Why ultrasonic espresso?

Researchers have developed an ultrasonic espresso brewing process that uses high-frequency sound waves instead of hot water to produce espresso coffee. And, not only did coffee consumers find it comparable to traditional espresso, but the brewing process reduced energy consumption by up to 75%.

“We have developed what we call ultrasonic espresso: a room-temperature brewing process that uses high-frequency sound waves to extract the flavor, oils, aroma and caffeine from coffee. The result is an espresso-like coffee that is brewed in less than three minutes, but requires much less energy than the conventional method.”

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Saving up to 75% of energy without heating water is a small benefit for home users or small coffee shops. But for companies that produce ready-to-drink coffee products on an industrial scale, it could be very significant indeed. A concentrated coffee at room temperature could be used directly in bottled drinks, milk-based drinks or cold coffee products. It could also be shipped as a concentrate and diluted later. This would reduce not only energy consumption, but potentially also processing time.

The key to the new process is ultrasound.

These are sound waves above the range of human hearing. In our system, a small metal device called a transducer presses against the side of a traditional espresso basket and causes it to vibrate rapidly. These vibrations travel through the water and coffee beans. This creates a phenomenon known as acoustic cavitation. Tiny bubbles form and flow through the liquid. When these bubbles flow near coffee particles, they generate forces that act much like scrubbing brushes. They create pits and break the surface of the coffee beans, helping the aromatic compounds, oils, and caffeine move into the water much faster than they normally would. In other words, ultrasound helps us replace heat with mechanical energy.

In previous work, we used ultrasound to dramatically speed up the preparation. But the challenge in this project was different:

Could we produce something with the strength, body, and intensity of espresso, without heating the water?

To do this, we adjusted several variables. The brewing ratio was one of the most important: how much water we used for each gram of coffee. Too much water and the drink is watery. Too little and extraction becomes difficult. The size of the grind also mattered. Finer beans allowed us to extract flavor more quickly.

Finally, we checked how long the ultrasound should be applied for. We found that the sweet spot was about two and a half to three minutes.

The real test, however, was the taste test. For the espresso samples, participants could not reliably distinguish between the traditional and the ultrasonic versions. There were no significant differences in aroma, flavor, bitterness, or overall preference. For the filter coffee, the ultrasonic version was preferred overall, with participants rating its bitterness as more pleasant.

DOI https://doi.org/10.1016/j.jfoodeng.2026.113193

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