Extraction (fragrance)

Fragrance extraction refers to the extraction of aromatic compounds from raw materials, using methods such as waxes in the extracted product.

To a certain extent, all of these techniques tend to distort the odour of the aromatic compounds obtained from the raw materials. Heat, chemical solvents, or exposure to oxygen in the extraction process denature the aromatic compounds, either changing their odour character or rendering them odourless.

Maceration/Solvent extraction

Certain plant materials contain too little volatile oil to undergo expression, or their chemical components are too delicate and easily denatured by the high heat used in steam distillation. Instead, the oils are extracted using their solvent properties.

Organic solvent extraction

Organic solvent extraction is the most common and most economically important technique for extracting aromatics in the modern perfume industry. Raw materials are submerged and agitated in a solvent that can dissolve the desired dimethyl ether.

In organic solvent extraction, aromatic compounds as well as other hydrophobic soluble substances such as lipophilic (oil soluble) plant material, since these solvents effectively remove all hydrophobic compounds in the raw material. The solvent is then removed by a lower temperature distillation process and reclaimed for re-use.

Although highly fragrant, concretes are too viscous - even solid - at room temperature to be useful. This is due to the presence of high-molecular-weight, non-fragrant waxes and resins. Another solvent, often ethyl alcohol, which only dissolves the fragrant low-molecular weight compounds, must be used to extract the fragrant oil from the concrete. The alcohol is removed by a second distillation, leaving behind the absolute. These types of essential oils, from plants such as jasmine and rose, are called absolutes.

Due to the low temperatures in this process, the absolute may be more faithful to the original scent of the raw material, which is subjected to high heat during the distillation process.

Supercritical fluid extraction

Supercritical fluid extraction is a relatively new technique for extracting fragrant compounds from a raw material, which often employs Supercritical CO₂ as the extraction solvent. When decaffeinated coffee.

Due to the low heat of process and the relatively unreactive solvent used in the extraction, the fragrant compounds derived often closely resemble the original odour of the raw material. Like solvent extraction, the CO₂ extraction takes place at a low temperature, extracts a wide range of compounds, and leaves the aromatics unaltered by heat, rendering an essence more faithful to the original. Since CO₂ is gas at normal atmospheric pressure, it also leaves no trace of itself in the final product, thus allowing one to get the absolute directly without having to deal with a concrete. It is a low-temperature process, and the solvents are easily removed.

In carbon dioxide gas (up to 100 atm.) is used as a solvent.

Ethanol extraction

Ethanol extraction is a type of solvent extraction used to extract fragrant compounds directly from dry raw materials, as well as the impure oils or concrete resulting from organic solvent extraction, expression, or enfluerage. Ethanol extracts from dry materials are called tinctures, while ethanol washes for purifying oils and concretes are called absolutes.

The impure substances or oils are mixed with ethanol, which is less hydrophobic [than the solutes?] and dissolves more of the oxydized aromatic constituents (alcohols, aldehydess, etc.), leaving behind the wax, fats, and other generally hydrophobic substances. The alcohol is evaporated under low-pressure, leaving behind absolute. The absolute may be further processed to remove any impurities that are still present from the solvent extraction.

Ethanol extraction is not used to extract fragrance from fresh plant materials; these contain large quantities of water, which would also be extracted into the ethanol.

Distillation

Distillation is a common technique for obtaining aromatic compounds from plants, such as orange blossoms and roses. The raw material is heated and the fragrant compounds are re-collected through condensation of the distilled vapour

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,

Steam distillation

Steam from boiling water is passed through the raw material for 60-105 minutes, which drives out most of their volatile fragrant compounds. The condensate from distillation, which contain both water and the aromatics, is settled in a leaves, and stems. Popular hydrosols are rose water, lavender water, and orange blossom water. Many plant hydrosols have unpleasant smells and are therefore not sold.

Most oils are distilled in a single process. One exception is fractionally distilled, producing several grades (Ylang-Ylang "extra", I, II, III and "complete," in which the distillation is run from start to finish with no interruption).

Dry/destructive distillation

The raw materials are directly heated in a still without a carrier solvent such as water. Fragrant compounds that are released from the raw material by the high heat often undergo anhydrous amber and fragrant woods where an intentional "burned" or "toasted" odour is desired.

Expression

Expression as a method of frangrance extraction where raw materials are pressed, squeezed or compressed and the oils are collected. In contemporary times, the only fragrant oils obtained using this method are the peels of fruits in the citrus family. This is due to the large quantity of oil is present in the peels of these fruits as to make this extraction method economically feasible. Citrus peel oils are 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 among the cheapest citrus oils.

Expression was mainly used prior to the discovery of alabaster vessels, was pressed in this manner.

Enfleurage

Enfleurage is a two-step process during which the odour of aromatic materials is absorbed into wax or fat, then extracted with denature through high heat. This technique is not commonly used in modern industry, due to both its prohibitive cost and the existence of more efficient and effective extraction methods.