A new espresso machine brews coffee at room temperature using ultrasonic waves, slashing energy consumption by up to 75% while producing a drink that coffee lovers cannot distinguish from traditional hot espresso. The process, developed by researchers at the School of Chemical Engineering in Sydney and led by senior lecturer Francisco Trujillo, takes less than three minutes — far faster than the 12 to 24 hours required for cold brew.
How ultrasonic brewing works
Instead of heating water, the machine uses sound waves at a frequency above human hearing. A transducer placed against a standard espresso basket vibrates at high frequency, creating a phenomenon called acoustic cavitation — tiny bubbles form and collapse in the water. As Trujillo explains, "When these bubbles collapse near coffee particles, they produce microscopic jets and forces that act a little like scrubbing brushes. They pit and fracture the surface of the coffee grounds, helping flavor compounds, oils and caffeine move into the water much faster than they normally would at room temperature."
The team found that the brewing ratio is critical: too much water produces weak espresso, while too little makes extraction difficult. The grind size also significantly affects the result.
Taste test results
In blind taste tests, 100 coffee drinkers could not tell the difference between ultrasonic espresso and traditional hot-brewed espresso. According to Trujillo, the ultrasonic espresso has "the same richness, the same boldness," and in some cases testers even preferred the ultrasonic version. The method uses only a quarter of the energy of conventional espresso machines.
Comparison of brewing methods
| Attribute | Traditional Espresso | Ultrasonic Espresso |
|---|---|---|
| Brew time | ~25–30 seconds | Under 3 minutes |
| Water temperature | ~90–96°C | Room temperature |
| Energy use | Baseline | 75% reduction |
| Taste distinction | — | Indistinguishable in blind tests |
"As someone from Colombia, I like to think coffee is in my blood — and I'm proud to come from a country known for producing some of the best coffee beans in the world. So perhaps that's why I have spent a lot of time in my laboratory with my team asking a simple question: does espresso really need hot water?" said Trujillo.
Potential applications
Although the technology is still experimental, Trujillo envisions multiple uses: in home coffee machines, in small coffee shops to save energy, and in ready-to-drink coffee products. "A concentrated room-temperature coffee could be used directly in bottled drinks, milk-based beverages or cold coffee products. It can also be shipped as a concentrate and diluted later," he explained. This could enable a new generation of cold coffee products with less energy and processing overhead.
The innovation comes from the School of Chemical Engineering in Sydney, and the research team continues to refine the process. While the current prototype takes three minutes — longer than a typical espresso shot — the potential energy savings and consistent flavor profile make it a promising development for the coffee industry.
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