Listeria monocytogenes biofilm formation as affected by stainless steel surface topography and coating composition

Abstract

Listeria monocytogenes (L. monocytogenes) biofilm formation on food-contact surfaces is a significant food safety concern. However, research on the ability of contact surfaces to resist fouling by L. monocytogenes biofilm is limited. With the objective of assessing the combined effects of substrate topography and coating composition on L. monocytogenes biofilm formation, we used stainless steel 304 with three surface topographies (native finish, #4 commercial brushed finish, and native finish with microfabricated pillars developed by a new process), in each case either uncoated or coated with one of five FDA-approved food-contact substances (chromium nitride, titanium nitride, Dursan, Ni–P-polytetrafluoroethylene (Ni–P-PTFE), and Lectrofluor 641). Results indicate that surface topography and composition significantly affected fouling resistance. Significant enhancement of resistance to L. monocytogenes fouling was observed on native finish coated by Ni–P-PTFE, which reduced L. monocytogenes by 1.5 Log CFU/cm2. Coating the brushed finish with Ni–P-PTFE, Lectrofluor 641, or Dursan reduced L. monocytogenes fouling by 0.5, 0.4, and 0.9 Log CFU/cm2, respectively. The greatest reductions in L. monocytogenes biofilm formation were obtained with Dursan coated on the native finish (3.4 Log CFU/cm2) and on the micropillar-modified native finish (2.8 Log CFU/cm2). The combined variation of substrate topography modification and coating composition provides a new approach to enhance fouling resistance of stainless steel against L. monocytogenes biofilm for improved sanitary design of food processing equipment.