CO2 is a gas at room temperature and pressure, but forms a supercritical fluid when heated under high pressure. Supercritical CO2, with its gas-like viscosity and liquid-like density, is an excellent solvent for various applications.
The tea to be decaffeinated is placed in a large column which can withstand relatively high pressures. Once sealed, liquid carbon dioxide is pumped into the column where it solubilizes the caffeine.
After the extraction process has been completed, the liquid carbon dioxide is pumped to a second column. When the pressure is released in this column, the liquid carbon dioxide vaporizes to form a gas. The gaseous carbon dioxide is then recompressed to go back into its liquid form and is used to decaffeinate a fresh batch of coffee or tea. The decaffeination processes run under normal, official food control and fully comply with the Swiss and European food laws.
Supercritical CO2 extraction is environmental but its selectivity depended on many factors such as cosolvent, pressure, temperature, extraction time and moisture content of tea leaf.
Supercritical Carbon Dioxide is the most widely used solvent for decaffeination of food products. The gas is odourless, tasteless and inert. Carbon dioxide processing leaves no toxic residues. In addition, extraction of the caffeine takes place at room temperature which protects product quality by preventing the breakdown of temperature-sensitive components.
This process was successfully developed on an industrial scale in the 1970s, based on two patents developed by Zosel: in the first, the process is presented for the recovery of caffeine, whereas, in the second one, a detailed description aimed at obtaining decaffeinated coffee was proposed.
Carbon dioxide process of tea decaffeination
