Sanitising wooden boards used for cheese maturation by means of a steam-mediated heating process

Abstract

The aim of this study was to describe the development and evaluation of a steam-mediated heating process for the sanitation of wooden boards used in cheese production. Wooden spruce fir boards from a cheese ripening centre were cut into small blocks and consecutively inoculated with suspensions of Listeria innocua at surface concentrations of 104 and 102 CFU/cm2, respectively. The inoculated blocks were stored at 12 °C and 94% relative humidity. Surface cell counts were determined after 24, 72, 144 and 240 h. Samples for the sanitising runs (steam treatment for 20 min with three different temperature programmes between 70 and 78 °C) were taken after 168, 192 and 216 h. Although a substantial decrease (>2 log CFU) in cell count occurred, L. innocua survived on the surface of the untreated wooden blocks for the entire timespan of the experiment (240 h), independent of the concentration of L. innocua in the inoculum. All three steam-mediated heating processes presented led to the Listeria-free hygienic status of the treated wood blocks. A comparison of abrasive (shavings) and swabbing (cotton rolls) sampling methods resulted in identical results.