Subjecting Coffee Grounds to Ultrasonic Waves Results in a 60-second Cold Brew

As temperatures rise, lots of coffee lovers are switching to iced coffee. However, folks with sensitive stomachs prefer cold brew because of its lower acidity, which makes it a go-to caffeine choice all year round. Cold brew is smoother, creamier, and sweeter compared to hot coffee. The brewing process involves steeping coarse coffee grounds in cold water for over 24 hours. This extended steeping time reduces acidity and allows the coffee to develop its full flavor.

Demand for chilled drinks like iced coffee and cold brew is increasing at coffee shops. However, this rise in popularity poses logistical challenges because cold brewing typically requires 24 hours of refrigeration to create a flavorful, less bitter concentrate.

Eager to speed up the process, researchers at Australia’s University of New South Wales tested an innovative brewing method: using ultrasonic waves to treat coffee grounds. According to chemical engineering professor Francisco Trujillo, this method has become his top choice for making coffee. Trujillo shared his preference for this rapid cold brew method in a recent conversation with New Scientist, along with details of his team’s research published in the journal Ultrasonics Sonochemistry.

Research Methodology and Findings

While conducting a separate soundwave experiment, the researchers stumbled upon the time-saving technique. Initially exploring the possibility of increasing antioxidant levels by further breaking up coffee grounds using acoustic cavitation, Trujillo and his team attached a Langevin transducer to a Breville Dual Boiler BES920 espresso machine. They then subjected the coffee to 38.8 kHz frequency sound waves. Although the antioxidant levels remained mostly unchanged, the researchers found that the resulting cup of coffee was remarkably delicious.

Optimizing the Ultrasonic Cold Brew Process

Continuing their experimentation, the researchers refined their cold brew process. In one setup, they exposed the espresso to 60 seconds of ultrasound waves while intermittently pumping ambient temperature water through the grounds at 12-second intervals. In another configuration, they extended the total time to 3 minutes. At the Queensland Alliance for Agriculture and Food Innovation, taste trials were carried out using these techniques to assess the texture, flavor, fragrance, and aftertaste of the coffee.

The results were in: the 1-minute brew yielded scores similar to the traditional 24-hour method, although it seemed to fall short in aroma intensity, suggesting under-extraction. On the other hand, the 3-minute brew regained the aroma intensity but also introduced a slightly more bitter taste. Essentially, it was found that somewhere between 1 to 3 minutes of ultrasonic acoustic cavitation could produce cold brew of arguably the same quality, eliminating the need for extended waiting times.

Implications and Future Directions

Certainly, while the scientists saved time, there was an initial cost hurdle to overcome. The first setup with the espresso machine and transducer required nearly $10,000 worth of equipment, as reported by New Scientist. However, Trujillo mentioned that subsequent refinements significantly decreased this expense to “a fraction of the cost.” Even if the ultrasonic method doesn’t transition out of the lab, Trujillo’s team will stay well-caffeinated, ready to pursue any future advancements in coffee technology.

Read the original article on: PopSci

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