Scientists in Austria have investigated wher biofilms hide and what bacteria can be found in them.

Biofilms are proven sources of contamination in the food industry. They can cause additional costs in production and can be a danger to consumer health.

Researchers at the unit of food microbiology at Vetmeduni Vienna looked at biofilms in an Austrian meat processing environment that included pork, poultry and beef. Knowledge gained on presence and composition, published in the International Journal of Food Microbiology, could help to prevent and reduce biofilm formation within food processing environments.

Positives after cleaning and disinfection
Scientists from the Feed and Food Quality, Safety and Innovation (FFoQSI) Competence Center examined 11 rooms in November 2018 within the plant and took 108 samples — 47 food contact surfaces before operation and 61 surfaces not directly in contact with food during daily operation — for the presence of biofilms.

Ten hotspots were identified, five on food contact surfaces such as cutting machines and accessories. Seven of the biofilm-positive samples were taken during work and three after cleaning and disinfection, including one at a screw conveyor.

Five biofilms were detected on non-food contact surfaces like drains and water hoses resulting in 9.3 percent of the sites being classed as biofilm positive.

Biofilms are microorganisms that cling to a surface in a very narrow space and form a protective layer, the so-called matrix. This matrix, which consists of carbohydrates, proteins and extracellular DNA, protects inhabitants of the biofilm from external influences such as disinfectants, UV radiation and dehydration. Food processing offers ideal conditions for biofilm formation.

Biofilms may include spoilage agents and food pathogens such as Listeria, E. coli and Salmonella. If food comes into contact with these biofilms, contamination may occur. Shelf life can be reduced and consumers may become ill by eating contaminated food.

Eva M. Wagner, from FFoQSI, said biofilms can also be found in a variety of places.

“We discovered further biofilms in drains and water hoses — places that are not cleaned by default, but are a potential source of contamination. Water hoses are often used to remove cleaning agents from disinfectant residues. If a biofilm is now in the water hose, freshly cleaned areas, including food contact surfaces, can be contaminated again.”

Multi-species biofilms
No pathogens were found in the work, however, detection of foodborne pathogens often requires specific enrichment methods or selecive agars. Researchers isolated bacteria from the biofilm-positive samples and characterized them. A range of bacteria from 29 different types were found.

Kathrin Kober-Rychli, of the University of Veterinary Medicine Vienna, said bacteria of at least four and a maximum of twelve different types were isolated.

“This clearly shows that these are multi-species biofilms, so different bacteria colonize the same biofilm. Most often we were able to assign the biofilm bacteria of the genera Brochothrix, Pseudomonas and Psychrobacter.”

Brochothrix and Psychrobacter are known to be meat spoilers, pseudomonads are recognized for their good biofilm formation. In milk processing and vinegar production, biofilms are used to achieve a certain effect, so are useful.

Kober-Rychli added further research is needed in the prevention, rapid detection and control of biofilms in the food sector. Until then, regular and thorough mechanical cleaning will remain the most important prevention measure.