Why do some people find coffee to taste more bitter than others?

20 February 2025
مصطفى الحداد
Why do some people find coffee to taste more bitter than others?

Why do some people find coffee to taste more bitter than others? Researchers from the Leibniz Institute for Food Systems Biology at the Technical University of Munich have come a step closer to answering this question. They have identified a new group of bitter compounds in roasted Arabica coffee and studied how they influence the taste of bitterness. In addition, they have demonstrated for the first time that an individual’s genetic predisposition also plays a role in determining how strongly a person perceives these bitter substances produced by the roasting process.

Although caffeine has long been known to be a bitter substance, decaffeinated coffee still tastes bitter. This suggests that other substances also contribute to the bitter taste of coffee. The starting point for this research was the compound mozambioside , found in Arabica beans, which has a taste about ten times more bitter than caffeine and activates two of the 25 types of bitter taste receptors found in the human body, the TAS2R43 and TAS2R46 receptors. “Our studies showed that the concentration of mozambioside decreases significantly during the roasting process, making it only a small contribution to the bitterness of coffee,” says lead researcher Roman Lang. “This prompted us to test whether the breakdown products of mozambioside produced by roasting also taste bitter and could influence the taste of coffee.”


The effect of molecular interaction and genetic predisposition


As the research team shows, seven different mosambiside breakdown products are formed during roasting. These compounds are present in roasted coffee in varying concentrations, depending on the temperature and duration of roasting, and are almost completely transferred to the beverage during brewing.

Studies in a cell-based test system developed at the institute showed that these roasting products activate the same bitter taste receptors as mosambicoside. Three of the products had a stronger effect on the receptors than the original compound. However, the researchers found that the concentration of these compounds in brewed coffee was too low to have a noticeable effect on taste on their own. Only when mosambicoside and its breakdown products were combined, eight of the eleven subjects were able to detect bitter taste. One person experienced an astringent taste, and two others did not detect any particular taste.

Genetic testing showed that taste sensitivity depended on the genetic predisposition of the subjects: two people had two defective copies of the TAS2R43 gene, seven people had one defective and one healthy copy of the gene, and only two people had two healthy copies of the gene.


What do these results mean for the future?

“These new findings enhance our understanding of how the roasting process influences coffee flavour, and open up new possibilities for developing coffees with harmonious and balanced flavours,” says Roman Lang. “They also represent an important breakthrough in flavour research, as well as in health research,” he adds. “Bitter substances and their receptors play other physiological roles in the body, most of which are still unknown.”

According to Lang, there is still a lot of work to be done, as for many of the bitter substances found in coffee alone, the bitter taste receptors that activate them have not yet been identified, even though millions of people around the world consume coffee daily.