Scientists develop smart tag to warn when food goes off

19 Mar 2014

The green smart tag on the bottle indicates that the product is no longer fresh. Photo via Chao Zhang, PhD

No doubt a relief to all who have had the displeasure of smelling gone-off milk, a team of scientists have developed a smart tag that will change colour when food in a container goes off.

At a meeting of the American Chemical Society in Dallas, Texas, the researchers revealed their smart tag could indicate whether a carton of milk has turned sour or a can of green beans has spoiled without the need to open the containers.

The tag, which would appear on the packaging, could also be used to determine if medications and other perishable products were still active or fresh, according to the team.

The gel-like tag will be relatively inexpensive and, most importantly, safe to be around food and health products.

It can also be widely programmed to mimic almost all ambient-temperature deterioration processes in foods.

Chao Zhang, PhD, as lead researcher of the study, explained the colour of the tag will start off red or reddish orange, indicating freshness, but over time, the tag will change colour to orange, yellow and later green, which will indicate the food is spoiled.

Zhang and his team tested the tag’s capabilities using e.coli that would be commonly found in spoiled milk.

Although the nanorods are made of gold and silver, a tag would still be inexpensive. All the chemicals in the tiny tag cost less than one cent: US$0.002 to be exact.

“In addition, all of the reagents in the tags are nontoxic, and some of them (such as vitamin C, acetic acid, lactic acid and agar) are even edible,” Zhang said.

Colm Gorey was a senior journalist with Silicon Republic