Methionine catabolism and production of volatile sulphur compounds by OEnococcus oeni.

Abstract

During malolactic fermentation (MLF), the secondary metabolisms of lactic acid bacteria (LAB) contribute to the organoleptic modification of wine. To understand the contribution of MLF, we evaluated the capacity of various wine LAB to metabolize methionine. Using gas chromatography (GC) coupled either with mass spectrometry (MS) or a flame photometry detector in sulphur mode (FPD), we studied this metabolism in laboratory media and wine. In laboratory media, several LAB isolated from wine were able to metabolize methionine. They formed methanethiol, dimethyl disulphide, 3-(methylsulphanyl)propan-1-ol and 3-(methylsulphanyl)propionic acid. These are known to have powerful characteristic odours and play a role in the aromatic complexity of wine. In various red wines, after MLF only the 3-(methylsulphanyl)propionic acid concentration increased significantly, as verified with several commercial starter cultures. This compound, which is characterized by chocolate and roasted odours, could contribute to the aromatic complexity produced by MLF. This study shows that LAB isolated from wine, especially OEnococcus oeni strains, the major species in MLF, are able to metabolize methionine to form volatile sulphur compounds. This is the first study to demonstrate the capacity of wine LAB to metabolize methionine.