How are coffee beans decaffeinated?

All coffees naturally have caffeine in them after they are roasted.  If you’ve heard that light coffees have more caffeine than dark roasts, that is partially true.  It all depends on if you measure by volume or by weight when brewing.  Either way, there is still a good amount of caffeine in any roast.  So then, how do we get decaf coffee?

There are several different decaffeination processes that can be used.  One way is to use a solvent that specifically targets caffeine, so as not to strip away other natural chemicals in the coffee bean that contribute to its flavor.  Methylene chloride is one such solvent that can be used.  It is applied to the green coffee beans before roasting and then evaporates during the roasting process. The use of methylene chloride is somewhat controversial because, as with any chemical, it can be harmful in high enough doses.  The FDA has banned its use in paint thinner and other products.  However, the FDA has determined that methylene chloride can be safely used in the decaffeination process, so long as any residue that remains after the roasting process (i.e. methylene chloride that did not evaporate) is less than 10 parts per million.  This method removes roughly 96% to 97% of the caffeine from a batch of coffee and some argue is the best method for flavor retention.

Those who prefer a more natural method of decaffeination may opt to use Ethyl acetate, which is found naturally in fruit sugars.  This method is often referred to as the Sugar Cane or “Natural” method of decaffeination since producers ferment sugarcane molasses to produce the ethyl acetate used in the process.  Ethyl acetate is used as a solvent just like methylene chloride.  This method also removes about 97% of the caffeine from a batch of coffee and tends to sweeten the coffee ever so slightly.

For a completely chemical-free decaffeination process, producers favor the Swiss Water Method, sometimes referred to as just the water method, because it only uses water to remove the caffeine.  This process must be used on multiple batches to be effective.  First, an initial batch of coffee is soaked in hot water.  This dissolves the caffeine as well as other flavor components of the coffee.  The water is then filtered through an activated charcoal filter, leaving flavorless beans in one tank and a vat of very flavorful, caffeinated water in the other.  The flavorless beans are then discarded, and a new batch of green coffee beans fills the tank. These beans are also soaked in hot water and then filtered like the first batch into the same vat.  However, because the tank of flavored caffeinated water is already saturated with flavor molecules and the filter is actually sized to catch the large caffeine molecules, this second batch ends up retaining its flavor but is dissolved of its caffeine.  This method is most often used to decaffeinate organic coffees and removes 99.9% of the caffeine from a batch.