Lecture Description
Electrostatic charging during coffee grinding can deeply influence the brewing behavior of espresso. Static electricity readily causes coffee particles to clump together and stick to other surfaces, increasing retention and changing the interface between coffee and water. Both processes influence the extraction of compounds that end up in the cup. Using a live experiment, participants will learn how roast color, residual moisture, and grind size influence the production of electrostatic charge during grinding.
Participants will also learn about ways to mitigate charging during grinding. We assess the effectiveness of the Ross droplet technique (RDT), a popular method involving the addition of a few drops of water added to whole beans. For espresso, RDT leads to a more uniform coffee bed, slower shot times, and an increase in % total dissolved solids. We also explore other charge reduction techniques—the ionization of air, for example—, highlighting their benefits and drawbacks. We will perform a live demo of these reduction strategies.
Lastly, characterizing coffee charging and implementing effective static reduction techniques must be tailored to individual environments and grinders. The final portion of the lecture will teach participants how to measure coffee charging in their own contexts using a open-source charge sensor.
Date: Saturday, April 13, 2024
Time: 9:00am - 10:00am
Room Number: S402AB
Instructor
Joshua Mendez (he/him)
Assistant Professor, Portland State University
Joshua Méndez is a volcanologist and assistant professor in the department of Electrical and Computer Engineering at Portland State University. His research focuses on understanding the interaction between solid particles, liquids, and gases in systems ranging from volcanic ash clouds to espresso pucks. Using sensors designed for geophysical applications, Dr. Méndez aims to better characterize a broad range microphysical processes that occur during coffee roasting, storage, grinding, and brewing. Additionally, he leverages of high-performance computing simulations (like discrete element models) to reveal aspects of coffee science that are difficult to access experimentally.