Can fluorescence avert food contamination?

It is dark in the little laboratory. The only light sources that can be seen with the naked eye are a PC screen and a fluorescent slice of salami. On the salami, a light spot is visible, which causes the people in the room to break out in restrained jubilation.

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What in the world is going on? The situation definitely requires an explanation.

The revelation

Suddenly, the light goes on, and four men are animatedly discussing their "discovery". The salami has been rubbed in a little cattle excrement. Then it had been washed twice with soap and water. The salami evidently appeared to be completely clean and normal, but the light spot in the fluorescent light revealed that there continued to be excrement on the slice.
"The goal is to find a method to detect undesirable bacteria on slaughtered animals. We know now that this is a project that will be able to function," says quite pleased senior researcher Jens Petter Wold of Matforsk. He is an expert in measuring with the use of spectroscopy, and has among other things participated in the development of a method that can measure the content of fat and water in live fish. For that, near-infrared spectroscopy was used. However in these experiments, where one has to demonstrate the presence of minute remnants of excrement, it is in fact fluorescence spectroscopy that must be used.

The dark room

The fluorescence laboratory at Matforsk looks like a darkroom. The ceiling, walls and floor are black, and the room has no windows and the door looks like it opens into a walk-in freezer. Not as much as a glint of daylight gets in here. On a table a connected-up PC is standing. A camera is mounted on another table. It contains a system that is well-suited for measuring the fluorescence spectrum and taking fluorescent pictures of quite large intact samples, for example sandwich toppings, meat, cheese, fruit, etc. This is possible because the camera is sensitive and contains optical filters in addition to a powerful light source.

The chlorophyll clue

Jens Petter Wold speaks excitedly with the other three in the room, who are experts in feeding technology and chlorophyll breakdown at the Institute of Grassland and Environmental Research (IGER) in Wales. Most domesticated animals eat plants. In plants, there is chlorophyll. Chlorophyll is not completely broken down in the digestive process, and in addition it is fluorescent. That means that with the aid of a Jens Petter’s camera one could find chlorophyll in, for example, excrement. And thereby find traces of excrement on an animal at the slaughterhouse – or on a slice of salami.
"The idea of detecting remnants of chlorophyll with fluorescence is not new, however in this project we have a clear and good idea of how such a method can be used efficiently and reliably at slaughterhouses. I believe in it very strongly," maintains Jens Petter Wold.


The reason the researchers from Wales and Norway were gathered together in the "darkroom" at Ås was the European research project named ProSafeBeef, which will help make better and safer meat products. One of the aspects of the project is hygiene, and there is room here for quite a number of improvements at the slaughterhouses. A scanner is being developed under ProSafeBeef that will remain online at the slaughterhouse and look for traces of undesirable components. Remnants of excrement are quite clearly such an undesired component. Many of the instances where people have become ill from eating food are due to intestinal bacterial having snuck into the production process.


"How did you decide to wipe poop on a salami?"
"We researchers are a creative bunch! And a salami was available. We had desired first and foremost to see whether the principle was possible: to use such a measurement instrument in order to detect chlorophyll, which is an indicator that there are remnants of excrement on the slaughtered animal. Now we know that the approach is promising, and we can continue with the experiments," says Jens Petter Wold.

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