Ditch boiling water: Researchers create espresso using sound waves

For many coffee enthusiasts, making espresso traditionally involves two key elements: extremely hot water and high pressure.

However, researchers at the University of New South Wales (UNSW) in Australia have challenged that idea by developing an espresso-like brew using room temperature water and ultrasonic sound waves.

This innovative method could cut the energy required for coffee production by up to 75%, while still delivering a flavorful, aromatic, full-bodied, and caffeinated beverage comparable to conventional espresso.

The study, published in the Journal of Food Engineering, revealed that most coffee drinkers couldn’t distinguish between the new “ultrasonic espresso” and a classic espresso shot.

Led by Dr. Francisco Trujillo and his team from UNSW’s School of Chemical Engineering, the project uses ultrasound—sound waves at frequencies beyond human hearing.

Traditionally, espresso is made by forcing hot water through finely ground coffee under high pressure, a process that consumes a significant amount of energy due to the heating step.

The UNSW team aimed to achieve the same result without applying heat.

Their approach involved converting a standard coffee filter basket into an ultrasonic reactor. A small device called a transducer attaches to the side of the basket, producing ultrasonic vibrations when activated, which travel through both the coffee grounds and water.

These vibrations trigger a phenomenon called acoustic cavitation, where tiny bubbles form and rapidly collapse within the liquid. When these microbubbles burst near coffee particles, they act like tiny brushes or jets, breaking open the surface of the grounds.

This process accelerates the release of flavor compounds, oils, and caffeine into the water at room temperature, much faster than normal diffusion.

As a result, the team could brew a concentrated coffee with strength similar to espresso in less than three minutes.

After extensive experimentation with different coffee-to-water ratios, grind sizes, and brewing times, they found that using finely ground coffee and applying ultrasound for around two and a half to three minutes yielded optimal flavor and concentration.

To test if consumers could tell the difference, the team conducted blind taste tests with roughly 100 regular coffee drinkers. Participants sampled four different drinks: traditional espresso, ultrasonic espresso, traditional drip coffee, and ultrasonic drip coffee.

The findings were unexpected. Most participants couldn’t reliably identify which coffee was brewed with sound waves versus conventional methods. They reported no significant difference in taste, aroma, or body.

Interestingly, many preferred the ultrasonic drip coffee, citing a more pleasing bitterness.

The researchers believe this technology could eventually find its way into home coffee machines. Still, the biggest potential may lie in large-scale commercial manufacturing.

Manufacturers of ready-to-drink coffee products could utilize this system to reduce energy costs and speed up production. Since the process produces a concentrated espresso strength, it could also be used to create coffee concentrates for bottled drinks, cold brews, and milk-based beverages.

If scaled successfully, future espresso might be crafted more with sound waves than boiling water.