Creating a new way to brew coffee – BeanScene

Researchers from UNSW Sydney have successfully created a new way of making coffee – one which can cut energy use by up to 75 per cent.

This new brewing process has been created using room temperature water and soundwaves to create an “espresso-strength” coffee. The researchers, led by Dr Francisco Trujillo, say it could be significant for businesses that prepare coffee-based RTD products.

“We call it an ultrasonic espresso,” says Dr Trujillo. “It’s a different process, but you get the same richness and concentration of a normal espresso in under three minutes.

“Traditionally, espresso is made by forcing hot water through coffee under pressure. But with ultrasound we can use room-temperature water instead.

“When we gave our ultrasonic espresso to 100 regular coffee drinkers in a randomised test, they could not tell it apart from a normal espresso.”

The process of creating an ultrasonic espresso starts with the filter basket, which is transformed into an ultrasonic reactor that generates high frequency soundwaves that help extract flavour, aroma, and body from the coffee grounds.

A small metal device called a transducer generates ultrasound while pressing against the side of the basket, causing it to vibrate rapidly.

This creates acoustic cavitation, which is the rapid formation and collapse of microscopic bubbles near the coffee particles which accelerate the brewing process and enable flavour compounds, oil, and caffeine to move into the water.

“We have been working on a range of parameters to discover how to make the perfect ultrasonic espresso,” says Dr Trujillo.

“The most important was the brew ratio – that is how much water is used per gram of coffee – because this helps ensure the final drink is concentrated and not too diluted.

“Another important factor is how finely the coffee beans are ground. We found that by grinding finer we could extract the flavour more rapidly.

“We also experimented with how long the sound waves were applied, as this can affect both the concentration and flavour of the coffee. What we found is that between two-and-a-half and three minutes is a sweet spot for producing a balanced cup.”

The findings have been published in the Journal of Food Engineering.