Food Technology and Biotechnology (Jan 2005)
Microbial Adhesion to Processing Lines for Fish Fillets and Cooked Shrimp: Influence of Stainless Steel Surface Finish and Presence of Gram-Negative Bacteria on the Attachment of Listeria monocytogenes
Abstract
Microflora adhering to surfaces of processing lines in a shrimp factory and a fish processing plant was identified in situ and adhesion of mixed culture of Listeria monocytogenes and Gram-negative bacteria on stainless steel surfaces (untreated, polished and glass beaded) was studied ex situ. The predominant genus attached to the surfaces was Pseudomonas spp. (66 %) in the shrimp factory and Enterobacteriaceae (27 %) in the fish factory. Shrimp juice was used as an enrichment broth during the study of adhered bacteria. Three different Gram-negative strains and a mixture of Pseudomonas spp. were selected to study their attachment together with L. monocytogenes to stainless steel surfaces. Highest numbers of the attached bacteria were obtained after the contamination with a mixed culture of L. monocytogenes and Serratia liquefaciens. A lower number of bacteria adhered to stainless steel surfaces when mixed cultures of L. monocytogenes and Pseudomonas fluorescens or Aeromonas spp. were tested. No significant differences (p<0.05) were observed in the bacteria attached to differently treated steel surfaces with different roughness (Ra=0.1–0.8 m). Bacterial adhesion increased with longer contact time. Colonisation of L. monocytogenes on stainless steel surfaces was significantly enhanced only in the presence of mixed Pseudomonas spp. These results indicate that smooth surfaces do not necessarily provide hygiene benefits over rougher surfaces.
