Super Critical Extraction

Super critical extraction is a fairly new way to extract active constituents by using gases and although a bit on the expensive side, does yield good quality extracts. The supercritical process uses compressed carbon dioxide, or CO₂. That is simply one of the constituents of normal air, and we breathe it and plants absorb it every moment. Other Gases suitable for super critical extraction include nitrogen, methane, ethane, ethylene, nitrous oxide, sulphur dioxide, propane, propylene, ammonia and sulfur hexa fluoride.

The carbon dioxide is furthermore inert and therefore does not chemically interact with the essence that is being extracted. To remove the carbon dioxide solvent, you simply need to remove the pressure under which it is kept. The supercritical process, then, uses a harmless, natural gas, heats it to some temperature over 31°C (the lower the better to avoid any temperature stress), and the gas is then highly compressed. The compressed gas has the density of a liquid, but is able to penetrate deeply into the plant and dissolve the lipophilic constituents. Then the pressure is carefully released.

Super critical method is not convenient for Ayurvedic Formulation. Ayurvedic Formulation is a combination of many herbs and all the herbs can not be extracted by supercritical method. For herbal constituents, like for certain phytochemicals in green tea, a water extract is preferred.

The supercritical process is an excellent process to use in the extraction of essential oils.

There are two major groups of plant constituents that are generally extracted. The first plant constituent “likes” water, and is thus willing to be dissolved in water (like in making a tea, which is simply a hot water extract) or a related solution like ethanol. The other type of plant constituent “dislikes” water, avoids it totally (like oil and water!), and is thus unwilling to be dissolved in it. These water-avoiding constituents are fatty or oily in nature, and they are willing to dissolve only in “lipophilic” or fat-loving solutions.

Not every herb or plant constituent is suitable for supercritical extraction.

However, for single herb formulation supercritical method is suitable.