Cold-brewing coffee can reduce its bitter taste, but it normally takes up to 24 hours as the grounds slowly steep. A new method that involves pummelling the grounds with ultrasound can drastically speed up the process
A high-tech method for producing cold brew coffee that uses ultrasonic waves to extract flavour could cut the time required from 24 hours to just a few minutes.
Cold brew coffee, which is made by steeping coffee grounds in cold water, is gaining popularity because it results in a less bitter drink than traditional methods using hot water. But the technique is also a headache for coffee shops as they need refrigerator space and must allow up to 24 hours to make a brew.
Now Francisco Trujillo at the University of New South Wales in Sydney and his colleagues have found a unique way to quickly extract a cold shot of coffee – by bombarding the grounds with ultrasonic waves. The resulting drink can be ready in less than 3 minutes.
Trujillo says the initial idea for using ultrasound, which smashes up the grounds in a process called acoustic cavitation, was that it might allow the extraction of more antioxidants. This turned out not to be the case, but their initial set up, requiring around £15,000 of ultrasonic equipment, produced a surprisingly good coffee.