This Simple Trick Will Help You Brew Better Coffee, According to Scientists

New research explores how moisture affects static electricity and clumping of ground coffee beans

Coffee pouring into small white cup from espresso maker
Adding water to beans before grinding them can help produce a more flavorful brew and cut down on mess, according to a new study. Pixabay

Sipping a cup of freshly brewed coffee is a beloved daily ritual in many households. And while some coffee aficionados invest in high-tech equipment or special beans, scientists have now described an even simpler way to achieve a satisfying brew.

Adding a bit of water to beans before grinding them helps boost the flavor of the ensuing drink, according to new research published Wednesday in the journal Matter. On top of that, this easy step helps reduce the messiness of the grinding process and cut down on wasted coffee.

Baristas and other coffee experts have long known that spraying beans with a bit of water or stirring them with a wet spoon helps reduce static during grinding. But the new research explains the scientific underpinnings of this intuited technique.

“The idea you get some type of electrical buildup in coffee grounds is a pretty old observation,” says William Ristenpart, a chemical engineer and director of the Coffee Center at the University of California, Davis, who was not involved in the research, to the Washington Post’s Carolyn Y. Johnson. “What’s cool about this paper is it’s putting some hard science, some hard data, behind understanding the mechanism.”

For the study, researchers gathered coffee beans that had been roasted for varying lengths of time and, thus, had different levels of internal moisture. Then, they sprayed the beans with differing amounts of water before grinding and brewing them into espresso shots. In each batch of ground coffee, they recorded the size of the coffee particles and the amount of static electricity.

But the effort wasn’t purely about coffee. The study’s first author is actually a volcanologist, and examining electrostatic charges in coffee grounds provided a small-scale model for understanding the particles of magma that spew from erupting volcanoes.

“During that whole [eruption] process, those particles are rubbing against each other and charging up to the point of producing lightning,” first author Joshua Méndez Harper, a volcanologist at Portland State University, says in a statement. “In a simplistic way, it’s similar to grinding coffee, where you’re taking these beans and reducing them to fine powder.”

As the team brewed their coffees, they found the moisture in the beans before grinding correlated with electrostatic charge: Drier beans—like darker roasts, which have been roasted for longer—gained more charge during grinding, and that charge was often negative. Wetter beans, like lighter roasts, gained less charge that was more positive.

The greater the amount of charge, the clumpier the grounds became—and vice versa. When it comes to brewing a tasty cup of joe, less clumping is better, because this allows the water to reach all the grounds evenly. The researchers found that adding a splash of water before grinding can lead to less charge, fewer clumps and a roughly 10 percent boost in concentration of the resulting coffee, per the Washington Post.

“Espresso is the worst offender [for clumping], but you would also see the benefit in brew formats where you pour water over the coffee or in small percolation systems like a stovetop Bialetti,” says study co-author Christopher Hendon, a chemist at the University of Oregon, in the statement. “Where you’re not going to see a benefit during brewing is for methods like the French press, where you submerge the coffee in water.”

So, next time you make coffee at home, you might consider skipping the fancy gadgets and expensive beans. Add a tiny bit of water to any beans before grinding, and treat yourself to a cup of scientifically optimized brew.

“It’s not about the origin or the processing method,” Hendon tells New Scientist’s Alex Wilkins. “It’s not about the quality of the coffee or the price that one might pay for those particular beans. It really boils down to the color of coffee and the internal moisture.”

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