Absolute (perfumery)

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.

First, an organic solvent, such as hexane, is added to the plant material to help extract the non-polar compounds. This solution is filtered and concentrated by distillation to produce a waxy mass called concrete. The more polar, fragrant compounds are extracted from the concrete into ethanol. When the ethanol evaporates, an oil—the absolute—is left behind.

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 raw materials are either too delicate or too inert 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, mimosa, and beeswax.

...
Wikipedia