New smart-patch promises to tell you if your leftovers are safe to eat

You may never need to sniff-test another piece of bad meat from your fridge again. A new biosensing patch, that looks like cling wrap, has been invented to tell you if your food is off and free of harmful bacteria.

[L to R] Hanie Yousefi and Dr Tohid Didar from the faculty of engineering at McMaster University, Canada. Source: Supplied

'Is this off?' It's one the most perplexing questions we face every time we look into our fridge and eye off a plate of leftovers or carton of milk past its best before date.

Most of us employ a very non-scientific way of working out if a food or drink product is free of bacteria that can make us very sick. You might sniff the milk to see if it smells funny or check the colour of your pre-cooked meat to see if it’s looking odd.

These methods are hardly fool-proof. But what if there was a way to confirm whether that two day old out take-out is okay to eat without having to Google, phone a friend or endure a seriously painful bout of food poisoning?  

Over in Canada, a group of scientists from McMaster University have invented a clever solution, which they hope to commercialise soon. It's a new smart patch to help us to determine whether our food is off and unhealthy to consume.

We have developed a method to modify the surface of packing material (plastic) so that it becomes fluorescent when a specific bacteria in the food comes in contact with that surface.

The biosensing patch is a transparent and flexible sensing surface – which looks like cling wrap to the untrained eye – that can detect harmful bacteria like E. coli and salmonella. The beauty of this gadget is that you don’t have to unwrap the food, smell it or touch it to work out if it’s off. The sensor is designed to test for contamination without human contact.  

“We have developed a method to modify the surface of packing material (plastic) so that it becomes fluorescent when a specific bacteria in the food comes in contact with that surface,” says paper co-author Dr Tohid Didar, assistant professor in the Department of Mechanical Engineering and member of the Institute for Infectious Disease Research (IIDR) at McMaster University. 

“It’s just a flexible thin plastic film printed with DNA molecules.”

The patch could one day replace ‘best before’ labels, possibly providing an exact indication of when each individual dish is unsafe to eat.

“Also you want to know if the food is still good beyond its expiration date to prevent waste,” he says. 

A study performed on the sensor, just published in the journal ACS Nano, says that the patch can detect very low concentrations of microbial contamination in products like apple juice and meat. The sensor stays on the package from the time of application and doesn’t need to be removed until after you wish to discard it.

“These sensors hold the potential to make a significant contribution to the ongoing efforts to mitigate the negative public-health-related impacts of food-borne illnesses,” reads the study, led by research assistant in the faculty of engineering at McMaster University, Hanie Yousefi.

Once the patch picks up that problematic bacteria are lurking in your food it will send a signal to your smartphone (or another device) to let you know if your your food is unsafe to eat.

These sensors hold the potential to make a significant contribution to the ongoing efforts to mitigate the negative public-health-related impacts of food-borne illnesses.

Dr Didar tells SBS that for this to happen, all you have to do is “add a filter to your cell phone camera and scan the sensor using your cell phone”.

“We are moving towards smart systems and Internet of things where you can get real-time information about the devices you use on daily bases, so our goal was to bring a smart packaging system into food.”

Around 4.1 million Australians are affected by food poisoning each year, after drinking or eating contaminated products.  

Dr Didar believes the sensor would work well in countries with hot climates like Australia, where high temperatures could put food at risk of contamination during summer seasons.

“We have shown that the sensors are stable at temperatures up to 45 degrees Celcius,” he says.

We are negotiating with industry partners to move this forward and bring it to the market.

The study showed that the sensor can remain stable for at least 14 days under set pH conditions - at least the shelf life of perishable packaged food products.

Dr Didar and his team are currently working on plans to commercialise the product.

“We are negotiating with industry partners to move this forward and bring it to the market.

“Although more tests are needed to bring it to the market and mass produce it, but we are very excited about this product.”