Ethyl acetate was used as a replacement for dichloromethane during the 80's and early 90's. Although it is moderately toxic, coffee makers touted ethyl acetate as "natural" because it was present in fruit.
Two nontoxic and more environmentally benign solvents are now used: water, and supercritical fluid carbon dioxide.
In the Swiss water process, caffeine-free "flavor charged water" is used to extract the caffeine from green coffee beans. Since the flavor charged water is already saturated with flavor ingredients, only caffeine moves from the beans to the water.
The extraction process is simple. Supercritical carbon dioxide is forced through green coffee beans. Its gaslike behavior allows it to penetrate deep into the beans, and it dissolves 97-99% of the caffeine present.
Coffee manufacturers recover the caffeine and resell it for use in soft drinks and medicines. The caffeine-laden CO2 is sprayed with high pressure water and caffeine is then isolated by a variety of methods, including charcoal adsorption, distillation, recrystallization, or reverse osmosis.
The final steps of caffeine synthesis in tea and coffee plants are catalyzed by an enzyme called caffeine synthase. Researchers in Japan and Scotland reported the first successful cloning of the gene that codes for caffeine synthase in 2000 . Subsequent investigations will probably reveal ways to inactivate the gene, leading to tea and coffee plants that are unable to produce caffeine.
A brief article by Saul Katz describes various methods for decaffeinating coffee. The article includes a step-by-step illustration of supercritical fluid carbon dioxide extraction of caffeine.
|A brief introduction to supercritical CO2 extraction, an economically important technology used to decaffeinate coffee and tea, extract hops flavors in brewing, and extracting aromas and flavors from spices and herbs.|
|An introduction to supercritical fluids and their applications, including decaffeination of coffee and waste treatment.|
|Robert Lancashire shows that there is more than caffeine behind the chemistry of coffee. Chime molecular models, gas chromatographs, and mass spectra for the major chemical components and flavor ingredients. |
|Details about various methods for decaffeination using methylene chloride, ethyl acetate, activated charcoal, triglycerides, and supercritical carbon dioxide.|
|Robert Lancashire's The Chemistry of Things Jamaican reveals the essential ingredients in tropical products. Created over the last four years, the site is a treasure trove that includes the chemistry and natural history of spices, Jamaican coffee, Carribean fruits and vegetables, Jamaican rum, and more. The pages are illustrated with many striking images and interactive Chime molecular models. Dr. Lancashire's pioneering work on interactive J-CAMP GC/MS spectra can also be found on the site.|
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Last Revised 02/15/10.URL: http://antoine.frostburg.edu/chem/senese/101/consumer/faq/print-decaffeinating-coffee.shtml