Scientists develop sensor to detect spoiled milk

Researchers have developed a sensor that can tell if milk is still fresh or has gone stale.

The sensor consists of chemically coated nanoparticles that react to the gas produced by milk and the bacterial growth that indicates spoilage, according to Shyam Sablani, one of the researchers.

"If it's going bad, most food produces a volatile compound that doesn't smell good. That comes from bacterial growth in the food, most of the time. But you can't smell that until you open the container," said Sablani.

The sensor detects these volatile gases and changes colour. The breakthrough is in the early stages, but Sablani and his colleagues showed in the study that their chemical reaction works in a controlled lab environment.

Though still early, Sablani envisions working with the food industry to integrate his sensor into a milk bottle's plastic cap so consumers can easily see how much longer the product will stay fresh.

One problem with current expiration dates is they are based on best-case scenarios. "The expiration date on cold or frozen products is only accurate if it has been stored at the correct temperature the entire time," Sablani said.

Temperature abuse, or the time a product has spent above refrigerator temperature, is very common, he said. And it can happen during shipment, or if a consumer gets delayed on the way home from the store.

"We'll have to work with the industry to make this work. But we're confident that we can succeed and help improve food safety and shelf life for consumers," said Sablani.