Color-Coded 'Smart Tags' Tell You If Food Is Fresh

by Adrienne Vogt

One of the grossest — and most upsetting — things in this world is when you're really, really looking forward to a delicious sandwich — and then you take a big bite and immediately spit out the contents, because the meat has spoiled. I know, #firstworldproblems. However, a new invention aims to determine the freshness of food before you take that first bite: Color-coded smart tags could save consumers unnecessary danger and disgust.

Food scientists in China have developed color-coded smart tags that can be placed on the outside of any container to measure its life cycle. The researchers say that the smart tags will cut down on trash and prevent people from guessing whether their food is safe to eat.

So how does the smart tag work? It's rather easy, actually: Simply place the tiny, gel-like tag on a perishable food container, and the tag will change from red to green over time. Food is freshest when the gel is red and should probably be tossed when it gets to green, but the color can extend to a violet color when dealing with longer-lasting foodstuffs. As explains:

The color change is caused by tiny silver and gold nanorods reacting with each other over time. Metallic silver is slowly deposited on the gold nanorod, changing the apparent color of the material. They don’t actually respond to what’s going on in the food — it’s an estimate based on common expiration dates.

The researchers tested the tags with milk, but they say the invention can be used for anything — even prescription drugs. Even better, they're very cheap to produce, costing less than a penny for each tag.

The development would make grocery shopping a lot easier. Instead of rifling through cartons of milk or boxes of frozen foods for expirations dates, shoppers could see right away how long a product has been sitting on the shelf. I'm guessing it may make grocery-store owners a bit uneasy, though, since they may have to toss more products that are only halfway through their shelf lives. But the tags were developed to protect both food-makers and consumers, according to Chao Zhang, lead researcher of the study.

A real advantage is that even when manufacturers, grocery-store owners and consumers do not know if the food has been unduly exposed to higher temperatures, which could cause unexpected spoilage, the tag still gives a reliable indication of the quality of the product.

Or, just go by what your mom told you: When in doubt, throw it out.