The indirect contact method of decaffeination is a decaffeination process that utilizes hot water to extract caffeine from green coffee beans (milled but not yet roasted). Chemical compounds are then used to extract the caffeine from the extract.
The coffee beans are first steamed or soaked for several hours in hot (nearly boiling) water to gradually draw the caffeine.
Drawing Out the Coffee Flavors
Slowly the solution surrounding the coffee beans draws the caffeine out of the beans, and also draws out the coffee’s flavor elements and oils, which are then removed from the liquid which contains caffeine as well as coffee flavor compounds.
Extracting the Caffeine
Next chemicals are used to extract the caffeine from the solution. The chemical used for this is usually either methylene chloride or ethyl acetate – a longer time is required if ethyl acetate is used, though both serve well to absorb the caffeine.
Separating the Caffeine from the Solvent
The caffeine is then separated from the organic solvent through the process of evaporation by heating the mixture. The same water is then used again (reunited with the beans) in the two-step process, and with the same batch of green coffee beans, so they can regain the coffee flavor elements and essential oils. The solvent itself never actually contacts or touches the coffee beans.
After several cycles of this process an equilibrium is reached, at which time the coffee beans and water have a similar composition with the exception of the caffeine. From this point on only the caffeine is removed from the coffee beans, so the coffee itself does not lose any flavor or strength.
“Water” or “Natural” Process
Since water is used at the beginning of this process, the coffee beans produced by the indirect method (indirect contact method; water process) of decaffeinating coffee are sometimes called Water processed coffee beans, though in fact chemicals are used in this process.
When ethyl acetate is used, this method is sometimes referred to as a “natural process” because ethyl acetate is a chemical compound found naturally in many fruits.
Decaffeinated Coffee and Espresso Tips
Want to cut out caffeine without cutting out coffee? Decaf coffee is the perfect way to reduce caffeine withdrawal side effects without eliminating the health benefits of coffee. For tips on brewing the perfect cup of decaffeinated coffee see our section on Coffee Brewing. You can also read detailed coffee flavor profiles of Gourmet Coffees and instructions on preparing Espresso Drink Recipes.