Canadian Researchers Create Plastic Patch to Warn Consumers When the Food is Spoiled or Contaminated

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Researchers at the McMaster University in Hamilton, Ontario have developed a plastic film that could make “best before” dates irrelevant. Soon enough, consumers will know if the food they buy is safe to eat.

Outbreaks from contaminated food often happen because some pathogens cannot be noticed only by smelling or looking at food. Usually, officials recommend consumers to either bring back the contaminated food or to throw it away.

As a solution for this issue, researchers at the McMaster University found a way to help consumers find out if packed meat or salad greens are safe to eat. They developed a small and thin plastic patch called “Sentinel Wrap.”

The Sentinel Wrap and a Smartphone App

The Sentinel Wrap is a transparent and durable strip which is coated on one side with many droplets of DNA molecules called DNAzymes. When pathogens like E. coli come into contact with the molecules, the strip lights up.

Consumers have to use an app on their smartphone which reads the light on the strip and tells the consumers if the food in the package is safe to eat or is spoiled.

Tohid Didar, an assistant professor in the chemical and mechanical engineering department at McMaster, said that it might all sound simple, but it took them 15 years to research and develop the tiny plastic film to make it work.

McMaster’s Prof. Carlos Filipe explains:

“If you can imagine that the DNAzyme is like a rope, and there are scissors that are going to cut that rope in a specific place, those scissors are the presence of E. coli. On one side of the rope, you have a fluorescence molecule, on the other side, you have a quencher. If the rope is intact, they cancel each other out. But if you cut it with the scissors, and the two pieces become separate, now the fluorescence can be detected because the quencher is no longer attached.”

The film is as big as two postage stamps. Researchers made it so that it can be mass produced and in a cheap way. The DNAzymes are tiny droplets put on a polymer using an inkjet printer.

At the moment, the team develops Sentinel Wrap patches for more types of bacteria found in food products, which also detect contamination in water and liquid foods: salmonella and listeria.

Didar explains that to detect E. coli now it takes a day:

“You need to take the package, open it, process it, take it to a lab, either culture that sample or try to do different laboratory-based experiments to find out what’s going on.” He concludes that their “goal is to avoid all that so you can get real-time information.”

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Andre Blair s is the lead editor for Advocator.ca. He holds a B.A. in Psychology from the University of Toronto, and a Master of Science in Public Health (M.S.P.H.) from the School of Public Health, Department of Health Administration, at the University of North Carolina at Chapel Hill. Andre specializes in environmental health, but writes on a variety of issues.


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