Espresso has always needed two things working together: hot water and high pressure. Researchers at UNSW Sydney have just shown that one of those may be optional. Their new method makes espresso-strength coffee with room-temperature water, using sound.
How sound brews a coffee
Dr Francisco Trujillo and his team in the UNSW School of Chemical Engineering turned a filter basket into an ultrasonic reactor. A small device called a transducer presses against the basket and fires high-frequency sound waves, far above what we can hear, straight through the grounds and the water.
That triggers acoustic cavitation: microscopic bubbles form and collapse against the coffee particles, fracturing them like tiny scrubbing jets. Flavour, oils and caffeine move into the water far faster than they normally would at low temperature. The team found two and a half to three minutes of sound is the sweet spot for a balanced cup, and that grinding finer pulls the flavour faster.
Does it actually taste like espresso?
This is the part that matters. The researchers ran a blind test with around 100 regular coffee drinkers, serving traditional and ultrasonic versions in identical coded cups. For the espresso shots, tasters could not reliably tell them apart, and had no clear preference either way. For filter coffee, they actually preferred the ultrasonic version, rating its bitterness as more pleasant. The work is published in the Journal of Food Engineering.
Where this really matters
The headline is the energy. Skipping the hot water cuts consumption by around three quarters. That is a big deal, but mostly at scale. The team is clear the biggest opportunity is for companies making coffee-based ready-to-drink products by the tank, where the energy and time savings add up fast. It could become a home machine one day. It is not one yet.
Our honest take
We love this. Real research, blind-tested, no hype. Anything that cuts energy across the industry is worth cheering for. But it does not change what happens at our counter. We will keep pulling traditional espresso on the machine, chasing a balanced shot around 27 seconds, because that is what the cup in front of you deserves.
And here is the quiet truth in all of it. The method matters less than the inputs. Cold water or hot, sound waves or pressure, a great cup still starts with fresh beans, a dialled grinder and someone who cares. That part has not changed since 2002, and it is not going to.
| Traditional espresso | Ultrasonic espresso (UNSW) | |
|---|---|---|
| Water | Hot, under pressure | Room temperature |
| Energy | Standard | Up to 75% less |
| Time | Seconds | 2.5 to 3 minutes |
| Blind taste test | Baseline | Indistinguishable for espresso |
| Best suited to | Cafes and home | Industrial ready-to-drink at scale |
FAQ
Is ultrasonic espresso real espresso?
Yes. It is espresso-strength, with the same concentration and caffeine. In a UNSW blind test, around 100 regular drinkers could not reliably tell it apart from a traditional shot.
Does it taste different?
For espresso, the blind testers found no clear difference. For filter coffee, they slightly preferred the ultrasonic version, calling its bitterness more pleasant.
Can I buy an ultrasonic espresso machine?
Not yet. The researchers say it could be developed into a home machine, but the near-term use is industrial, for ready-to-drink coffee made at scale.
Does King Carlos use it?
No. We pour traditional espresso at our Hurstville bar, aiming for a balanced shot around 27 seconds. The method matters less than fresh beans and a dialled grinder.
Whatever brews it, a great cup starts with fresh beans.
Shop the beansNot sure where to start? Find your coffee in two minutes, or build something that is entirely yours in the blend builder.
