Lovers of cold coffee can now look forward to an innovation that significantly shortens the preparation time, while maintaining the highly valued taste qualities.
Engineers from the University of New South Wales (UNSW) in Sydney developed a technique using sound waves to reduce the brewing time of cold coffee from hours to just minutes. This innovative method allows you to prepare cold coffee in less than three minutes, without compromising the taste.
The process relies on the use of an ultrasonic reactor to accelerate the cooking of ground coffee beans.
Ultrasonic reactor
To tackle the challenge of speeding up the cold brew process, the UNSW team, led by Dr Francisco Trujillo, used an existing Breville espresso machine model and integrated their own transmission system into its patented sound. The system connects a screw-on probe to the coffee basket via a metal horn, turning a standard espresso filter into a powerful ultrasonic reactor.
The reactor works by injection sound waves at a frequency of 38.8 kHz at several points across its walls, thus creating several areas of acoustic cavitation inside the reactor. This configuration doubles the extraction performance and caffeine concentration compared to non-sonic samples.
Advantages of ultrasound
Dr. Trujillo, lead author of the study and a food processing engineer at UNSW, explains that the ultrasonic process speeds up the extraction of oils, aromas and flavors from ground coffee. “Ultrasound accelerates the extraction process through acoustic cavitation“, He said. “When the acoustic bubbles gather near the ground coffee, they create micro-jets powerful enough to dig and break the coffee beans, intensifying the extraction of aromas and flavors from the beverage..”
He adds that the acceleration is enormous, because the preparation time is reduced from 12 to 24 hours to less than three minutes. The goal was to make the process as simple as preparing a classic espresso.
The same taste in less time
In collaboration with researchers from the University of Queensland, coffee samples were sent to the Queensland Agriculture and Food Alliance (QAAFI) for in-depth sensory analysis. Samples included coffee cold sonicated at room temperature for one minute, another for three minutes, and the third infused for 24 hours at four degrees Celsius without resonance.
They were evaluated based on their aroma, texture, flavor and aftertaste attributes. “Compared to the 24-hour beverage, the 1-minute sound sample received similar ratings, particularly for taste and aftertaste, including bitterness, acidity, texture, and aroma“, explains Dr. Trujillo. However, it scored lower in aroma intensity and dark chocolate aroma, indicating a slightly lower extraction compared to the 24-hour infusion.
A revolution for the beverage industry
THE ultrasound it can be applied in several areas of the food industry, including drying, extraction, emulsification and crystallization, making the process faster and more efficient. dr. Trujillo points out that this technology can also be used to accelerate procedure for preparing teas.
“With this technology, we offer coffee shops, restaurants, and even coffee lovers at home the ability to produce beverages on demand, eliminating the need for large brewing and cooling units.“, he concludes.