Biogenic amines in wine: gene transcription as a tool for selection of Oenococcus oeni starter strains

Abstract

Wine is a complex environment where the microbial flora can have both a positive (e.g. malolactic fermentation) and a negative (e.g. production of biogenic amines) impact on the quality of wine. Biogenic amines are nitrogenous compounds of low molecular weight that can be found in fermented food and beverages, including wine. Biogenic amines are formed primarily by decarboxylation of the corresponding amino acids by microorganisms through substrate-specific decarboxylases. Some authors consider the presence of biogenic amines to be a fundamental parameter for detriment of alcoholic beverages. These compounds can have adverse health effects on sensitive individuals at high concentrations. The role of microorganisms in wine involves two important fermentation processes, the alcoholic fermentation conducted by yeasts and the malolactic fermentation conducted by lactic acid bacteria. The malolactic fermentation refers to the conversion of L-malic acid into L-lactic acid and CO2, catalysed by the malolactic enzyme. This mechanism contributes for deacidification, bacterial stability and flavour changes in wine. Oenococcus oeni is the leading lactic acid bacteria responsible for malolactic fermentation, mainly due to its adaptability to such a chemically harsh wine environmental (low pH and high ethanol concentrations). The two main goals of this PhD thesis were to contribute to the: (1) increase of knowledge of biogenic amines occurrence in wine; (2) oenological characterization and selection of Portuguese autochthonous O. oeni strains, isolated from different winemaking regions, to be used as malolactic starters on the wine industry.(...)