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TLDR: Using science for better coffee! Using water while grinding prevents the grounds from clumping due to preventing buildup of static charge.
We’ve got ourselves a nice straight-forward one today about a topic dear to my heart: coffee. It’s taking “get work to pay for coffee” to the extreme. Enjoy.
Credit: J. Harper, C. Hendon, et al, Matter, 2024.
Big Takeaways
Coffee often clumps up during grinding.
These clumps are due to static charge building up on the grounds.
The roast, water content, and ground size all impacted charge.
Adding water to the beans before grinding helped prevent charge buildup, leading to less clumping and better coffee.
The Problem
The people (me) want better coffee. More coffee. Cheaper coffee. I’ve had 3 cups today but maybe I’d have a 4th if it was better.
A common problem with grinding coffee beans into coffee grounds is the grounds sticking together and forming an annoying clumpy mess. This can make the brewing less effective and the resulting coffee worse.
At the industrial level, clumping can clog machines. At the personal level, clumping can leave you with a gross cup of coffee/espresso.
It turns out clumping is due to charge building up on the grounds. As the grounds are made they experience large amounts of friction and fracturing - leading to charge building up on their surface.
But don’t be concerned, some overly caffeine addicted scientists sat down, got annoyed by their sub-par coffee, and figured out a way to make it better (I’m assuming anyway).
The Solution
The authors found that the type of coffee beans, their internal water content, and how small the resulting grounds were all effected the charging, and thus clumping, of the grounds.
Importantly, they found that beans with higher water content ended up with less charge and therefore less clumping. You can see this in the graph below. The sweet spot for 0 charge seems to be in the ~2-2.5% water content range. As you add water from left to right the average charge approaches 0.
Higher water content = less charge. Credit: J. Harper, C. Hendon, et al, Matter, 2024.
I LOVE that the authors just went ahead and got a whole coffee roasting setup for this project. I’m not sure if one of them already had it or they just found a creative way to get the lab to pay for it, but I’m a fan regardless.
There is academic value in standardizing roast profiles across the industry, thereby allowing for direct comparisons between coffees…. Instead, we developed our own profiles with the aim of isolating roast through the development of systematically “darker” coffees.
Basically “we’ll just do it ourselves”. Incredible. Why have a shared building coffee machine when you can just build yourself an entire roastery in the back?
One of the best parts of this paper is that it’s solid science. They make a number of findings that should translate to other systems, they compare homemade roasts to industry standards (literally Starbucks), and they systematically march through their variables.
Adding water to beans before grinding reduces charge. Credit: J. Harper, C. Hendon, et al, Matter, 2024.
To wrap this up, they looked at adding water to the beans right before grinding. They found that this simple trick of adding water helped reduce the charge of the resulting grounds and made the whole process smoother.
As you can see below, adding water helped increase the amount of espresso they got out over time. A little water = more espresso. Good deal.
Credit: J. Harper, C. Hendon, et al, Matter, 2024.
Next time you find your beans clumping, just add a few drops of water. We love some practical science.
See you next week for more science,
Neil
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