We have been heating water to make coffee for a century. It wasn’t necessary: ​​just ultrasounds

For many people, making coffee is practically as important a ritual as drinking it. Because by the way: anyone can make coffee, but not everyone does it well. Following scrupulously the Specialty Coffee Association recipe, To make the canonical espresso you need 7 to 9 grams of coffee and force the passage of water at 90.5 – 96.1ºC at 9 – 10 atmospheres of pressure. The coffee grind should be such that the extraction time is 20 to 30 seconds. That’s what any barista or super-automatic machine should aspire to. Next to nothing.

Although the coffee maker is not on the list of appliances that increase the electricity bill at home the most, on an industrial scale things change: this process of bringing the water to those temperature and pressure conditions represents a significant energy cost. So an Australian research team has found another way to do it without the need for heat: ultrasound.

The invention. To make coffee with ultrasound and without heat, the first thing you need is a filter holder tuned in an ultrasonic reactor where high-frequency sound waves induce acoustic cavitation. It sounds backwards, but in practice the ultrasonic coffee maker that the University of New South Wales has patented looks like a normal coffee maker with a small accessory.

Let’s go back to the acoustic cavitation. Roughly speaking, the waves create thousands of tiny bubbles within the water that, when collapsing with the ground coffee, act as if they were a hammer: they break the surface of the heat and release what is inside, that is, flavors, oils, aromas and caffeine. The result is an espresso with a concentration equivalent to conventional espresso in less than three minutes.

Why is it important. Because you can make coffee consuming much less: for the same amount of drink, this ultrasonic system consumes only 24.3% of the energy required by a conventional espresso machine. On a domestic scale the savings are small, but for a factory that 75% saving is significant. And it has another win-win for the industry: the coffee obtained comes out cold and concentrated, so there is no need to wait for it to cool (or chill it), it is ready to be mixed directly with milk or water in a factory, which saves time, energy and money.

Context. Although it sounds exotic, ultrasounds are not new in the food industry. Without going any further, They have been used for decades for the processing of juices, oils or dairy products. In fact, its application to coffee is not new either: at least two manufacturers have brought similar infusion devices to the marketbut they didn’t go that far: the UNSW project goes one step further. Thus, it is the first that has achieved an espresso (not a diluted cold brew, your previous job) that passes for a conventional espresso in a sensory tasting with 100 participants.

In detail. The study analyzed the influence of variables such as grind size, extraction ratio and duration of ultrasonic treatment. And he came to the conclusions that a finer grind managed to extract the flavor more efficiently and an infusion time of between 2.5 and 3 minutes gave the best results.

For sensory tasting, the team conducted random blind tests with four beverages: traditional espresso, ultrasonic espresso, traditional filter coffee, and ultrasonic filter coffee. In the case of espresso, those who participated were unable to clearly distinguish which had been prepared traditionally and which had been prepared ultrasonically as there were no significant differences in aroma, flavor, bitterness or overall rating. Curiously, for filter coffee the ultrasonic version was preferred.

Yes, but. The first limitation of this peculiar way of making coffee is time: compared to less than half a minute, with ultrasound the process lasts up to three minutes. A time that can be interesting (due to energy savings) on an industrial scale, but not for hospitality and homes.

On the other hand, and although it comes out with flying colors in the blind tastings, they have not analyzed the presence of healthy compounds in coffee, such as polyphenols or antioxidants, nor their proportion. Drinking coffee is a pleasure that also has health benefits. Finally, the ultrasonic coffee maker is currently a prototype: the enormous leap from the laboratory to the industrial scale remains to be made.

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