Scientists have invented a sensor film that changes colour to show when fresh produce has gone off.
The plastic film, developed by the Fraunhofer Research Institution for Modular Solid State Technologies in Munich, which changes from yellow to blue to indicate when meat or fish has gone bad, could be incorporated into packaging.
The film responds to biogenic amines, the molecules produced when foods such as meat and fish decay. They are also responsible for the unpleasant smell from food, which has gone off.
If amines are released into the air within the packaging, the indicator dye on the sensor film reacts with them and changes its colour from yellow to blue.
"Once a certain concentration range is reached, the colour change is clearly visible and warns the consumer," the Daily Mail quoted Dr Anna Hezinger, one of the researchers on the project, as saying.
"This is not only interesting when it comes to identifying foods that have become inedible.Many people are also extremely sensitive to the presence of certain amines, which makes a warning all the more important for them.
"Unlike the best-before date, the information on the sensor film is not based on an estimate but on an actual control of the food itself," Hezinger added.