Water Reduces Coffee’s Charge

Grinding coffee beans builds up electrical charge as the beans fracture into smaller and smaller pieces. The polarity of the charge depends on the bean’s moisture content; lighter roasts tend toward a positive charge, and darker roasts skew negative. The finer the grind, the stronger the electrical charge and the greater the problem of clumping grains becomes. Adding a few drops of water to the beans before grinding, researchers found, drastically reduces the electrical charge and clumping. This, the team reports, would let espresso lovers brew a stronger cup with less material. A well-compacted bed of unclumped grains has less void space, which slows down water’s percolation and increases the amount of coffee the water can extract. The authors encourage readers to try adding water in their own home brews, but they caution that coffee mass and grind setting should also be variables in the experiment. (Image credit: N. Van; research credit: J. Harper et al.; via APS Physics)