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A group of physicists claim they have discovered how to make the perfect cup of coffee, while using fewer beans. Not only that, they recenty shared their findings in the journal Physics of Fluids.
“We tried finding ways where we could use as little coffee as possible and just take advantage of the fluid dynamics of the pour,” study co-author Ernest Park, a graduate researcher in the Mathijssen Lab at the University of Pennsylvania, explained to The Debrief.
“Coffee is one of the most consumed beverages in the world,” the researchers wrote. “However, issues such as climate change threaten the growth of the temperature-sensitive Coffea arabica plant, more commonly known as Arabica coffee. Therefore, it is crucial to make beverages more efficient by using less coffee while still meeting the high demand for the beverage.
“Here, we explore pour-over filter coffees, in which a water jet impinges on a water layer above a granular bed. To reveal its internal dynamics, we first substitute opaque coffee grounds with silica gel particles in a glass cone, imaged with a laser sheet and a high-speed camera.
“We discover an avalanche effect that leads to strong mixing at various pour heights, even with a gentle pour-over jet. We also find that this mixing is not significantly impacted by a layer of floating grains, which is often present in pour-overs.
“Next, we perform experiments with real coffee grounds to measure the extraction yield of total dissolved solids. Together, these results indicate that the extraction of the coffee can be tuned by prolonging the mixing time with slower but more effective pours using avalanche dynamics. This suggests that instead of increasing the amount of beans, the sensory profile and the strength of the beverage can be adjusted by varying the flow rate and the pour height. In this way, the extraction efficiency could be better controlled to help alleviate the demand on coffee beans worldwide.”
Basically, what they are saying is that by stirring the ground coffee as water flows through it in carefully controlled, non-turbulent manner can more evenly penetrate the coffee grounds and increase the flavor during the brewing process. Just don’t pour the water from too great of a height. If the water flow breaks into droplets it reduces the extraction efficiency. However, pouring the water from a greater height with a thicker water flow (i.e. no droplets), actually creates the strongest brews.
So, not only did the researchers learn how to make the perfect cup of coffee with their study, they also, as co-author Margot Young pointed out, studying “this kind of fluid behavior” also helps them to better “understand how water erodes rock under waterfalls or behind dams.”
Which one of those two things is the most important is up to you. And probably what time of day it is.