A major breakthrough in the scientific community’s quest to “taste” coffee without all those pesky humans getting in the way came this week courtesy of a group at the University of Oregon.
Published April 28 in Nature Communications, the study describes a technique called cyclic voltammetry — in which electrodes are immersed directly in brewed black coffee and a controlled electrical current is applied — to quantify key elements affecting coffee’s flavor.
The method focuses on two main variables: beverage strength and roast color.
“The reason you have an enjoyable cup of coffee is almost certainly that you have selected a coffee of a particular roast color and extracted it to a desired strength,” Christopher Hendon, a computational and food chemist who led the research, said in an announcement from the university. “Until now we haven’t been able to separate those variables. Now we can diagnose what gives rise to that delicious cup.”
Decoupling Strength and Color
Roasted coffee color, typically measured before brewing, and beverage strength, typically measured by a refractometer and expressed as total dissolved solids (TDS), are already two major areas of quality-control focus within the industry. Both have proven, in lab testing and through cuppings, to have outsize influence on the qualities of the finished cup.
Yet part of what the new study proposes is an “in situ” solution that might someday soon be used by working baristas to more consistently dial in extractions on the fly, complementing more time-intensive cuppings.
Refractometers remain a standard tool for estimating TDS, by measuring how light bends through liquid. But TDS captures only one part of the picture. Two coffees brewed to the same TDS can still taste very different if their roast colors differ.
The study authors said the voltammetric method serves to “decouple” the beverage strength from roast color, which “offers a strategy for rapidly assessing flavor-correlated chemical properties of coffee.”
Battery Testing Tech
The method repurposes a lab tool called a potentiostat, often used to test batteries and fuel cells. When a platinum electrode is immersed in coffee and voltage is applied, molecules in the coffee bind to the electrode surface. That binding suppresses the electrical current in a measurable way.
The stronger the coffee, the more current passes on the first scan. The darker the roast, the more aggressively subsequent scans are suppressed, because darker roasts produce more of the specific organic molecules that stick to the electrode.
The result is two independent readings from a single test, with one indicating strength and the other indicating roast color. Together, they capture what the study calls the coffee’s chemical fingerprint, producing a quantifiable target a barista or roaster could use.
“Since the 1950s, the coffee industry has sought quantitative methods to assess beverage qualities beyond those informed by sensory panels,” the study states. “In the meantime, a litany of research on the topic has revealed that beverage concentration, and roasted bean color, are the two primary and independent factors that dictate the sensory perception of coffee.”
History and Funding
The study was supported by the Coffee Science Foundation (CSF), the research arm of the Specialty Coffee Association (SCA), and underwritten by Italian coffee equipment company Nuova Simonelli, as well as by the U.S. National Science Foundation and the Camille and Henry Dreyfus Foundation. The paper also discloses that Hendon and co-author Doran Pennington have a financial interest in Overpotential, a company commercializing electrochemically modified food.
The study arrives as the SCA works to standardize measurement of roasted coffee color. The group supported research led by the UC Davis Coffee Center that proposed a “universal color curve” for roasted coffee. The SCA subsequently released a white paper called “Developing Roast Color Standards for the Specialty Coffee Industry.”
Hendon’s name may be familiar to many coffee professionals. DCN previously covered his involvement in the “Water for Coffee” research and book project with Maxwell Colonna-Dashwood. More recently, he led research on the Ross Droplet Technique to decrease static in espresso grinding.
Other authors on the new study include Robin Bumbaugh, Lena Wehn, Elias Rheingold, Joshua Williams and Benjamín J. Alemán.
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