Espresso brewed with soundwaves instead of heat tastes just as good
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Making espresso literally boils down to two major components: extremely hot water and high pressure. Add up the world’s espressomakers, and all those shots of caffeine make for a sneakily energy intensive industry. However, researchers at Australia’s University of New South Wales Sydney recently discovered a way to sidestep one of these brewing needs. According to their study published in the Journal of Food Engineering, firing ultrasonic soundwaves into room temperature water makes equally strong and flavorful espresso shots that are indistinguishable from the traditional morning fuel.
“It’s a different process, but you get the same richness and concentration of a normal espresso in under three minutes,” chemical engineer and study co-author Francisco Trujillo said in a university profile.
This isn’t Trujillo’s first time introducing ultrasonic frequencies to coffee. He previously patented a similar system for cold-brew coffee. However, those conditions were tailored for the popular drink’s smoother, more diluted flavor with around one-fifth of espresso’s caffeine concentration.
That said, the underlying principles and technology remain the same for ultrasonic espresso. Researchers converted a standard filter basket into a soundwave generator using a transducer. After placing the small metal mechanism against the basket, ultrasound soundwaves shake the container strongly enough to pass along the vibrations through both the coffee grounds and water. This generates a phenomenon called acoustic cavitation, in which microscopic bubbles quickly form and pop in the liquid. The collapsing bubbles then function like miniscule brushes whenever they come into contact with the coffee grounds, which break open to release their flavor molecules, caffeine, and oils.
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“The most important [part] was the brew ratio—that is how much water is used per gram of coffee—because this helps ensure the final drink is concentrated and not too diluted,” explained Trujillo, adding that the team also tinkered with additional factors including the coffee ground’s consistency and length of exposure to soundwaves.
After settling on the optimum ingredient balance and brewing time, researchers conducted a blind taste-test with 100 coffee drinkers using traditional espresso and filter coffee, as well as their ultrasonic alternatives. The team noted that the participants could not consistently differentiate between standard and ultrasonic espressos, and actually had an even harder time assessing between filter and frequency-aided coffee.
Ultrasonic brewing machines may make their way into home kitchens, but the real promise is the technique’s scalability. Trujillo hopes mass production coffeemakers can eventually use his designs to manufacture their drinks much more quickly while using barely 25-percent of the normal energy.
“These findings showed that using ultrasound did not harm taste, and in some cases even improved it, despite brewing at room temperature and without the heat normally associated with coffee making,” said Trujillo.
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