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The nitrogen source impacts major volatile compounds released by Saccharomyces cerevisiae during alcoholic fermentation

Barbosa, Catarina, Mendes-Faia, Arlete, Mendes-Ferreira, Ana
International journal of food microbiology 2012 v.160 no.2 pp. 87-93
Saccharomyces cerevisiae, alcoholic fermentation, beverages, biomass, cysteine, grape juice, methionine, nitrogen, nitrogen content, odor compounds, odors, phosphates, sulfides, vigor, winemaking, yeasts
Sulphur-containing amino acids, cysteine and methionine, are generally found in very low concentrations in grape-juice. The objective of this study was to identify the effects of methionine on aroma compounds formation. Nitrogen source effects on growth, fermentative behaviour and aroma compounds formation were evaluated in three strains of Saccharomyces cerevisiae cultivated in batch under moderate nitrogen concentration, 267mg YAN/L, supplied as di-ammonium phosphate (DAP), a mixture of amino acids with (AA) or without methionine (AAwMₑₜ), and a mixture of AA plus DAP. Fermentative vigour and final biomass yields were dependent on the nitrogen source, for each of the strains tested, in particular for EC1118. Additionally, despite the strain-dependent behaviour with respect to the basal level of H₂S produced, the comparison of treatments AA and AAwMₑₜ showed that presence of methionine suppressed H₂S production in all strains tested, and altered aroma compound formation, particularly some of those associated with fruity and floral characters which were consistently more produced in AAwMₑₜ. Moreover, DAP supplementation resulted in a remarkable increase in H₂S formation, but no correlation between sulphide produced and yeast fermentative vigour was observed. Results suggest that the use of different nitrogen sources results in the production of wines with divergent aroma profiles, most notably when EC1118 strain is used. Methionine determination and its management prior to fermentation are crucial for suppressing H₂S and to endowing beverages with diverse sensory traits.