Decaffeinated Coffee

Decaffeinated coffee was first developed on a commercial basis in Europe about 1900. The basic process is described in a 1908 patent (19). Green coffee beans are moisturized by steam or water to a moisture content of at least 20%. The added water and heat separate the caffeine from its natural complexes and aid its transport through the cell wall to the surface of the beans. Solvents are then used to remove the caffeine from the wet beans.

Up to the 1980s man-made organic solvents were commonly used. The caffeine is removed either by direct contact of solvent with the beans or by contact with a secondary water system that has previously removed the caffeine from the beans (13). In either case additional steaming or stripping is used to remove solvent from the beans. The beans are dried to their original moisture content of about 10 to 12% prior to roasting.

In the 1980s decaffeination processes were commercialized making use of solvents that occur in nature or can be made from substances that occur in nature. The use of these processes are the basis of positioning a coffee product as naturally decaffeinated.

In a 1970 patent, Studiengesellschaft Kohle of Mulheim, Germany, showed that dense supercritical carbon dioxide is a very specific solvent for caffeine. Subsequent patents (20) describe use of this technology to decaffeinate coffee in a semicontinuous commercial process. Caffeine selectively transfers from wetted green coffee beans to supercritical carbon dioxide and then transfers from the carbon dioxide to water, thereby regenerating the carbon dioxide for reuse and recovering the caffeine.

Fats and oils, including oil from roasted coffee, (21) and edible esters, including ethyl acetate, which is present in coffee, are also used to selectively extract caffeine from coffee. Direct water contact with green beans is used in another process. This contact removes caffeine as well as some noncaffeine solids. The caffeine is adsorbed on activated carbon or an ion exchange resin, and the noncaffeine solids, containing flavor precursors, are reabsorbed on green beans prior to drying and roasting.

In all of the preceding decaffeination processes, pre-wetting of the green beans is necessary, and drying afterward is needed prior to roasting. These steps, in addition to caffeine removal, cause changes in the beans that affect roast flavor development.

The degree of decaffeination as claimed on the product is based on the caffeine content of the starting material and the time-temperature process conditions used by the manufacturer to achieve a desired end point.

Roasted decaffeinated coffee is vacuum packed as ground coffee or whole beans for consumer use. Roasted and ground decaffeinated coffee is made into instant coffee by methods previously described. Decaffeinated coffee represents about 9% of the coffee consumed in 1997 in the United States, declining from a peak of 18% in 1987 (22).

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