App controlled sensor can tell when beer has gone stale

Chemists have developed a method that allows brewers to measure the freshness of beer, using a polymer sensor that changes colour upon detecting furfural, a compound that appears when this beverage ages and gives it a stale flavour.

The sensors change from yellow to pink when they come into contact with a beer containing furfural. CREDIT: UCM

The sensor can be controlled from a smartphone app also created by the team.

As beer ages, depending on the beer type and its storage conditions, its flavour may be altered as a result of changes in the chemical composition. This has a negative effect on the quality of the flavour.

Now, a team of chemists, led by the researchers Elena Benito-Peña and María Cruz Moreno-Bondi from the Complutense University of Madrid (UCM), has developed a simple, low-cost method capable of measuring whether or not beer has gone stale, simply by using a sensor and a smartphone app.

The system developed by the researchers at the UCM consists of sensor discs that detect the presence of furfural in beer. These sensors, made from a polymer similar to the one used to manufacture contact lenses, have been designed to change colour (from yellow to pink) when they come into contact with a beer containing furfural.

“We have incorporated an aniline derivative into the sensor material which reacts with the furfural and produces a pink cyanine derivative that allows us to identify the presence of the marker in the sample. The intensity of the colour increases as the concentration of furfural in the beer rises and, thus, as more time passes since the beer was produced,” explains the Benito-Peña.

The results of the tests on the new system “have been very satisfactory,” explain the scientists. “The measurements have been taken using samples sent directly from the brewing company with different production dates and distinct degrees of aging. These same samples were also sent to a laboratory where they were analysed using gas chromatography coupled with mass spectrometry. The results we obtained were completely comparable.”

Mobile app allows for the identification of furfural

The team has also created a mobile app that, by taking a picture of the sensor disc, allows for the identification of the amount of furfural present in the beer. With this data, the degree of freshness can be determined.

The application is available as open source, meaning that any programmer can utilise and modify it to be used on other platforms. At the moment the app is available for Android phones but in the future it will also be available for Apple IOS.

The researchers also indicate that the method could be adapted to be used with other food products such as honey, milk and coffee.