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Biological ageing is an essential process for obtaining some distinctive Sherry wines, such as Fino and Manzanilla. It occurs after the fermentation of the grape must due to the appearance of a biofilm on the surface of the wine called "veil of flor". Yeasts belonging to the Saccharomyces cerevisiae species mainly comprise such biofilm. Although other species have also been found, these have been traditionally considered spoilage. Indeed, it has even been hypothesised that they may not be able to form biofilm on their own under such conditions. In the present work, four different non-Saccharomyces yeasts isolated from barrels in the Jerez area under biological ageing have been characterised through their physiological abilities, including extracellular enzymatic and biofilm-forming capabilities. Results showed not only a surprising ethanol tolerance, above 15.5% in all cases, but also a significant degree of extracellular enzyme production, highlighting the urease and proteolytic activities found in Pichia manshurica, as well as lipolytic activity in Pichia kudriavzevii, Pichia membranifaciens and Wicherhamomyces anomalus. As a conclusion, these non-Saccharomyces could be very interesting in the oenological field, beyond improving the organoleptic characteristics as well as technological features in these wines. [ABSTRACT FROM AUTHOR]

Non- Saccharomyces yeast species assume an important role in wine flavor. Notwithstanding, the chemical basis for the flavor characteristics of wines from some grape varieties is not yet defined. The value of this work lies in the use of Malvar white grape, an autochthonous variety from Madrid (Spain) winegrowing region to conduct spontaneous fermentations. This is the first time that a comparative characterization of a wide range of non- Saccharomyces species and a comprehensive analysis of these yeast-derived volatiles has been carried out in this grape variety. β-glucosidase and pectinase (polygalacturonase) extracellular activities were tested on agar plates as primary selection criteria among the 504 non- Saccharomyces isolated from Malvar spontaneous fermentations during four consecutive harvests. Analysis of the wines obtained after fermentation using the selected yeast strains indicates that non- Saccharomyces yeasts isolated along the fermentative process seem that could have a positive impact, showing a high variability in the volatile compounds contributing to the organoleptic characteristics of Malvar wines. Torulaspora delbrueckii CLI 918 was defined as the yeast strain with potential interest for its contribution to the aromatic wine profile with flowery and fruity aromas and could be used in mixed starter cultures with Saccharomyces cerevisiae. However, Hanseniaspora guilliermondii increased the volatile acidity and ethyl acetate, but this species along with the genus Pichia and Candida seem to provide a high quantity of extracellular enzymes which may be beneficial in wine making. [ABSTRACT FROM AUTHOR]

Fino wine is one of the most important Sherry wines and it is obtained through a complex and dynamic biological aging system. In this study, wine and veil of flor samples from fifty-two barrels with different aging levels and distributed in three different wineries from the Jerez-Xèrés-Sherry winemaking area have been analyzed during two years. Some of the wine compounds most deeply involved in flor yeast metabolism were analyzed to take into account the blending effect of this system. On the other hand, veil of flor was analyzed by molecular methods, finding five different species: S. cerevisiae , W. anomalus , P. membranaefaciens, P. kudriavzevii and P. manshurica, being the first time that the three last species have been reported in this biological aging system. Since S. cerevisiae was the vast majority of the isolates, its intraspecies variability was also analyzed by the simultaneous amplification of three microsatellite loci, obtaining nine different S. cerevisiae genotypes, also differentiated according to their physiological properties. Biodiversity analysis showed there were significant differences between the three wineries in the three aging scales, although the overall diversity was relatively low. Moreover, variations in the relative frequency of the different S. cerevisiae genotypes were found to be seasonal-dependent. • Biological aging in Jerez area is more diverse in yeasts than previously thought. • Is the first time that some non- Saccharomyces are described in this system. • Population biodiversity analysis revealed low differentiation among wineries. • S. cerevisiae populations dynamically changed due to climatic conditions. [ABSTRACT FROM AUTHOR]