Incidence of nitrogenous compounds of must on ethyl carbamate formation induced by lactic acid bacteria

Abstract

Aims: Ethyl carbamate (EC) is a toxic compound of major concern for the hygiene quality of wines. Its natural synthesis in wine is connected to the ethanolysis of molecules such as urea (alcoholic fermentation metabolite) and citrulline and carbamyl phosphate (malolactic fermentation metabolites) during ageing. This study reports the effect of adenine, arginine, urea and ammonium phosphate of Vitis vinifera L. cv. Tempranillo must, on EC synthesis in fermented wine using two lactic acid bacteria strains under different microbiological and physicochemical conditions. Methods and results: EC was quantified by gas chromatography-mass spectrometry detection. The Lactobacillus hilgardii strain evaluated was associated with particularly high EC production. No significant effect on EC formation was observed for nitrogen enrichment of the starting must. Conclusion: Residual arginine levels at the end of alcoholic fermentation from arginine- and ammonium-enriched musts showed no direct relationship to EC levels found after incubation with either of the LAB strains. Overall results suggest that the different nitrogenous substrates added to V. vinifera L. cv. Tempranillo must do not have any influence on EC formation due to LAB growth in wines under the experimental conditions used. Significance and impact of study: The composition of the nitrogen status of must has frequently been said to be a factor of concern on the final urethane concentration of wines. High contents of arginine coming from over fertilised vineyards are known to render significant levels of urea after alcoholic fermentation if conducted by arginase (+) yeast strains. This urea is always likely to undergo ethanolysis. No significant correlations were found between any of the nitrogenous compounds tested and final EC. High levels of arginine in the starting must did not lead to greater EC concentrations in the resulting wines.

Keywords

• ethyl carbamate
• must nitrogenous status
• ethyl carbamate precursor
• malolactic fermentation
• lactic acid bacterium