Hot water outperforms UV-C and commercial cleaning agents and disinfectants in reducing Listeria monocytogenes on woven conveyor belts

Conveyor belts are recognized as common niches for persistent Listeria monocytogenes contamination in food processing environments. This study evaluated the efficacy of 24 commercially available cleaning and disinfection (C&D) agents, UV-C irradiation, and heat treatments against L. monocytogenes, using a laboratory biofilm model on woven conveyor belt material. Selected treatments were further tested on a used conveyor belt from food industry harboring a persistent outbreak strain.
Cleaning followed by disinfection, using concentrations recommended by manufacturers, achieved limited reductions (1.2–2.5 log) of L. monocytogenes after 10 min exposure in the laboratory biofilm model. Extreme concentrations of cleaning agents improved efficacy in the laboratory model but failed to eliminate L. monocytogenes from the used belt. All C&D agents applied at recommended concentrations led to >3.8 log reduction against a dried suspension of L. monocytogenes on stainless steel.
UV-C treatment resulted in dose-dependent but modest reductions (≤2.4 log) and the combination of C&D and UV-C improved efficacy in the laboratory model, but failed to eliminate L. monocytogenes from the used belt from food industry.
Heat treatment in a water bath at 60 °C for 1 h completely eliminated L. monocytogenes (>4 log reduction, negative after enrichment) from both types of conveyor belts, whereas hot dry air was less effective. Extended enrichment times revealed prolonged lag phases of stressed cells, highlighting the risk of false-negative results when standard detection protocols are applied.
Overall, the findings highlight the potential of hot water treatment as an effective strategy for eliminating L. monocytogenes from hard–to reach sites where chemical C&D and UV-C treatments are insufficient.