Extraction by volatile solvents in perfumery

Volatile solvent extraction is one of the extraction processes used in perfumery. It consists of dissolving the perfume of the plant in a solvent which is then evaporated. This method makes it possible to obtain very noble and rich products.

Raw materials on the perfumer's organ 

Remember that there are 1000 natural and 3000 synthetic raw materials available to the perfumer. 

According to their taste, they will select about 1000 raw materials, synthetic or natural, for their perfume organ.

New raw materials are discovered and marketed every year, while others disappear due to increasingly strict legislation.

 

Extraction processes in perfumery

Here are the different extraction processes of raw materials that exist in perfumery.

 

History of extraction 

At the beginning of the 18th century, fragile raw materials were treated by cold or hot enfleurage, a technique developed in Grasse. 

Today, extraction using volatile solvents has replaced the enfleurage technique. Here are the two enfleurage techniques used:

  • Cold enfleurage: it is used for flowers that cannot be heated, such as jasmine, daffodils or tuberose. This method consisted of spreading a layer of grease in which the flowers were placed by hand for about 24 hours. The grease had the capacity to absorb the scents of the flowers; the operation was repeated several times. The flowers were then removed one by one by hand until the fat was saturated with their scent. The fat impregnated with the scent was then washed with alcohol in threshing machines and separated from the scent molecules, making it possible to obtain the precious absolute after evaporation.

  • Hot enfleurage: also called maceration, is a process that infuses flowers or other vegetables in oils and fats and is heated to 40 or 50 degrees. After 24 hours, the fat is recovered by draining it through large sieves and then filtered through napkins. The product was then washed with alcohol in the threshing machines. This hot enfleurage was used for the May rose and the orange blossom. The final product was called ointment absolute.

This method was very labour-intensive and very expensive. This old technique was therefore abandoned and replaced by extraction with volatile solvents and by extraction with C02, which largely contributed to improving the extraction techniques of the raw materials.

 

 

What is volatile solvent extraction?

Volatile solvent extraction aims to dissolve the fragrant components of the plant in a solvent, which is then evaporated. This technique has been used since the 18th century, but with products that were unsuitable at the time because they were flammable.

This method of extraction, which really became operational in the 19th century, consists of immersing the flowers in a large vat called an extractor. They are placed on plates stacked on different levels, and pierced with a multitude of small holes, so as not to crush the plants. 

The extractor is then closed, and the contents immersed in a solvent (ethanol, hexane, benzene, or another naturally highly volatile solvent), which carries the plant molecules away. Three washes will be necessary to capture as many olfactory compounds as possible.

Depending on the fragility of the raw material, the solvent can be used cold or hot. 

Hexane is preferred for fresh raw materials, such as flowers (orange blossom, rose, jasmine, mimosa). Ethanol is preferably used for dry raw materials, gums, resinoids or beeswax. 

Once the operation is completed, the compartments in which the flowers and plants are placed are dewatered and then taken out of the extractor. 

The solvent is then recovered and heated under vacuum, and will also be recycled at the end of the process.

 

The concrete and the absolute, noble products obtained by extraction

The evaporation of the solvent will reveal a liquid which as it dries, will turn into wax. This fragrant paste is called concrete.

At the end of the process, the flowers deprived of their scent, are taken out of the extractor and used as fertilizer. 

The concrete contained in the vats is then washed and purified with alcohol. This wax will also be treated and filtered. 

The result is a liquid product called absolute. Thus, the term pink absolute will necessarily mean that the flowers have been treated with volatile solvents.

Absolutes are present in heart and base notes, and are therefore generally richer, rounder, and more enveloping than the essences, which, present in top notes, will therefore be fresher and more volatile. The absolutes do not reflect the exact identity of the plants. Indeed, as the raw material is heated, certain olfactory molecules disappear. This extraction technique is more technical and often more expensive than distillation.

 

Raw materials treated with volatile solvents

Extraction treatment using volatile solvents allows the treatment of certain flower petals, leaves and roots. Here are the main raw materials treated with this process:

  • Jasmine
  • Tuberose plant
  • Daffodil
  • Rose
  • Orange blossom
  • Tree moss
  • Violet leaf
  • Sage 
  • Mimosa 
  • Broom
  • Tonka bean 
  • Vanilla 
  • Resinoids (benzoin, opoponax, incense) 

 

Conclusion

The extraction technique using volatile solvents has made it possible to obtain precious, noble and rich products. 

There is now another extraction technique, extraction by supercritical C02, or sofact, which makes it possible to obtain even purer products. 

Indeed, the solvent used is odourless, which in this case is carbon dioxide. In addition, the raw material is heated less, and therefore even more respected. 

The scent obtained is therefore much closer to that of the fresh raw material, however the cost of this method is very high.

 

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