The objectives of this study were to explore bacterial community assembly from cow teat skin to raw milk cheeses and to evaluate the role of farming systems on this assembly using 16S rRNA gene high-throughput sequencing. The two grazing systems studied (extensive vs. semi-extensive) had a greater effect on the microbiota of cow teat skin than on that of raw milks and cheeses. On teat skin, the relative abundance of several taxa at different taxonomic levels (Coriobacteriia, Bifidobacteriales, Corynebacteriales, Lachnospiraceae, Atopobium, and Clostridium) varied depending on the grazing system and the period (early or late summer). In cheese, the abundance of sub-dominant lactic acid bacteria (LAB) varied depending on the grazing system. Overall, 85% of OTUs detected in raw milks and 27% of OTUs detected in ripened cheeses were also found on cow teat skin. Several shared OTUs were assigned to taxa known to be involved in the development of cheese sensory characteristics, such as Micrococcales, Staphylococcaceae, and LAB. Our results highlight the key role of cow teat skin as a reservoir of microbial diversity for raw milk, and for the first time, that cow teat skin serves as a potential source of microorganisms found in raw-milk cheeses.
Our case study of Salers cheese production in south-central France highlights how place-specific knowledge grounds the various networks shaping the rise of geographical indications (GI) in food production. In 1961, Salers cheese producers created a "Protected Designation of Origin" (PDO). To preserve the distinctive character of their product, they opted to require use of the gerle, a traditional wooden vat, and an on-farm cheese making process. The gerle came recently under scrutiny from French governmental hygiene regulation enforcement, and the subsequent public controversy jeopardized the entire supply chain and destabilized Salers cheese-making methods. Prevailing in their efforts to protect Salers, producers established the gerle as mandatory and have since set up a governance board to ensure PDO brand integrity. Our analysis suggests that the diversity of technical choices and associated set of knowledge in Salers cheese production has paradoxically been both its strength and weakness. Local agricultural know-how forges links among participants in Salers networks, connecting cheese producers and consumers, to cattle, microbes, landscapes, wooden tools, and cheeses. Yet, diversity of local expertise creates a tension among producers who must collaborate to achieve unified standards within a PDO while resisting homogeneity. Such results contribute to discussing on PDO governance: an arena to share, compare, and unite local knowledge is critical for GI and thus for sustainable agricultural systems.
Aim: Development of a nested-PCR single strand conformation polymorphism (SSCP) assay targeting the 16S rRNA genes of the Staphylococcus genus, to monitor staphylococci in cheese. Methods and Results: New primer sets to specifically amplify 16S rDNA of staphylococci were designed to be used in a nested-PCR SSCP assay. The method was efficient in discriminating the staphylococcal species most frequently found in cheese. It was validated by monitoring Staphylococcus populations in three productions of raw milk cheese. Analysis of milk samples revealed dominant SSCP peaks corresponding to Staphylococcus aureus, Staphylococcus equorum and Staphylococcus saprophyticus. After 12 h, the S. aureus peak became dominant. Conclusions: The combination of specific Staphylococcus nested-PCR and SSCP allows rapid and direct monitoring of staphylococci diversity and dynamics in milk and cheese. In the core of the cheeses studied, S. aureus may have ecological advantages against other Staphylococcus populations. Significance and Impact of the Study: This approach is a promising tool to study the ecology of staphylococci in cheeses and in other food samples.
Les consommateurs sont de plus en plus attentifs aux qualités sanitaire et sensorielle des produits laitiers et des fromages en particulier. Ces qualités dépendent en grande partie de la composition et de la vie des communautés microbiennes, en perpétuelle évolution lors de la fabrication et de l'affinage des fromages. Elles doivent maintenant être réfléchies dans le cadre de plus en plus strict de la législation européenne en matière de normes microbiologiques. Le contrôle de ces communautés microbiennes, pour favoriser les flores utiles et inhiber les flores pathogènes, est donc un des facteurs-clés de la maîtrise de la qualité des fromages. Il est particulièrement complexe car la vie de ces communautés résulte toujours d'interactions -synergie, antagonisme, compétition- entre les microorganismes, répondant à des changements environnementaux (combinaison de stress divers pH, sel, acides) et interagissant avec les structures physiques (répartition, attachement) et les constituants biochimiques du lait puis du fromage. La maîtrise de la communauté microbienne débute dès l’élevage, d'une part parce qu'une partie d’entre elle est présente dans le lait de fabrication et, d'autre part, parce que la composition biochimique de la matière première lait, qui dépend des conditions d’élevage des animaux, va influencer la vie des populations microbiennes. Elle doit être effective tout au long de la fabrication et de l'affinage. Voir la suite de l'article à l'adresse suivante :https://www6.inrae.fr/productions-animales_eng/content/download/3822/39529/version/1/file/Prod_Anim_2003_16_4_06.pdf
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