What's good about foodstuffs is the goodness they contain. To ensure that no contaminating particles get into the products, many areas of production in the food and pharmaceuticals industries are subject to strict regulations. Machines can be cleaned and work surfaces can be disinfected. But monitoring the air in the production rooms is a much more difficult task. An optical particle counter developed jointly by researchers at the Fraunhofer Institute for Manufacturing Engineering and Automation IPA and the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB has two advantages. It detects troublesome contaminating particles floating in the air and is capable of distinguishing between biotic particles – from living organisms – and abiotic particles – of inanimate origin. The quality of the air is monitored online, in other words during the manufacturing process.

Airborne germs such as bacteria and fungi present the greatest risks. If the air contains too many, the result may be that the products fail to meet the required quality standard. Dust and mineral particles can also negatively affect product quality. In the past, tests to verify the presence of biotic particles took several days, making it impossible to trace the source of the problem directly. The two-stage method devised by the Fraunhofer researchers is different. Air is drawn out of the area of production and directed through an optical particle counter developed by the project team. A laser beam scans the stream of particles. The particles diffract the light differently depending on their size, type and properties. In this way, the researchers are able to determine the proportion of abiotic particles. To detect the biotic particles, they heat the stream of air. This makes the airborne germs lose water content and shrink, and denatures their proteins. When they are then directed through the second particle counter, the changes in the diffracted light signals allow precise information to be obtained on the nature, size and number of particles present in the air.

“This instrument allows us to obtain proof of the microbial contamination of the air, quickly and promptly”, emphasise Iris Trick and Andreas Schüle. “Consequently, rapid action can be taken to deal with excessive levels, ensuring safe production and high quality”. At present, the particle counter exists as a laboratory prototype only.