Next time you take a sip of coffee and scrunch your nose at its bitter taste, your DNA might be to blame. New research from scientists in Germany has uncovered fascinating insights into why Arabica coffee’s signature bitterness varies from person to person, and it’s not just about how dark the roast is.
The study, published in Food Chemistry, was conducted at the Technical University of Munich’s Leibniz Institute for Food Systems Biology. Researchers have identified a new group of bitter compounds formed during coffee roasting.
“Indeed, previous studies have identified various compound classes that contribute to bitterness. During my doctoral thesis, I have now identified and thoroughly analyzed another class of previously unknown roasting substances,” says study author Coline Bichlmaier, a doctoral student, in a statement.
While caffeine has long been known as coffee’s primary bitter component, even decaffeinated coffee tastes bitter, indicating other compounds are at work. At the heart of this bitter business is a compound called mozambioside, found naturally in raw coffee beans. It’s about ten times more bitter than caffeine and particularly abundant in naturally caffeine-free coffee varieties. However, this may not be at the root of that bitter taste.
“Our investigations showed that the concentration of mozambioside decreases significantly during roasting so that it only makes a small contribution to the bitterness of coffee,” says principal investigator Roman Lang.
Through detailed chemical analysis, researchers tracked mozambioside as coffee beans roasted. They found it breaks down into seven specific compounds, each contributing its own bitter properties. Using ultra-high-performance liquid chromatography and mass spectrometry, essentially very precise chemical detection methods, they measured exactly how much of each compound forms during roasting and transfers into your cup.
When studying Colombian Arabica coffee specifically, they found that not everyone experiences these bitter compounds the same way. A specific gene called TAS2R43, which codes for one of our approximately 25 bitter taste receptors, plays a crucial role. About 20% of Europeans have a deletion in this gene, meaning they’re missing that particular bitter taste receptor entirely.
In standardized taste tests with 11 volunteers, researchers analyzed each participant’s DNA using saliva samples to determine their TAS2R43 gene status. Their genetic test revealed that two participants had both copies of the TAS2R43 gene variant defective, seven had one intact and one defective variant, and only two people had both copies fully intact.
The results revealed striking differences in bitter perception based on genetics. When combining mozambioside with its roasting products in a sample, eight out of eleven test subjects perceived a bitter taste, one found it astringent, and two didn’t notice any particular taste.
During roasting experiments at different temperatures, researchers discovered that some bitter compounds peaked at 240°C, while others continued increasing up to 260°C. These findings join our existing knowledge about other bitter-tasting substances formed during roasting, including compounds called caffeoylquinides (from chlorogenic acids), diketopiperazines (from coffee proteins), and oligomers of 4-vinylcatechols (from caffeic acids).
Bitter taste receptors aren’t only found in our mouths. They exist throughout the body in various organs and tissues. Studies indicate they help fight pathogens in our respiratory tract, assist with defense mechanisms in our intestines and blood cells, and may play a role in metabolism regulation.
“The new findings deepen our understanding of how the roasting process influences the flavor of coffee and open up new possibilities for developing coffee varieties with coordinated flavor profiles,” says Lang. “They are also an important milestone in flavor research, but also in health research. Bitter substances and their receptors have further physiological functions in the body, most of which are still unknown.”
With global production reaching 102.2 million 60-kilo bags of Arabica coffee in 2023/24, understanding these bitter compounds and their perception is major. For coffee lovers and producers alike, this research provides scientific validation for something many have long suspected: we really do experience coffee differently from one another, and it’s written in our genes.
Source : https://studyfinds.org/why-coffee-tastes-different-to-everyone/
