Although you may sniff meat to see if it's still OK to eat, doing so is a very subjective method of detecting spoilage, as it's dependent on the sensitivity of your sense of smell. With that in mind, scientists have now developed a more objective alternative, in the form of a gas sensor that communicates with your smartphone.

Developed by a team led by Lijia Pan, Yi Shi (both from China's Nanjing University) and Guihua Yu (from The University of Texas at Austin), the sensor is incorporated into a small flat NFC (near field communication) tag. The sensor itself is made of a nanostructured conductive polymer that is capable of detecting compounds known as biogenic amines (BAs), which are responsible for the unpleasant odor of decomposing meat.

In a lab test, the sensor-equipped tags were placed next to pieces of raw meat which were then left for 24 hours at a temperature of 86 ºF (30 ºC). The sensors were subsequently able to detect amounts of BAs that were significant enough to indicate spoilage, yet not necessarily strong enough to be picked up by a human nose. Upon doing so, the sensors automatically switched on the NFC tags, allowing them to wirelessly transmit an alert to an app on a smartphone held within about 4 inches (10 cm) of the meat.

It is now hoped that a commercialized version of the technology could be packaged with raw meat, allowing both food distributors and consumers to know if it's rotten simply by holding their phone near it.

A paper on the research was recently published in the journal Nano Letters.