Cambridge, Mass. – Scientists at Massachusetts Institute of Technology (MIT) have created a device that could provide more accurate food safety information than the expiry dates on food packaging.
This MIT device, based on modified carbon nanotubes, can detect amines produced by decaying meat.
Photo: Sophie Liu
The tiny device is a sensor, which consists of chemically modified carbon nanotubes, that could be incorporated into smart packaging.
The portable sensor can detect gases emitted by rotting meat, allowing consumers to determine whether the meat in their grocery store or refrigerator at home is safe to eat.
The sensor could also cut down on food waste, says Timothy Swager, the John D. MacArthur professor of Chemistry at MIT.
“People are constantly throwing things out that probably aren’t bad,” says Swager.
The sensor is similar to other carbon nanotube devices that Swager’s lab has developed in recent years, says the MIT website, including one that detects the ripeness of fruit.
All the devices work on the same principle: carbon nanotubes can be chemically modified so that their ability to carry an electric current changes in the presence of a particular gas.
In this case, the researchers modified the carbon nanotubes with metal-containing compounds called metalloporphyrins, which contain a central metal atom bound to several nitrogen-containing rings. Hemoglobin, which carries oxygen in the blood, is a metalloporphyrin with iron as the central atom.
For this sensor, the researchers used a metalloporphyrin with cobalt at its centre. Metalloporphyrins are very good at binding to nitrogen-containing compounds called amines.
Of particular interest to the researchers were the so-called biogenic amines, such as putrescine and cadaverine, which are produced by decaying meat.
When the cobalt-containing porphyrin binds to any of these amines, it increases the electrical resistance of the carbon nanotube, which can be easily measured.
In this study, the researchers tested the sensor on four types of meat: pork, chicken, cod and salmon.
When refrigerated, all four types of meat stayed fresh over four days. Left unrefrigerated, the samples all decayed but at different rates.
There are other sensors that can detect the signs of decaying meat, says the MIT website, but they’re usually large and expensive instruments that require expertise to operate. The advantage with these sensors, says Swager, is that they’re the cheapest, smallest and easiest-to-manufacture.
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Raw cuts of beef image courtesy of KEKO64 at FreeDigitalPhotos.net