Similar to essential oils, absolutes 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.
Production
First, an organic solvent, such as hexane, is added to the plant material to help extract the hydrophobic compounds. This solution is filtered and concentrated by distillation to produce a waxy mass called concrete. The lower molecular weight, fragrant compounds are extracted from the concrete into ethanol. When the ethanol evaporates, an oil—the absolute—is left behind.
Character and use
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 botanicals are too delicate 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, and mimosa.
This production method leaves trace amounts of solvents in the absolutes. Therefore, absolutes are considered undesirable for aromatherapy, since it is believed that they could cause allergies and affect the immune system. However, absolutes are used extensively in perfumery because the aromatic compounds in absolutes have not undergone processes involving high temperatures. This makes them smell fresher, brighter, and jam-like. Although the solvent traces produce off-notes in the final product, this is not a problem if the absolute is of a decent quality.
References
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