Hardcore coffee lovers are always on the lookout for the next big evolution in the world’s favorite caffeinated beverage, and these days it’s brewed coffee that turns heads and tickles the taste buds with its signature fruity aroma. Scientists in Switzerland have been conducting experiments with brewed coffee in hopes of identifying the specific chemical compounds behind the beverage’s unusual profile.
“There are now flavors that people make that no one would have associated with coffee in the past,” Shahan Yertzian saida scientist at the Coffee Center of Excellence at Zurich University of Applied Sciences, who Submit your search During the recent American Chemical Society meeting in Indianapolis. “The flavors in brewed coffee, for example, are often more akin to fruit juices.”
Most coffee is lightly brewed because it naturally occurs when the processed beans are soaked with moisture, which breaks down enzymes and produces sugars. It also facilitates the removal of peels and pulp. In this case, we are talking about green coffee beans that have already undergone that initial processing. The beans are then soaked in water mixed with carefully selected strains of yeasts and bacteria and left to ferment for a few days. Fruit or other flavorings are often added during this stage or the beans are fermented in casks formerly used to store whisky, rum, or other liqueurs. The beans are then washed, dried, and roasted as usual.
Yeretzian and research partner Samo Smrke used Arabica beans and split them into three batches. In the first batch, the beans were washed, removing the degumming (the inner layer of pulp) before drying. For the second batch, they removed the shell (shell) from the beans but left the gummy. For the third batch, they fermented the beans in stainless steel tanks using Carbon soak, the same process for making wine. This process involves infusing carbon dioxide into ponds to create an anaerobic environment to lower the pH while the beans are fermenting.
For the chemical analysis, Yertzian and his colleagues used a combination of gas chromatography, which separates volatile chemical compounds in a given substance into individual components, and mass spectrometry, which identifies those components. They also recruited a group of human “sniffers” because flavor and aroma are closely related. And the human nose can sometimes detect odors at concentrations so low they would escape a mass spectrometer, although the perception of odors can be completely subjective.
“We use people to detect smells, and everyone perceives flavors a little differently,” said Smrke. But in this case, the panel was very consistent in the scents they described. So, what is traditionally considered a challenge wasn’t actually a problem because the aromas were so obvious.”
The experiments yielded six distinct compounds that contribute to the unique flavor of brewed coffee. However, the team was only able to definitively identify three: 2-methylpropanal, 3-methylbutanal and ethyl 3-methylbutanoate, all of which are associated with the “distinctive raspberry notes with a hint of rose water” of both Yeretzian and Smrke. The other three compounds were detected by human sniffing, but eluded mass spectrometry.
Understanding how aromas are produced will help producers perfect and possibly standardize their brewing processes, according to Yeretzian, which is currently done largely by trial and error. Brewed coffee is expensive and not always readily available, but standardization can increase its availability. “We hope to bring these flavors to the average consumer so that they can also experience these coffees with unique and delicious flavours,” said Smrke.
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