Mycobiota dynamics and mycotoxin detection in PGI Salame Piemonte.

AIMS: The complex mycobiota that colonizes traditional fermented sausages plays an important role in the organoleptic properties of such products. The aim of the present study was to investigate fungal diversity and mycotoxin production during maturation of PGI Salame Piemonte. METHODS AND RESULTS: Casing and meat samples were collected at five sampling times from three different batches produced in the same factory and analysed using culture-dependent and independent approaches. Penicillium nalgiovense, which was deliberately inoculated, and Debaryomyces hansenii were the most dominant taxa in casings. Several other fungi mainly belonging to Penicillium crustosum, Penicillium glabrum, Penicillium nordicum, Cladosporium spp., Candida sake, Candida zeylanoides and Yarrowia divulgata were also identified. The casing mycobiota was compared to that of the meat using a metataxonomic approach and a higher fungal diversity was observed in meat as compared to casings. Mycotoxins and penicillin G were monitored using QTOF LC-MS and only trace amounts of roquefortine C were detected in two batches. CONCLUSIONS: The present study highlighted the diversity of Salame Piemonte mycobiota and the important contribution of autochthonous fungi to its diversity. The absence of mycotoxins and penicillin G confirmed the high hygienic quality of the studied product regarding fungal and mycotoxin contamination. SIGNIFICANCE AND IMPACT OF THE STUDY: For the first time, this study provides insights about Salame Piemonte mycobiota, which together with the bacterial microbiota and Salame Piemonte process specifications, are responsible for the product organoleptic properties.

Application of capillary electrophoresis single-stranded conformation polymorphism (CE-SSCP) analysis for identification of fungal communities in cheese.

As major contributors of the ripening process, yeasts and filamentous fungi play a fundamental role in cheese-making. Still, there is no rapid and affordable identification method available for both yeasts and filamentous fungi encountered in cheeses. In the present study, we developed a method based on CE-SSCP analysis of nuclear ribosomal DNA ITS amplicons, along with a species pattern database comprising 37 fungal species. By combining analyses of the ITS1 and ITS2 conformers, 25 out of 37 species were discriminated using CE-SSCP analysis. This reproducible and sensitive method was applied to determine the fungal community composition of 36 cheeses including blue-veined, pressed-cooked, pressed-uncooked, red-smear and surface-mould ripened cheeses. Overall, each cheese contained between 1 and 6 fungal species and 23 different species of fungi were detected including 8 yeast species, 9 filamentous species and 6 unidentified species. Comparison of the fungal diversity obtained after cloning and sequencing (rDNA ITS) versus CE-SSCP for 8 cheeses showed that CE-SSCP was at least as exhaustive as cloning and sequencing of thirty clones per cheese. In conclusion, this CE-SSCP method was an effective tool to identify the fungi present in various cheese varieties and may be of interest for the cheese industry to rapidly describe the composition of cheese fungal communities.

Application of denaturing high-performance liquid chromatography (DHPLC) for yeasts identification in red smear cheese surfaces.

AIMS: To evaluate and optimize the use of denaturing high-performance liquid chromatography (DHPLC) for yeasts identification in red smear cheese surfaces. METHODS AND RESULTS: The resolution of DHPLC was first evaluated and optimized using a mixture of PCR amplicons of the internal transcribed spacer 2 (ITS2) region of 19 yeast reference strains representing 18 species that are common in the cheese microbiota. Sixteen of the 18 yeast species could be resolved by combining runs at temperatures of 57.5 and 59 degrees C. Then, DHPLC was used to investigate the yeast microbiota of pasteurized Maroilles, Munster and Livarot cheese surfaces by comparing their peak profiles with our reference yeast database and by collecting/sequencing of peak fractions. Debaryomyces hansenii and Geotrichum candidum for Munster and Maroilles cheeses, and Candida catenulata, Candida intermedia and G. candidum for Livarot cheese were identified using the reference database and collecting/sequencing of peak fractions. CONCLUSIONS: DHPLC technique was found to have good resolution properties and to be useful for investigating the yeast microbiota of red smear cheese surfaces. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first time that DHPLC is applied to study the yeast microbiota of red smear cheese surfaces.