February 7, 2025, 4:46 pm | Read time: 5 minutes
Coffee is one of the most popular drinks in Germany. And yet, coffee tastes different to everyone. Some enjoy the bitter substances in black coffee; others only like it with milk and sugar. A study from Germany has now found out why people taste coffee differently.
According to the German Coffee Association, an average of three and a half to four cups of coffee are drunk per capita in Germany.1 Per day, mind you. And since not all Germans drink coffee, many coffee lovers probably drink more than four cups a day. At home, at least, the majority (45 percent) drink coffee with milk, whereas 34 percent enjoy it black.2 The remaining 21 percent indulge in specialty coffees such as espresso, cappuccino, or latte macchiato. Obviously, not everyone likes the bitter taste of coffee. However, as previous studies have shown, black coffee, in particular (without sugar and milk), is healthy due to its bitter substances. German scientists have now discovered why people taste coffee differently and may not like it for this reason.
Overview
It’s Not Just Caffeine that Makes Coffee Bitter
The fact that coffee tastes bitter is nothing new. But why do people experience different levels of bitterness? Researchers from the Leibniz Institute for Food Systems Biology at the Technical University of Munich have now clarified this question in a study.3 It is interesting to note that although caffeine is one of the bitter substances responsible for the taste, decaffeinated coffee also tastes bitter. From this, the researchers from the Leibniz Institute concluded that other bitter substances must also be present in coffee.
“Previous studies have indeed identified various classes of compounds that are formed during roasting and contribute to bitterness. During my doctoral thesis, I have now identified and analyzed in detail another class of previously unknown roasting compounds,” explains study author Coline Bichlmaier in a press release from the institute.4
Researchers Investigated Mozambioside in Arabica Beans
To get to the bottom of the bitterness, the scientists focused on the ingredient mozambioside, which is found in Arabica beans. According to the researchers, it tastes around ten times more bitter than caffeine. It also activates two of the 25 or so bitter receptor types in humans: TAS2R43 and TAS2R46. However, during the course of the study, it was discovered that the concentration of mozambioside decreases significantly when roasted. Surprisingly, in the end, it only made a small contribution to the bitterness of the coffee, states study leader Dr. Roman Lang. “This gave us the idea of testing whether roasting produces degradation products of mozambioside, which also taste bitter and can influence the taste of coffee,” explains study leader Dr. Lang.
And indeed, the research team found that seven different degradation products of mozambioside are formed during roasting. The decisive factors here are roasting temperature and roasting duration, which lead to the different concentrations of these degradation products in the roasted coffee. These are then released into the popular hot drink during brewing. The researchers were then able to prove in cellular studies that these roasting substances activate the same bitter receptors as mozambioside.
Genetic Factors Influence the Perceived Bitterness
Nevertheless, the roasting substances alone were not enough to be perceived as bitter. Only in combination with mozambioside did test subjects perceive the drink as bitter. Interestingly, the researchers found that not everyone perceived these bitter substances to the same extent. Only eight out of eleven test subjects perceived a bitter taste in the coffee infusion. One person perceived the taste as astringent, and two other test subjects did not perceive any particular taste. Astringent means a dry, sharp mouthfeel – perhaps you know it from drinking red wine.
But why was the perception of taste so different? To find out, the scientists looked at the bitter receptor type TAS2R43 in the test subjects. To do this, they analyzed the participants’ DNA using saliva samples. The genetic tests revealed that both copies of the TAS2R43 gene variant were defective in two participants, while seven had one intact and one defective variant of the receptor. Only two subjects had completely intact copies of TAS2R43. This was a clear indication that taste sensitivity depended on the genetic predisposition of the test subjects.
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Coffee Taste Could Be Better Adapted in the Future
Other studies have already shown that our genetics apparently determine whether we like bitter substances and therefore like black coffee or dark chocolate – which are known to have a positive influence on health. However, this also means that many people who do not like bitter substances could develop unhealthy routines and, for example, sweeten a lot.
The current study by the Leibniz Institute for Food Systems Biology can help us to understand our perception of taste better. And also make a contribution to health research, as Dr. Roman Lang emphasizes. “Bitter substances and their receptors have other physiological functions in the body, most of which are still unexplored,” says Dr. Lang. A great deal of research is still needed, however, as many of the bitter substances in coffee alone are not yet known, nor which bitter receptors they activate. However, the study could also contribute to enjoyment by better adapting the roasting processes in future so that coffee does not taste too bitter.