Coffee-making, but not as we know it. A must-try technique for anyone seeking the perfect espresso shot, according to science.
Is this the secret to a perfect shot of Espresso? “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 simple trick that can make your espresso more consistent and intense.
Grinding coffee beans generates static electricity due to bean fracturing and friction, leading to clumping and adherence to the grinder.
A study published today in the journal Matter reveals that beans with more moisture generate less static, reducing waste and cleaning efforts.
Adding a bit of water to beans before grinding can mimic this effect. This practice results in a more uniform and robust espresso.
The study’s senior author, computational materials chemist Christopher Hendon from the University of Oregon, explains: “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.
“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 favorable flavors.
This advancement in coffee extraction has significant potential economic benefits for the coffee industry, valued at $343.2 billion, or 1.5% of the US GDP.
“Pushing the concentration up by 10%–15% for the same dry coffee mass has huge implications for saving money and improving quality,” comments Hendon.
The phenomenon of static electricity generation during coffee grinding is a well-known issue in the coffee industry, leading to clumping of grounds and occasional electric shocks.
However, the specific attributes of coffee that contribute to this electrification and its effect on brewing were less understood. To explore this, Hendon collaborated with volcanologists who study similar electrical phenomena in volcanic eruptions.
Volcanologist Joshua Méndez Harper from Portland State University draws a parallel between volcanic eruptions and coffee grinding.
He explains, “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.
“In a simplistic way, it’s similar to grinding coffee, where you’re taking these beans and reducing them to fine powder.”
In their research, the team analyzed the static electricity produced when grinding various types of coffee beans. These beans differed in several aspects, such as their origin, processing methods (like natural, washed, or decaffeinated), roast degree, and moisture levels. They also investigated how the coarseness of the grind affected the generation of static electricity.
The study found no link between static electricity and the coffee’s origin or processing technique. However, it did uncover correlations with factors like water content, roast color, and particle size. Coffee with higher internal moisture and a coarser grind generated less static. Light roasts had a lower, often positive, charge, while darker, drier roasts had a negative charge and produced more static. Additionally, dark roasts yielded finer particles than light roasts under the same grinding conditions.
Further experiments focused on the impact of adding water during grinding on espresso brewing. The team compared espressos made from the same beans, ground with and without water. They observed that grinding with water led to longer extraction times and a stronger brew, offering more consistency across different shots. This discovery is particularly beneficial for baristas and commercial coffee producers.
Although the study primarily examined espresso, the researchers believe these findings apply to various brewing methods.
“The central material benefit of adding water during grinding is that you can pack the bed more densely because there’s less clumping,” remarks 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 or in small percolation systems like a stovetop Bialetti. 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.”
The team aims to continue their research into perfecting coffee preparation.
Hendon notes, “Now that we know what grind settings to use to make reproducible espresso, we can start to try to understand what factors give rise to sensory differences in coffee taste.”
This research also has broader implications in fields like material science, geophysics, and engineering, where the electrification of granular materials is a key area of study.
“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,” adds Méndez Harper, “but I think there are a lot more opportunities for this sort of collaboration, and there’s a lot more to know about how coffee breaks, how it flows as particles, and how it interacts with water. These investigations may help resolve parallel issues in geophysics—whether it’s landslides, volcanic eruptions, or how water percolates through soil.”
Source:10.1016/j.matt.2023.11.005
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