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 10 4 and 10 2 CFU/cm 2 , 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.

Background The biodiversity of the mycobiota of soft cheese rinds such as Brie or Camembert has been extensively studied, but scant information is available on the fungi colonizing the rinds of cheese produced in the Southern Switzerland Alps. This study aimed at exploring the fungal communities present on rinds of cheese matured in five cellars in Southern Switzerland and to evaluate their composition with regards to temperature, relative humidity, type of cheese, as well as microenvironmental and geographic factors. We used macro- and microscopical morphology, matrix-assisted laser desorption/ionization–time of flight (MALDI-TOF) mass spectrometry, and sequencing to characterize the fungal communities of the cheeses, and compared them with metabarcoding targeting the ITS region. Results Isolation by serial dilution yielded 201 isolates (39 yeasts and 162 filamentous fungi) belonging to 9 fungal species. Mucor and Penicillium were dominant, with Mucor racemosus, M. lanceolatus, P. biforme, and P. chrysogenum/rubens being the most frequent species. All but two yeast isolates were identified as Debaryomyces hansenii. Metabarcoding detected 80 fungal species. Culture work and metabarcoding produced comparable results in terms of similarity of the fungal cheese rind communities in the five cellars. Conclusions Our study has shown that the mycobiota on the rinds of the cheeses studied is a comparatively species-poor community influenced by temperature, relative humidity, type of cheese, and manufacturing steps, as well as microenvironmental and possibly geographic factors.

Background: The fungal biodiversity on cheese rinds has been extensively studied for some soft cheeses such as Brie, Camembert, and Roquefort, but scant information is available on the microbiota colonizing the rinds of cheese produced in the Southern Switzerland Alps. This study aimed at exploring the fungal communities present on rinds of cheese produced and matured in Southern Switzerland. We used classical techniques such as dilution series, culturing and macro- and microscopical morphology, matrix-assisted laser desorption/ionization–time of flight (MALDI-TOF) mass spectrometry, and sequencing, as well as metabarcoding targeting the ITS and β-tubulin gene regions, to characterize the fungal communities present of cheese rinds collected in five ripening cellars. Results: Isolation by serial dilution yielded 201 isolates, of which 39 were yeasts and 162 filamentous fungi. Mucor and Penicillium were the dominant genera. Mucor racemosus, M. lanceolatus, P. camemberti, and P. chrysogenum/rubens were the most frequent species. All but two yeast isolates were identified as Debaryomyces hansenii. Overall, metabarcoding detected 80 fungal species, with Mucor spp. and Penicilliumspp. being the dominant taxa, as opposed to only 9 species recovered by serial dilutions. Culture-dependent and independent methods produced similar results in terms of dominant taxa and similarity of the fungal communities in the five cellars, metabarcoding, however, providing more detailed information. Conclusions: Our study has shown that the mycobiota on the rinds of alpine cheese is a complex community defined by different parameters, including temperature, relative humidity, and type of cheese, as well as microenvironmental and possibly geographic factors.