in oil until it has taken on some the material properties.
Oleo gum resin : odoriferous exudation from botanical material consisting of essential oils, gum, and resin.
Oleoresin (OR): Natural resinous exudation from plants or aromatic liquid preparation extracted from botanical material. Solvent extraction of properly ground plant parts subsequent removal of solvent distillation gives dark coloured viscous products.
Resin : they are natural exudations from trees, prepared resins are OR from which the essential oils has been removed.
Resinoids : perfumed substances extracted from natural resinous material by using solvent.
Terpeneless : EO from which monoterpene hydrocarbons have been removed.
Tincture : either a herbal or perfume substances prepared in an alcohol base.
Volatile : substance that is unstable an evaporates easily, like an EO, then give distinct aroma
Spice oil : EO obtained by steam or water distillation of ground spices and in some cases whole spices.
Perfume : liquid with a specific favour produced by mixing or blending two or more EO in a solvent
Different types of essential oils showed the effect on their chemical composition, properties, proper application, and application concentration, although it used the same raw materials.

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