Specialty coffee has become increasingly popular in recent years, with some experts questioning whether the specialty coffee segment is growing faster than the global coffee industry itself. Now, a new fermented coffee offering could further diversify the growing range of coffee available on the market. The underpinnings of the fermented coffee's unique raspberry-like flavor and aroma have been a mystery, however.
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Now, scientists from the Coffee Excellence Center at Zurich University of Applied Sciences have identified six compounds that are crucial to the sensory experience of fermented coffee. Their findings, presented at the spring meeting of the American Chemical Society (ACS) 2023, unravel the mystery of fermented coffee's fruity flavors.
Specialty coffee gains popularity
Americans are drinking coffee more than in the last 20 years; for 60% of the US population, coffee is a daily habit. The global coffee market was valued at $126.38 billion in 2022 and is expected to grow at a CAGR of 6.7% from 2023 to 2028. The specialty coffee market accounts for a significant segment of this global market, as it is predicted to grow rapidly over the next decade, growing at an annual rate of 12.8% from 2022 to 2030.
Due to this growing demand for specialty coffee, unique flavors, such as those produced by fermented coffee, can garner a high price. By establishing fermented coffee in the coffee market, farmers can benefit from sales of their beans, and the Earth can benefit from the more environmentally-friendly bean preparation method, which uses less water than traditional methods. To support fermented coffee's rapid growth in popularity, researchers at Zurich University recognized the need to gain a deeper understanding of how its flavor profiles are achieved.
Unveiling compounds responsible for scent and taste with gas chromatography sniffing
Smell and taste are intrinsically linked. So to understand the flavors of fermented coffee, that are, according to the study's lead researcher, Chahan Yeretzian, PhD, "are much more akin to fruit juices," the team designed a study to investigate the scents of fermented coffee.
The researchers prepared arabica beans in three distinct ways. For the first group, they used the wash process, a common method used in the preparation of average coffee. For the second group, they used the pulped natural process, another frequently used method. Finally, they fermented the third group using carbonic maceration, commonly used in winemaking and has only been used in coffee preparation since 2015. In this process, the entire coffee fruits are fermented and infused with carbon dioxide to reduce the pH, resulting in coffee that smells similar to raspberries with a hint of rose.
Next, each preparation of coffee was brewed and analyzed with gas chromatography sniffing. The preparation components were separated, identified by a mass spectrometer, and finally smelled by a human nose to detect the scent that its chemical signature cannot define. While the human perception of smell is vulnerable to subjectivity, the panel was consistent in how they described the smells.
The team concluded that three compounds were responsible for the fruity scent and flavor of the coffee, of which they identified three: 2-methyl propanal, 3-methybutanal, and ethyl 3-methyl butanoate.
Future work to identify remaining compounds
The researchers intend to follow up their research with future studies to identify the remaining compounds. Furthermore, they aim to discover more about how these compounds form. It is theorized that farming practices, coffee bean type, microbes present during fermentation, and the farm microclimate may be contributing factors. This research could help coffee producers standardize their production methods and make producing fermented coffee at a large scale possible.
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