Biofilm formation in the dairy industry: applications to cheese

In the cheese industry, most contamination is caused by microbial biofilms. Bacteria can be present on wet surfaces and in other difficult-to-clean environments, such as floors, steps, drains, conveyor belts, walls, the regenerative sections of pasteurisers, ultrafiltration and reverse osmosis membranes, wood, milking systems and refrigerated tanks. Wood, which is often used in utensils, packaging or the ripening support used in the production of cheeses, has been shown to support microbial biofilm growth in some cases. The main concern related to environmental biofilms in cheese plants is the presence of Listeria monocytogenes. Other microbial risks include thermoduric bacteria (e.g., Streptococcus thermophilus and Bacillus cereus) and gram-negative bacteria. The use of chemicals and enzymes is the most common approach toward removing and killing an established biofilm. Biological strategies, such as the use of bacteriocins, bacteriophages and their enzymes, can also be used to eliminate biofilms. Other approaches are based on physical treatments (e.g., power ultrasound), which appear to be promising strategies for the inactivation of surface microbial biofilms in the cheese industry.