3.1 Introduction:biofilmformation and detection
This chapter deals with biofilm formation, sampling and detection methods,
pathogens in biofilms, persistent and non-persistent microbes, prevention of
biofilm formation and biofilm removal as well as future trends in biofilm control
in the food industry. Microbes that inhabit contact and environmental sites in food
processing are mostly harmful because microbial communities in the wrong
places lead to contamination of surfaces and of the product produced in the
process (Wirtanen, 1995). Documented biofilms have been almost entirely
composed of bacteria, and the types of bacterial biofilms particularly related to
pathogens are detailed in Section 3.2. There are, however, very few published
studies concerning yeast biofilms in food processing. Storga rdset al. (1997)
studied the tendency of spoilage yeasts isolated from brewery samples to form
biofilms. This study showed that the slow-growing strains covered tested surfaces
with 2±4% biofilm in 10 days; fast biofilm producers had already covered the
whole surface in 2 days. In addition to the problems in food industry, biofilm
formation also causes problems in food-related systems, e.g. industrial water
systems as well as the paper and packaging industry (Bryers, 2000; Alakomiet al.,
2002). On the positive side, however, biofilms have also been applied successively
in food-related processes, e.g. in brewing and in water treatment (Kronlo»f, 1994;
Zottola and Sasahara, 1994; Wong and Cerf, 1995; Bryers, 2000).
3.1.1 Factors affecting biofilm formation
In order to be able to survive hostile environmental factors such as heat and
chemicals, microbes in microcolonies have a tendency to form protective
3 Biofilm risks
G. Wirtanen and S. Salo, VTT Biotechnology, Finland