Decaffeination is the process of removing caffeine from coffee beans.
Since coffee contains an estimated 400 different chemicals that contribute to its overall flavor and aromatic qualities, the goal of decaffeination is to leave these valuable chemicals intact while removing the one undesirable chemical, caffeine. There is no way to accomplish this 100%, but modern methods are fairly refind and produce a cup of coffee almost as good as the unaltered (full caffeine) version.
Standards for Coffee Decaffeinaton
The United States standard for decaffeination is removing at least 97% of the caffeine from the coffee beans (e.g., about 5 milligrams of caffeine in a 5 ounce cup of coffee). The standard for decaffeination for the European Union (EU) - which includes 27 member states - is to provide coffee beans that are 99.9% free of caffeine as compared to their total mass (weight).
Decaffeination of coffee beans may be accomplished through the direct contact method or the indirect contact method of decaffeination.
Direct Contact Decaffeination
In the direct contact method of decaffeination chemicals (other than water) are used on green coffee beans (milled but not yet roasted) with the goal of dissolving and extracting the caffeine.
A direct contact decaffeination method uses chemicals in direct contact with the coffee beans and also may utilize supercritical carbon dioxide, which is carbon dioxide stored at a high pressure and temperature so it may be used as a decaffeination agent.
The direct contact method typically involves steaming green coffee beans for ½-hour and then rinsing them repeatedly with ethyl acetate or methylene chloride for approximately ten hours.
After the solvent is drained from the coffee beans they are steamed again for another ten hours with the goal of removing any residual solvent.
Indirect Contact Decaffeination
In the indirect contact method of decaffeination hot water is used to extract caffeine from green coffee beans and then chemical compounds are used to extract the caffeine from the extract.
In the indirect method, the coffee beans are first steamed or soaked for several hours in hot (nearly boiling) water to gradually draw the caffeine.
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.
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 coffee 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.
Achieving Equilibrium in the Coffee Decaffeination Process
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.
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.
Flavored Decaf Coffee Beans
Decaf coffee can be flavored in the same way that regular coffee beans can, meaning any flavor is available as a decaf coffee. Due to the work involved and the number of flavors available on the market, there are sometimes minimums required, but these can be as low as 10 pounds.
For more detailed information see the Espresso Coffee Guides Coffee and Espresso Glossary and also the detailed descriptions of the world's top gourmet coffee and Espresso Drink Recipes.
If you like history then see the World's Best History of Coffee.
For tips on preparing excellent espresso drinks see Pulling A Perfect Espresso Shot and How to make Lattes and Cappuccinos.
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