How many of you have looked at the milk container in the fridge and wondered if the milk is still safe to drink? Do you then do the awful smell test or even taste it? Researchers in China have come up with a solution that uses smart gel tags to tell us when milk has turned sour. The gel technology can be used on many other foods and medications too.

The color-coded gel tags are attached to the outside of a food container and will change colors to indicate whether the food inside is spoiled. We don't even need to open the container.

This wonder gel was recently presented by a Chinese research team from Peking University in Beijing at the American Chemical Society's national meeting held in Dallas, Texas. The size of a corn kernel, the gel tag changes color over time, mimicking the time it takes microbes to grow in foods. The tag also takes into consideration temperature changes that can affect food before the expiration date.

According to lead researcher, Chao Zhang, Ph.D., the tag starts out the color of red to mean fresh. Over time, the tag changes its color to orange, yellow and later green, which indicates the food is spoiled.

The following is a video from the American Chemical Society about the gel tags:

Even more amazing is that the smart gel tag costs only a fifth of a penny each, when it is estimated that an average American family throws away US$2,000 of spoiled food each year.

I do have one suggestion for Dr. Zhang. Change the safe color to green and the unsafe color to red and then it will be easier to remember, just like traffic lights.