A team of researchers led by Colombian scientist Francisco Trujillo at the University of New South Wales in Australia has developed a revolutionary method to brew espresso using ultrasonic waves instead of hot water. This process, called "ultrasonic espresso," harnesses high-frequency sound waves to extract flavor, oils, aroma, and caffeine from ground coffee, all at room temperature. The result is a 75% reduction in energy consumption compared to traditional machines, a significant benefit for coffee shops, restaurants, and industrial coffee producers.
The Science Behind Ultrasonic Espresso
The experimental system directs ultrasonic waves directly into the filter containing ground beans in water. Instead of relying on heat, the technology leverages a phenomenon known as acoustic cavitation. This involves the formation and collapse of tiny bubbles that generate microcurrents, facilitating the extraction of soluble compounds from the coffee. To generate these microcurrents, the scientists designed a device capable of transmitting ultrasonic vibrations throughout the entire filter basket, transforming it into a sort of acoustic reactor. This design allows the waves to hit multiple points simultaneously and accelerate the movement of liquids around the coffee particles. "Ultrasound helps us replace heat with mechanical energy," explains Trujillo.
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The goal of the entire process, detailed in this month's issue of the Journal of Food Engineering, is to achieve a concentration comparable to that of an espresso. To do so, the researchers adjusted variables such as grind size, ultrasound power, and brewing time. Using a fine grind and 100 watts of power, they obtained beverages with levels of dissolved solids and extraction yields equivalent to those considered ideal by the Specialty Coffee Association. When experiments were repeated under the same conditions without ultrasound, these values could not be achieved. The ultrasonic system made it possible to produce coffee with an intensity similar to espresso in just a few minutes: the optimal time was between two and a half and three minutes, using water at room temperature.
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Sensory Tests and Results
A group of 100 people participated in sensory tests comparing ultrasonic espresso with conventional espresso. Ultimately, participants showed no significant preference for either method. Scores for aroma, flavor, bitterness, and overall acceptance were virtually equivalent. They also compared filtered coffee prepared using the conventional method and with ultrasound. "In the case of filtered coffee, the ultrasonically processed version was generally preferred, and participants rated its bitterness as more pleasant," noted Trujillo.
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Beyond replicating the sensory characteristics of espresso, the new technique could offer environmental benefits. Measurements taken by the researchers indicate that, to produce beverages of the same intensity, the ultrasonic system consumed just 24% of the energy used by a typical espresso machine. This suggests enormous potential for reducing the energy footprint of large-scale coffee production, a hot topic in other tech sectors as well. For instance, companies like Meta are facing internal debates about energy consumption in data centers, as highlighted in a recent article analyzing tensions between engineers and management.
Energy Impact and Future of the Technology
The authors emphasize that coffee produced using ultrasound is not identical to traditional espresso. However, the results suggest that it is possible to produce beverages with comparable chemical and sensory characteristics without heating the water. The research opens the possibility of developing new coffee makers capable of preparing everything from espresso to filtered coffee and cold brew using the same technology. If such systems ever reach the market, the characteristic sound of an espresso machine could be replaced by the inaudible vibrations of ultrasound. For a deeper understanding of the physics behind the phenomenon, refer to Wikipedia's entry on ultrasound.
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In summary, ultrasonic espresso represents a significant step forward in the coffee world, offering an energy-efficient and sensory-equivalent alternative. The future may see coffee shops and industries adopting this technology to reduce costs and environmental impact, revolutionizing how we drink coffee.
Source: https://www.wired.com/story/scientists-brew-espresso-with-ultrasonic-waves
