Control of inoculated fermentations in wine cellars by mitochondrial DNA analysis of starter yeast

The main purpose of this work was to test the effective dominance of the inoculated strain during the fermentation process. During this research activity, two Saccharomyces cerevisiae selected strains, isolated from Aglianico del Vulture grapes, were tested during inoculated fermentations at pilot scale in three wine cellars producing Aglianico del Vulture wine and characterized by different typologies. Yeast colonies sampled during the processes of fermentation were identified by restriction analysis of the internal transcribed spacer (ITS) region, and S. cerevisiae strains were differentiated by restriction fragment length polymorphism of mitochondrial DNA (RFLP-mtDNA). Analysis of the yeast population during the inoculated fermentations evidenced a significant presence of non-Saccharomyces, which varied with the cellar. The presence of non-Saccharomyces yeasts at different levels affected the aromatic composition of the experimental wines, as determined by gas-chromatographic analysis. The RFLP-mtDNA of S. cerevisiae isolates revealed the differing dominance of inoculated strains as a function of the wine cellar. In two cellars, all the isolates showed the same restriction profile, which was identical to that of the starter pattern. In contrast, in the third cellar, a significant percentage of S. cerevisiae isolates exhibited mtDNA-RFLP patterns different from the yeast starter profile, showing that, in this case, the starter exhibited low dominance in the fermentation. Our results demonstrate that, although the inoculated strains were found with high frequency, other yeasts (S. cerevisiae and non-Saccharomyces) developed, contributing to the fermentative process and to organoleptic quality of the final wine.