By grinding your coffee with a splash of water, espressos can be made more consistent and intense. Here’s why.
There are all sorts of fancy tools and expensive devices that can drastically improve the taste of your coffee, but now scientists have discovered a new trick that involves just a few drops of water.
When coffee is ground, the process creates both friction and some fracturing of the beans. This generates electricity that can cause the particles of coffee to clump and stick together against the grinder.
Publishing their findings in the journal Matter, the team of researchers reported that coffee beans that featured a higher internal moisture level produced less static electricity. This meant a more intense espresso, with less coffee wasted.
The moisture level was achieved by simply adding a little bit of water to the beans before grinding them.
“Moisture, whether it’s residual moisture inside the roasted coffee or external moisture added during grinding, is what dictates the amount of charge that is formed during grinding,” says senior author Dr Christopher Hendon, a computational materials chemist at the University of Orgeon.
“Water not only reduces static electricity and therefore reduces mess as you’re grinding, but it can also make a major impact on the intensity of the beverage and, potentially, the ability to access higher concentrations of favourable flavours.”
It wasn’t just coffee experts involved in this research. In a strange twist of events, a volcanologist was brought in to better understand what was going on during the static electricity generation of coffee grinding.
“During an 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,” says volcanologist Joshua Mendez Harper, an author on the paper from Portland State University.
“In a simplistic way, it’s similar to grinding coffee, where you’re taking these beans and reducing them to fine powder.”
In the process of research, the team measured the amount of static electricity produced by grinding a selection of different commercially and in-house roasted coffee beans. These varied by factors including country of origin, roast colour, and moisture content.
There was no association between static electricity and the coffee’s country of origin or processing method (natural, washed or decaffeinated), but the researchers did find associations between electrification and water content, roast colour and particle size.
Less electricity was produced when coffee had a higher internal moisture content and when coffee was ground at a coarser setting. The team also found a difference in static electricity produced between lighter and darker roasts.
When they compared espresso made with identical coffee beans ground either with or without a splash of water, they found that grinding with water made a longer extraction with a stronger brew. Equally, grinding with water increased consistency between shots, overcoming a hurdle for baristas looking to get consistent results all day.
“The central material benefit of adding water during grinding is that you can pack the bed more densely because there’s less clumping,” says Hendon.
“Espresso is the worst offender of this, but you would also see the benefit in brew formats where you pour water over the coffee like a stovetop. Where you’re not going to see a benefit is for methods like the French press, where you submerge the coffee in water.”
While the results of the research are primarily focused on coffee, it has implications in other areas too.
“It’s sort of like the start of a joke – a volcanologist and a coffee expert walk into a bar and then come out with a paper,” says Harper.
“But I think there are a lot more opportunities for this sort of collaboration. These investigations may help resolve parallel issues in geophysics – whether it’s landslides, volcanic eruptions, or how water percolates through soil.”
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