Science to save you from sour milk

Trusting those expiration dates on food is always a bit of a guessing game. Knowing if refrigerating the item extended its lifespan, or whether a lack of smell means that it is still fresh isn’t always an exact science. Now, thanks to researchers at Peking University in Beijing, China, there may soon be a new “smart tag” on your perishables that will answer those questions.

These tags, made of a gel-like substance, will stick onto the outside of containers to indicate the freshness of the product. The tags can be used to show whether food is fresh, or if medicine is still active.

Ranging from 100% fresh to 100% spoiled, the color-coding of the tags can be programmed to imitate the deterioration process of a product, changing color gradually until it indicates that the product is no longer safe.

While counter-intuitive, the color-coding system is simplistic and gives clear indication of the freshness. When at the peak freshness, the tag will show red, and will slowly change color to orange, yellow, and then green when it is spoiled. The tags use non-toxic metallic nanorods, which begin red in color, that react to the length of time that bacteria grows in food, along with silver chloride and vitamin C to regulate the color change.

In addition to the useful nature of the product, they also carry a very minimal price tag. Costing significantly less than a penny each, these tags could be a cost-efficient addition to food and pharmaceutical products.

The tags are not available yet in the United States, but the technique has been patented in China. These findings were taken to the national meeting of the American Chemical Society on Monday and the researchers said they are reaching out to manufacturers for the tags.

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