In France, and throughout Europe, fermented products are of considerable economic importance and must reconcile sensory and health qualities. Coagulase-negative staphylococci (CNS) are naturally present in many cheeses and cured meats, and some species are used as ferments. They intervene in development of the organoleptic qualities that ensure the typicality and diversity of these products. Integrating safety criteria regarding the species and strains used for the selection of ferments is essential to comply with the guidelines issued by the French Food Safety Agency (Agence Française de la Sécurité Sanitaire des Aliments, AFSSA) and the European Food Safety Authority (EFSA) regarding the Qualified presumption of safety (QPS).
The diversity of staphylococcal species in dried sausages and cheeses
The identification of staphylococci is essential, because some species are of technological value while others are pathogenic. The development of tools based on genotyping methods (DNA chips) has made it possible to reveal the diversity of species in two fermented foods (cured meats, cheeses) and in their manufacturing environment; INRA researchers have thus identified some fifteen staphylococcal species, amongst which S. equorum and S. xylosus predominate.
The diversity and safety of S. xylosus strains
The INRA scientists focused their research on S. xylosus, one of the two predominant species in naturally fermented foods and in their manufacturing environment. S. xylosus is also widely used as a ferment for meat products and certain cheeses. This species plays an important role in the fermentation process by contributing to the development of flavour in fermented products. It is historically recognised as being non-pathogenic, although some strains have been associated with animal diseases and hospital-acquired infections. The study of strains from different sources revealed their broad phenotypic and genotypic diversity. However, the strains can be divided into two groups of either food strains and those found in the manufacturing environment, or potentially high-risk strains associated with animal infections.
The researchers also evaluated the risk factors (toxins, antibiotic-resistance, biogenic amines, substances produced by the bacteria which at excessive levels can cause disorder such as migraine or allergy, etc.) present in strains of mainly food origin. This work, carried out using genotyping methods (DNA chips) did not demonstrate any gene coding for toxins. Only determinants of resistance to certain antibiotics were identified. Overall, these results supported the use of S. xylosus in the manufacture of fermented products.
Practical tools to help professionals control the health quality of traditional charcuterie products
Control of the health quality of products is a permanent challenge for different actors in the agri-food industry, while traditional producers encounter technical and financial obstacles when trying to comply with official food safety standards. In this context, the European project Tradisausage was designed to evaluate certain aspects of the health quality of traditional sausages, and aimed to provide the producers concerned with the means of manufacturing safe products that would, in particular, comply with European hygiene standards.
The INRA researchers developed an in-house ferment composed of strains of S. equorum (dominant species) and S. succinus (species present) in combination with Lactobacillus sakei, selected after verification of their safety. This ferment provides a response to the need to improve health safety (reduction of populations of Listeria monocytogenes and enterococci, and the levels of biogenic amines) while maintaining the flavour of farm-produced sausages.
Through their results obtained in the context of Tradisausage, INRA scientists have thus contributed to compiling Good Hygiene Practice guidelines that provide producers with a working tool suited to traditional charcuterie products which comply with the food safety regulations laid down by European law. This guide, in four sections, identifies the critical points to be monitored throughout the manufacturing chain, proposes/recommends actions to ensure control and describes good practices to be applied in farm production workshops. It also supplies templates for control sheets that will enable producers to monitor and improve the critical points they encounter, and collates all relevant regulatory texts and standards.
The overall results of the European Tradisausage project regarding French production workshops were circulated to the profession through publication of a special issue of the journal Viandes et Produits Carnés (2006, volume 25) and via the website at: http://www.clermont.inra.fr/tradisausage
References:
Talon, R., Leroy S., Lebert I., Giammarinaro P., Chacornac J.P., Latorre-Moratalla M.L., Vidal-Carou M.C, Zanardi E., Conter M., Lebecque A. 2008. Safety improvement and preservation of typical sensory qualities of traditional dry fermented sausages using autochthonous starter cultures. International Journal of Food Microbiology, Vol 126, 227-234.
Dordet-Frisoni E., Dorchies G., De Araujo C., Talon R., Leroy S. 2007. Genomic diversity in Staphylococcus xylosus species. Applied and Environmental Microbiology Vol. 73, 7199-7209.
Giammarinaro P, Leroy S., Chacornac J.P., Delmas J., Talon R. 2005. Development of a new oligonucleotide array to identify staphylococcal strains at species level. Journal of Clinical Microbiology. Vol 43, N° 8, 3673-3680.
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