US-based researchers have investigated how fewer beans and fluid dynamics can be used to reduce the rising demand for coffee beans. The study highlights an “avalanche effect” that suggests that instead of increasing the amount of beans, the sensory profile and the strength of the beverage can be adjusted by changing the flow rate and the pour height.

According to the International Coffee Organization, global coffee exports reached approximately 7.7 million metric tons between 2023 and 2024, indicating the rising demand for coffee beans.

Meanwhile, the coffee industry is grappling with high Arabica bean costs due to climate change’s impact on the temperature-sensitive Coffea arabica plant. Over the past year, arabica coffee prices have nearly doubled, with ground roast coffee averaging US$7.25 per pound.

“We tried finding ways wher we could use less [or] as little coffee as possible and just take advantage of the fluid dynamics of the pour from a gooseneck kettle to increase the extraction that you get from the coffee grounds — while using fewer grounds,” says coauthor Ernest Park, a graduate researcher in the Mathijssen Lab at the University of Pennsylvania, which conducted the study.

The team examined pour-over filter coffee dynamics by substituting coffee grounds with silica gel particles for laser and high-speed camera imaging.

“Coffee’s opacity makes it tricky to observe pour-over dynamics directly, so we swapped in transparent silica gel particles in a glass cone,” Park explains.

The findings are published in Physics of Fluids and provide a scientific approach to improving extraction efficiency so fewer coffee grounds can go further “without diminishing overall quality.”

“Avalanche effect”

The team discovered that when water is poured from a height, it creates a stronger mixing effect.

“When you’re brewing a cup, what gets all of that coffee taste and all of the good stuff from the grounds is contact between the grounds and the water. So, the idea is to try to increase the contact between the water and the grounds overall in the pour-over,” explains Margot Young, another scientist who worked on the study.

Water poured from a height produces the “avalanche effect” that stirs the bed of particles and improves extraction.

When the water was poured quickly with a thicker stream, higher pours made the coffee stronger due to increased mixing. On the other hand, with a thinner stream of water, the coffee strength stayed about the same no matter how high the pour was, possibly because it took more time to pour the right amount of water, notes the study.

The scientists believe that in the future, the study’s findings can help uncover mechanisms that matter at environmental or industrial scales.