UNSW Sydney engineers have developed a new technology that allows cold brew coffee to be made in under three minutes – without compromising taste.
Traditional cold-brew coffee requires 12 to 24 hours to steep the grounds and extract the flavours using only cold water. However the new process involves using an ultrasonic reactor, which speeds up the brew of the grounded coffee beans.
The research, published in Ultrasonics Sonochemistry, shows this setup can also double the extraction yield and caffeine concentration compared to unsonicated samples.
Led by Dr Francisco Trujillo, a food processing engineer at UNSW, the team used an existing model of a Breville espresso machine and superimposed their own patented sound transmission system.
“Ultrasounds accelerate the extraction process due to acoustic cavitation,” explained Dr Trujillo.
“When acoustic bubbles collapse near the grounded coffee, they generate micro-jets with enough force to pit and fracture the coffee grounds, intensifying the extraction of the aroma and flavours of the brew.”
The samples were then evaluated on their aroma, texture, flavour, and aftertaste attributes.
Compared to the 24-hour brew, the sonicated one-minute brew sample received similar ratings, especially in flavour and aftertaste attributes, including bitterness, sourness, fullness, texture, and aroma.
However, it scored lower in aroma intensity and dark chocolate aroma, suggesting 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 intensity to the 24-hour cold brew but was slightly more bitter.
Prof Heather Smyth, a co-author of the paper, said the new method created coffee that was as good as cold brew steeped overnight.
“Once again, Australia has new technology at our fingertips that moves on from traditional methods to modern methods of coffee making to give consumers a new premium experience,” Smyth concluded.
