A Colombian chemical engineer has used sound waves to make what he calls “ultrasonic espresso.” The method can reduce energy consumption in preparing coffee by 75%.
Most of us think of espresso as a hot, high-pressure ritual. We put finely ground coffee in a machine, force boiling water through it and, in around 30 seconds, we obtain a concentrated dose, with cream, aroma, bitterness, body and caffeine.
As a Colombian, the chemical engineer Francisco Trujilloinvestigador da UNSW Sydney, likes to think he has coffee in his blood — and is proud to come from a country known for producing some of the best coffee beans in the world.
Maybe that’s why he spent so much time in his lab, with his team, asking a simple question: what espresso really needs hot water?
The result of these hours of investigation, presented in a recently published in Journal of Food Engineeringsuggests that the answer may be noexplains Trujillo no.
The team created what it calls a ultrasonic espresso: a room temperature extraction process that uses high-frequency sound waves to extract the flavor, oils, aroma, and caffeine from ground coffee.
The result is a coffee with the intensity of an espressoprepared in less than three minutes, but with much less energy than the conventional method.
Save up to 75% energy by not heating the water it is a modest benefit for home consumers or small coffee shops. But for companies that produce ready-to-drink coffee drinks on an industrial scalecan be very significant.
A concentrated coffee at room temperature could be used directly in bottled drinks, milk-based drinks or cold coffee products. It could also be transported as a concentrate and diluted later. This would not only reduce energy consumption, but also potentially processing time.
Ultrasounds replace heat
The key to the new process lies in ultrasound. These are sound waves above the threshold of human hearing, explains Trujillo.
On your system, a small metal device called a transduceris placed against the side of a traditional espresso basket and easy to vibrate quickly. These vibrations spread through water and ground coffeeo.
This creates a phenomenon known as acoustic cavitation. Tiny bubbles form in the liquid, which then collapse.
When these bubbles collapse near the coffee particles, they produce microscopic jets and forces that act a bit like cleaning brushes. They score and fracture the surface of ground coffee, helping flavor compounds, oils and caffeine pass into the water much faster than they normally would at room temperature.
In other words, ultrasounds allow us replace heat by mechanical energy.
This is not the same as cold brewwhich is typically prepared by steeping coffee in cold water for 12 to 24 hours. It tends to be smooth, balanced and much less concentrated than an espresso. In previous work, Trujillo used ultrasound to dramatically speed up cold brew.
But the challenge of this project was different: would it be possible to produce something with the intensity, body and strength of an espresso, without heating the water?
To achieve this, the team adjusted several variables. THE extraction ratio was one of the most important: the amount of water used for each gram of coffee. With too much water, the drink becomes diluted; With less water, extraction becomes difficult.
The degree of grinding was also important. Finer grinds allowed the flavor to be extracted more quickly. Finally, we tested how long the ultrasounds should be applied. We concluded that the sweet spot was between about two and a half and three minutes.
The taste test
Of course, making concentrated coffee in a laboratory is one thing. The real test is know if people want to drink it.
The team then conducted a “blind test” with around 100 regular coffee consumers. They were not trained tasters; were common consumerswho drink coffee at least once a week.
Participants proved four coffees in identical cupss: traditional espresso, espresso prepared with ultrasound, traditional filter coffee and filter coffee prepared with ultrasound. All were freshly prepared, cooled to the same temperature and presented in random order.
In the case of espresso samples, participants couldn’t distinguish reliably the traditional version of the ultrasonic version. There were no significant differences in aroma, flavor, bitterness or overall enjoyment.
In the case of filter coffeethe version prepared with ultrasound even had better general acceptance; participants considered its bitterness more pleasant.
These results show that espresso may not need to start with hot water after all. By using sound waves to agitate ground coffee, we are able to create the same richness, body and intensity, but with much less energy.
