Although caffeine is water soluble above 175 F, water alone is generally not used to decaffeinate coffee because it strips away too many of the essential flavor and aroma elements. Decaffeination usually involves the use of a solution containing water and coffee flavor elements, plus a decaffeinating agent.
Methods of Decaffeination:
There are basically two methods of decaffeination: direct and indirect contact. In the first the beans come directly in contact with the decaffeinating agents, after being softened by steam. In the latter method, a water/coffee solution is normally used to draw off the caffeine; after being separated from the beans, the solution containing the caffeine is then treated with a decaffeinating agent. In both methods, the agent is removed from the final product.
Agents of Decaffeination:
The following agents are commonly used in decaffeinating coffee:
Methylene Chloride:
This solvent may be used in two ways to decaffeinate coffee. In the direct contact method, the green, unroasted beans are placed in a rotating drum and softened by steam for approximately 30 minutes; they are then repeatedly rinsed - for about 10 hours - with methylene chloride, which removes the caffeine from the beans. The caffeine-laden solvent is drained away, and the beans are steamed a second time, for 8 to 12 hours, so the remaining solvent can evaporate. Finally, air or vacuum drying removes excess moisture from the decaffeinated beans. Virtually no solvent residue remains after roasting the beans. In the indirect contact method, sometimes referred to as the "water process," the green beans soak for several hours in a water/coffee solution at almost boiling temperature. Gradually the solution draws out the caffeine, as well as other flavor elements and oils, from the beans. The caffeine/water mixture is drained away and treated with methylene chloride, which absorbs the caffeine. The resulting mixture is then heated to evaporate the solvent and caffeine. Next, the mixture is reunited with the beans, allowing them to regain most of the coffee oils and flavor elements. The solvent never touches the beans.
Ethyl Acetate:
Using this substance to decaffeinate coffee is often referred to as a "natural" process because ethyl acetate is a compound found in many fruits, such as apples, peaches, and pears. This process is similar to the indirect contact method using methylene chloride described above, although ethyl acetate requires more time to absorb the caffeine. The process begins when green coffee beans soak in a heated water/coffee solution, which gradually draws off the caffeine and flavor elements. The solution is separated from the beans and treated with ethyl acetate, a compound that absorbs caffeine. A steaming process removes the caffeine-laden ethyl acetate from the water. The water is then retuned to the beans, which reabsorb the flavor elements. Finally, the beans are dried. NOTE: The United States Food and Drug Administration - FDA, has authorized by regulation the use of both methylene chloride and ethyl acetate for coffee decaffeination, According to an FDA report in the Federal Register, most decaffeinated coffee has less than 0.1 parts per million - ppm, of residual methylene chloride, 100 times less than The maximum level of 10 ppm allowed by the FDA.
Charcoal or Carbon:
In this indirect contact method, unroasted beans soak in hot water to draw off the caffeine. The resulting solution, which contains caffeine as well as other flavor and aroma elements, is separated from the beans and sent through a bed of activated charcoal or carbon filters to remove the caffeine. Next, as in other methods, the water containing the remaining flavor compounds is returned to the beans. The beans are then dried. The coffee industry often refers to this decaffeination method as "Swiss Water Process" because a Swiss company originally developed and patented the procedure.
Triglycerides:
Green coffee beans are soaked in a hot water/coffee solution to draw the caffeine to the surface of the beans. Next, the beans are transferred to another container and immersed in coffee oils that were obtained from spent coffee grounds. After several hours at high temperatures, the triglycerides in the oils remove the caffeine - but not the flavor elements - from the beans. The beans are separated from the oils and dried. The caffeine is removed from the oils, which are reused to decaffeinate another batch of beans. This is a direct contact method of decaffeination.
Supercritical Carbon Dioxide:
In this direct contact method, green beans are first softened by steam, to bring caffeine to the beans surface. Next, they are immersed in carbon dioxide at a high temperature and pressure - in this "supercritical" state the carbon dioxide behaves as if it were a liquid while remaining a gas. It penetrates
