The CO2 (carbon dioxide) extraction method of essential oils is usually referred to as CO2 extraction or supercritical abbreviation. In short, CO2 extraction is extracted by pressurized carbon dioxide until it becomes a critical point in liquid state. The liquid carbon dioxide then acts as a solvent to obtain natural plant matter and volatile oil content and dissolve the carbon dioxide in the liquid. Then, the CO2 is brought back to natural pressurization, the carbon dioxide evaporates back to its gaseous state and what remains is the resulting oily substance
This set of extraction methods using “high pressure and low temperature” began in the 1980s. Its instruments and equipment are very complicated and expensive, and its essential oils are labeled “CO2 Extraction”. This extraction method is carried out in a closed reaction tank in the whole process, and the time required is very short, as long as a few minutes (the distillation method requires at least 1 hour).
supercritical CO2 extraction advantage:
Compared with the solvent extraction method, this extraction method will not leave any solvent residue.
Carbon dioxide extracts usually smell thicker than distilled essential oils, and often smell closer to natural grass. Carbon dioxide extract has been said to contain additional components than those extracted from the same plant using steam distillation. This seems to make sense, because carbon dioxide extracts are usually thicker oils and often seem to have a more comprehensive aroma.
This method is a highly specialized extraction method. Due to the volatilization of the solvent, the essential oil contains no solvent impurities and the separation is relatively thorough. The extracted molecules can be larger than those extracted by distillation. There is a situation that needs to be explained. The distillation method uses steam to bring out aromatic molecules, but larger molecules cannot be extracted, such as the diterpene molecules in clary sage. This is already the limit, that is to say 20 It is rarely seen that terpenes with three carbon atoms are extracted by distillation.
supercritical CO2 extraction Disadvantages:
Of course, some people questioned that carbon dioxide is an acid gas, so this extraction method will more or less destroy the chemical structure of essential oils.
Although the plant essential oil extracted in this way will be very close to the original composition of the aromatic substances in the plant, it is a quite perfect extraction method. However, the equipment used in this extraction method is not only huge, but also very expensive. Using it to extract essential oils often takes several years to balance the cost. To this day, the price of essential oils extracted with supercritical carbon dioxide is still very expensive.
Surprisingly, it may not be good to be so close to nature. Take ginger as an example. The scent of ginger essential oil extracted with supercritical carbon dioxide is naturally better than that of distilled ginger essential oil, but it is also easy to irritate sensitive skin. In addition to the high price, the essential oil extracted by supercritical carbon dioxide has another drawback, that is, few manufacturers are willing to provide it, and it is not easy to buy.