Fermentation performances and aroma production of non-conventional wine yeasts are influenced by nitrogen preferences
Résumé
Saccharomyces cerevisiae is currently the most important yeast involved in food fermentations, particularly in oenology. However, several other yeast species occur naturally in grape must that are highly promising for diversifying and improving the aromatic profile of wines. If the nitrogen requirement of S. cerevisiae has been described in detail, those of non-Saccharomyces yeasts remain poorly studied despite their increasingly widespread use in winemaking. With a view to improving the use of non-Saccharomyces yeasts in winemaking, we explored the fermentation performances, the utilisation of nitrogen sources and the volatile compound production of 10 strains of non-conventional yeasts in pure culture. Two different conditions were tested: one mimicking the grape juice's nitrogen composition and one with all the nitrogen sources at the same level. We highlighted the diversity in terms of nitrogen preference and amount consumed among the yeast strains. Some nitrogen sources (arginine, glutamate, glycine, tryptophan and gamma-aminobutyric acid) displayed the largest variations between strains throughout the fermentation. Several non-Saccharomyces strains produced important aroma compounds such as higher alcohols, acetate and ethyl esters in significantly higher quantities than S. cerevisiae.