Researchers at the University of New South Wales have developed a method using sound waves to make a cold brew coffee in mere a few minutes.
They have developed an ultrasonic machine to speed up the cold brew of ground coffee beans–a process that normally takes 12 to 24 hours.
Now, without sacrificing the taste experience, people can make a cold brew coffee in three minutes– just like a regular hot brew.
Published in Ultrasonics Sonochemistry, the process involves using an ultrasonic reactor to speed up the brew of the grounded coffee beans with the research.
Patented sound transmission system
According to UNSW, the team led by Dr Francisco Trujillo, used an existing model of a Breville espresso machine and superimposed their own patented sound transmission system.
The system connects a bolt-clamped transducer with the brewing basket via a metallic horn – transforming a standard espresso filter basket into a powerful ultrasonic reactor.
The reactor works by injecting sound waves at a frequency of 38.8 kHz at multiple points through its walls–generating multiple regions for acoustic cavitation within the reactor, according to researchers.
Double the extraction yield
The new setup has the capability to double the extraction yield and caffeine concentration compared to unsonicated samples.
“Ultrasounds accelerate the extraction process due to acoustic cavitation,” said Dr Trujillo, corresponding author of the paper and UNSW food processing engineer in the School of Chemical Engineering.
“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.”
“And the acceleration is enormous – we are reducing what would typically take 12 to 24 hours to less than three minutes,” added Trujillo.
Process can be adapted to existing espresso machines
Researchers’ aim was to make the process easy like making a regular espresso coffee. They have also pointed out that the process can be adapted to existing espresso machines.
Researchers claimed that their technology can be used by companies that already manufacture coffee machines. “So consumers can enjoy an ultrasonic cold brew at home in less than three minutes,” said Trujillo.
“Very importantly, this breakthrough opens the door for coffee shops and restaurants to produce on-demand brews comparable to 24-hour cold brews, supplying the rising demand while eliminating the need for large semi-industrial brewing units and the associated requirement for extensive refrigeration space,” explained Trujillo.
Sensory analysis
Researchers sent samples of coffee to the Queensland Alliance for Agriculture and Food (QAAFI) for a thorough sensory analysis.
Three samples were sent – cold brew sonicated at room temperature for one minute, the second was sonicated for 3 minutes, and the third was a regular 24-hour stepped brew at four degrees Celsius without sonication.
Researchers evaluated the samples on their aroma, texture, flavour, and aftertaste attributes.
They found that 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,” said Trujillo.
