Miquel Iribarren

Non-Saccharomyces yeasts, particularly Metschnikowia pulcherrima, are considered alternatives to SO₂ in winemaking, combating specific microorganisms. The sensory profile of the wine is contingent upon the type of yeast, the fermentation conditions, and the concentration and mode of application with Saccharomyces cerevisiae strains (whether pure or used in mixed/sequential co-fermentation). This study assessed the aroma in red wines produced with S. cerevisiae (Sc) and M. pulcherrima (Mp, non-Sc), incorporating variations in the method of addition and the inclusion or exclusion of SO₂. The enological parameters of the wines were slightly affected. Volatile compounds were analysed in the wines through gas chromatography–mass spectrometry (GC-MS) at three moments: at the end of malolactic fermentation (MLF) and after 6 and 9 months of bottle ageing. Sequential fermentation of Sc and Mp reduced the concentration of most identified alcohols and acids, which is favourable, as these compounds can yield undesirable aromas at high concentrations. Regardless of the yeast mixture and Mp dose, a majority of the acetate esters and ethyl esters were quantified at concentrations above their perception thresholds, thus enhancing the sensory quality of the wines. Sensory analysis of wines showed generally positive evaluations. Using non-Saccharomyces as an alternative to SO₂ improves the aromatic profile of wines.

Volatile and phenolic compounds play a key role in the sensory properties of wine, especially aroma and color. During fermentation, yeasts produce enzymes that affect the skin’s phenolic compounds extraction and synthesize some of the most important wine volatile compounds. Generally, selected yeasts of the Saccharomyces cerevisiae (Sc) strains are inoculated, which are responsible for carrying out the wine fermentation, enhancing and highlighting its sensory characteristics and contributing to help achieve the wine typicity, according to the winemaker’s criteria. After fermentation, all wines require aging in a bottle to modulate their composition and stability over time. Thus, four different Sc strains (Sc1–Sc4) were inoculated into tanks with Tempranillo grapes to carry out, in duplicate, their fermentation and subsequent aging in bottles (9 months), comparing the aromatic and phenolic composition between them. Results showed differences in the fermentation process (kinetic, ethanol yield), CI, TPI and content of alcohols, esters, anthocyanins, flavonols and flavanols in wines from the different Sc strains studied. Moreover, in the content in wines of most groups of aromas and phenols, except for total acetate esters and flavonols, aging in a bottle had more influence than the yeast strain used for fermentation.