Electrical current might be the key to a better cup of coffee

Source: Ars Technica

Background

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 discovers 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 Nature Communications.

We’ve been following Hendon’s work for several years. In 2020, his lab helped devise a mathematical model for brewing the perfect cup of espresso while minimizing waste. Espresso flavors derive from roughly 2,000 different compounds extracted from the coffee grounds during brewing, making it challenging for baristas to reproduce the same perfect cup repeatedly.

Extraction Yield Model

Hendon and his colleagues built a model for a more easily measurable property known as the extraction yield (EY)—the fraction of coffee that dissolves into the final beverage. EY 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, analogous to how caffeine molecules dissolve from coffee grounds.

Static Electricity and Clumping

Three years later, the team turned its attention to why microscopic clumps form, especially at very fine grind levels. The culprit is static electricity arising from the fracturing and friction between beans during grinding. Reducing that static could eliminate clumps. The technical term is triboelectricity, which occurs when opposite electric charges accumulate on the surfaces of two different materials due to contact.

A similar charge buildup also occurs during volcanic eruptions. Hendon collaborated with volcanologists Josef Dufek and Joshua Méndez Harper, who noted striking similarities between the science of coffee and plumes of volcanic ash, magma, and water.

Water Trick and Experimental Confirmation

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 reduction lessens clumping during brewing, yielding less waste and the strong, consistent flow needed for a tasty espresso. Good baristas already employ the water trick, known as the Ross droplet technique. This study is the first rigorous test of that hack, measuring the actual charge on different types of coffee.