Giacomo Buscioni

Effects of Microbial Populations on Anthocyanin Profile of Sangiovese Wines Produced in Tuscany, Italy

The effects of wine yeasts and malolactic bacteria on the anthocyanin profile of Sangiovese wines produced by both commercial- and laboratory-scale winemaking processes were investigated. The mean anthocyanin profile of the wines obtained from commercial winemaking processes, carried out in several wineries in Tuscany, showed a distinctive anthocyanin pattern characterized by high percentages of malvidin-3-glucoside, without appreciable levels of acylated anthocyanins. This anthocyanin pattern, also shared by all wines produced in the laboratory, reproduces the peculiar profile of Sangiovese grapes and distinguishes Sangiovese wines from Merlot and Cabernet Sauvignon wines. Principal component analysis of all anthocyanin data showed that the Sangiovese wines did not group on the basis of wine-producing area, harvest year, or winery but were distributed along a longitudinal axis, owning to the variability of cyanidin-3-glucoside, peonidin-3-glucoside, and malvidin-3-glucoside percentages. This variability was independent of the yeast ecology during fermentation, at least if the yeast ecology was described at the level of yeast species. In both commercial and experimental wines, higher percentages of vitisin A, a malvidin-3-glucoside derivative, were dependent on the growth and dominance of Candida zemplinina in the early stages of vinification. The anthocyanin profile of the Sangiovese wines was also maintained after malolactic fermentation.

Effect of Saccharomyces cerevisiae and Candida zemplinina on quercetin, vitisin A and hydroxytyrosol contents in Sangiovese wines

Quercetins, vitisin A and hydroxytyrosol are phenolic compounds possessing several positive properties to human health. This paper refers on the possible effects of two wine yeast species, Saccharomyces cerevisiae and Starmerella bacillaris (synonym Candida zemplinina) on the accumulation of these compounds in experimental Sangiovese wines. A single lot of Sangiovese grapes was fermented by S. cerevisiae alone or by sequential inoculum of C. zemplinina and S. cerevisiae under two aeration conditions. The accumulation of quercetin and its glycosides resulted only influenced by must aeration. However, yeast species occurring in the fermentative process affected the relative abundances among the different forms of quercetin. Vitisin A contents were higher in wines produced in the presence of C. zemplinina. Finally, higher concentrations of hydroxytyrosol and tyrosol were found in wines produced by S. cerevisiae alone under non-aerated condition. The fermentation of different Sangiovese grape musts carried out by the assayed S. cerevisiae strain pointed out that slow fermentation kinetics lead to higher levels of hydroxytyrosol and tyrosol. The study underlines the role of yeast species in determining the accumulation of bioactive compounds in Sangiovese wine.

Influence of Interannual Meteorological Variability on Yeast Content and Composition in Sangiovese Grapes

Kloeckera apiculata and Candida zemplinina represent almost the totality of non-Saccharomyces yeasts in grape and fresh musts. These yeasts can accumulate secondary metabolites that are commonly known to increase the aromatic complexity of wine; thus, variations in their total number and ratio may lead to changes in wine taste and flavor. These variations are determined by numerous variables, including climate conditions and viticultural practices that can affect the environment of the yeasts and, in turn, their quantity and composition. This may consequently give rise to changes in the final sensory characteristics of a wine. This work assessed the long-term relationship (1997–2012) between yeast quantity and composition and the main meteorological variables (air temperature, relative humidity, and rainfall) in a Sangiovese vineyard located at the Brunello di Montalcino Wine Consortium (Tuscany). Results indicated that weather conditions 25 to 30 days before harvesting were correlated with total yeasts, particularly rainfall and relative humidity (r ~0.8). Moreover, K. apiculata and C. zemplinina were found to be correlated with temperature 10 days before grape harvest at the same time as leaf pulling (r = −0.66 and r = 0.52, respectively). These results suggest that both climate and management may affect microbial community and its composition.