Reporting in the journal ACS Sensors from the American Chemical Society, the scientists showed that the highly fluorescent, hollow nanotubes grow dim when they react with compounds given off by meat as it decomposes.
The scientists were looking for a new method to test meat, as current methods, despite high sensitivity, require bulky, slow equipment, which prevents real-time analysis.
Some newer methods designed to speed up the testing process have fallen short in sensitivity. Yanke Che and colleagues wanted to develop one simple test that could deliver both rapid and sensitive results, and ensure meat and fish reach shops safely.
The tubes detect chemicals called amines in the vapours given off by meats.
To test the nanotubes, the team sealed commercial samples - 1 gram each - of pork, beef, chicken, fish and shrimp in containers for up to four days.
When they exposed the portable system to a teaspoon of vapour emitted by the samples, it reacted in under an hour, fast enough to serve as a real-time measure of freshness. The researchers also found that if the tubes' glow dulled by more than 10 per cent, this meant a sample was spoiled.
The authors concluded that the nanotubes represented an "expedient technology that is suitable for the real-time and in situ monitoring and assessment of the deterioration of meat freshness".
