Has that week-old yogurt really gone bad?

Is the chicken you bought just three days ago already spoiled?

Your smartphone might one day be able to tell you, new research suggests.

A group of scientists is developing a portable, inexpensive and easy-to-use electronic tag to send wireless alerts to smartphones when a telltale gas is emitted by rotten food.

Smartphones to the rescue

“As we know, spoiled food can be very harmful to our health,” said study author Guihua Yu.

“But sometimes we cannot easily notice the slightly degraded food by smell or vision. Therefore, we aim to develop a cost-effective wireless sensor for food spoilage detection with the assistance of mobile phones,” he explained.

Yu is a professor of materials science and mechanical engineering at the University of Texas at Austin.

Reality of food poisoning

Food-borne illnesses strike 48 million Americans each year, leading to over 128 000 hospitalisations and 3 000 deaths, according to the US Centers for Disease Control and Prevention.

According to the Food Advisory Consumer Service (FACS), food poisoning statistics in South Africa is relatively scarce. Only a few hundred cases of food poisoning are reported in South Africa every year. However, FACS believe that these numbers are not a true reflection of the situation. Their belief is that due to poor surveillance, the number of food poisoning cases in South Africa may actually be in the thousands.  

Last year’s Listeria outbreak was believed to be the worst outbreak ever, according to the WHO. Over 1 000 reported cases were filed and around 200 people died from the food-borne illness. 

Unpacking the app

To tackle the problem, Yu and his colleagues first put together a tiny gas sensor with a very high sensitivity to the odour-causing “biogenic amines” that are released when food goes bad.

Then, the team embedded the sensors into “near-field communication” (NFC) tags, of the sort already deployed by businesses to track product shipping.

The NFC sensor tags were then put through a bad meat test, because slightly spoiled meat is a good example of something that can prove very harmful but also difficult to detect.

After placing tags next to meat, the researchers left it out in a temperature of 30°C, guessing that a notable amount of telltale biogenic amines would be produced by the end of the test period.

Sure enough, the sensor tags detected the biogenic amines, and communicated the presence of bad meat to a smartphone located within reach of the NFC’s wireless range (usually less than 10cm).

The findings were published in the journal Nano Letters.

Yu noted that the investigation was preliminary and that “it will still take some more time before it is ready for market” so that he and his team can try to improve the phone interface and device-packaging design.

“We developed the sensor possibly for both individual consumer households and industrial purposes,” said Yu.

Not everyone’s convinced

But the concept doesn’t appeal to food-safety expert Lona Sandon. “My concern with a sensor such as this is just how sensitive is it. If it detects gases at very low levels, will we end up throwing food out when it is still edible, further increasing the problem of food waste?” she said.

“I am also not sure we need a smartphone to tell us whether the food is past its prime or not. Smell, sight and common sense usually are pretty good for indicators,” Sandon added.

“A quick visual inspection of fruits, vegetables, cheeses and meats can tell you a lot about whether or not the food is still good to eat. Discoloration, soft spots, bruising, or fuzzy stuff growing on the food are easy to spot. Off-putting smells from things like milk and meat are also pretty easy to detect without a fancy gadget,” she suggested.

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