New Sensor Detects When Fruits And Vegetables Are Spoiling

Lee Rannals for

A new sensor may one day be able to help U.S. supermarkets prevent the loss of produce due to spoilage.

According to the Department of Agriculture (USDA), supermarkets in America lose about 10 percent of their fruits and vegetables every year to spoilage.

MIT chemistry professor Timothy Swager and his students have built a new sensor that could help grocery stores get more efficient at combating the loss.

Plants discharge ethylene, a gas that helps ripen plants, throughout their maturation process.  Once the ripening process starts, more ethylene is produced, and the ripening accelerates.  The gas is responsible for turning fruits like bananas from green and stiff to brown and mushy.

Fruit distributors try and slow the process of fruits going bad by keeping ethylene levels low in their warehouses.  These warehouses are able to separate gases and analyze their composition through gas chromatography or mass spectroscopy.

The authors wrote in the journal Angewandte Chemie that their inexpensive sensor can detect tiny amounts of ethylene.

Swager said he envisions the inexpensive sensors attached to cardboard boxes of produce, and scanned with a handheld device that would help reveal the how ripe the fruit or vegetable is.

“If we can create equipment that will help grocery stores manage things more precisely, and maybe lower their losses by 30 percent, that would be huge,” Swager, the John D. MacArthur Professor of Chemistry, said in a press release.

The MIT team built a sensor made up of tens of thousands of carbon nanotubes, with an additive of copper atoms to help detect ethylene gas.

Copper atoms are able to slow the electrons a little bit, but when ethylene is present, it binds to the copper atoms and slows the electrons even more, thus helping to detect the rate at which a banana becomes mushy.

In order to make the device even more sensitive, Swager and his team added tiny beads of polystyrene to absorb ethylene and concentrate it near the carbon nanotubes.

The team said they were able to detect concentrations of ethylene as low as 0.5 parts per million.  The concentration required for fruit ripening is between 0.1 and one part per million.

Swager told RedOrbit via email that the researchers are planning “for a development phase wherein the sensors will undergo more comprehensive testing.”

“We are optimistic that the fabrication processes we have developed are very robust and will provide the required reproducibility,” he told RedOrbit.

The professor said they expect the sensor could have an “abundant” applications, such as when plants need to be monitored during transportation.

“It is even possible that distributed sensors based on this technology could be useful in guiding harvesting,” Swager added. “Food/plant production, distribution, management is extremely expansive and we believe there are many possibilities.”

He believes that the system for would cost about 25 cents for the carbon nanotube sensor, as well as another 75 cents for the RFID chips.

“This could be done with absolutely dirt-cheap electronics, with almost no power,” he said.

A patent has been filed on the technology, and Swager said he hopes to start a company to commercialize the sensors.

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