Coffee that matches the taste profile that usually takes a day to achieve through cold brewing can now be produced in 1-3 minutes using ultrasound, with more caffeine to boot. The technology could make the cold brew experience available to the impatient and the housebound, making most coffee fans happy and forcing coffee snobs to find some other way to distinguish themselves.
Cold brew coffee has rocketed in popularity in the last decade, with those who imbibe for more than the caffeine hit praising the extra sweetness and aroma and reduced acidity compared to traditional methods. However, the 12-24 hours it takes to make using cold brewing techniques is far too long for those ill-prepared to wait, restricting cold brew to well-equipped cafes and patient home brewers.
Scientists at the University of New South Wales calculated the conditions required to combine an ultrasound transducer, metallic horn, and coffee basket to get the flavor out of ground coffee faster. They demonstrated the acoustic bubbles produced by sound waves at 38,800 Hz dissolve small grains of coffee in cold water within minutes when they collapse. Larger grains become pitted by the micro-jets produced in this process, releasing more of the 2,000 compounds in coffee beans into the water. Most importantly, caffeine levels almost double compared to traditional cold-brewed counterparts, which probably also means it’s higher than espresso.
Having proved the chemical profile of the infused water resembled or exceeded the product from 24 hours of cold brewing, it was time for the taste test. It might be expected that this was a task volunteers would be lining up for, with hundreds of graduate students easily on hand. Instead, the inventors sought help from the Queensland Alliance for Agriculture and Food Innovation (QAAFI) at the University of Queensland who provided paid testers.
Eleven individuals were recruited from a panel maintained by QAAFI to compare the taste profiles of coffee using three methods; exposure to ultrasound for either one or three minutes, or 24 hours of traditional cold brewing. The same bean blend was used throughout, but a wide variety of basket loading percentages were tried. This was just to make sure the results were right of course, nothing to do with extending the time in which testers were paid to drink top-of-the-range coffee.
If you’re wondering how one gets what must sound to many like a job from heaven, QAAFI’s Dr Jaqueline Nadolny told IFLScience; “We have tests that prospective panelists do to see what flavors they can distinguish. Most have been on the panel for years.” Performance on each study is monitored to see if someone is no longer suited.
While Nadolny admits it; “Sounds like a fun job,” she says not all the foods people have to test are as beloved as coffee. “Last year people had to consume 24 burger samples a day and they got sick of it,” she noted.
It’s a tough job but someone has to be paid to spend weeks comparing the taste and aroma of ultrasonic coffee with traditional cold brew.
Image Credit: Megan Pope/University of Queensland
In this case however, the testers drew up a list of 23 attributes on which to rate the coffees on scales of 1 to 100 before they’d taken a sip. They concluded the 1-minute sonicated coffee matched ordinary cold brew on measures of flavor and aftertaste. When sound waves were used for three minutes, the match was even closer, proving similar for aroma intensity and scent of dark chocolate.
“Hence, it is expected that a sonication time between 1 and 3 min is ideal for creating a coffee comparable with 24-hour cold brew coffee, depending on the interest of customers,” the researchers write in their paper.
“Our trained sensory panel tastings proved that we can achieve a taste profile very similar to either a traditional cold brew or an espresso in the time it takes to brew a hot espresso,” Nadolny said in a statement.
The test involved turning the coffee basket into an ultrasonic reactor using an ultrasound-producing technology previously patented by UNSW. “We’re able to demonstrate that this can be adapted to an existing espresso machine,” Dr Francisco Trujillo said. “We are very excited about developing this technology, which can be used by companies that already manufacture coffee machines, so consumers will be able to enjoy a 3-minute ultrasonic cold brew at home.”
Few other foods may have the popularity of coffee, but Nadolny told IFLScience there might be a few other applications for the technology, perhaps in getting more flavor out of tea or milk powder.
Cafes will save on refrigeration space and what Trujillo calls “semi-industrial brewing units,” while maintaining their edge over home brewers, can apply the technology to single-origin beans or in-house blends.
Just as long as you don’t drink it first thing after waking up.
The work is published open access in Ultrasonics Sonochemistry, a journal that has possibly never had such widespread interest before.
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