Extraction using volatile organic solvents
Volatile organic solvent extraction is a process that was only developed on an industrial scale in the 19th century in Grasse. It is an alternative to the enfleurage technique that was very widespread at one time. This method entails placing the natural aromatic raw material into a vessel with a solvent. Fragile materials are placed on racks, while other plants are packed inside the extractor. Depending on the fragility of the raw material, the solvent can be used hot or cold. The choice of solvent depends on the type of odor molecules present in the material and what is desired as content in the extract. Hydrocarbon-type (hexane) solvents are favored for extracting raw materials such as fresh flowers (rose, jasmine, etc.), while ethanol-type solvents are for dry materials (concrete, gum, or beeswax). Ethanol is primarily used to obtain absolutes and resinoids. It is the solvent that extracts the fragrance from the raw material; it continuously flows through the extractor by means of pump action. Several washes with solvent are often needed to fully extract the available odorant molecules from the raw material. The used solvent is removed from the extract through concentration and is then recycled.