The chemicals used to decaffeinate coffee are related to cleaning fluid, yes, but different. Like my Uncle Leon. In chemical families, as in human families, there are both similarities and idiosyncrasies.
Caffeine itself, for example, is a member of the alkaloid family of powerful plant chemicals that includes such bad actors as nicotine, cocaine, morphine, and strychnine. But then again, tigers and pussycats belong to the same family.
The methylene chloride that’s used in some decaffeinating processes is related to, but quite different from, the toxic perchlorethylene used in dry cleaning. But it’s still no pussycat.
Chemists have identified from eight hundred to fifteen hundred different chemicals in coffee, depending on whom you ask. As you can imagine, removing the 1 or 2 percent of caffeine without ruining the flavor balance of all the others is no small trick. Caffeine dissolves easily in many organic solvents such as benzene and chloroform, but those are obviously out because they’re toxic. (No, chloroform wouldn’t cancel the caffeine’s effects by putting you to sleep.)
Since 1903, when a German chemist named Ludwig Roselius lost sleep over how to remove the caffeine from coffee and finally settled on methylene chloride, that has been the solvent of choice.
It dissolves other components minimally and vaporizes easily, so that its remaining traces can be driven off by heat. Herr Roselius marketed his coffee under the name Sanka, a word he invented from the French sans caffeine. Sanka was introduced into the United States in 1923 and became a brand name of General Foods in 1932.
But in the 1980s methylene chloride came under fire as a carcinogen. It is still used for decaffeinating, but the FDA limits its amount in the finished product to ten parts per million. Industry sources point out that the actual amount is less than a hundredth of that.
Caffeine is removed from the green coffee beans before they are roasted. First they are steamed, which brings most of the caffeine up to the surface, and then the caffeine is dissolved out by the solvent. To be called decaffeinated, a coffee must have more than 97 percent of its caffeine removed.
An indirect method, sometimes called the water method, is often used: The caffeine, together with many desirable flavor and aroma components, is first extracted into hot water. (Caffeine dissolves in water, of course, or we wouldn’t be worrying about its presence in our cups.) The caffeine is then removed from the water by an organic solvent, and the now caffeine-free water, with all of its original flavor components, is returned to the beans and dried onto them. The solvent never actually touches the beans.
An interesting new wrinkle is the use of the organic solvent ethyl acetate instead of methylene chloride. Because this chemical is found in fruits and, indeed, in coffee itself, it can be said to be “natural.” The label of an ethyl acetate–treated coffee may therefore claim that it is “naturally decaffeinated.” But don’t be impressed. A similar claim could be made for using cyanide, because it occurs “naturally” in peach pits.
Much decaffeinated coffee today is made by a recently developed process that extracts the caffeine into familiar, harmless old carbon dioxide, but it’s in a peculiar form that chemists call super critical; it’s neither gas, liquid, or solid.
Finally, there’s the ingenious “Swiss water process,” which washes the beans with hot water that is already fully loaded with all possible coffee chemicals except caffeine, so there’s no room for anything but caffeine to dissolve into it from the beans.
How does all this percolate down to your supermarket’s coffee aisle?
First of all, you may see the words naturally decaffeinated on the can. It may refer to the ethyl acetate method or it may mean nothing at all. Doesn’t everything come from Nature? What else should we expect? Supernaturally decaffeinated coffee?
Nor do the words water process mean much, because water is used in several methods, not just in the Swiss water process.
The best advice is to forget about the technology, they’re all safe methods, and choose your decaf on the basis of objective intellectual criteria, such as whether you’re more partial to Juan Valdez or Mrs. Olson.