Grinding coffee is a complicated job. Static electricity builds up on the floor, leaving a sticky mess inside the grinder. Now, a team of chemists and volcanologists at the University of Oregon have uncovered exactly how moisture affects static formation, and they’ve found a simple solution.
According to researchers, spraying the beans with some water before grinding cuts static electricity. It also creates a more consistent, stronger-tasting espresso shot.
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The new study, published in the journal Matter, may not come as a shock to passionate coffee enthusiasts who have honed their techniques over years of intuition, experience and tips traded in online forums. For example, some baristas use an already wet teaspoon to stir coffee beans or squirt water over the beans to reduce static; this is a practice known as the “Ross Droplet Technique” or RDT. But the new paper systematically shows how moisture in coffee beans affects charge formation and how this can be manipulated.
“The idea that there is some sort of electrical build-up in the coffee grounds is a pretty old observation. If you’ve never seen an industrial-scale roastery, you can see the coffee grounds flying into the air and sticking everywhere,” said founder William Ristenpart. is the director of the Coffee Center at the University of California, Davis, who was not involved in the research. “The nice thing about this paper is that it puts some solid science, some solid data behind understanding the mechanism.”
The paper also sheds further light on the emerging field of coffee science, which brings together experts from seemingly incompatible disciplines to conduct dozens of drinkable experiments and investigate the basic science behind a cup of coffee.
Case in point: The new study was a partnership between scientists interested in coffee grinding and volcanologists fascinated by the lightning storms created during eruptions. These scientists not only work in different laboratories; They live in fundamentally different scientific universes, publish in specialized journals, and attend separate conferences.
But over a cup of coffee, the two teams realized they were studying the same fundamental phenomenon. Whether it’s a burr grinder that shatters beans or an explosive explosion that turns rocks to ash, friction and fractures result in tiny particles that accumulate an electrical charge in the process.
While many details of their research may be difficult to understand for the casual coffee drinker, their article contains simple, actionable results for a person trying to keep a tidier kitchen or a barista trying to create an efficient and more intense shot of espresso.
“If you are going to grind whole bean coffee, adding a small amount of water to the whole beans before grinding will make the coffee more accessible when you brew it,” said coffee chemist Christopher Hendon. University of Oregon and one of the leaders of the research.
So by using this method you “get more coffee out of your coffee.”
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Discovering common ground
The collaboration began in Hendon’s coffee lab at the University of Oregon, which hosts regular coffee hours.
Josh Méndez Harper, then a postdoctoral researcher in a volcanology laboratory, began participating as a casual coffee drinker; the kind of person who swallows everything given to him without a second thought. However, over time, he became a regular and started drinking coffee.
One day he overheard Hendon and others discussing how electricity was generated during grinding.
“I said, ‘Oh! I’ve spent the last five years doing this, but in a different context,'” Méndez Harper said. he recalled. To study how charge builds on volcanic ash, volcanologists sometimes use a device called a Faraday pot. Despite its name, this has nothing to do with booze; It’s a conductive metal container, and scientists can use it to measure the charge of individual particles, then calculate the density of that charge by weighing them.
Scientists decided to cooperate. Using a simple, custom-made Faraday cup machined to fit the groove of their coffee grinder, they set out to see if they could make similar measurements for coffee grounds.
In experiments ranging from grinding commercially produced coffee to roasting its own beans at different levels, the team found that moisture modulated the amount of charge in the coffee grounds. Lighter roasts with more internal moisture gained less static charge during grinding and tended to become positively charged. Darker roasts, which were drier, gained more charge and tended to accumulate negative charge.
Scientists were intrigued by the fact that coffee sometimes charges in one direction and sometimes in the other, and that internal humidity plays an important role.
“This was something no one could have predicted,” said analytical chemist Samo Smrke of the ZHAW Zurich University of Applied Sciences in Switzerland, who was not involved in the study.
One approach used in the coffee industry involves a beam of charged particles called an ion beam, Smrke said. Sending positive or negative ions can neutralize the coffee’s charge, but without knowing whether the coffee will create a charge in both directions, the beam that neutralizes the charge in one type of coffee may worsen the condition of the other.
In this case, scientists found that they could suppress the charge completely by simply adding external moisture, such as a squirt of water, before grinding.
Reducing static not only reduced mess, but also prevented clumps in the coffee. This means that when brewing espresso, water reaches all the coffee grounds evenly, increasing the concentration of the final product by approximately 10 percent. (Brewing results do not apply to coffee made with a French press or other brewing methods that involve soaking the grounds in water.)
Experts said the study is an important example of how much scientific fruit remains in the coffee world, with opportunities to bring rigorous experimental techniques and measurements to something many people do once or more a day.
“There are a lot of things that haven’t been researched properly,” said Chahan Yeretzian, head of the Center of Coffee Excellence at ZHAW Zurich University of Applied Sciences, who was not involved in the new research.
Josef Dufek, a volcanologist at the University of Oregon, says coffee is a fascinating model system and plans to apply similar techniques to understand volcanic ash. Méndez Harper sees connections to even more exotic questions. Dunes of carbon-rich sand on Saturn’s moon Titan can be similarly affected by static charging as particles rub against each other.
But Méndez Harper is addicted to coffee. He plans to continue this multidisciplinary research as he establishes his own laboratory at Portland State University.
“If you brew pour-over coffee, the physics and mathematics there are the same as when you apply it to water percolating through soil or magma moving through a porous rock matrix,” Méndez Harper said. “There are many parallels between coffee and earth sciences beyond static formation.”
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