Chlorinated compounds were the first caffeine extractants used with coffee. To expedite removal of caffeine, coffee beans are steam treated to bring about swelling for greater solvent permeability and to break down caffeine complexes. In all extraction processes it is necessary to wet the coffee for efficient caffeine removal. Green beans are decaffeinated to prevent extraction and loss of the aromatic components that are generated only during roasting. After solvent removal by steam distillation, the beans are roasted.

Trichlorethylene was commonly used as the solvent until it was eliminated in 1977 because of its suspected carcinogenicity. Methylene chloride then became the decaf-feinating solvent of choice (36). A residue level of 10 ppm is approved by the U.S. Food and Drug Administration. An unofficial standard providing for the removal of 97% of the original caffeine has come into use for decaffeinated coffee. The beverage therefore contains 2 to 4 mg of caffeine per cup. To eliminate residues of chlorinated compounds, other decaffeinating solvents are now used. Ethyl acetate is approved in the United States. The process has some disadvantages: 5 to 6% solids loss and more difficult de-solventization.

Decaffeination using water as the only solvent to contact the coffee is also carried out. A concentrated coffee extract freed of caffeine contacts the green beans. Noncaf-feine solids are not removed under these conditions. The extract is then regenerated for use by adsorbing the caffeine on activated carbon (52). Coffee oil expressed from beans is used as a decaffeinating solvent along with other vegetable oils in another operating process. Caffeine is removed from the oils by a liquid-liquid extraction system with water as the second solvent (53).

Supercritical C02 extraction is now widely used for de-caffeination (54). The process is carried out at 300 bars and at 60 to 90°C. Caffeine solubility increases as temperature and pressure are raised. The extracted caffeine may be removed from the supercritical fluid by reducing the pressure, thereby decreasing its solubility or by passing the mixture over activated carbon. Techniques that avoid the necessity for repressurizing the gas are preferable. Supercritical processes are capital intensive but result in products of superior quality with no solvent residues. In 1997 supercritical extraction was used to prepare about 50% of the decaffeinated coffee in the United States.

The commercial procedures for the decaffeination of tea are, in principle, similar to those used for coffee. For practical reasons it is necessary to utilize manufactured black tea rather than fresh green leaf. Conservation of aroma during processing is desirable. Decaffeinated tea appeared on the market in 1978. Similar process evolution took place as with coffee. Decaffeination with supercritical C02 became a commercial process in 1984 (55). Aroma may be previously stripped with dry supercritical C02 or with the moist gas at atmospheric pressure for later addition to the product (56).

The Mediterranean Diet Meltdown

The Mediterranean Diet Meltdown

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