Decaf coffee is growing in popularity, but many people do not know how decaf coffee is made. If you're looking to buy decaf coffee, it's important to know what goes into it and how it's processed. In the past, shockingly, coffee was decaffeinated using chemical solvents that were used in paint strippers! The use of such harmful chemicals raised alarm amongst consumers, and today there are safe ways to decaffeinate coffee without the use of said chemicals.
That being said, we hope to provide some insight and clarity to the various ways decaf coffee is made and if it's safe to consume.
History of Decaffeination
The first commercially successful decaffeination method for coffee was invented in 1903 by Ludwig Roselius, a German coffee merchant and founder of the company Kaffee HAG. His method was coined the Roselius process. In the Roselius process, coffee beans are steamed with a brine solution (salt water) and then treated with the chemical solvent benzene to extract the caffeine. (Source)
This process is no longer used though, because it was discovered that benzene causes cancer in humans. However, there are now safer and better ways to decaffeinate coffee beans.
Here's a quick video on how decaf coffee is made:
The Four Main Decaffeination Methods Today
There are two groups of decaffeination methods, with two variations in each group. There are two solvent-based processes and two non-solvent based processes.
In the solvent-based decaffeination processes, there is the indirect-solvent and the direct-solvent method. With non-solvent based processes, there is the Swiss water method and the carbon dioxide method. As the names suggest, the categories differ based on the use of solvents.
The solvents used in solvent-based decaffeination include benzene, trichloroethylene (TCH), dichloromethane, chloroform, methylene chloride, and ethyl acetate. The first four were chemicals used in the early stages of decaffeination and have since been marked as carcinogenic or toxic solvents, so methods today using solvents use either methylene chloride or ethyl acetate.
While the FDA states that methylene chloride, a volatile, colorless liquid with a chloroform-like odor, has little to no health risk, it is a chemical often used in paint stripper. However, very little amounts of it end up decaffeinated coffee beans because it is usually evaporated during the roasting process (it vaporizes at 109 Fahrenheit).
On the other hand, ethyl acetate is a colorless liquid with a characteristic sweet smell and the synthetic version is used in glues and nail polish removers. However, it’s found naturally (it's the source of the sweet smell in ripe fruit), so often people think it is safer than other solvents. Most decaffeination processes will use the synthetic version since the natural version is very expensive to use.
In this method, coffee beans are soaked in water at a rolling boil for several hours. The water collects the flavor and oil components from the beans, which are then drained and transferred to another tank and washed for about 10 hours with either methylene chloride or ethyl acetate. The chemical solvent selectively bonds with the caffeine molecules and extracts them out of the coffee.
The remaining mixture is then heated to evaporate the solvent and caffeine. The beans are then recombined with the water to reabsorb the coffee oils and flavor compounds.
This method is popular in Europe and primarily uses methylene chloride as the solvent. So this method is also known as “The European Method” or “Euro Prep.”
In this method, coffee beans are steamed for about 30 minutes to prime them for caffeine extraction. Then, they are rinsed with either methylene chloride or ethyl acetate for about 10 hours. The caffeine-laden solvent is then drained away and residual solvent is removed by steaming the beans again.
The solvent of choice in this method is usually ethyl acetate, so you’ll often see it referred to as “Natural Decaffeination Method" or "Natural Decaf" or "Sugar Cane EA Decaf.
This process uses Ethyl Acetate, a natural byproduct of sugar production as a solvent to remove caffeine. Keep in mind not all EA coffees use the natural byproduct. More commonly they have to use EA that was created in a lab. EA coffees, when fresh, are our favorites for espresso. We find that they tend to be sweeter and have more body than water process coffees. Unfortunately, they have a short shelf-life after roasting, degrading quickly, definitely within a couple weeks to a more beefy stew like flavor. Of course the level of this degradation depends on the bean itself, the EA, the roast etc.
Typically, if a process is not named for a decaffeinated coffee, it has been treated with Methyl Chloride. This method is not commonly listed on a bag of beans, because who wants to advertise the use of harsh chemicals to decaffeinate the coffee? Most Decaf's will state if they are 'water processed' or 'Natural/Sugar processed.' If the company doesn't mention any of these things, there is a strong possibility the coffee was decaffeinated using the MC process.
MC coffees are purchased for one reason: they are cheap. If you are paying less than $12 for a 12oz bag of beans, this is what you are getting: coffee that has little to no caffeine but tastes like someone poured gasoline on it.
Non-Solvent Based Decaffeination
Water Processed Decaf or Swiss-Water Process (SWP)
The Swiss Water Process, also known as Water-Processed Decaf, relies on caffeine solubility and osmosis to remove caffeine from coffee beans. First, coffee beans are soaked in hot water to "dissolve" caffeine, however, sugars and other flavor compounds in coffee also dissolve into the water. In order to create flavorful coffee, the resulting mixture is run through a charcoal filter. Caffeine is a large molecule, so it gets filtered out while the sugars and flavor compounds remain in the water, which is called Green Coffee Extract. The extract is used to soak the next batch of green coffee beans, so the flavor is retained by the beans and only caffeine is removed and the process repeats.
This method will consistently be better over time. This process leads to tasting notes from the specific coffee to be retained, being that the process uses water as a solvent for caffeine as opposed to other solvents. You may see Mountain or Swiss water processes on a given bag of coffee. These are pretty much the same exact processes.
Swiss water is a patented name and can only be done a few places in the world. So often this process, although very much the same as mountain water process, is less sustainable because the beans usually need to be transported to another country before going to the beans' final destination. Water-Processed coffees have cleaner, more pleasant flavors, although slightly less intense or muted and they degrade in quality slower over time.
Carbon Dioxide Process (CO2)
Which Process is the Best Decaffeination Process?
Decaffeination processes have their pros and cons, so your next cup of decaf coffee will depend on your preferences. However, it's good to be aware of how each process works and what chemicals to look out for if a coffee roaster does decide to process their coffee with solvents.