Wet coffee beans entering the grinding hopper. Credit | University of Oregon
What happens when a volcanologist and a coffee expert walk into a bar? They come out with a paper and an improved method to brew espresso.
The unique collaboration between Portland State University’s Josh Méndez, assistant professor of Electrical and Computer Engineering, and Christopher Hendon, a chemist at University of Oregon, may sound like the start of a joke, but Méndez argues their mutual interest in coffee can lead to more opportunities for collaboration between disciplines.
“There’s a lot more to know about how coffee breaks, how it flows as particles, and how it interacts with water,” he said. “These investigations may help resolve parallel issues in geophysics — whether it’s landslides, volcanic eruptions, or how water percolates through
soil.”
The new paper, “Moisture Controlled Triboelectrification During Coffee Grinding” published in Matter this week explores a long-known issue in the coffee industry: the static electricity produced by coffee grinding that causes clumping. The electrification process is not unlike a process that occurs during volcanic eruptions.
“During eruption, magma breaks up into lots of little particles that then come out of the volcano in this big plume, and during that whole process, those particles are rubbing against each other and charging up to the point of producing lightning,” Méndez said. “In a simplistic way, it’s similar to grinding coffee, where you’re taking these beans and reducing them to fine powder.”
Measuring the amount of static electricity produced by grinding various beans showed that moisture content was a factor. It turns out that spritzing beans with a little water before grinding reduces the amount of static electricity that produces clumping. This small change means a more consistent brew, more concentrated espresso, and less waste, Méndez said. Increases in concentration mean that a few cents worth of coffee may be saved per cup. Roughly, these savings could result in $250,000,000 per year in coffee saved in the European or American markets.
Although the primary focus of PSU’s new Hazards and Coffee lab, led by Méndez, is the development of sensors and lab experiments to study natural hazards such as volcanic eruptions, wildfires and earthquakes, the coffee experiments will continue. At the moment, his lab is exploring the physics involved in preparing pour over coffee, degassing of CO2 during coffee storage and the traditional grinding techniques used in La Huasteca region in Mexico.
Doing this work in Portland is particularly rewarding for Méndez given the city’s vibrant coffee culture, but studying coffee has a number of similarities with the natural disasters he researches. For example, comminution — the process by which solid materials are reduced from one average particle size to a smaller average particle size — occurs during both coffee grinding and rock avalanches. The mathematics that dictate how water flows through ground coffee also apply to groundwater traveling through soil, or how magma percolates through porous structures.
“Studying the granular and fluid dynamics of coffee may help us produce tastier cups of coffee, but may also give us insight into complex phenomena that occur at large scales on Earth and other worlds,” Méndez said.