Now, 'colour-coded' smart tags to tell if food is spoiled

Researchers have come up with colour-coded smart tags which will tell the customers if the food has spoiled without even opening the container.

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

Chao Zhang, the lead researcher of the study said that the tags have a gel-like consistency, are really inexpensive and safe, and can be widely programmed to mimic almost all ambient-temperature deterioration processes in foods.

The tags contain tiny metallic nanorods that, at different stages and phases, can have a variety of colours like red, orange, yellow, green, blue and violet.

Zhang said that the gold nanorods they used are inherently red, which dictates the initial tag colour and silver chloride and vitamin C are also in the tags, reacting slowly and controllably.

According to the researchers, the metallic silver gradually deposits on each gold nanorod, forming a silver shell layer, which changes the particle's chemical composition and shape.

The study was published in ACS Nano.