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If you drink only decaf coffee, you’re in a pretty exclusive group. According to research conducted by the National Coffee Association, about 10 percent of men and 15 percent of women only drink decaf coffee when they drink coffee. Another 30 percent or so sometimes choose decaf coffee instead of regular coffee. This may seem counterintuitive to those who drink coffee for its stimulant effects — effects that are due almost entirely to the presence of caffeine in a cup of coffee. Those who drink coffee because they like the flavor but can’t deal with the jitters and sleeplessness that caffeine can cause in sensitive people have their choice of coffee decaffeinated by one of several different methods. Each of these decaf coffee methods offers different levels of effectiveness and different effects on flavor.
Organic solvent extraction
Decaf coffee was originally made by using organic solvents to dissolve the caffeine and carry it away without also removing the sugars, peptides and other components of coffee that give it its flavor. In early years, those solvents included benzene, chloroform and trichloroethylene, all of which are quite toxic. In the early 1970s, coffee chemists used a substance called CH2C12, or dichloromethane, to remove caffeine from coffee. When scientists identified CH2C12 as a possible carcinogen, however, it fell out of favor. In the 80s and 90s, several major coffee processors claimed that their coffee was “naturally” decaffeinated because they used ethyl acetate to dissolve and carry off caffeine. Ethyl acetate is natural enough — you can find it in fruit — but it’s also moderately toxic.
Today, coffee processors use two environmentally safe and nontoxic solvents to produce decaf coffee: water and supercritical fluid carbon dioxide.
Water Extraction is simple in concept. Green coffee beans are soaked in hot water, which extracts caffeine, along with many of the ingredients that make coffee taste so good. The beans are soaked and rinsed several times, and the water from each soak is filtered through an activated charcoal filter to remove the caffeine. Once the caffeine is removed from the coffee extract, the flavored water is poured back over the decaffeinated beans to allow them to soak up the flavor that was removed from them by the first part of the decaf coffee process. After the soaking period, the beans are dried and go on to either be packaged or roasted.
The Swiss water decaf process, a variation of the water decaf process, the first soak is eliminated. Instead, the green beans are soaked in “flavor-charged water,” which is essentially decaffeinated coffee extract. Since the water is already saturated with the peptides, sugars and flavor ingredients, the extraction process only removes the caffeine from the beans.
Supercritical fluid CO2 extraction
Supercritical fluid CO2 is an anomalous substance that acts like both a gas and a liquid. Scientists obtain supercritical fluid CO2 by heating a sealed vial that contains carbon dioxide in both liquid and gaseous form. When the vial is heated to 304.2K at a pressure of 72.8 atmospheres, the liquid and gas reach identical densities. The resulting supercritical fluid carbon dioxide is an excellent solvent for caffeine, as well as many other organic compounds.
The processors force supercritical carbon dioxide through green coffee beans, where it dissolves up to 99 percent of the caffeine in the beans. The caffeine is absorbed by a number of different methods, including reverse osmosis, distillation, recrystallization and charcoal adsorption.
The newest technology in making decaf coffee is genetic manipulation. Researchers in Scotland and Japan have isolated the gene that synthesizes caffeine in the coffee bean. Organic chemists are working to find ways to deactivate that gene and produce 100 percent naturally decaffeinated coffee.