Electrochemistry Technique “Tastes” Coffee’s Flavor Profile

Grind size, roasting time and temperatures, brewing length, water temperatures… There’s a lot that goes into making a good cup of coffee.

Making a consistently good cup is a challenging task. In addition to there being so many variables to juggle, there is also the fact that scientists aren’t entirely sure exactly how these variables all come together to affect the flavor profile of a particular cup of coffee. Human taste testers can provide valuable feedback, but without measurement techniques that can empirically assign numerical values to a cup, it can be hard to separate out all those variables and identify how they influence the perfect brew.

Scientists at the University of Oregon have developed a simple way to evaluate the flavor profile of a cup of coffee—by harnessing electrochemistry.

Chasing the perfect cup

Coffee beans are agricultural products and so, just like any other fruiting crop, there are many different variables that might affect the attributes of a given harvest.

While those factors are outside the control of your standard coffee aficionado, most coffee drinkers will agree that differences in roast darkness and extraction strength can make a big impact on taste. Artisan coffee roasters and specialty cafes invest a lot of effort into fine-tuning these variables to deliver a consistent product to their customers.

“The absolute quality [of a coffee] depends on the seed quality, but the attributes the seed will exhibit depends heavily on how the coffee is roasted and prepared. That is, darker roast coffee will exhibit different qualities to that of a light roast analogue,” study author Christopher H. Hendon, associate professor of chemistry at the University of Oregon, told Technology Networks. “Regardless, looking more closely at the preparation side, there are five basic variables that affect coffee flavor and intensity: mass of coffee, mass of water, water temperature, grind setting, and brew time. Different brew methods affect the qualities of the extract to different extents.”

For professional baristas and coffee roasters (and perhaps the most dedicated coffee enthusiasts), it’s relatively easy to assess the intensity or the strength of a coffee. Commercially available refractometers can be used to measure how light bends as it passes through a beverage, with higher refractive indices indicating a stronger brew. However, this method does not tell you much about the coffee’s overall flavor profile—for that, there needs to be a measurement of both strength and roast darkness.

While liquid chromatography–mass spectrometry could perform this task, slow run times, high equipment costs, and the technical expertise needed to parse out useful data in the complex coffee matrix make this an impractical solution.

“In 2020, we received research funding to help pioneer quality measurements in coffee. The industry had coalesced around other indirect measurement techniques that provided some information about concentration, but omitted information about composition,” Hendon said.

“Electrochemistry offered a strategy to probe both concentration and composition together. Other groups had invoked the technique to study portions of coffee composition, but there remained this knowledge gap that prevented electrochemistry from being a practical technique to parse both flavor and intensity.”

Electrochemistry can determine a coffee’s strength and roast type

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The solution Hendon’s team found was hiding in plain sight. In the battery industry, a potentiostat is used to test the performance of batteries and fuel cells by manipulating the voltage between a working electrode and a reference electrode, providing an accurate measurement of current flow. This process, known as cyclic voltammetry, is extremely sensitive to the material composition of the electrodes. In a similar fashion, the team hoped it would be very sensitive to minor changes in the coffee’s qualities.

“Cyclic voltammetry is a technique where an electrical power source is used to apply a controlled voltage and measure the current passed through the circuit. In the case of cyclic voltammetry on coffee, the coffee acts as a resistor—the resistance depends on the number of molecules and types of molecules in solution. Different molecules react to different applied voltages, so the technique can separate molecular families using their voltage response,” Hendon explained.

“The voltammetry technique allows you to simultaneously determine the strength of a cup of coffee (i.e., the number of grams of coffee per liter of water), and separately, how darkly roasted the coffee is that is imparting the coffee flavors. Thus, the technique is sensitive to both concentration of coffee and roast color, independently,” he continued.

“The approach therefore allows you to determine whether coffee has been brewed to a consistent concentration, if the coffee itself does not vary in color. It also allows you to determine whether the roasts are different for coffees with the same concentration. Roasters may make this determination with their tongues, and we can perform at least as well as the human tongue to discern the same differences in roasts.”

To prove how well the potentiostat works in practice, the team sourced four batches of coffee from a specialty coffee roaster in England. While all four batches of beans looked identical to the human eye—they had all been roasted to the same target color—one of the four batches had been rejected by the roaster for being slightly too light and thus not having the desired flavor during taste testing.

The roaster provided the beans in bags labelled 1–4 and did not specify which bag had failed their internal quality control. After brewing in triplicate to account for manual variations, color analysis and refractive index tests failed to identify any differences between coffees made from the four bean batches.

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However, cyclic voltammetry measurements correctly determined that the coffee made from bag 1 was statistically dissimilar to those made from bags 2–4. Once this conclusion was reached, the roaster confirmed that bag 1 was indeed the rejected batch.

“Every coffee ever consumed has gone through a quality control protocol to determine the consistency and attributes of the resultant extracts. Presently, this process relies entirely on the tongues of select tasters working for importers, exporters, roasters, and cafes. While the quality of a coffee does terminally depend on human preference, our approach assigns a numerical value to a property otherwise assigned by taste and discussion,” Hendon said.

“Of course, we are not trying to replace the critical step of tasting coffee, but rather the technique is extremely valuable in placing a numerical value on roast-dependent qualities. The technique will certainly expand in use with time. Some cafes and roasters are already implementing the techniques and teachings of this work.”

Reference: Bumbaugh RE, Pennington DL, Wehn LC, et al. Direct electrochemical appraisal of black coffee quality using cyclic voltammetry. Nat Commun. 2026. doi: 10.1038/s41467-026-71526-5

About the interviewee:

Prof. Christopher H. Hendon is a computational chemist with interests in energy materials and coffee extraction. He obtained his BSc. Adv. HONS from Monash University (2011) and PhD from the University of Bath (2015). After a two-year postdoc at the Massachusetts Institute of Technology, he joined the University of Oregon in 2017, where he is an associate professor of chemistry. His research group focuses on materials with useful defects. He has published over 150 papers, was named a Cottrell Scholar in 2021, a Camille Dreyfus Teacher-Scholar in 2022, the Samuel R. Scholes Jnr. Lecture for excellence in scientific communication, and has been awarded the Rippey Award for Innovative Teaching twice. In coffee, he authored, “Water for Coffee”, and has written numerous peer-reviewed articles on the topic. Presently, he leads a laboratory studying the chemical physics of coffee beverage production.