Fundamental Food Microbiology, Third Edition - Fuad Fathir

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APPENDIX A
Microbial Attachment to Food and
Equipment Surfaces
I. IMPORTANCE
The normal tendency of a microbial cell when it comes in contact with a solid
surface is to attach itself to the surface in an effort to compete efficiently with other
microbial cells for space and nutrient supply and to resist any unfavorable environmental
conditions. Under suitable conditions, almost all microbial cells can attach
to solid surfaces, which is achieved through their ability to produce extracellular
polysaccharides. As the cells multiply, they form microcolonies, giving rise to a
biofilm on the surface containing microbial cells, extracellular polysaccharide glycocalyx,
and entrapped debris. In some situations, instead of forming a biofilm, the
cells may attach to contact surfaces and other cells by thin, thread-like exopolysaccharide
materials, also called fimbriae.
Attachment of microorganisms on solid surfaces has several implications on
the overall microbiological quality of food. Microbial attachment to and biofilm
formation on solid surfaces provide some protection of the cells against physical
removal of the cells by washing and cleaning. These cells seem to have greater
resistance to sanitizers and heat. Thus, spoilage and pathogenic microorganisms
attached to food surfaces, such as carcasses, fish, meat, and cut fruits and vegetables,
cannot be easily removed by washing, and later they can multiply and
reduce the safety and stability of the foods. Similarly, microbial cells attached to
equipment surfaces, especially those that come in contact with the food, may not
be easily killed by chemical sanitizers or heat designed to be effective against
unattached microbial cells (like in a suspension), and thus they can contaminate
food. This problem increases if cleaning and sanitation are delayed following
equipment use. Finally, microbial attachment and biofilm formation in the foodprocessing
environment, such as floors, walls, and drains, enable the cells to
establish in the environment; and they become difficult to control effectively by
the methods developed and designed against the unattached microorganisms from