How are coffee beans decaffeinated?
Two methods are generally used. In the first, the beans are placed in a rotating drum and softened with steam for 30 minutes. They are then rinsed in a chemical solvent for about 10 hours. When the chemical has absorbed the caffeine from the beans, it is drained away, and the beans are steamed for 8 to 12 hours more so that any remaining solvent will evaporate. A minute amount of the chemical (0.1 parts per million) remains in the beans. In the second method, green coffee beans are soaked in hot water until the caffeine is drawn out of them. The water is drained and treated with a chemical, which absorbs the caffeine. Then the mixture is heated until both the chemical and the caffeine evaporate. The remaining water is returned to the beans, which, according to coffee experts, allows the beans to regain most of their flavor.