Friday 27 April 2018

This laser can tell if your food has gone off

Madhumita Murgia

The easiest way to detect if last night’s dinner is still edible is the sniff test. Usually, that strange smell is the only thing standing between you and food poisoning.

Now, researchers from the Korea Advanced Institutes of Science and Technology have developed a more precise method to test for poisonous food bacteria – using lasers.

There are existing technologies that test food for specific poisonous chemicals or microbes, but they are complex, unwieldy - and won't fit in your refrigerator. “Conventional methods require laboratories, high-cost equipment, and professionals,” the researchers said in the paper published in the Quantitative Biology journal. The food samples have to be prepared and results analysed by experts.

The team’s goal was to design a device that can scan food quickly and cheaply at home.

The study blitzed fresh chicken breast meat with a red laser, and did the same to a similar cut of meat contaminated with E. coli and B. cereus, bacteria that often cause food poisoning. Since bacteria are living creatures, contaminated food is usually covered with swarms of these tiny germs that move.

This movement causes changes in the laser’s refraction pattern, which can be picked up by a camera over a few seconds.  The team took 30 photos per second, for 20 seconds and the resulting images showed easily distinguishable patterns for edible and contaminated food.

According to the researchers, this “simple but powerful” method does not require anyone to touch the food. This means you can zap leftovers or production line meat, even if samples are wrapped up in transparent plastic.

The laser-camera combination is also cheap and quick. The live bacteria can be identified within a few seconds, and a consumer device could be installed in your home refrigerator or in a food manufacturing factory.

The method isn’t infallible: viruses like norovirus are too small to spot, and it cannot distinguish between various types of bacteria.

However, it will spot and warn you about a range of nasty bugs such as Salmonella, E. coli or Listeria growing in your fridge. The bad news is the technique is still an experiment, so until it is commercialised, you’ll just have to trust your nose.

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