The act of removing caffeine from coffee beans, cocoa, tea leaves and other caffeine-containing materials is called decaffeination. Despite this process, many drinks considered to be decaffeinated still contain roughly 1 to 2 percent of the original caffeine in them. Caffeine-free soft drinks may be referred to as "decaffeinated," but a better term would be "uncaffeinated," since no caffeine was added to them during production.
Various methods are use to decaffeinate coffee. Since coffee contains more than 400 chemicals that affect the taste and aroma of the final drink, removing only the caffeine while leaving the other chemicals at their original levels can be challenging. The process is usually done on green beans that have not been roasted, and starts with steaming. The beans are then rinsed with a solvent that extracts the caffeine and leaves the other essential chemicals in the beans. This process is repeated 8 to 12 times until it meets one of two standards: The EU standard of having the beans 99.9 percent caffeine free by mass, or the international standard of having 97 percent of the caffeine in the beans removed.
Generally, coffea arabica contains about half the caffeine of coffea robusta. A coffea arabica bean containing little caffeine was discovered in 2004 in Ethiopia.
Ludwig Roselius and Karl Wimmer invented the first commercially successful decaffeination process in 1903. Coffee beans were steamed with a saltwater solution and then benzene was used as a solvent to remove the caffeine. Coffee decaffeinated by this method was sold as Kaffee HAG after the company name Kaffee Handels-Aktien-Gesellschaft in most of Europe; as Cafe Sanka in France and later as Sanka brand coffee in the U.S. Cafe HAG and Sanka are now worldwide brands of Kraft Foods. This process is no longer used commercially because of health concerns regarding benzene. Coffee Hag and Sanka are produced using a different process.
This method of decaffeination was developed by the Swiss Water Decaffeinated Coffee Company in the 1930s. The Swiss Water process works by soaking green, unroasted beans in hot water to release caffeine. When the caffeine and coffee solids are released into the water, the beans are discarded. The water then passes through a carbon filter that traps caffeine but lets the coffee solids pass through. The resulting solution is called "green coffee extract” or GCE. New green coffee beans are mixed with the GCE. Since the GCE is coffee solids without caffeine only the caffeine diffuses from the new beans. The GCE passes through proprietary carbon which captures the caffeine. The process repeats until the beans are 99.9 percent caffeine-free. These beans are removed and dried, and retain a great deal of their flavor.
The world's only Swiss Water Process decaffeination facility is based near Vancouver, British Columbia, Canada.
Under this process, coffee beans are steamed for 30 minutes and then repeatedly rinsed with either dichloromethane or ethyl acetate for about 10 hours. The solvent is then drained away. Beans are steamed for another 10 hours to remove any residual solvent. Coffees that are decaffeinated using ethyl acetate are sometimes referred to as naturally processed because ethyl acetate can be derived from various fruits or vegetables. However, because of gathering natural ethyl acetate is not practical, the chemical used for decaffeination is synthetic.
Using the indirect method, which is also sometimes called the “water process” method, beans are soaked in a solution of hot water and coffee for several hours to remove caffeine. Once the water is drained from the beans, either dichloromethane or ethyl acetate is used to absorb the caffeine from the water. Heat then evaporates the solvent and caffeine, leaving the original water solution. That same solution is then used to soak the beans again, restoring flavor that was lost during the initial soaking.
This process, also known as “supercritical fluid extraction,” strips the caffeine directly from the beans with a highly compressed semi-liquid form of carbon dioxide. Pre-steamed beans are soaked in a bath of supercritical carbon dioxide at a very high pressure. After a thorough soaking for around ten hours, the pressure is either reduced to allow the CO2 to evaporate, or the pressurized CO2 is run through water or charcoal filters to remove the caffeine. This process avoids the use of potentially harmful solvents.
In this process, green coffee beans are soaked in a solution of hot water and coffee to draw caffeine to the surface of the beans. The beans are then transferred to another container and immersed in the oils of spent coffee grounds.
After several hours of high temperatures, the triglycerides in the oils remove the caffeine from the beans, while retaining the flavor elements. The beans are removed from the oils and dried. After the caffeine is removed, the oils are reused to decaffeinate another batch of beans.
Caffeine Content of Decaffeinated Coffee
Almost all brands of decaffeinated coffee still contain a small amount of caffeine. Research at the University of Florida Maples Center for Forensic Medicine found that drinking five to 10 cups of decaffeinated coffee could deliver the same amount of caffeine in one or two cups of regular coffee. Another study has shown that of 10 popular decaffeinated coffees, all but one contained detectable caffeine. The 16 ounce cups of coffee samples contained anywhere from 8.6 milligrams to 13.9 milligrams of caffeine. Another study of popular brands showed caffeine content of 3 milligrams up to 32 milligrams. Because these two studies tested caffeine content of store-brewed coffee, it’s possible that the caffeine may be residual from the normal coffee served, rather than poorly decaffeinated coffee.
Coffee beans that contain no caffeine may be a reality in the near future. A term to describe this type of noncaffeinated coffee, “Decaffito,” has been trademarked in Brazil. The prospect was heightened by the 2004 discovery of the naturally caffeine-free Coffea Charrieriana, a Coffea Arabica plant. It has a deficient caffeine synthase gene, leading it to accumulate theobromine instead of converting it to caffeine. Crossing other coffee plants with Carrieriana could breed this trait into them. The same effect may be achieved by knocking out the caffeine synthase gene in normal coffee plants.