University of Oregon chemist Christopher Hendon loves his coffee—so much so that studying all the factors that go into creating the perfect cuppa constitutes a significant area of research for him. His latest project: discovering a novel means of measuring the flavor profile of coffee simply by sending an electrical current through a sample beverage. The results appear in a new paper published in the journal Nature Communications.
We’ve been following Hendon’s work for several years now. For instance, in 2020, Hendon’s lab helped devise a mathematical model for brewing the perfect cup of espresso, over and over, while minimizing waste. The flavors in espresso derive from roughly 2,000 different compounds that are extracted from the coffee grounds during brewing. So it can be challenging for baristas to reproduce the same perfect cup over and over again.
That’s why Hendon and his colleagues built their model for a more easily measurable property known as the extraction yield (EY): the fraction of coffee that dissolves into the final beverage. That, in turn, depends on controlling water flow and pressure as the liquid percolates through the coffee grounds. The model is based on how lithium ions propagate through a battery’s electrodes, similar to how caffeine molecules dissolve from coffee grounds.
Three years later, Hendon’s team turned their attention to studying why the microscopic clumps form in the first place, particularly at very fine grind levels. The culprit is static electricity arising from the fracturing and friction between the beans during grinding. Hendon thought reducing that static would be a good way to eliminate those clumps. The technical term is triboelectricity, which arises from the accumulation of opposite electric charges on the surfaces of two different materials due to contact with each other.
A similar charge build-up also occurs during volcanic eruptions. So Hendon collaborated with volcanologists Josef Dufek and Joshua Méndez Harper, who were regulars at the same local coffee house and had noted striking similarities between the science of coffee and plumes of volcanic ash, magma, and water.
Their experiments confirmed that adding a single squirt of water to coffee beans before grinding can significantly reduce the static electric charge on the resulting grounds. This, in turn, reduces clumping during brewing, yielding less waste and the strong, consistent flow needed to produce a tasty cup of espresso. Good baristas already employ the water trick; it’s known as the Ross droplet technique. But this was the first time scientists had rigorously tested that well-known hack and measured the actual charge on different types of coffee.