Many ways to decaffeinate coffee
Dear Dr. Blonz: I drink decaffeinated coffee and have been hearing about dangers from the methods used to remove the caffeine. Is organic decaf any safer? — S.A., San Diego
Dear S.A.: To make decaf coffee, you want to remove caffeine and leave all other substances. This requires the use of a caffeine solvent and specialized methods. Solvents currently in use include water, methylene chloride, ethyl acetate, triglycerides or pressurized carbon dioxide.
One “indirect” method involves taking a load of green coffee beans and placing them in water. All water-soluble substances, including caffeine, are drawn into the water. This solution is separated from the coffee beans, and that first batch of beans is discarded. The next step is a process that selectively removes the caffeine from the solution. This can be done using a different solvent that is subsequently eliminated, along with its caffeine, or by passing the caffeine-rich water extract through a specially treated charcoal filter that grabs only the caffeine.
The latter process is referred to as the Swiss Water Process. What’s left is a working solution containing all water-soluble components, minus caffeine.
The next batch of green coffee beans gets put into the working solution. Only caffeine gets extracted, because an equilibrium exists between the concentration of the other watersoluble components in the beans and that which is present in the working solution. The decaffeinated second batch moves on to get roasted, and that second solution goes through its caffeine-extraction step to be used with subsequent batches.
A “direct” method involves mixing the selected caffeine solvent directly with the beans. Methylene chloride or ethyl acetate are the solvents most often used. After it has had a chance to dissolve the caffeine, the solvent is removed, with the caffeine in tow. The beans are gently steamed to eliminate any remaining solvent residue.
Methylene chloride is a carcinogen, but there shouldn’t be any left on the beans to pose a health risk. This is because methylene chloride evaporates around 110 degrees — well below steaming temperature, and also well below the temperature at which coffee is brewed. Ethyl acetate is a compound that naturally occurs in fruits and vegetables, and is often used when decaffeinating tea leaves. In all the above, the green coffee beans (or tea leaves) are ready for drying, roasting or further processing after the caffeine is removed.
Other, more expensive methods utilize carbon dioxide that has been liquefied under high pressure. (This is a process approved for organic coffee and tea production.) The liquefied CO2 dissolves the caffeine from the tea leaves or coffee beans and is then drained off. Another method utilizes the fatty substances called triglycerides.
Whatever the method, decaffeination technology has improved greatly over the years, and flavor differences are often hard to detect. Much also depends on the quality of the beans and tea leaves, together with the particular practices of the roaster.
Note that the use of the term “water process” with decaffeinated beans doesn’t tell you the whole story, since most indirect methods utilize a water extraction somewhere along the way. If the label specifically states “Swiss Water Process” or has other additional information, a better determination can be made.
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