Color-changing “smart labels” track food freshness

By Casey Frye, CCNN Writer

advanced food label
The tiny labels change color based on time and temperature, just like food freshness.

According to recent studies, people tend to throw out perfectly edible food on a daily basis. Why? Because the expiration dates on products are confusing as heck, and people would rather be safe than sorry. The Food and Drug Administration announced their plans to remake the dates in a way that’s clear for everyone, but in the meantime, Chinese researchers have created a tag that will change color based on freshness. The label is accurate, easy to read, and number-free.

These high-tech labels are officially called “time-temperature labels”, and as you might have guessed, it’s because both the time and temperature cause it to change color. For example, say there’s a gallon of milk in your fridge with the label attached. As the days pass, the label will morph from a rich red color, to bright orange, to murky yellow, to grungy green, and then eventually a  nasty neon green shade. However, the process will happen a lot faster if the temperatures are higher, just like milk will expire faster if kept in warm atmospheres.

The genius design of the labels is based on silver and gold materials. Over time, the silver will react with the gold and cause it to change colors. So, the more that time passes, the faster the colors change. Also, the changing rates can be altered for specific food items, so that the labels will change faster for food that rots quickly, or change slower for items with long shelf lives.

Even though using precious metals like gold and silver in food labels sounds expensive, each one costs a small fraction of a penny to make!

Images courtesy of the American Chemical Society on YouTube.