Survival of Listeria monocytogenes after cleaning and sanitation of wooden shelves used for cheese ripening

International audienceThe effect of cleaning and heat disinfection processes of wooden shelves used for cheese ripening on the survival of was examined. The cut boards were inoculated with a suspension containing 5.5 × 10 colony forming units (CFU)/ml of . Survival of was investigated in the wood shavings. During the 24-hour incubation period in a humidity chamber, Listeria counts increased by 0.8 log units on average ( = 9), compared to results 1 h after incubation, indicating the absence of antimicrobial properties of the wood in use. Additionally, after incubation for 24 h at room temperature, the boards were cleaned by soaking them for 15 min in a solution of hot alkaline detergent followed by brushing and rinsing with warm water. Some of the cleaned boards were subsequently heat treated at 80°C for 5 min and at 65°C for 15 min, respectively. The cleaning procedure alone was not sufficient to render from the upper 2 mm wood layer inactive. In the case of both temperature-time combinations for heat disinfection, however, was not detectable