The subject of fermentation and the fermentable state of coffee has opened a new door for us, qualified coffee makers. The chocolate/hazelnut/caramel flavors that we have been accustomed to for centuries in coffee have now been replaced by rich, aromatic flavors of red fruits. But what lies beneath the feelings that the complex structures of these red fruits leave in us?
While scientists / we have not been able to summarize the exact structure and complexity of this matrix as a result of our long-term studies on coffee chemistry, the fermentation step has taken things to a more complicated but equally exciting stage. As of today, scientists can present six basic compounds that contribute to the fermented coffee experience. The researchers will present all their results at the American Chemical Society spring meeting, and we will be sharing them with you here.
This unusual beverage type offers a unique taste experience for consumers, and the increasing demand for it means that fermented coffee beans can be sold for a premium, potentially benefiting farmers. And the process of preparing the beans requires much less water than traditional methods, making it a more environmentally friendly alternative to a standard cup of coffee. But despite the drink’s growing popularity, the compounds responsible for its distinctive aroma were unknown. So, at the Coffee Center of Excellence at the University of Applied Sciences Zurich, they set out to identify the compounds responsible for these new and exciting flavours. Since flavour and smell are closely linked, studying the scents of the drinks could help the team better understand how the complex flavour of fermented coffee is created. To isolate the compounds specific to fermented coffee’s aromas, the researchers took arabica beans and separated them into three groups. One was prepared using a washing process, which is probably how your average afternoon brew is made. Here, a gelatinous substance known as mucilage is scraped from the coffee beans, which are washed with water before being dried. The researchers prepared the second group using another common approach, the natural pulping process, where the hulls are removed from the beans but the mucilage is left intact. Finally, the team fermented the third group of beans using carbonic maceration, a process often used in winemaking. This method was first introduced to the world of specialty coffee in 2015, when the winning competitor used it to prepare his entry at the World Barista Championship. With this process, which has been covered in detail on the blog before (you can find the posts here ), whole coffee berries are fermented in stainless steel tanks and infused with carbon dioxide to lower the pH of the fermentation. Unlike other brews, the coffee made with the fermented beans has been described as having an intense scent, like raspberry with a hint of rose.
Next, the researchers brewed coffee using each type of bean and analyzed the samples using gas chromatography (GC) sniffing, also called GC olfactometry. First, the GC device separated individual components in the air above each sample. Then, as the compounds exited the device, they went into a mass spectrometer for identification and someone sitting at the exit to describe what they smelled like. "Since the chemical signature doesn't tell us what a compound smells like, we have to rely on the human nose to detect the odor as each compound exits the chromatography device individually," says Yeretzian, who led the study.
This methodology can be misleading because it has a subjective element. “We use humans to perceive odors, and everyone perceives tastes a little differently,” says the research assistant at the lab presenting the results. “But in this case, the panel was very consistent in what they described. So what would traditionally be seen as a challenge wasn’t really a problem because the aromas were so clear.” GC sniffing has a key advantage. The human nose can sometimes detect odors from compounds at concentrations too low to be detected by mass spectrometry. In this case, the team was able to identify only three of the compounds that appeared to contribute to the intense fruitiness and raspberry smell of fermented coffee: 2-methylpropanal, 3-methylbutanal, and ethyl 3-methylbutanoate. In the future, the researchers hope to identify the remaining compounds, as well as assess the intensity of the different tastes and smells. Additionally, the researchers are determined to learn more about how these unique compounds are formed. Potential factors include farming practices, the variety of coffee beans, the microclimate of specific farms, and the microbes present during fermentation. “There are a lot of unknowns surrounding this process,” the researchers added.
A better understanding of the sources of these compounds could help all of our teams standardize production methods, making it easier to produce fermented coffee on a larger scale and allowing even more people to enjoy its distinctive flavor.
The subject of fermentation opens new doors for us in the unique coffee bean and seems to occupy our agenda with pleasure for a long time. We continue to expand our work in this direction and contribute in synchronization with the world.
DUYGU KURTULUŞ
Co-Founder / Chemist / Nanotechnology Engineer / Hazardous Chemical Consultant / Chemical Evaluation Specialist