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So you wanted a decaf    Nov 19, 2018

So you wanted a decaf
Nov 19, 2018


De heer Wouter MARCHAL



You enter a bar with some friends, still rubbing your hands together to overcome the freezing cold of the winter wonderland you just escaped from. You’re craving for a hot drink. A delightful cup of coffee perhaps? However, it’s already late and you don’t want to give up a good night’s sleep. Luckily for you, the place you just entered offers decaf coffee. A couple hours later you’re turning around in bed for the 200th time wondering why you can’t seem to fall asleep. Was it truly decaf coffee that you drank earlier that night? Or did they screw you over with a regular one? Let’s find out.


“Without coffee, something’s missing.” – Al Pacino. 

When you order a decaf cup of coffee somewhere, do you really get one? In order to settle this urban myth once and for all Hasselt University and local newspaper ‘Het Belang van Limburg’ joined forces. Together they collected 30 cups of decaf coffee from bars all over the province, which they then subjected to some rigorous and thorough testing.

“Coffee is a complex mixture of various substances, including caffeine, antioxidants, and aromas. However, it is not that difficult to separate and determine the amount of caffeine in it”, lab assistant Jenny Put explains. “Our chemistry students do these type of experiments during one of their courses to learn how to work with the technique.”

“The 30 samples are evaluated using a technique called high-performance liquid chromatography”, dr. Wouter Marchal tells us. “We dilute and inject the coffee sample into the device after which it is passed over a column. This column is a type of special separation system, consisting of functionalized silica micro-particles, that will slow down substances like caffeine as compared to others by a certain amount based on their polarity. As a result, the different components that are present within the coffee mixture are excreted out of the column at different time points. We can identify their chemical composition using a special detector and register not only which molecule it is but also how much of it is present. We can then calculate this back to the amount present in a standard cup of coffee.“


“The results were quite surprising. A cup of decaf will always contain a small account of caffeine, due to its production process. Decaf is made out of real coffee beans from which the caffeine is extracted before they are roasted using chemical processes without trying to lose the characteristic flavors and aromas.  Unfortunately, this production process is of course not perfect resulting in 0 - 3 % of caffeine remaining behind."

"However, a stunning 1 out of 6 cups of decaf coffee contained a dose of caffeine that was even higher than the regular coffee standard we used and are therefore not decaf. Variations in a normal cup of coffee are caused by a wide array of factors such as the species of coffee, the grain size, the brewing process, the filtering time, the ratio of coffee to water and the temperature of the water.”

“In addition to this, over 50 % of the tested decaf coffees contained more than double the amount of caffeine as compared to the standard decaf coffee we used. This is likely due to insufficient cleaning of the machine, but this is of course more of an educated guess.

So next time when you order that delicious cup of decaf coffee on a cold evening there might be a chance that it will be a sleepless evening.