Engineers use ultrasonic reactor to make cold brew coffee in under 3 minutes

Researchers at the University of New South Wales in Sydney have developed a way to make velvety cold brew coffee in under 3 minutes — without sacrificing that distinctive smooth flavor.

The typical cold brew process involves steeping the grounds in cold water for 12-24 hours to gently extract the oils, aromas and flavors.

Enter the ultrasonic reactor. By retrofitting an espresso machine with their patented sound wave system, the UNSW team turned the machines filter basket into a powerful acoustic chamber. Injected with sound frequencies of 38.8 kHz, it generates cavitation bubbles that explosively fracture the coffee grounds, accelerating extraction.

The result? A supercharged cold brew process that cuts the brew time from a day to around 180 seconds. Sensory tests validated that the 1-3 minute brews matched the taste of a 24-hour cold brew, including that signature dark chocolate aroma.

"Compared to the 24-hour brew, the sonicated one-minute brew sample received similar ratings, especially in flavour, aftertaste attributes including bitterness, sourness, fullness texture and aroma," says the project's team leader, Dr Francisco Trujillo. "However, it scored lower in aroma intensity and dark chocolate aroma. This suggests that the sonicated 1-minute sample is slightly under-extracted compared to the 24-hour cold brew. Meanwhile, the sonicated three-minute sample provided a similar dark chocolate aroma and aroma intensity to the 24-hour cold brew, but slightly more bitter. The results of the sensory study showed that a sonication time between one and three minutes is ideal for creating a coffee comparable with 24-hour cold brew coffee, depending on the interest of customers."

More than just a curiosity, the ultrasonic reactor could be a game-changer for the beverage industry. Companies can now brew cold coffee on-demand without expensive equipment or copious refrigeration. And it's not just coffee — the reactor can shake up production of teas and other steeped drinks too.

Previously: How to Make Cuban Coffee