Chemical strategies to mitigate electrostatic charging during coffee grinding

The process of grinding coffee generates particles with high levels of electrostatic charge, causing a number of detrimental effects such as clumping, particle dispersal, and spark discharges. At the brewing level, electrostatic aggregation between particles affects liquid-solid accessibility, leading to variable extraction quality. In this study, we quantify the effectiveness of four charge mitigation strategies. Our data suggests that adding small amounts of water to whole beans pre-grinding, or bombarding the grounds with ions produced from a high-voltage ionizer, are capable of de-electrifying the granular flows. While these techniques helped reduce visible mess, only the static reduction through water inclusion was found to impact the brewing parameters in espresso format coffee. There, wetting coffee with than 0.05 mL / g resulted in a marked shift in particle size distribution, in part due to preventing clump formation and also liberating fine particles from sticking to the grinder. With all other variables kept constant, this shift resulted at least 15% higher coffee concentration for espresso prepared with darker roasts. These findings have significant financial and sustainability implications, and encourage the widespread implementation of water use to de-electrify coffee during grinding.