Sniffing out salmonella

Researchers at Strathclyde University have developed an oxygen sensor which indicates how long the contents of food packaging have been exposed to air.

The unique ‘oxygen sniffer’ changes colour as soon as it is exposed to air, can be cast onto paper, plastic or foil and can be set to change colour after a predetermined amount of time – hours, days or weeks.

This means the public need never eat food that’s gone off again, lessening the risk of salmonella or food poisoning. 

What’s more, the sensors cost less than 1p per unit and can also be deployed in medical situations to detect oxygen leaks, in museums to protect artefacts in oxygen-free environments, in double-glazing or to safeguard tamper-proof packaging in banks.  

Professor Andrew Mills of the University’s Department of Pure and Applied Chemistry developed the sensor with support from PhD student Soo-Keun Lee.    

“Given the public’s interest in food safety and long-lasting, fresh food, oxygen exposure is a major problem for the food industry,” said Professor Mills.  

“Oxygen is the element that makes food perish, even if there is only 1% present in the packaging, and the health implications of food deterioration can be serious. The benefit of this device is that it allows consumers to gauge whether or not their purchases are still edible.”  

 “Although an oxygen sensor sounds like a simple concept, it was actually extremely difficult to develop. Most such sensors themselves deteriorate when exposed to air, but our sensor is novel because it is not activated until exposed to UV light. This means it can be stored indefinitely. At packaging stage a UV light is used to activate the sensor and oxygen exposure begins to be monitored.”

If the packaging is damaged by even a tiny pinprick, the sensor then changes colour, while in normal, safe circumstances the sensor stays clear until the package is opened.  As a major breakthrough for the food packaging industry, the sensors can also be re-used in a variety of environments if re-set by UV light.