There are several reasons to choose decaf coffee, and while not everyone is a big fan (though we hope to convert you with the Decaf Pouch) the decaffeination process is quite interesting. In our previous post, you read about when decaffeination happens in the coffee bean-to-cup process. Now, you’ll read more about the how.
Traditionally, decaffeination happens in the green bean stage, that is: after the coffee beans have been dried but before roasting. These green beans are sent to an industrial decaffeination facility before they are sent to the roasters, adding an extra transportation step. In the decaffeination facility, there are three commonly used methods to get as much of that caffeine out of the beans as possible: the chemical solvent method, the CO2 method, and the water method.
Decaffeination using chemical solvents
As the name suggests, the chemical solvent method uses chemical solvents to extract the caffeine from the bean. In the first step, coffee beans are steamed so the pores open, allowing the solvents to seep deeper into the bean. In the second step: repeated rinsing by either methylene chloride or ethyl acetate - the two most common solvents used in decaffeination. Caffeine is very soluble in both of these solvents, and is therefore almost completely removed from the bean. The beans are then steamed again, to remove any traces of the chemicals. While decaffeination with a chemical solvent is the most widely used method for decaffeination, both chemicals are very volatile and can react with the atmosphere to produce smog, which will damage the environment.
Decaffeination using CO2
The CO2 method uses “supercritical CO2” as a solvent. When CO2 gas is heated above its critical temperature while pressurized above its critical pressure, it starts behaving as a supercritical fluid, which have both gaseous and liquid properties. Coincidentally, one of those properties is that it acts as an excellent solvent for molecules such as - you guessed it - caffeine. Similar to the method described above, beans are soaked in the solvent, which dissolves and drains the caffeine out. This process is very energy intensive, the gas has to be compressed to 3500 psi, and therefore also quite expensive, and not used that often.
Decaffeination using water
But decaffeination does not have to rely on solvents necessarily. A third often-used method for specialty coffees just uses water. In the water methods, a batch of beans is soaked in hot water to dissolve the caffeine. This also dissolves all the wonderful coffee flavor molecules and oils. The now flavorless beans are discarded, and the water is passed through an activated charcoal filter which removes the caffeine molecules, but not any of the oils or flavor molecules. This water is the “green coffee extract”. The green coffee extract is used to osmotically remove caffeine from a new batch of beans. Osmosis means that caffeine molecules are drawn out of the beans, while all the flavor remains in the beans - the green coffee water is already saturated with flavor molecules! This process, known as the Swiss Water process or the Mountain Water process (depending on the location of the industrial plant) sounds a lot “cleaner” than the other two, but causes a lot of CO2 emissions in the process of cleaning the charcoal filters. In addition, a whole batch of beans is wasted in the first step to make that green coffee extract.
Are there other ways?
As we touched on in our previous post, the process of pre-roast decaffeination damages the green coffee beans making them difficult to roast and often resulting in a lower quality product that might not taste as good. In addition, none of these methods are particularly environmentally friendly. Volatile solvents, high energy costs, or CO2 emissions, in addition to transporting beans halfway around the world; we would all like to avoid those. Perhaps a green, environmentally friendly, post-brew decaffeination method would be preferable? We sure think so!
Written by Valerie Bentivegna
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