Decaffeinization

Stupid Question ™
April 29, 1999
By John Ruch
© 1999

Q: How do they remove caffeine from caffeine-free coffee and soda? And what do they do with it?
—Shannon Patke


A: Almost all the caffeine in soda is an added ingredient. So in caffeine-free brands, they just don’t put it in.

And where do the soda-makers get their caffeine? Mostly from manufacturers of decaf coffee, who also sell caffeine to drug companies. (There are other sources: Coke used to get it from tea dust. Caffeine can also be synthesized from uric acid; during World War II scarcity, Coke considered making it from bat guano.) A hundred pounds of coffee will yield about three-quarters of a pound of pure caffeine.

There are several decaffeinization methods. In all cases, unroasted coffee beans are first steamed, loosening the caffeine and swelling the surface size to increase the caffeine outflow.

The two basic methods are direct contact and indirect contact. In direct contact, the beans are immersed for hours in a chemical solvent that extracts the caffeine. The solvent is then removed and cleansed of caffeine by evaporation or one of several other methods. Solvent residue is removed from the beans by re-steaming them.

In indirect contact, the beans are immersed in what’s basically a batch of already-decaffeinated coffee—hot water and coffee oils and flavors. This solution draws the caffeine out of the beans, but doesn’t suck out the beans’ oils and flavors because it’s already saturated with them. The solution then enters a chamber where solvents remove only the caffeine. The again-decaffeinated water is then recycled through the system.

The most common solvents are ethyl acetate (found naturally in fruits), methlyene chloride (less popular since a 1985 study identified it as a carcinogen) and triglycerides, which are alcohol compounds that occur naturally in coffee grounds. The best is highly pressurized carbon dioxide, an expensive direct-contact solvent used mostly by specialty coffee companies.

The fames Swiss Water method was so named because a Swiss company originally patented it. It’s just an indirect contact method that uses a specially treated charcoal filter rather than a chemical solvent. It’s the least-effective method. (Direct contact methods usually remove more caffeine and preserve more flavor.)

The methods used to today vary from company to company. Folgers uses direct-contact ethyl acetate; Maxwell House uses an unspecified indirect-contact method.

Whatever the method, there’s almost always some caffeine left behind. In the US, coffee must be 97 percent caffeine-free to be labeled as such. Caffeine-free sodas may also contain trace amounts of caffeine if they use natural ingredients containing the substance.

All this techno stuff may become moot one day. Researchers at the University of Hawaii are working to engineer coffee plants that are genetically decaf.