The Science of Fermented Coffee: Scientists Discover the Compounds Behind Fermented Coffee’s Unique Flavor Profile
The world of speciality coffee is constantly evolving, and the latest innovation could transform your morning brew into a fruity sensation. Fermented coffee is the new buzz, boasting a raspberry-like taste and aroma that has puzzled coffee enthusiasts for some time.
But fear not, as scientists have finally demystified the six compounds responsible for this unique flavor experience.
Their groundbreaking research has the potential to increase the production of this delicious beverage, making it more accessible to coffee lovers worldwide.
These exciting findings are set to be presented at the upcoming ACS Spring 2023 meeting.
“There are now flavors that people are creating that no one would have ever associated with coffee in the past,” adds lead author Chahan Yeretzian. “The flavors in fermented coffee, for example, are often more akin to fruit juices.”
Fermented coffee is a unique beverage that provides a one-of-a-kind flavor experience for coffee drinkers. With an increasing demand for this delicious drink, farmers stand to benefit greatly from the high prices that fermented coffee beans can fetch. Moreover, the environmentally friendly process used to prepare these beans requires much less water than traditional methods, making it a sustainable alternative to your standard cup of coffee.
Despite its growing popularity, the compounds that give fermented coffee its distinctive flavor have remained a mystery, causing concern for some who worry about distinguishing genuine fermented coffee from adulterated versions. This is especially important as fermented coffee gains popularity in competitive events. Nonetheless, the recent breakthrough in identifying the six compounds responsible for its fruity aroma and taste offers new opportunities for the industry to standardize production methods, ensuring the availability of this unique and delicious brew for all to enjoy.
The team at the Coffee Excellence Center at Zurich University of Applied Sciences, led by Chahan Yeretzian, embarked on a mission to unravel the mystery behind the unique flavors of fermented coffee. Recognizing the intimate connection between flavor and smell, they conducted a study to better understand the complex flavor profile of this unusual beverage.
To pinpoint the compounds that contribute to fermented coffee’s distinctive aromas, researchers divided arabica beans into three groups. One group was processed using the washing method, which is commonly used in traditional coffee brewing. In this method, the mucilage layer is removed from the coffee bean by washing it with water before drying. The second group was prepared using the pulped natural process, where the coffee bean’s skin is removed, but the mucilage layer is left intact.
Moving on to the third group, the team took a novel approach by fermenting the beans using a winemaking technique called carbonic maceration. This method was first introduced to the speciality coffee industry in 2015 when the winner of the World Barista Championship used it to prepare their entry. In this process, whole coffee fruits are fermented in stainless steel tanks and infused with carbon dioxide to lower the pH of the fermentation. The resulting coffee was described as having an intense aroma of raspberries with a hint of rose, setting it apart from the other brews.
To analyze the samples and identify the specific compounds responsible for the unique aromas of fermented coffee, the researchers brewed coffee using each type of bean and used gas chromatography (GC) sniffing, also known as GC olfactometry. Using this technique, the GC instrument separated the individual components in the air above each sample, and as the compounds left the instrument, they were sent to a mass spectrometer for identification. The aroma and flavor notes were then described by a person sitting at the outlet, providing a comprehensive understanding of the compounds responsible for the fruity aromas of fermented coffee.
“Because the chemical signature doesn’t tell us how a compound smells, we have to rely on the human nose to detect the scent as each compound comes out of the chromatography instrument individually,” adds Yeretzian.
The methodology employed by the researchers has a subjective element to it, which can make it challenging to obtain accurate results.
“We’re using people to detect scents, and everybody perceives flavors a little differently,” adds Samo Smrke. “But in this case, the panel was very consistent in the smells they described. So, what is traditionally considered a challenge was actually not an issue because the aromas were so clear.”
One significant advantage of using GC sniffing is its ability to detect scents from compounds that are present in low concentrations and may not be detected by mass spectrometry. The researchers were able to identify three of the six compounds responsible for the intense fruity flavor and raspberry aroma of fermented coffee, namely 2-methylpropanal, 3-methylbutanal, and ethyl 3-methylbutanoate. However, there are still compounds that remain unidentified, and the team hopes to identify them in the future, along with assessing the intensity of different flavors and scents.
Moreover, the researchers aim to investigate the factors that influence the formation of these unique compounds, such as farming practices, coffee bean varieties, microclimate conditions, and the microbes present during fermentation. This knowledge could aid in the standardization of production methods and increase the availability of fermented coffee, further promoting sustainable and environmentally friendly coffee practices.
“There’s still quite a lot of unknowns surrounding this process,” points out Smrke.
Obtaining a deeper understanding of the sources of the compounds responsible for the fruity aroma and taste of fermented coffee could be instrumental in standardizing production methods. This knowledge could make it easier to produce fermented coffee on a larger scale, which would allow more people to enjoy this distinctive and delicious flavor.
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