UNSW unveils ultrasound espresso made with cold water

UNSW Sydney researchers have developed an ultrasonic brewing method that makes espresso-strength coffee with room-temperature water, cutting energy use by up to 75%. Blind tastings with about 100 regular coffee drinkers found the drink matched traditional espresso, while the process could help industrial coffee production move faster and use less power.

Why it matters: - UNSW Sydney’s ultrasonic brewing method could lower the energy cost of espresso production by up to 75%. - The process may be especially useful for industrial coffee makers that need faster brewing for ready-to-drink products. - The team says the method delivers espresso-strength coffee without boiling water, which could change how coffee is brewed at scale.

What happened: - Researchers at UNSW Sydney developed a new espresso-making process that uses room-temperature water and ultrasound instead of hot water. - Dr Francisco Trujillo and the School of Chemical Engineering team published the research in the Journal of Food Engineering. - The method produces espresso-strength coffee in under three minutes. - The research included blind taste tests with about 100 regular coffee drinkers.

The details: - The system turns a traditional filter basket into an ultrasonic reactor for ground coffee. - A transducer presses against the side of the basket and generates high-frequency sound waves. - The basket vibrates rapidly, sending vibrations through the coffee grounds and water. - The ultrasound creates acoustic cavitation, forming and collapsing microscopic bubbles in the liquid. - Those collapsing bubbles help fracture the coffee grounds and speed extraction of flavour compounds, oils and caffeine. - The team found three brewing variables were especially important: brew ratio, grind size and ultrasound duration. - Finer grinding improved extraction speed. - The best brewing window was between two-and-a-half and three minutes. - In blind tests, espresso brewed with ultrasound showed no significant differences from traditional espresso across aroma, flavour, bitterness or overall liking. - About 100 everyday coffee drinkers, not trained tasters, took part in the sensory test. - The coffees were prepared fresh, cooled to the same temperature, served in identical coded cups and randomized. - Filter coffee brewed with ultrasound performed better than traditional filter coffee in the taste test. - Participants rated the ultrasound filter coffee as more pleasant overall, including a less harsh bitterness. - Dr Trujillo said the team’s ultrasonic espresso delivered the same richness and concentration as a normal espresso in under three minutes. - Dr Trujillo also said the 75% energy saving comes from not heating the water. - The researchers say the system could be adapted into an automatic home coffee machine. - The larger opportunity is likely industrial production of coffee-based drinks. - The concentrated coffee could be used directly in ready-to-drink products or shipped as a concentrate for later dilution into drinks such as cold brew and milk-based coffee drinks. - Dr Trujillo previously developed a patented ultrasound system that made cold-brew coffee in as little as three minutes, compared with the usual 12 to 24 hours. - Cold brew has a different flavor profile from espresso and typically contains around one-fifth the caffeine concentration.

Between the lines: - The research suggests ultrasound is not just a shortcut for cold brew; it may also preserve or even improve taste in some coffee styles. - The strongest commercial case appears to be manufacturing, where shorter brewing times and lower energy use can affect costs at scale. - The taste results matter because they address the main question for any new brewing method: whether efficiency gains come at the expense of quality.

What's next: - UNSW researchers say the system could be scaled up for industrial coffee producers. - The team is also interested in developing the process into a consumer coffee machine. - The researchers’ next practical hurdle is likely engineering the ultrasonic system into a reliable commercial product. - More testing could determine how the method performs across different beans, roast levels and final drink formats.

The bottom line: - UNSW’s ultrasound espresso shows coffee may not need hot water to taste like espresso, and that could save energy, speed production and reshape commercial brewing.