Decaffeinated coffee actually does have some caffeine - but according to US federal regulations, it should not make up more than 2.5% of the total product in order to be labelled decaffeinated.

Caffeine can be removed using four main methods:

- Methylene chloride processing
Coffee beans can be softened in a water or steam bath and then either: 1. soaked directly in methylene chloride to remove the caffeine; or 2. soaked in water to remove the caffeine, as well as certain oils and flavours. This mixture is then treated using methylene chloride, to remove only the caffeine, and then the flavours and oils are returned to the beans for reabsorption.

- Ethyl acetate processing
This is often called "naturally decaffeinated" on goods packaging, as many fruits contain ethyl acetate. This uses exactly the same process as the one described above, but with a different solvent (ethyl acetate).

- Carbon dioxide processing
The coffee beans are softened in water and then "pressure cooked" with carbon dioxide. At high temperatures and high pressures, carbon dioxide can act as both a liquid and a gas - it then becomes a solvent, and attracts the caffeine molecules. Flavour molecules are larger than caffeine molecules, and so remain within the coffee bean. This is why this process is good for retaining the original flavour of the coffee bean.

- Water processing (or Swiss water processing)
This is one of the main methods of decaffeination for coffee. It is similar to method number 2 for the methylene chloride processing, but does not use chemicals. Instead, when the caffeine has been removed using water, the solution is passed through a carbon filter - this removes only the caffeine, and then the flavours and oils can be returned to the water for reabsorption by the coffee beans. In "Swiss" water processing, a coffee-flavoured liquid is used instead of water - this removes the caffeine without removing the flavours of the beans.

Most of the caffeine removed in these process is then used in other products like medicines and soft drinks.

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