One of the most exciting prospects in decaf coffee is the possibility of growing coffee trees that are naturally free of caffeine and while researchers are currently conducting field trials, we’re probably at least a decade away from that becoming a commercial reality. Until then, we will need to rely on removing caffeine from coffee after it has been harvested and before it is roasted. If you care about decaf tasting its best, it’s worth knowing a little about how caffeine is extracted and how the different processes affect the coffee and your health. There are four common methods of decaffeination:
The Swiss Water Process
The Swiss Water Process, or the Mountain Water Process as it is known in Mexico, is probably the most widely used method in specialty coffee. As the name suggests, the caffeine is removed using only water. While the benefit of this process is that it doesn’t use “chemicals” (though water is a chemical - dihydrogen monoxide - albeit a natural one), it does have its drawbacks. When decaffeinating coffee, we want to remove as much caffeine as possible without removing or adding anything else, while also minimising the damage to the structure of the coffee bean. The problem is that water isn’t selective in terms of what it removes from coffee. Along with caffeine, other beneficial, water-soluble compounds are removed by the water. The Water Process tries to offset this by filtering the caffeine out of the water and then recirculating the water through the coffee beans for 8-10 hours so that they reabsorb the beneficial water-soluble compounds. In my experience, coffee that has been through this process often has a grain or cereal flavour not originally present in the coffee that I personally don’t enjoy.
The other drawback of the Swiss Water Process is that the only plant is in Canada. Coffees decaffeinated using this method need to be shipped from their country of origin to Canada, and then onto Australia - sometimes via a third location. This adds additional cost, reduces freshness and increases the carbon footprint of the coffee. Coffee grown in Mexico can be decaffeinated using the Mountain Water Process at Descamex in Mexico. I’ve enjoyed some of the Mexican decafs I’ve tasted, so I can’t help but feel that decaffeinating coffee close to where it was produced helps create a better tasting coffee.
Ethyl Acetate Sugarcane Process
Ethyl Acetate (EA), better known as the Sugarcane Process, is also widely used to decaffeinate specialty coffee. Despite the menacing name, EA is a naturally occurring ester formed from acetic acid (vinegar) and ethanol (alcohol) and is present in fruit, including coffee cherries. In fact ethyl acetate is the most common ester in fruit. EA is often extracted by fermenting sugarcane, hence why it’s called the Sugarcane Process. This process has a number of advantages:
EA is very effective at binding to caffeine, making it easier to remove the caffeine while leaving behind the tasty stuff;
It’s a less destructive process, avoiding excessive heat or pressure, thereby maintaining the structure of the coffee, as well as the original flavour of the coffee;
EA has a low boiling point of 77 degrees, making it easy to remove any traces of ethyl acetate in the coffee after processing. After processing, the coffee will have a maximum 10ppm of EA - a banana contains 200ppm.
Ethyl Acetate tends to be the preferred method of decaffeination for high quality Colombian coffee as they have an EA plant in Colombia, allowing their coffee to be decaffeinated straight after harvest and without needing to ship the coffee to the other side of the globe. In my experience, this method of decaffeination does a very good job of maintaining the original character of the coffee.
Carbon Dioxide Process
A less common method of extracting caffeine from coffee is to use liquid carbon dioxide. Without getting overly technical, when carbon dioxide is in a liquid state, it’s able to bind with caffeine, but not when it’s a gas. Decaffeination plants like CR3 pass liquid carbon dioxide through the green coffee beans where it binds with the caffeine. The liquid carbon dioxide and caffeine solution is then moved to an evaporation vessel where the carbon dioxide is returned to its gaseous state, leaving behind the caffeine. Like EA, CO2 is a very selective solvent, binding almost exclusively with caffeine, leaving other good things intact. This process does require very high pressure (7000kpa or 1015psi) in order to keep the CO2 in a liquid state. It’s also a very slow process, resulting in the decaffeination process taking 1 week to complete. Both the high pressure and length of process are likely to detract from the quality of the end product.
Carbon dioxide is another example of a safe process that uses a natural chemical (water, ethyl acetate and carbon dioxide are all naturally occurring chemicals) to remove caffeine from coffee. I have only sampled a CO2 decaf once, as a part of James Hoffman’s The Decaf Project and I was impressed with the taste of the coffee. Unfortunately I have never seen a CO2 decaf in Australia.
Methylene Chloride
Mass produced decaf is often decaffeinated using Methylene Chloride (DCM). Similar to other processes, DCM binds with the caffeine, allowing it to be removed from the coffee. While some feel that DCM maintains coffee flavour better than other processes, DCM is known to be a neurotoxin and has been banned by the EPA for various industrial uses like paint stripper. The FDA, however, still allows its use in decaffeination as there is very little residual DCM in the coffee. Despite this, we feel that the other processes listed above do a great job of removing caffeine with zero risk. We know that many women drink decaf when pregnant or breastfeeding, a time when you don’t want to take any health related risks, regardless of how small. Do Coffee Roasters does not, and will never, sell coffee that was decaffeinated using DCM.
There’s a lot of noise and disinformation around decaf. The near ubiquity of the Swiss Water Process and their marketing have created the illusion that this is the safest and best process for removing caffeine, and that we don't need to look any further. If you’re drinking specialty decaf, you can be confident that the water process, EA Sugarcane process and CO2 process are all safe. The question is, do you have a personal preference for the taste of one of the processes? It’s worth trying coffees processed using different methods to see which you like, because there’s no point drinking coffee if it isn’t delicious.