Drinking a freshly brewed cup of coffee early in the morning is essential to ring in the day, and if you like cold brew coffee that takes the whole day to make, you can't help it, but now, using ultrasound technology, researchers have managed to achieve cold brew coffee in a matter of minutes.
We're always looking for quicker ways to brew coffee. But cold brew coffee requires the ground coffee to be soaked in water for 24 hours (or more). Espresso coffee can be said to be a real treat for the senses, but who wants to wait that long?
Back in 2022, German researchers used pulsed lasers to reduce cold brewing times to minutes – but as far as we know, this method hasn't made its way out of the research lab yet. Now, an Australian team has achieved a similarly fast cold drink time using an ultrasonic unit connected to an off-the-shelf coffee machine.
Engineers at the University of New South Wales (UNSW) have developed a "patented sound wave transmission system" that concentrates 38.8 kilohertz of sound waves through a horn into the strainer of the Breville espresso machine, turning the coffee basket into a powerful ultrasonic reactor. Ultrasound effectively speeds up the cold brew process, extracting oils, flavors and aromas from coffee in about the same amount of time as a steaming espresso.
Dr. Francisco Trujillo, corresponding author of the research paper and University of New South Wales, explains: "Ultrasound accelerates the extraction process due to acoustic cavitation. When sonic bubbles collapse near ground coffee, they create microjets that are strong enough to dent and crack the coffee grounds, enhancing the extraction of the coffee's aroma and taste. And this acceleration is very noticeable – we have reduced what would normally take 12 to 24 hours to less than three minutes. "
In addition, the researchers also found that the smaller the loading in the coffee basket, the higher the extraction rate and caffeine concentration. While it only takes one minute to get a fragrant coffee, extending the ultrasonic blasting time to three minutes results in a better cup of coffee, albeit with a slightly heavier bitterness.
The University of Queensland tasting team evaluated samples from the University of New South Wales team's cold brewing experiment in terms of aroma, texture, flavour and aftertaste
For taste testing, researchers at the University of New South Wales sent some samples to colleagues at the University of Queensland to assess aroma, texture, flavour and aftertaste.
Professor Heather Smyth, Queensland sensory scientist and flavour chemist, noted: "Our highly trained sensory panel tasting proves that we can achieve a taste very similar to a traditional cold or espresso in the time it takes to brew a hot espresso. "
"We were able to demonstrate that this can be applied to existing espresso machines," Dr. Trujillo added, adding that the technology could also be used to speed up the brewing of tea. "We're very excited about developing this technology, which can also be used by companies that already produce coffee machines, so consumers can enjoy 3 minutes of ultrasonic cold brew coffee at home."
A paper detailing the project has been published in the journal Ultrasonic Acoustic Chemistry. There's more to it in the video below.