CO2 extraction is a process of separation of the miscible liquids. The CO2 forms as a solvent. Owing to its peculiar properties to exist in different forms with respect to the temperature & pressure, CO2 Extraction is used in the extraction of the aromatic compounds. The CO2 can exist in the frozen form also. It is called dry ice in the solid state. At STP(Standard Temperature Pressure) CO2 is a gas. At a particular pressure temperature & pressure the CO2 become fluid. This increased temperature & pressure is called the critical point of CO2.
Types of CO2 Extraction
CO2 extraction is basically of two types.
- Low pressure cold extraction : It involves chilling CO2 between 35-55 degrees F and pumping at 800-1500 psi through the plant material. It is often considered the best method for producing high quality botanical extracts. In this state CO2 has a high loading rate meaning that you will have to pump several volumes of CO2 through a given volume of botanical. The loading rate is typically 10-40 volumes.
- Supercritical Fluid Extraction: It involves heating the CO2 to above 87degree F and pumping it above 1100 psi. This process has a much faster loading rate 2-10 volumes and a wide range of uses. However its drawback is that some extracts can be damaged by either the high pressure breaking molecular ring structures or the fact that moisture in the botanicals can react with the CO2 and form carbonic acid which can turn some oils rancid.
The highly technical process of Supercritical or liquid CO2 is illustrated by the heavy apparatus taken into account. The extraction vessel, evaporator, separator, pump, condenser & storage vessel all work together to make the process simplified. The plant material is put in a pressure vessel. Pumping is done on the CO2 liquefied gas or liquid solvent at a specific pressure and temperature called the critical point. The pressure so formed forces the solvent into the wall of the cells of the botanical and separates the desired constituent rapidly. The fluid so formed from CO2 enhances the solvent characteristics.
- In the Coffee industry to minimize caffeine
- In the Biomedical industries to sterilize tools & equipments
- The method is used extensively in thermoplastic/fired ceramics