This work describes the influence of yeast population on the chemical characteristics of wine obtained by spontaneous and inoculated fermentation of must from Vitis vinifera Lado, a minor white grapevine autochthonous to Galicia (NW Spain). The study was carried out for two consecutive years. The results showed that musts derived from Lado presented a high acidity though the potential alcohol level was acceptable. The genetic diversity of S. cerevisiae strains isolated from spontaneous fermentations was low, probably due to must characteristics, although these did not interfere with the implantation of the commercial strains used. Analyses showed that the wines subsequently produced had high alcoholic levels and very high acidities (pH 3.0) as was expected from must composition. Wines obtained from spontaneous fermentations had a lower alcohol content but higher total acidity than those from inoculated fermentations. Monovarietal wines produced from Lado were poorly evaluated in sensorial tests because of their unbalanced structure and sourness; however, when they were mixed with other autochthonous white varieties with less acidity, the resulting wines were well accepted.

Yeast plays an essential role in winemaking. Saccharomyces cerevisiae strains involved in fermentation determine the chemical and sensory characteristics of wines. S. cerevisiae XG3, isolated in Galicia (NW Spain), has desirable oenological potential, which has been proved at a pilot scale to produce quality wines. This study applies XG3 as active dry yeast at an industrial scale for Treixadura wine elaboration, and compares it with commercial yeast and spontaneous fermentation within three wineries included in Denomination of Origin Ribeiro over two vintages. Fermentations are monitored using conventional methods, and microbiological implantation controls are carried out by mtDNA-RFLPs analysis. Wine basic chemical parameters are determined using OIV official methodology, and volatile aroma compounds are determined by GC-MS. Finally, wine sensory analysis is also performed. S. cerevisiae XG3 shows an acceptable implantation ability—as compared to commercial control strains. The wines from XG3 have a higher total acidity and lower alcohol content. Their volatile composition differs from control wines, since XG3 produces significantly higher concentrations of acetates, volatile acids, esters and volatile phenols, depending on the vintage and winery. However, lower differences are perceived at the sensory level, where fruity and floral descriptors are perceived by the panellists in XG3 wines. Therefore, XG3 constitutes an alternative to differentiate Treixadura wines.