Coffeemen, throw out teapots.
Delicious espresso is impossible without three things: small grinding, pressure and hot water. Engineers from the University of New South Wales in Sydney showed that one point from this bundle can be removed. They prepared coffee espresso fortress on the water of room temperature, and the heating was replaced by ultrasound.
Dr. Francisco Trujillo’s team from UNSW’s School of Chemical Engineering has developed a brewing method in which high-frequency sound waves help water faster pull out of the ground a coffee aromatic compounds, butter and caffeine. The study was published in the Journal of Food Engineering. According to the authors, the refusal to heat water can reduce energy consumption by about 75%.
Ultrasound is a sound wavelength with a frequency above the audible range. A person does not hear them, but in the liquid they create strong local pressure drops. In the UNSW coffee system, these waves pass through the water and layer of ground grains, accelerating extraction - the transition of taste substances from coffee to water.
In the usual espresso coffee machine is: hot water under pressure passes through a tightly rammed coffee in a filter basket. The temperature speeds up the dissolution of the desired compounds, and the pressure helps the water pass through the dense layer of grinding. In the new system, hot water replaces the water of room temperature, and the main work to accelerate the extract is performed by ultrasonic fluctuations.
At the heart of the installation is an ultrasonic transducer - a small metal element that is pressed to the side of the coffee cart. It creates vibrations and causes the basket to vibrate quickly. Vibrations pass through ground coffee and water, turning the usual filter basket into a small ultrasound reactor.
The main physical process is called acoustic cavitation. Microscopic bubbles quickly appear and collapse in the liquid. When the bubble collapses next to a coffee particle, a tiny jet of liquid and a local impact on the surface of the grain occurs. As a result, the surface of the particles is damaged, microcracks appear in it, and the water quickly reaches the inner layers.
That is why cold water has time to extract from coffee what usually requires heating. The water is faster than facilitators, butter and caffeine. At the output, a concentrated drink with a density, taste and caffeine content, close to the classic espresso, but without boiling water and with less energy.
For Trujillo, this is not the first work with ultrasonic coffee. Previously, his team patented a system that reduces the preparation of sorcered brew from 12-24 hours to a few minutes. But the witch palm is in taste and composition different from espresso: it is usually softer, less sharp, more diluted and contains about five times less caffeine by the same volume. The new task was more difficult: to get the espresso fortress, and not fast cold coffee.
The researchers had to select the parameters of the brewing. One of the main was the brew ratio - the ratio of water and coffee. If there is too much water, the drink is diluted. If not enough, the extraction goes worse and the taste can become unbalanced. The team also checked grinding: smaller particles are delivering substances faster into the water because they have more open surface.
Separately, scientists adjusted the time of exposure to ultrasound. Too short treatment does not have time to stretch the desired concentration. Too long can change the taste and increase excess bitterness. In experiments, the best balance was in the range from two and a half to three minutes.
To check the taste, the team held a blind tasting. Participants didn’t know what kind of coffee was being tasted. The test includes four drinks: classic espresso, ultrasonic espresso, ordinary filter coffee and filter coffee prepared with ultrasound. All samples were cooked fresh, cooled to the same temperature, served in the same encoded cups and placed randomly to remove bias.
About 100 regular coffee lovers participated in the tasting. These were not professional tasters, but ordinary consumers who drink coffee at least once a week. Each appreciated the aroma, taste, bitterness and general impression on a nine-point scale.
The result for espresso turned out to be the main argument in favor of the method. Participants did not find significant differences between the classic drink and the version on the water of room temperature with ultrasound. Most could not reliably distinguish one option from another, there was no explicit preference either.
With filter coffee, the picture was even more interesting. The ultrasonic version was liked by the participants more than usual. Particularly noticeable was the assessment of bitterness: coffee cooked with ultrasound was perceived more pleasantly. For researchers, this is an important result, because the technology has not just accelerated the process, but in some variants has improved the taste.
A homemade drug with ultrasound is theoretically possible, but scientists see the main commercial interest in the kitchen technique. Industrial production of coffee-based beverages is more important. Factories that produce cold coffee in bottles, coffee concentrates and dairy coffee drinks need to quickly get large amounts of stable extract. There is energy and time savings especially noticeable.
Concentrated coffee can be used immediately in the production of ready-made drinks or transported as a basis, and then diluted with water, milk or other components. If the technology can be scaled, manufacturers will be able to quickly receive espresso strength extract without constant heating of the water. For the industrial line, the reduction of energy consumption to 75% is converted not into a pleasant laboratory figure, but in direct savings on each production cycle.
The researchers believe that the system can be brought to an automatic coffee machine and scaled up for businesses. The next practical question is not only taste, but the reliability of work in the flow: the stability of the extract, the service life of ultrasonic elements, sanitary requirements and the cost of equipment. The laboratory result has already shown the main thing: strong coffee does not need to start with hot water.
