Comment fonctionne l'extraction avec le CO2?

The main feature of supercritical fluids (SCF) is the tunability of their properties as solvent, supercritical CO2 or SC-CO2 extraction processes present an important advantage over low pressure methods, i.e., the selectivity of supercritical CO2 can be adjusted by varying temperature and pressure to obtain fractions containing specific compounds. Since the enhanced solubility effect is selective, a supercritical fluid can form the basis of a system for separating components of mixtures. At the same time, vapor pressure effects are also enhanced.

The recovery of extracts concentrated in target compounds, even during the extraction process, can lead to a product with high economic value and simplify subsequent fractionation steps.

As the supercritical CO2 density increases, its transport capability also increases, to the point that it can entrain significant amounts of relatively nonvolatile compounds. Under proper conditions, supercritical CO2 separations combine the phenomena of solvent extraction and distillation. The behavior of supercritical substance changes with a rise of its density. In particular, it can dissolve substantial quantities of compounds that would be at best sparingly soluble in the same substance in its ordinary liquid or gaseous states.

The supercritical method has the advantage that it can be used for separating mixtures of high-boiling components that would decompose during fractional distillation.

Another strong point of supercritical CO2 extraction is that once the oil is extracted from the plant material, the CO2 is simply returned to its gaseous state by lowering its pressure, allowing the gas to quickly and completely dissipate.

The supercritical CO2 extraction and purification process is also more important because it supports the separation without any contamination or degradation.

Recently many researchers have proved that the performance of the supercritical fluid technology increases with the use of alternative solvents or addition of the modifiers to SC-CO2 because it has limitations resulting from its lack of polarity and associated lack of capacity for specific solvent–solute interactions. Thus, there is a great incentive to improve solvent polarity. For these purposes, small amounts of a highly polar co-solvent can be added to CO2 in order to increase its solvating power.

CO2 science

Qu'est-ce qu'un extrait/huile de CO2 ?

Supercritical CO2 extracts display some of the characteristics of both essential oils and absolutes. Like essential oils, they contain many beneficial therapeutic properties. But unlike absolutes, they are not solvent extracted.

The composition of a supercritical CO2 or subcritical CO2 extract is generally different from the equivalent essential oil. Because of these differences, CO2 extracts can have distinct therapeutic properties. For example, Ginger CO2 contains gingerols, constituents that give ginger its pungent taste. There two principal types of CO2 extract:

Select extracts: are generally more similar to essential oils
Total extracts: contain more heavier molecules and could be compared to absolutes.

Because the plant material is not exposed to air (oxygen) or heat, as compared to steam distillation, none of the compounds change or oxidises during extraction. Hence, the final extract is just the same as in the plant – the same composition and aroma. In the case of German Chamomile CO2 extract, matricin is not converted to the dark blue chamazulene, as in the steam distilled oil.

Major benefits of CO₂ extracts

Extractions occur at lower temperatures than steam distillation, so more delicate botanicals are not destroyed
Carbon dioxide is nontoxic, odorless, and is easily removed from the extracted oil
More stable with a long shelf life
Contain no carbohydrates, inorganic salts, proteins, allergens, or germs
Meet strict heavy metal requirements

CO2 science