what are you doing need to do good espresso? Low coffee, of course; machine the ability to generate pressure; and hot water, preferably heated to between 195 and 205 degrees Fahrenheit. And that’s it. But can one do without that last element? No, not the water itself, but the need to heat it.
Colombian researcher Francisco Trujillo led a team at the University of New South Wales in Australia that claims to have invented what it calls “ultrasonic espresso.” As Trujillo explains, it’s a “warm room brewing process that uses high-frequency sound waves to extract flavor, oil, aroma, and caffeine from ground coffee.”
Although the process takes longer than the conventional method (three minutes vs. 30 seconds), it uses 75 percent less energy—a huge advantage for coffee shops and restaurants, but especially for businesses that produce industrial quantities of coffee, such as those that make ready-to-drink products.
Sonic Alcohol
The test system directs the ultrasonic waves directly into the filter containing the ground beans in the water. Instead of relying on heat, the technology uses a phenomenon known as acoustic cavitation. This involves the formation and collapse of tiny bubbles that generate small currents that, in this experiment, facilitate the extraction of soluble compounds from coffee.
To create these small currents, scientists developed a device capable of transmitting light vibrations through the entire filter basket, transforming it into a type of acoustic reactor. This design allows the waves to hit multiple points at the same time and accelerate the movement of liquids around the coffee particles. “Ultrasound helps us replace heat with mechanical energy,” explains Trujillo.
The purpose of this whole process, is explained in more detail in this month’s edition of the Journal of Food Engineering, is to achieve a concentration comparable to that of espresso. To do this, the researchers adjusted variables such as grinding size, ultrasound power, and brewing time. Using a fine grind and 100 watts of power, they obtained drinks with dissolved solids levels and extraction yields similar to those considered excellent by the Specialty Coffee Association.
When the experiments were repeated under the same conditions but without ultrasound, it was not possible to reach these values. The ultrasonic system made it possible to produce coffee as strong as espresso in just a few minutes—researchers found the ideal time to be between two and a half to three minutes—using water at room temperature.
The team also analyzed various chemical parameters. The levels of caffeine and chlorogenic acid were similar to those obtained by conventional methods. No significant differences were observed in pH or in the total composition of volatile compounds responsible for odor.
Taste Test
A group of 100 people took part in a sensory experiment where they compared ultrasonic espresso with regular espresso. Finally, participants did not show any preference for either method. Scores for aroma, taste, bitterness, and overall acceptability were similar.
They also compared filtered coffee prepared using the conventional method and with ultrasound. “In terms of filtered coffee, the ultrasonically processed version was generally preferred, and participants rated its bitterness as more pleasant,” Trujillo noted.
In addition to replicating the sensory properties of espresso, the new technique could provide environmental benefits. Measurements taken by the researchers show that, to produce drinks with the same strength, the ultrasonic system used only 24 percent of the energy used by a conventional espresso machine.
The authors emphasize that coffee produced using ultrasound is not the same as traditional espresso. However, the results show that it is possible to produce drinks with similar chemical and sensory properties without heating water.
The research opens up the possibility of developing new coffee makers capable of preparing everything from espresso to filtered coffee and cold brew using the same technology. When these systems are introduced to the market, the distinctive sound of the espresso machine can be replaced by inaudible ultrasound vibrations.
This story was originally published by WIRED in Spanish and translated from Spanish.
