Traditional espresso depends on very hot water and high pressure, but researchers at the University of New South Wales Sydney have tested another method. In a study published in the Journal of Food Engineering, they used ultrasonic sound waves and room-temperature water to brew a drink with the strength and flavor of espresso.
"It's a different process, but you get the same richness and concentration of a normal espresso in under three minutes," said chemical engineer and study co-author Francisco Trujillo.
The team converted a standard filter basket into a sound-wave generator by adding a transducer. The vibrations travel through the water and coffee grounds, creating a process called acoustic cavitation. Tiny bubbles form and quickly collapse in the liquid. When they meet the grounds, they act like microscopic brushes, helping release flavor compounds and oils.
The researchers adjusted factors including the amount of water used per gram of coffee, the size of the grounds and the length of exposure to ultrasound. Trujillo said the brew ratio was especially important because it kept the drink concentrated rather than diluted.
After choosing the best combination, the team held a blind taste test with 100 coffee drinkers. Participants compared traditional espresso and filter coffee with versions made using ultrasound. They could not consistently tell the standard and ultrasonic espressos apart.
Ultrasonic machines could eventually reach home kitchens, but the researchers see greater potential in large-scale coffee production. Trujillo hopes the method can make drinks faster while using about a quarter of the usual energy. The findings suggest that brewing at room temperature did not harm the taste and, in some cases, may even have improved it.