Coffee Facts - Decaffeination processes

To make coffee caffeine free, the stimulating supplement needs to be derived from the beans. Since coffee develops most of its flavour during roasting, the caffeine is extracted from the raw green coffee beans. Various methods exist to achieve this, of which the water-carbon (H2O/C) and dichloromethane (commonly known as DCM) methods are the most used. Both of these techniques extract the caffeine with a caffeine-selective solvent, which therefore leaves the other substances in the bean. Modern decaffeinating methods have no effect upon the flavour and aroma of the coffee. Good decaffeinated coffee therefore tastes almost the same as coffee containing caffeine.

Water-carbon method
This process uses water (H2O) as a solvent. The green beans are rinsed with water for a long period, during which time the caffeine dissolves into the water. The water, with its dissolved caffeine, is then pumped through an active carbon (C) filter which absorbs the caffeine. The decaffeinated beans are dried using warm air and then cooled with cold air. They are then roasted, ground and packed in the usual way. The water is re-used for the decaffeination process.

Dichloromethane process
This method employs dichloromethane (DCM) as a solvent and has been developed to suit the requirements of the out of home industry. The green beans are moistened with water in order to make the surface of the bean porous, and soaked in the solvent for 30 minutes. This is repeated several times. The beans are removed from the solvent once the caffeine has dissolved. They are then steamed for some time in order to remove any remaining solvent. Afterwards the beans are dried using warm air, then cooled with cold air. They are roasted, ground and packed in the usual way. The dichloromethane is reused for further decaffeinating.