Reduction of Listeria monocytogenes Biofilm Formation in RTE Meat Processing Environments

This research investigated methods to reduce biofilms of L.m. on equipment and floor surfaces in RTE meat processing environments, by removal and inhibition of initial attachment and biofilm formation. The research evaluated the efficacy of cleaners and sanitizers on L.m. biofilms, including the assessment of various surface coatings that will inhibit attachment.

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Objectives

To determine the effect of RTE product and fat residues on biofilm formation by L. monocytogenes and survival of biofilm cells on materials used for equipment and floors; and to evaluate the efficacy of detergents and sanitizers on L. monocytogenes biofilms developed on different surfaces.

Conclusions

Results indicate that L. monocytogenes can develop biofilms in a low nutrient medium at 10ºC on all surfaces tested. Small amounts of meat extract, hot dog or fat residue reduced biofilm formation initially; however, on prolonged incubation, the biofilm cell numbers increase. Biofilms of L. monocytogenes can survive storage at 4 or 10ºC for at least 5 days. Presence of hot dog or fat residues enhances survival of biofilm cells on storage. Sodium lactate or sodium diacetate does not significantly affect biofilm formation.  Both detergents tested are effective in removing or inactivating biofilm bacteria; application of a sanitizer further reduces the biofilm numbers, with the hypochlorite more effective than the peracid sanitizer. Cleaning efficacy depends on the materials on which biofilms are developed; biofilms developed on the brick and conveyor materials are the most resistant to cleaning. Biofilm formation and survival of L. innocua and L. ivanovii are similar to L. monocytogenes. Stainless steel surfaces plasma-modified with 12-crown-4 ether can reduce Biofilm formation without altering the ability to clean the surface. This technology can be applied to other types of surfaces.

Deliverable

This study provides plant engineers, sanitation and maintenance employees with enhanced knowledge of Listeria biofilms and potential factors that may affect Listeria survival in an RTE meat plant environment.  A paper resulting from this research has been submitted to the Journal of Food Protection.