A new sensor for detecting spoiled meat

The sensor, which was developed by chemists from the Massachusetts Institute of Technology (MIT), and which includes chemically modified carbon nanotubes, could be integrated into "smart packages" that would provide much more accurate information about food safety compared to the expiration date of the product, as That this is done today

[Translation by Dr. Nachmani Moshe]
Chemists have succeeded in developing a portable and cheap sensor capable of detecting gases emitted from rotting meat, which will allow consumers to determine whether the meat sold to them at the grocery store or in their freezer is safe to eat.

The sensor, which was developed by chemists from the Massachusetts Institute of Technology (MIT), and which includes chemically modified carbon nanotubes, could be integrated into "smart packaging" that would provide much more accurate information about food safety compared to the product's expiration date, says Principal investigator, Professor of Chemistry Timothy Swager. In addition, the sensor could lead to a reduction in the amount of food thrown into the trash. "People tend to regularly throw away products that are not necessarily spoiled," says the lead researcher who published the results of the study in the scientific journal Angewandte Chemie.

The sensor is similar to other devices based on carbon nanotubes developed in the same laboratory in recent years, including a device capable of measuring the ripeness of a fruit. All of these devices work on the same principle: carbon nanotubes can be chemically modified so that they can transmit a changing electric current in the presence of a specified gas. In this case, the researchers modified the carbon nanotubes with compounds containing metal atoms called metalloporphyrins, compounds consisting of a central metal atom linked to several nitrogen-bearing rings. The biological compound hemoglobin, which carries the oxygen in the blood, is an example of a compound from this family, where iron is the central atom. In their current study, the researchers used cobalt metal as the central metal atom. This family of compounds (Metalloporphyrins) is particularly good at binding to nitrogen bearing compounds called amines. Substances that have been of particular interest to the researchers are substances known as biogenic amines, such as putrescine and cadaverine, which are formed and released as the meat decays. When the porphyrin bearing the cobalt atom binds to this type of amine, it increases the electrical resistance of the carbon nanotube, which can be easily measured.

"We used these porphyrins in order to develop a very simple device through which we passed an electric voltage and measured the resulting current. When the device is exposed to these amines, which are markers of spoiled meat, the current of the device weakens," explains one of the researchers. As part of this study, the scientists tested their sensor on four types of meat: pork, chicken, cod fish and salmon. They found that when these meats are in the freezer, they stay fresh for four days. When the meats were thawed all the samples spoiled, but at a different rate.

Although there are other sensors capable of detecting signs of spoiled meat, they are often bulky and more expensive and require expertise in their operation. "The advantages of our device are that these sensors are cheaper, smaller and simpler to manufacture," says the lead researcher. The new device is also operated with a very low amount of energy and can be operated wirelessly from smartphones as well.

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