Okay but seriously, how is decaffeinated coffee made? How does this process affect the flavour? (I'm assuming it does because decaffeinated coffee seems to be the source of much derision...)
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Basics
Decaffeination (decaf) is the removal of caffeine from coffee beans, cocoa, and other caffeine-containing materials. While soft drinks which do not use caffeine as an ingredient are sometimes described as "decaffeinated", they are better termed "uncaffeinated" because decaffeinated implies that there was caffeine present at one point in time. Decaffeinated drinks contain typically 1–2% of the original caffeine content or sometimes as much as 20%.
In the case of coffee, various methods can be used. The process is usually performed on unroasted (green) beans, and starts with steaming of the beans. They are then rinsed with a solvent that extracts the caffeine while leaving other constituents largely unaffected. The process is repeated from 8 to 12 times until the caffeine content meets the required standard (97% of caffeine removed according to the international standard, or 99.9% caffeine-free by mass as per the EU standard). Coffee contains over 400 components important to the taste and aroma of the drink, so it is difficult to remove the caffeine without affecting other components.
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Well, then, let's talk about the two most common types of decaffeination:
Swiss Water process
The use of water as the solvent to decaffeinate coffee was originally pioneered in Switzerland in 1933 and developed as a commercially viable method of decaffeination by Coffex S.A. in 1980.
This method is different in that it does not directly or indirectly add chemicals to extract the caffeine. Rather, it relies entirely on two concepts - solubility and osmosis - to decaffeinate coffee beans. The process begins by immersing a batch of green coffee beans in very hot water in order to dissolve and extract the caffeine. The water is then drawn off and passed through an activated charcoal filter. The porosity of this filter is sized to only capture larger caffeine molecules, while allowing smaller oil and flavor molecules to pass through it. However, this extraction process will also extract desirable oils and other solids from the beans, resulting in beans with no caffeine and no flavor in one tank, and caffeine-free but with flavor water in another tank. The Swiss Water process method attempts to overcome this difficulty by first discarding the flavorless caffeine-free beans, and then reusing the flavor rich water to remove the caffeine from a fresh batch of coffee beans. Water saturated in this way is referred to as green coffee extract or GCE. It is created using a separate batch of green coffee beans, which are immersed in water and then discarded. In a pre-loading tank water, cane sugar and formic acid are mixed and heated and used to preload carbon filter columns. The GCE is then filtered over the columns to extract caffeine from it. A fresh batch of green coffee beans is then immersed in the GCE to remove caffeine but retain other components. The other components can be retained because the water is already saturated with flavor ingredients, therefore, the flavors in this fresh bath cannot dissolve - only caffeine moves from the coffee beans to the water. This results in decaffeination without a massive loss of flavor. The process of filtering the GCE to remove caffeine and immersing the beans is repeated until the beans are 99.9% caffeine free by mass, meeting the required standard. This process takes 8 to 10 hours.
CO2 process
it is technically known as supercritical fluid extraction. This method is the most recent method developed by Kurt Zosel, a scientist of the Max Plank Institute, and uses liquid CO2 in place of chemical solvents.
The supercritical CO2 acts selectively on the caffeine, releasing the alkaloid and nothing else. Water soaked coffee beans are placed in an extraction vessel. The extractor is then sealed and liquid CO2 is forced into the coffee at pressures of 1,000 pounds per square inch to extract the caffeine. The CO2 acts as the solvent to dissolve and draw the caffeine from the coffee beans, leaving the larger-molecule flavor components behind. The caffeine laden CO2 is then transferred to another container called the absorption chamber where the pressure is released and the CO2 returns to its gaseous state and evaporates, leaving the caffeine behind. The caffeine is removed from the CO2 using charcoal filters and the caffeine free CO2 is pumped back into a pressurized container for reuse on another batch of beans. This process has the advantage that it avoids the use of potentially harmful substances. Because of its cost, this process is primarily used to decaffeinate large quantities of commercial-grade, less-exotic coffee found in grocery stores.
There are like 3 more common processes but I believe 2 is enough, even for coffee enthusiasts like us.
Sourced from https://en.wikipedia.org
