Posted in Reference
The direct method involves first steaming coffee beans and then repeatedly rinsing them in the solvent ethyl acetate, each rinse reducing the caffeine content. The beans are then steamed again to remove any residual solvent.
The indirect method involves soaking coffee beans in hot water for several hours essentially making an upsized coffee drink. The beans are then removed, and ethyl acetate used to remove the caffeine contained in the water. By using the same water over and over again, an equilibrium is established where the beans and the water maintain a similar composition, preventing the loss of flavours or strength in the beans.
The use of ethyl acetate is touted as a 'natural' means to remove caffeine, as it can be derived from certain fruits and vegetables- however, the difficulty of actually attaining it naturally means that the ethyl acetate used is typically synthetic.
The triglyceride process is similar to the direct method, but instead of using ethyl acetate, coffee beans soaked in hot water are then moved to a vessel containing coffee oils. With this vessel heated, triglycerides in the oils remove the caffeine from the beans. The caffeine can then be removed from the oil and the same oil used again. This method has the added benefit of not removing the flavours from the beans.
The CO2 process, entertainingly known as a supercritical fluid extraction, involves steaming coffee beans and then placing them in a high pressure chamber with supercritical carbon dioxide- a liquid form brought on by holding it above a certain temperature and pressure. The caffeine is absorbed into the CO2, and can then be extracted from the CO2 using charcoal filters.
A process that boasts the use of no chemicals whatsoever and provides 99.9% caffeine reduction is the Swiss water process, which uses water, Green Coffee Extract or GCE, and carbon filters. GCE is a substance made up of water containing coffee solids without the caffeine, and like the triglyceride process allows the transfer of caffeine from beans to it without compromising the bean's flavours. The process involves coffee beans being pre soaked before being introduced to the GCE and heated, transferring the caffeine. The GCE is then passed through carbon filters to remove the caffeine.
Despite the apparent complexity, each process essentially boils down to heating the beans to draw the caffeine to the surface and then repeatedly rinsing them in a substance that removes the caffeine.
However, it is important to know that decaffeinated coffees typically still retain a very small percentage of caffeine, and are not really caffeine free. Luckily for those who either try to or indeed have to avoid caffeine, in 2008 a new species of coffee known as coffea charrieriana from Cameroon was found to be naturally caffeine free.