Decaffeination may refer to any one of the many
chemical processes used to remove the
caffeine from coffee. It should be noted that
every method of decaffeinating the beans will make the final coffee taste different after brewing, and -- according to personal preference -- mostly in an
unpleasant way. My writing here shouldn't be construed as condoning this anemic beverage, but rather is my self-chosen penance for sometimes brewing coffee with pre-caffeinated
yuppie water. Neither decaffeination nor over-caffeination is the greatest
travesty, however;
one writeup recommends brewing with
Dr Pepper (
Yecch!) to make one's coffee more interesting.
Coffee was first decaffeinated in 1820 by a German chemist named Runge, at a request by Goethe to end his coffee-induced insomnia. Runge's discoveries were forgotten for nearly a century, until the German coffee importer Ludwig Roselius rediscovered them accidentally. One of Roselius' shipments of beans had been damaged by water en route to delivery, and it was subsequently found that the "buzz" wasn't present in coffee brewed from these beans. A team of chemists was put to task finding out why, and they ended up developing a process much like modern solvent decaffeination but using benzene. Even though benzene is rather toxic, the method was popularized with Sanka coffee.
Common to all of the brewing methods is pre-treating the beans with steam, which opens all of the beans' pores and swells them to 50% greater size and weight. This step is useful because caffeine is very soluble in water, so exposure to water will aid further extraction by any means. Also, the increased surface area and lessened tendency to float are helpful to all decaffeination processes.
The most common method of decaffeination uses solvents to remove the caffeine. In the direct version coffee beans are exposed to the solvent for hours to let it leach the caffeine out, then cleansed of the solvent and dried as normal. Indirect decaffeination steeps the beans in water for the same amount of time, then mixes that water with solvent to remove all the caffeine, and removes the solvent from the water. Once the water is clear of solute caffeine, the beans are put back, and the whole mess is allowed to dry, theoretically infusing all of the flavor back into the beans.
Methylene chloride is the older of the modern solvents used to decaffeinate coffee, but it was discovered to be a carcinogen in the early 1980's and was mostly phased out of use. Since it produces (arguably) the best results of any decaffeination method, the FDA still allows its usage, so long as the final beans are no more than 10 ppm methylene chloride. Ethyl acetate is also used, which is considered non-toxic but takes a longer time to take up the caffeine. Every now and again you'll see references to the "natural" method of decaffeination, which uses ethyl acetate as the solvent, and can be marketed as such because a tiny amount of the chemical is found in some fruits.
Another, more expensive, way of extracting caffeine is by steeping it in supercritical carbon dioxide. This requires exposing the beans to the hellish conditions required to make CO2 go supercritical, 300 atmospheres of pressure and 70° C. CO2 under these conditions has the density of a liquid but the viscosity (rather, the lack of viscosity) of a gas, so it can integrate itself pretty deeply into the beans. It's then drawn off and filtered to be used again, and the beans are allowed to dry, removing any remaining (non-toxic) carbon dioxide.
One final method is known as the Swiss Water Process -- and patented as such by Kraft/Philip Morris, even though it was invented in Switzerland. This is much like an indirect extraction, only instead of using solvents on the water, it is filtered through activated charcoal. This removes not only the caffeine but many of the chemicals that make coffee yummy, leading to a final product which is to be despised by any serious coffee drinker. Feh!
As for the future, a few companies are engineering coffee beans that are missing the enzyme which converts other chemicals to caffeine. This will hopefully lead to coffee that tastes completely normal, but has zero caffeine content.
Decaffeinated Tea is easy to make at home, and can be done with whatever variation of tea suits your fancy. First, boil up two or three times the amount of water you usually do. Then, for twenty or thirty seconds, steep the tea in a regular-sized portion of water, and throw that water out. This can be done twice for the truly paranoid or caffeine sensitive. After these washes the tea leaves have an order of magnitude less caffeine, and basically normal-tasting tea can be brewed from them. Industrial tea companies use either this method (though it doesn't remove enough caffeine to be FDA labeled "decaffeinated") or one of the chemical methods noted above.