холодный звонок (self_made_man2) wrote,
холодный звонок

Caffeine Extraction Methods (TOEFL text)

caffeine is a naturally occuring compound found in the nuts, seeds, and leaves of over sixty plants. When it is extracted from these plants, it is a white, bitter-tasting powder. Caffeine affects the body in various ways: stimulating the cerebral cortex, increasing the heart rate, and causing several other psysiological reactions, including insomnia and irritability. Because of its potentially harmful effects, processes have been developed extract caffeine from coffee, giving the consumer the option of tasting a flavorful drink without the concominant side effects. Once the caffeine is removed, it is sometimes added to other beverages, in particular soft drinks, and can also be used as an additive in many medications, especially nonprescription pain relievers.
Several methods are used to extract caffeine from coffee beans. A method commonly favored until recently uses methylene chloride, a compound with solvent properties whose molecules bind to molecules of caffeine. Methylene chloride can be aplied in two ways: directly or indirectly. In the direct method, the unroasted green coffee beans are soaked in this chemical solvent and the oils are removed along with the caffeine. To overcome this problem an indirect method was developed. In this method the caffeine is extracted from the coffee beans by soaking in hot water. The resulting solution is then treated with methylene chloride to extract the caffeine and the remaining flavors and oils are returned to the coffee beans and reabsorption. In this indirect method, the chemical solvent never actually touches the beans.
Methylene chloride has been found to have several potentially dangerous effects. It can cause faintness, dizziness, and headaches if inhaled at high concentrations, and in mice it has been shown to cause cancer when ingested at high doses. However, at lower doses no carcinogenic effects have been shown. Nevertheless, due to the potential dangers, other more natural methods of caffeine-extraction have been introduced in some production plants.
The most common alternative solvent is ethyl acetate, which is a chemical compound found naturally in many kinds of fruit. Because it is naturally derived, it is regarded as a safer alternative/ The process of caffeine extraction is the same as with methylene chloride, although using ethyl acetate is generally more time-consuming.
Another method of decaffeinating coffee is known as supercritical carbon dioxide extraction. At high pressures and high temperatures, carbon dioxide is in a supercritical state, which means it acts both as a gas and a liquid. Supercritical carbon dioxide is forced through green coffee beans and penetrates into the beans dissolving up to 99 percent of the caffeine. The carbon dioxide is then drawn off and any residue left on the beans dissipates as a gas when the beans are allowed to cool to room temperature.
The charcoal, or carbon filter, method uses how water to dissolve the caffeine and other substances from the coffee beans. The resulting liquid solution is passed through a carbon filter, which removes the caffeine. The remaining solution containing the original flavors and oils is then reunited with the beans. A variant of this method called Swiss Water Process uses a coffee-flavored solution as the solvent. This takes away the caffeine while leaving the flavors and oils.
Because of the time and expense of all of the above methods, a controversial new approach has been developed but is not yet approved. This involves genetic enineering to delete or turn off genes associated with caffeine production in the plant itself. This idea has provoked much criticism from certain quarters due to the fact that the caffeine helps plants to protect beans against fungi. Beans that cannot produce caffeine could become coated with fungi, which might prove toxic to human consumers.
Tags: toefl

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