We developed a polymer film that is able to detect amines with high sensitivity and selectivity. This can be used to detect the freshness of fish and meat.


In the food industry there is a great need to determine the shelf life of food routinely and non-invasively. When food of animal origin gets old, protein breakdown products such as amines are released into the environment into the gas phase. By detecting this, the shelf life of food can be determined and a change in shelf life (spoilage, ripeness, etc.) can be indicated accordingly. So far, amines can only be detected with complex laboratory analysis.
At the Institute for Biomedical Optics at the University of Lübeck, a polymer film was developed that is able to detect amines with high sensitivity and selectivity in the gas phase. This sensor film consists of a phosphorporphyrine, which is suspended in a polymer that is permeable to amines. Even traces of amines cause the sensor foil to change color from green to red. This color change can be seen with the naked eye as well as with a camera or spectrometer. This can be used, for example, in the field of intelligent food packaging, where the shelf life of the food can be read directly by the user through a sensor spot in the package (green = fresh, red = no longer fresh - first signs of spoilage). This approach impresses with the simple, mobile detection of amines without complex laboratory analysis and is currently being patented.
The absorption and fluorescence spectra of the sensor show a clear change after the reaction with amines. The changes in the fluorescence spectrum are very sensitive and the freshness can be quantified with easy measurement technology.

Key Benefits

1. The substances produced during spoilage, amines and biogenic amines, are detected directly.
2. Detection takes place in the gas phase. The sensor substance does not necessarily have to come into contact with the food, which increases flexibility when choosing the type of packaging.
3. The detection of amines and biogenic amines is very sensitive and selective. The integrative behavior of the sensor even makes it possible to detect traces of the low-volatility biogenic amines (such as cadaverine and putrescine).
4. The sensor reacts with the amine in an irreversible reaction, so "back staining" is not possible. This makes any manipulations on the part of the user more difficult.
5. Compared to other dye indicators, the porphyrins used are not toxic or carcinogenic. The changes in absorbance and fluorescence of the sensor are far more pronounced than in previously explored dye indicators. Especially in the case of fluorescence, new fluorescence maxima are formed. The color change of the absorption that can be seen with the eye is "consumer-friendly" from green to red.


food package, smart packaging

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