Cheese model to assess the production of biogenic amines by coagulase negative Staphylococci in paste

Coagulase Negative Staphylococci (CNS) may be naturally present in some foods. They are also used as starters in dairy fermentation processes where they are involved in the development of the flavour and typicity because of their aromatic, enzymatic and pigmentary capacities. Most speciesof CNS are generally regarded as safe but their inoccuousness in food processing need to be prooved at a species and infra-species level. Indeed starter producers and food manusfacturer are having to face to more and more severy sanitary criteria and rules. In particular the capacity to produce biogenic amines in food matrices need to be evaluate for the CNS strains which own thecoding gene of decarboxylase and exhibit in vitro production. A semi-hard pasteurised milk cheese model was developed to optimize biogenic amines productionby CSN added. Two starters were combined in either low/high or high/low levels: (1) thecommercial EzalMA400 (lactococci and Streptococcus thermophilus) and (2) a thermophilic proteolytic Lb helveticus + Lb delbrueckii mixture. In comparison to starters on their own, we tested the addition either of a decarboxylase plus (dc+) lactobacillus as control or dc- or dc+ CNS strains (106). The cheeses were salted in brine to reach a sodium chloride content of 25 g kg-1 water, covered with wax and ripened for four months at 14°C. We adopted the low/high level starter combination because it produced more favorable environmental conditions for the survival of dc+ or dc- CNS which initial count was maintained until 4 months of ripening, a higher proteolysis and higher production of biogenic amines by dc+ lactobacilli. When dc+ CNS was added, biogenic amines were produced in higher amounts than with starters on their own or when dc- CNS wasadded. The nature and amount of amines was strain dependent and in relation to their in vitro capacity.