Stale-beer tester could prove food freshness

It’s the worst of things for a seasoned beer drinker — chugging down a beer, only to find that it is stale. By then it’s too late. The tastebuds have been ruined and you might as well embrace an early night’s sleep.

But a solution is at hand: chemists from the Complutense University of Madrid have found a cheap and quick way for people to measure how fresh their beer is.

Their solution uses a polymer sensor that changes colour when it detects furfural. This is a compound that pops up when beverages age to the point where they start going stale. The sensor can be dropped in a drink, and changes colour from yellow to pink when it comes in contact with any beer that contains furfural.

Writing in the journal Analytical Chemistry, chemist Elena BenitoPeña said: “The intensity of the colour increases as the concentration of furfural in the beer rises as more time passes since the beer was produced.”

That reaction is sensitive enough for beer drinkers to take a chance on only slightly stale drinks — if they’re stuck in the desert and have no other option. The linked smartphone app then tells would-be drinkers how stale the beer is, depending on the intensity of the colour change.

Until now, breweries have had to use a complicated and expensive process to check whether their beverages had gone off. This has made it prohibitively expensive for bars and consumers to check their drinks. Elena Benito-Peña said: “These methods i nvolve the use of expensive equipment and sample preparation is very time-consuming.”

The system has been tested at breweries, where its findings were measured against the results from the breweries’ own — much more expensive — checks. It was also tested against freshness tests at a laboratory.

Beer is just the start, according to the team’s research paper. “The global market for this product is huge. But it can also be used with other food products, such as honey, milk, coffee, etcetera.”

That application could be greatly beneficial in countries where a great deal of food is thrown away because it goes stale right after purchase. In South Africa, nine million tonnes of food are thrown away every year, according to the Institute of Waste Management.

Fixing a problem for beer drinkers could go a long way towards fixing a great problem for all consumers.