Formation and Control of Listeria monocytogenes Growth and Accumulation on Food Processing Surfaces in the Fresh Produce Industry

The ability of L. monocytogenes, a common foodborne pathogen, to form biofilms significantly contributes to its persistence and contamination risks. Understanding L. monocytogenes aggregation is crucial to develop effective control strategies. This study assessed the growth and accumulation of L. monocytogenes on common food processing surfaces in the produce industry and evaluated the efficacy of commercially available sanitizers alone or simultaneously with UV-C light for 30 s, 1 min, or 5 min. L. monocytogenes was allowed to aggregate on stainless steel, nylon, high-density polyethylene (HDPE), polyvinyl chloride (PVC), and Teflon for 24 h (initial biofilm aggregate) and 96 h (mature biofilms). Treatments included 120 ppm peracetic acid (PAA), silver dihydrogen citrate (SDC), 4% lactic acid, and UV-C light (254 nm). After sanitizer application, cells were dislodged and enumerated by serial dilution and plating. Confocal images were obtained before and after treatments to evaluate biofilm architecture. All liquid sanitizers significantly reduced L. monocytogenes independently of the surface type (P < 0.05). UV-C treatment application time had no significant effect on biofilm reduction (P > 0.05), though its efficacy on 24 h aggregates varied significantly depending on the surface material. Peracetic acid and lactic acid were the most effective treatments across surfaces, while UV-C alone was the least effective. Combined sanitizer and UV-C light application for up to 5 min did not necessarily improve treatment efficacy compared to sanitizers alone. Confocal images displayed surface cleanability and alterations in microbial architecture before and after treatments. Mature biofilms exhibited extensive surface coverage on all surfaces, which was visibly reduced following sanitizer application. This study provides insightful information to the produce industry for using sanitizing approaches on various surfaces based on cleanability, topographical, and architectural characteristics.