Researchers at UNSW Sydney have figured out how to brew espresso-strength coffee without heating any water. The method replaces hot water and high pressure with ultrasonic sound waves, and in blind taste tests involving 100 regular coffee drinkers, participants could not tell the two apart.
How it works
Dr. Francisco Trujillo and his team at UNSW’s School of Chemical Engineering converted a traditional espresso machine filter basket into an ultrasonic reactor. A transducer attached to the side of the basket generates high-frequency sound waves that vibrate through the coffee grounds and water simultaneously.
Those vibrations trigger acoustic cavitation, a process where microscopic bubbles form and collapse rapidly against coffee particles, effectively fracturing them and forcing flavor compounds, oils, and caffeine into the room-temperature water. The entire process takes under three minutes.
The research, published in the Journal of Food Engineering, tested four drinks in a randomized blind evaluation: traditional espresso, ultrasonic espresso, traditional filter coffee, and ultrasonic filter coffee. For espresso, participants found no meaningful difference between the two methods. The ultrasonic coffee actually scored better than its traditional counterpart, with participants rating its bitterness as more pleasant.
Energy savings at scale
The ultrasonic brewing method cuts energy consumption by up to 75% compared to conventional espresso brewing, according to UNSW. The team says the biggest opportunity is at the industrial level, where large-scale producers of ready-to-drink coffee products could see significant reductions in both energy use and processing time. The system can also produce a concentrate that manufacturers could later dilute into cold brew and milk-based beverages.
Trujillo previously used a related ultrasound system to produce cold-brew coffee in under three minutes, though that method yielded a distinctly different, lower-caffeine result. This latest work extends the approach to full espresso strength.
The concept of ultrasonic extraction is not entirely new to the beverage world. A machine called Teamosa explored the same principle for tea brewing years ago, though it never gained mainstream traction.
