How Do You Remove Caffeine From Coffee?

It's no coincidence that the two most popular non-water drinks in the world, tea and coffee, contain robust amounts of society's most-consumed drug: caffeine. In America, consumers overwhelmingly prefer the morning joe; a recent Pew study showed that over three-quarters of those surveyed opted for coffee over tea. Of that, the vast majority never order decaf. Still, that hasn't stopped science from perfecting the methods of decaffeination, developing a process that is a miracle of modern chemistry.

Decaffeination dates back to 1903, when a German coffee merchant, Ludwig Roselius, began experimenting with ways to remove its energizing component. As to why Roselius would be inspired to mess with what was arguably his product's chief selling point, legend says it was out of personal vendetta. He believed too much caffeine played a role in the early death of his father, a professional coffee taster, and sought to exact revenge against the murderous chemical. The "Roselius process," as it became known, involved steaming coffee beans in a brine solution, before using benzene to extract the stimulant.

While a good premise for a revisionist action film, Roselius' quest to avenge his father's death probably did more harm than good. Scientists later identified benzene as a particularly nasty carcinogen. Still, the seeds had been planted, and Roselius' foundation would soon be adapted upon, this time with more refined, less cancerous results.

Today, coffee is most often decaffeinated through three main methods. You might want to grab a cup of the real stuff now, because this is where it all gets a bit complicated.

In around 70 percent of the market, solvent-based processing is by far the most popular means of decaffeination, in which methylene chloride or ethyl acetate is used to extract it from the coffee bean. In the indirect method, beans are soaked for a few hours in near-boiling water to remove a large portion of the caffeine, as well as other flavor and oil components. The beans are then transferred into a separate tank and washed for around 10 hours in a mixture containing one of the solvents. During this time, the solvent selectively bonds with the remaining caffeine, and it's then heated to evaporate both undesired elements. The beans are then returned to the original water containing the flavorful oils and other aromatic compounds to absorb them.

Ethyl acetate is more often included in the direct-solvent process, in which liquid waves of the chemical are run through a bed of previously steamed beans, then captured by an evaporator. Because ethyl acetate is found in some ripening fruits, this process is often touted as an "all-natural" or "organic" method. But rarely—if at all—is the solvent extracted from actual fruit. Instead, the chemical is synthetically produced from other ingredients, sometimes including petroleum derivatives.

"In reality, they're extremely volatile compounds—any residual chemical that people would be worried about is generally not an issue," explains Matt Cronin, co-owner of Mojo Coffee Roasters in New Orleans, Louisiana. "They cook off at about 100 degrees. I roast coffee at 400 degrees."

If you're still leery about coffee that includes—and tastes like—fossil fuel, a couple other methods are gaining traction. The Swiss Water Method, patented and owned by a single operator in Vancouver, British Columbia, is a method to use just water in its decaffeination (and thus, making it the rare certified "organic" decaf coffee). Unlike the previous solvent-reliant steps, superheated water is run through coffee beans, extracting the caffeine as well as almost all of the flavor components. The bland beans are discarded while the water containing all the coffee chemicals is run through an activated charcoal filter—pretty much the same process as a Brita filter—that's only porous enough to capture caffeine. What's left is a nearly 99.9 percent caffeine-free liquid known as "Green Coffee Extract," or GCE. The GCE is used in lieu of water for a new batch of coffee beans so that, this time, the flavor is never lost as the caffeine is once again removed.

The most recently developed method relies on liquid carbon dioxide circulated through green, pre-moistened coffee beans at a force of nearly 1,000 pounds per square inch, or 70 times normal atmospheric pressure; think of this as deep sea coffee-making. At this high intensity, liquid CO2 takes on "supercritical" properties that make it highly effective as a solvent, so that it selectively adheres to caffeine molecules as it's pumped through factory vessels. The caffeine-laden CO2 is then depressurized in a separate container, returning the carbon dioxide to gas while leaving the caffeine behind to be sold to beverage manufacturers for such things as energy drinks. Because it's so naturally occurring, CO2 is one of the cheapest solvents to employ. As such, the "Supercritical Carbon Dioxide Method"—while sounding a lot like a Bond villain plot—is also the process most often used in the high-batch decaf yields needed for the generic brand coffee found at your grocery store.

In summation, the process to decaffeinate coffee has a pretty lousy labor-to-yield ratio, given that only about 12 percent of the coffee market consumes it. Worse yet, the end product is often derided by coffee purists.

"Ninety-five percent of the time, as a person who drinks coffee professionally, I find it very difficult to drink decaffeinated coffee," says Cronin. "Just certain aromatic qualities are inevitably taken out during the process. I have had [only] one decaffeinated coffee in my life that was so good it blew my mind."

That being said, Cronin is the first to admit that decaf isn't a totally lost cause, especially when viewed as something not necessarily made for the general populace.

"Look, there's plenty of good decaf out there," he says. "If you have a heart condition or something, and you've been told by your doctor you can't drink caffeine—that decaf is a godsend."