How is caffeine eliminated from coffee beans?
While modern decaffeination methods are exceedingly effective and selective, they do have the potential to modify the coffee's flavor and aroma.
Caffeine is present in some products of vegetable origin that humans routinely consume, with coffee being the main and most characteristic source. From a chemical point of view, it is a molecule of the alkaloid type whose effects on human physiology have been desirable.
For example, it can induce a state of alertness, minimizing the sensation of tiredness and favoring concentration, which makes it a psychoactive type compound (with an effect on the central nervous system). But some people may not like or even be able to handle these effects, which is why the market for decaffeinated coffee grew.
Methods for removing caffeine from coffee beans
The general process to remove caffeine from coffee beans is based on one of four possible methods; two based on the use of organic solvents directly or indirectly; the use of water (without organic solvents); and the use of carbon dioxide (CO2).
In the direct method, the solvent comes into contact with the bean and directly removes the caffeine from it. In the indirect method, water is used to extract the caffeine, then the solvent removes the dissolved caffeine, and the water (without caffeine or solvent) is subsequently placed in contact with the coffee beans so that they reabsorb the aroma or flavor compounds that may have been extracted initially.
The method that only uses water is similar to the indirect method, but instead of using solvents to get rid of the caffeine that the water extracted, activated carbon is used.
Finally, the process based on carbon dioxide uses this compound as a solvent, for which it must be compressed at high pressures until it reaches a state known as supercritical, which increases its capacity to dissolve and extract caffeine.
The solvent-based methods were the first to be used since about 1900. Before that, different substances were used, but methylene chloride and ethyl acetate were two of the safest.
Methylene chloride was commonly used until the seventies as it was of minimal toxicity to humans, even more so at the low concentrations at which it could be detected in coffee treated with it. Later, ethyl acetate, a compound naturally present in coffee and many other foods, was used. Since people often drink it, ethyl acetate is a safe chemical to use in the decaffeination process.
One of the first water-based processes was developed in the 1930s and continued to be perfected during the following decades. Even though not using organic solvents has its benefits, water can't be used to only extract caffeine. This makes coffee with less aroma and flavor, so solvent-based methods were generally thought to be better.
The use of supercritical carbon dioxide is the most modern option. This allows the efficient extraction of caffeine with minimal impact on the rest of the components of the bean. Among its advantages is that it is non-toxic, is eliminated from the coffee, and does not contaminate. However, it requires specialized equipment and methods of high cost, which makes the final product more expensive.
In the last twenty years or so, researchers have looked into other methods, such as hybridization, which creates plants that don't have caffeine or have much less of it. However, decaffeination methods are still the best choice.
Although decaffeination is considered highly efficient and selective in modern times, the process can alter some of the desirable characteristics of coffee, especially its aroma or flavor, but techniques continue to be modified so that the impact is minimally perceptible. There is evidence that a moderate amount of coffee, even decaffeinated coffee, can be good for your health in many ways, no matter how it was made.
Source: CIAD, Food and Development Research Center