Delicious espresso is impossible without three things: small grinding, pressure and hot water. Engineers from the University of New South Wales in Sydney showed that one point from this bundle can be removed. They prepared coffee espresso fortress on the water of room temperature, and the heating was replaced by ultrasound.
Dr. Francisco Trujillo’s team from UNSW’s School of Chemical Engineering has developed a brewing method in which high-frequency sound waves help water faster pull out of the ground a coffee aromatic compounds, butter and caffeine. The study was published in the Journal of Food Engineering. According to the authors, the refusal to heat water can reduce energy consumption by about 75%.
Ultrasound is a sound wavelength with a frequency above the audible range. A person does not hear them, but in the liquid they create strong local pressure drops. In the UNSW coffee system, these waves pass through the water and layer of ground grains, accelerating extraction - the transition of taste substances from coffee to water.
In the usual espresso coffee machine is: hot water under pressure passes through a tightly rammed coffee in a filter basket. The temperature speeds up the dissolution of the desired compounds, and the pressure helps the water pass through the dense layer of grinding. In the new system, hot water replaces the water of room temperature, and the main work to accelerate the extract is performed by ultrasonic fluctuations.
At the heart of the installation is an ultrasonic transducer - a small metal element that is pressed to the side of the coffee cart. It creates vibrations and causes the basket to vibrate quickly. Vibrations pass through ground coffee and water, turning the usual filter basket into a small ultrasound reactor.
The main physical process is called acoustic cavitation. Microscopic bubbles quickly appear and collapse in the liquid. When the bubble collapses next to a coffee particle, a tiny jet of liquid and a local impact on the surface of the grain occurs. As a result, the surface of the particles is damaged, microcracks appear in it, and the water quickly reaches the inner layers.
That is why cold water has time to extract from coffee what usually requires heating. The water is faster than facilitators, butter and caffeine. At the output, a concentrated drink with a density, taste and caffeine content, close to the classic espresso, but without boiling water and with less energy.
For Trujillo, this is not the first work with ultrasonic coffee. Previously, his team patented a system that reduces the preparation of sorcered brew from 12-24 hours to a few minutes. But the witch palm is in taste and composition different from espresso: it is usually softer, less sharp, more diluted and contains about five times less caffeine by the same volume. The new task was more difficult: to get the espresso fortress, and not fast cold coffee.
The researchers had to select the parameters of the brewing. One of the main was the brew ratio - the ratio of water and coffee. If there is too much water, the drink is diluted. If not enough, the extraction goes worse and the taste can become unbalanced. The team also checked grinding: smaller particles are delivering substances faster into the water because they have more open surface.
Separately, scientists adjusted the time of exposure to ultrasound. Too short treatment does not have time to stretch the desired concentration. Too long can change the taste and increase excess bitterness. In experiments, the best balance was in the range from two and a half to three minutes.
To check the taste, the team held a blind tasting. Participants didn’t know what kind of coffee was being tasted. The test includes four drinks: classic espresso, ultrasonic espresso, ordinary filter coffee and filter coffee prepared with ultrasound. All samples were cooked fresh, cooled to the same temperature, served in the same encoded cups and placed randomly to remove bias.
About 100 regular coffee lovers participated in the tasting. These were not professional tasters, but ordinary consumers who drink coffee at least once a week. Each appreciated the aroma, taste, bitterness and general impression on a nine-point scale.
The result for espresso turned out to be the main argument in favor of the method. Participants did not find significant differences between the classic drink and the version on the water of room temperature with ultrasound. Most could not reliably distinguish one option from another, there was no explicit preference either.
With filter coffee, the picture was even more interesting. The ultrasonic version was liked by the participants more than usual. Particularly noticeable was the assessment of bitterness: coffee cooked with ultrasound was perceived more pleasantly. For researchers, this is an important result, because the technology has not just accelerated the process, but in some variants has improved the taste.
A homemade drug with ultrasound is theoretically possible, but scientists see the main commercial interest in the kitchen technique. Industrial production of coffee-based beverages is more important. Factories that produce cold coffee in bottles, coffee concentrates and dairy coffee drinks need to quickly get large amounts of stable extract. There is energy and time savings especially noticeable.
Concentrated coffee can be used immediately in the production of ready-made drinks or transported as a basis, and then diluted with water, milk or other components. If the technology can be scaled, manufacturers will be able to quickly receive espresso strength extract without constant heating of the water. For the industrial line, the reduction of energy consumption to 75% is converted not into a pleasant laboratory figure, but in direct savings on each production cycle.
The researchers believe that the system can be brought to an automatic coffee machine and scaled up for businesses. The next practical question is not only taste, but the reliability of work in the flow: the stability of the extract, the service life of ultrasonic elements, sanitary requirements and the cost of equipment. The laboratory result has already shown the main thing: strong coffee does not need to start with hot water.
