The UNSW team that used ultrasound to speed up cold brew to three minutes has pushed the technique further — producing espresso-strength shots with room-temperature water. A transducer pressed against a coffee filter basket generates sound waves that create acoustic cavitation, collapsing microscopic bubbles that fracture the grounds and pull out flavor compounds far faster than cold water alone.
"When we gave our ultrasonic espresso to 100 regular coffee drinkers in a randomized test, they could not tell it apart from a normal espresso," says Dr. Francisco Trujillo, who led the research published in the Journal of Food Engineering.
The process cuts energy use by about 75% by skipping the hot water entirely. The team sees the biggest opportunity at an industrial scale, where companies producing ready-to-drink coffee products would save both energy and brewing time.
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