Researchers at the University of New South Wales (UNSW) Sydney, led by Dr. Francisco Trujillo from the School of Chemical Engineering, have developed a brewing process that produces espresso-strength coffee using room-temperature water and high-frequency ultrasonic sound waves instead of heat and pressure. The findings are published in the Journal of Food Engineering. The process works by converting a standard portafilter basket into an acoustic reactor: a transducer pressed against the basket generates ultrasound waves that travel through the water and coffee bed, inducing acoustic cavitation — microscopic bubbles that form and collapse near coffee particles, releasing flavor compounds, oils, and caffeine without any heating element. The full brew takes under three minutes, comparable to a traditional shot and far faster than cold brew, which requires 12 to 24 hours. Energy consumption is reduced by up to 75% relative to conventional espresso machines, a saving the researchers note could be especially significant for industrial-scale ready-to-drink coffee production.
To validate cup quality, the team ran a blind sensory evaluation with 100 regular coffee drinkers who were served traditional and ultrasonic espresso in identical cups at matched temperatures and asked to rate aroma, flavor, bitterness, and overall preference. Most participants could not reliably distinguish between the two methods, and there was no clear overall preference for either. In some sub-groups, tasters slightly preferred the ultrasonic version. Trujillo described the result as “the same richness, the same boldness” — produced without hot water. The same UNSW team previously applied ultrasound to accelerate cold-brew filter coffee, and Trujillo indicated the technique could scale to industrial extractors if a commercial partner brings sufficient engineering resources to the transition.