Scientists have developed a sensor that can 'smell' if milk has gone bad, an advance that could make expiration dates on cartons a thing of the past.
The sensor consists of chemically coated nanoparticles that react to the gas produced by milk and the bacterial growth that indicates spoilage, said Shyam Sablani, professor at Washington State University in the US.
The sensor does not touch the milk directly.
"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," Sablani said in a statement.
The sensor detects these volatile gases and changes colour, according to the study published in the journal Food Control.
The next step for the team is developing a way to visually show how long a product has before it spoils. Currently the sensor only shows if milk is ok or spoiled.
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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, researchers said.
"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 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," Sablani said.