Saccharomyces cerevisiae strains from spontaneous fermentations in Pantelleria island and their use in Zibibbo wine production

Saccharomyces cerevisiae strains are commonly used in wine production and are responsible for alcoholic fermentation and fermentative flavours. In the last years interest for yeast natural populations is growing and wineries prefer to produce wines with yeast strains selected in their own territory. We have studied natural Saccharomyces populations in spontaneous fermentations in Pantelleria, a small island situated 70 km from the African coast and 85 km from Sicily, to find new yeast strains for the wine production from Zibibbo (Muscat of Alexandria), the typical grape variety of the island. 119 yeast colonies from spontaneous fermentations were collected in the same winery during 2004 and 2005 vintages and all of them were identified as Saccharomyces cerevisiae by microbiological assays. mtDNA-RFLP patterns of 59 yeast isolates of 2004 vintage showed 13 different strains in this population and PCR-RFLP analysis of the rDNA ITS region confirmed belonging to S.cerevisiae species. Important characteristics for wine production were investigated in these 13 strains, as growth pattern, fermentative vigor, alcohol and volatile acidity productions, alcohol, sulphite and copper tolerances, sulphide formation, zymocidal and ?-glucosidase activities. Six different strains showing the most desirable characteristics were assayed in one litre must fermentations and the produced wines were analysed for seven chemical parameters and subjected to olfactive analysis. In 2006 vintage three of these S.cerevisiae strains were used for the production of Zibibbo wines in 100 L fermentations. Every day microbiological assays were conducted during fermentation, 17 chemical parameters were determined in wines, blind tasting compared these wines with that produced from the same must by a commercial yeast strain. Our preliminary results indicate that in Pantelleria island S.cerevisiae strains bring spontaneous fermentations to a close and a considerable fraction of them can be employed as yeast starters for production of wines with distinguishing high-quality bouquet.