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Associate Professor Jian Zhao, lecturer in Food Science and Technology, School of Chemical Engineering, The University of New South Wales
How is caffeine removed to create decaffeinated food products?
Decaffeination methods are proprietary and details are commercial secrets, although they do gradually become known. The earliest techniques used organic solvents to extract caffeine from green coffee beans. These were then dried and roasted, which is when most of the coffee flavour is generated. Solvent residue concerns led to water decaffeination processes, initially in Switzerland and France, although these methods were not commercialised until the late 1970s. The latest innovation is decaffeination by supercritical carbon dioxide, a liquid form of this chemical compound we usually know as a gas. It exploits the fact that CO becomes liquid under extremely high pressure and acquires some very useful properties including the preferential dissolution of compounds such as caffeine. Supercritical CO decaffeination produces coffee with flavour superior to conventional methods but the process is considerably more expensive.