How Does Decaf Coffee Get Decaffeinated?

Whether it’s drip, cold brew, French press, or pour over, coffee is a part of many people’s routines in the morning — and beyond — thanks to the burst of energy we get from caffeine.

But sometimes you want to enjoy an afternoon cup of coffee without getting too wired or disturbing your sleep. That’s where decaf comes in. Decaf coffee doesn’t come from a different type of plant than the caffeinated stuff. It’s the same exact beans, but with the caffeine physically extracted from them before brewing. 

But how does that work? And is any cup of coffee truly free of caffeine?

Bean Baths

On its own, caffeine is an organic crystal compound made of carbon, hydrogen, nitrogen, and oxygen atoms. It’s naturally present in harvested coffee beans, which are actually seeds of ripe fruit from coffee plants, and removing it to create decaffeinated coffee requires several steps — regardless of what method is used. 

Solvent-based methods are the most popular, due to their affordability, and can be conducted directly or indirectly. In the direct method, coffee beans are steamed before they are roasted. (Since they come from plants, coffee beans are actually green and only turn brown when roasted.) 

This makes them more porous and absorbent, allowing a chemical solvent (typically methylene chloride or ethyl acetate to be more effective).

After they’re steamed, beans are soaked for several hours in the solvent, which binds to the caffeine. Chemically speaking, the caffeine molecules jump ship, from the beans to the solvent. The beans are then rinsed and steamed again, washing away and evaporating the solvent — and with it, the caffeine.

In the indirect solvent-based method, coffee beans are soaked in hot water rather than the solvent. The water draws out the caffeine, as well as the flavors from the beans. Then, the beans are removed, and the solvent is added to the flavored, caffeinated water — never coming in direct contact with the beans. 

The caffeine still binds with the solvent, though. Instead of being transferred from the beans, it makes a pit stop in the water first. What’s left is caffeine-free, coffee-flavored water, in which the beans are soaked again to reabsorb their flavor, aroma, and oils. This indirect solvent-based method is commonly referred to as the “European method.”

Both methods that use solvents such as methylene chloride or ethyl acetate are somewhat controversial, as these chemicals are also used in harsh substances such as paint stripper and nail polish remover, and trace amounts may remain in the beans. Methylene chloride is suspected to be a carcinogen and can cause eye, skin, liver, and heart injuries and damage, but the FDA permits coffee beans to be sold if they only contain 10 parts per million (0.001%) of the chemical. 

Chemical-Free Decaf

For those who would prefer leaving chemicals out of the decaffeination process completely, other methods exist. One uses carbon dioxide, introducing CO2 to the beans in a high-pressure chamber, where it binds to the caffeine to extract it. 

The principle is essentially the same, using CO2 instead of controversial chemicals. However, the equipment needed makes it a much more expensive alternative. Another option is the Swiss Water Process, which is common for organic decaf coffee. In this method, water is used to extract caffeine from coffee beans through several steps.

First, the beans are soaked in hot water, which absorbs both their caffeine and flavor. The caffeinated water then passes through activated charcoal filters that catch larger caffeine molecules but let flavor pass through. A new batch of coffee beans are soaked in the remaining flavored water, which will dissolve the caffeine. This time, though, the flavors aren’t removed, since the beans are already saturated in water with the same flavor. 

No matter which method is used to decaffeinate coffee beans, around 3% of caffeine remains. That means an 8 oz cup of decaf has 5-10 mg of caffeine, compared to the 95 mg you’d find in regular coffee. 

You’d need to drink more than 10 cups of decaf to get the amount of caffeine present in just one regular cup of joe. Then again, for some serious coffee drinkers, 10 cups is nothing.