New ‘Smart’ Gel Tags Aim To Prevent Leftovers From Becoming Science Experiments

Most of us aren’t scientists, but every once in awhile, nearly everyone unintentionally runs a science experiment in their refrigerator. If left long enough, for example, milk turns into a foul smelling yogurt analog. Empirical fact. Most of us know this because, distrusting the ‘sell by’ label, we take a sniff before pouring.

Researchers at China’s Peking University want to save you a few retch-inducing moments in your life with a new simple measurement method. Led by Chao Zhang, Ph.D, the group invented a gel-like, color-coded “smart tag” to alert consumers if perishable foods have gone bad or old medicines are still active.

The Peking University gel tags contain metallic nanorods specially calibrated to change color at about the same rate microbes grow in food. Additionally, the process is sensitive to temperature—a printed date tells you when a product was packaged, but it doesn't tell you anything about how it's been stored since then. The tag would register whether the product was exposed to temperature fluctuations and communicate that to consumers.

"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 says.