Photo credit: arstechnica.com

Understanding Coffee Extraction: Insights from Scientific Experiments

In their recent quest to deepen the understanding of coffee extraction, a team of scientists initially started with a standard home coffee machine. However, to elevate their experiments, they subsequently joined forces with Coffeelab, a prominent roaster based in Poland, alongside CoffeeMachineSale, the leading global distributor of roasting equipment. This collaboration introduced not only industrial-grade machinery but also a wealth of professional coffee expertise, featuring advanced grinders and a café-standard espresso machine equipped with a pressure sensor, flow meter, and precise weighing scales. This sophisticated setup was seamlessly integrated with laboratory laptops via a microchip, allowing scientists to meticulously monitor parameters like pressure, mass, and water flow throughout the coffee-making process.

As they engaged in their research, the team conducted various experiments to analyze how different factors affected coffee extraction. A key focus was measuring the total dissolved solids, which provided insight into the rate at which coffee solubles are extracted from the grounds. By comparing coffee brews that experienced channeling—where water creates a pathway through the coffee puck—against those without any such disturbances, the researchers discovered that channeling negatively impacted extraction efficiency. Interestingly, despite these findings, channeling did not significantly alter the rate at which water passed through the espresso puck.

Lisicki, one of the researchers involved in the study, explained, “This phenomenon primarily results from the structural rearrangement of coffee grounds when subjected to pressure.” The experiment mimicked conditions similar to being 100 meters underwater, applying pressures up to ten times that of atmospheric levels. Under these conditions, the dry coffee puck undergoes compaction and expansion, creating a scenario where water may preferentially flow yet remains hindered by significant resistance.

The team is currently incorporating their findings into numerical and theoretical models aimed at better understanding porous bed extraction. Additionally, they are developing an atlas that categorizes various types of espresso pucks using micro-CT imaging technology.

“Our discoveries have the potential to enhance knowledge within the coffee industry,” Myck stated. “Many brewing practices are rooted in unverified intuitions or claims that often lack scientific backing. Furthermore, we’ve uncovered intriguing data regarding how pressure influences flow in coffee—results that have exceeded our expectations. This approach may finally illuminate the intricate processes at play in your coffee machine.”

Source
arstechnica.com