CO2 Extraction: A Primer

Carbon dioxide, which gives sparkling water its bubbles, is also used in extracting volatile compounds ~ antioxidants, essential oils, and fatty oils ~ from plants. The process is known as supercritical CO₂ extraction. Because this process subjects raw materials to high pressure instead of high temperatures, these extracts more closely resemble the original plant material in smell, taste, and constituents, lending the resulting oils the plant’s properties, including in some cases antimicrobial and antioxidant benefits. The sophistication of the supercritical extraction process means that extracts can be standardized for quality. The process is gentle and leaves no chemical solvent residues. Produced without oxygen, the resulting extracts are also sterile and need no preservation.
CO₂ extracts are categorized in two ways, as “select” and “total”:

• Extracted at lower pressures, Select extracts contain only the volatile compounds that are CO₂ soluble. Waxes, resins, and compounds that lend color remain in the plant material. Selects are often thick but pourable, with an appearance similar to steam-distilled essential oils, though some of the volatile compounds they contain will not be found in a steam-distilled version of the oil.
• A Total CO₂ extract, on the other hand, does contain both volatile and non-volatile CO₂ soluble compounds. This means total extracts tend to be thick like paste, though they will solubilize in vegetable oils with little or no warming necessary. More similar to the plant themselves, totals are extracted at higher pressure and include some of the plant waxes and resins.

by Marianne Griffeth ©2013