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Spoilage-sensing refrigerator
A diagram indicates the location of chemical sensors in a proposed spoilage-detecting refrigerator. (Amazon Illustration via USPTO)

Years after making its application, Amazon has won a patent for a refrigerator that uses cameras and chemical sensors to sniff out spoiled food.

But if you’re waiting to get one-day shipping for a fridge that knows your fruit has gone bad before you do, you might want to put those hopes on ice. Or look to similar spoilage-detecting gizmos that are already out there.

The concept is suited to our foodie age, as well as the age of the Internet of Things.

In the newly approved patent application, Amazon inventor Simon Kurt Johnston starts with the obvious: “Food or drinks in the refrigerator will eventually spoil.”

It almost sounds as if Johnston is speaking from experience when he explains why a spoilage-sensing fridge is needed: “A user may not notice that food or drinks within the refrigerator are spoiling because these items may be stored out of sight (e.g., at the back of the refrigerator, in a drawer or bin, or behind another item).”

The solution? Seal off every bin, and put cameras and sensors inside. The camera system could be programmed to capture regular images of the items inside a drawer, and then upload them for processing with machine-learning algorithms to recognize the foodstuffs and compare them with a database of food spoilage.

Such algorithms would be trained to spot the signs of rot, mold, mildew or fungus. And you could add infrared imagery to aid in identification.

On the sensor side, the refrigerator could sniff for the presence of ethylene (a by-product of ripening), various alcohols (by-products of fermentation), acetic acid (a by-product of fermentation or oxidation), short-chain fatty acids (by-products of oxidation and oxidative rancidity) and other volatile organic compounds.

“Examples of chemical sensors include potentiometric sensors, chemical field-effect transistor (ChemFET) sensors, chemiresistors, chemoreceptors, or other sensors,” the application says.

If something looks or smells fishy, the refrigerator could send an alert (including color-coded pictures!) via a smartphone app. And there’s a side benefit: Because the fridge is keeping track of all of the goods stored inside, it can give you an inventory of what you’ve got to work with for dinner.

Amazon typically doesn’t comment on its patents, and the fact that it’s won a patent doesn’t mean the concept described therein will ever be turned into a product. This application has been stewing since 2016 and incorporates previous ideas about refrigerators with sensors and cameras – so it’s possible that the concept for a spoilage-sensing icebox has already gone stale.

But “smart refrigerators,” equipped with devices to document what’s inside, are becoming all the rage. Seattle-based, for example, has been working on edge-based (or, in this case, fridge-based) technology that uses computer vision and artificial intelligence to identify food and create recipe-specific shopping lists.

It wouldn’t be unheard of for Amazon to field a smart refrigerator. Last year, the company made a splash with its voice-controlled AmazonBasics microwave oven (even though our reviewers weren’t blown away). But if Amazon ever does go ahead with a spoilage-sensing fridge, it might have to contend with other market entrants. In fact, a different international patent application for a similar sensor-based technology was filed years ago.

In the meantime, there are other tools being developed to recognize the signs of food spoilage. Researchers at Britain’s Imperial College are working on low-cost, smartphone-linked patches known as paper-based electrical gas sensors, or PEGS. A team at Clemson University is studying ways to track cell-to-cell communication as a spoilage indicator. Other scientists have proposed packaging that changes color when perishables go bad – for example, when milk spoils.

At least one do-it-yourself spoilage sensor is already on the market: The FoodSniffer is a handheld gizmo that measures the levels of gases given off by raw meat and fish, analyzes the results and beams the thumbs-up or thumbs-down to your mobile device. It retails for $129.99 – a price tag that’s less than what a smart refrigerator would cost, but more than the most sophisticated tools available for detecting spoilage: your eyes and nose.

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