Volatile sulfur compounds produced by Micrococcaceae and coryneform bacteria isolated from cheeses.

Bacteria, containing both Micrococcaceae and coryneform bacteria, isolated from traditional cheeses, are classified with respect to flavor families from the smell of the cultures in a cheese model, 7 Micrococcaceae, 13 coryneform bacteria and 2 Brevibacterium linens for reference, representative of the aromatic families, are studied for their sulfur compound production. The sulfur compounds produced in the cheese model are analysed through gas chromatography and identified through mass spectrometry. The production of free sulfhydryls from methionine, hydrogen sulfur from cysteine and the use of these amino acids as carbon source are investigated using a synthetic medium. The bacteria display a very wide pattern of sulfur compound products. All the coryneform bacteria and most Micrococcaceae are able to produce methanethiol from methionine, several strains as much as Brevibacterium linens. All the strains produce hydrogen sulfide from cysteine. However, the main point is the large variety of the produced sulfur compounds: sulfides (methyl, dimethyl and trimethylsulfide), thiols (2-propanethiol, 2-methylpentanethiol), thioesters (methylthioacetate, methylthuiobutanoate, methylthiopentanoate) and many not yet identified. All these compounds have a low threshold. Moreover, most of them have already been described in cheese volatile fractions. Altogether, the variety of such compounds and their proportion in bacteria cultures suggest that they might have an important role in cheese flavor diversity.