SPARKLING WINE PRODUCTION BY CHAMPENOISE METHOD IN LOMBARDY REGION: YEAST POPULATION BIODIVERSITY AND TECHNOLOGICAL ASPECTS OF INDIGENOUS SACCHAROMYCES CEREVISIAE AS POTENTIAL STARTERS

Abstract

Sparkling wine obtained through the Champenoise method represents a relevant cultural and outstanding economical fact in Italy. There are two Lombardy sparkling wines belonging to DOCG: (Denominazione di Origine Controllata e Garantita) Franciacorta DOCG and Oltrepo Pavese Metodo Classico which high quality production is remarkable. Commercial starters belonging to Saccharomyces species currently used in Italy for sparkling wine production have been isolated from French territories on the basis of the quality characteristics of Champagne wine since they possess very good fermentative and oenological capabilities. Winemaking is a process on which interactions between Saccharomyces and non-Saccharomyces yeasts take place, influencing wine quality at both levels, sensory and chemical; so assessment of yeast biodiversity is relevant for understanding their evolution in winemaking and consequently increasing the control capability on such processes. Despite the Lombardy region is a very important region for sparkling wines production, a biodiversity analysis of yeast involved in the winemaking process in this region, has still not been carried out. This PhD was focused on the study of yeasts population biodiversity involved in winemaking process in Franciacorta and Oltrepo pavese areas as well as the evaluation of technological aspects of indigenous S. cerevisiae to be used as potential new starters in the sparkling wine production made by Champenois method. In particular, the main research activities and corresponding results were: Genetic identification of yeast population involved in winemaking process in Franciacorta and Oltrepo Pavese areas Samples of vineyard air, must before SO2 addition and base wine were collected during 2009, 2010 and 2011 vintages in Franciacorta and Oltrepo pavese areas. For genetic identification of yeast isolates, genomic DNA was extracted according to Querol et al.(1992). Analysis of RFLP-ITS (Fernandez-Espinar et al., 2000) and D1/D2 of 26S rDNA sequence (Kurtzman and Robnett, 1998) were performed. For the identification at strain level, interdelta analysis (δ-PCR) (Legras and Karst, 2003) was carried out for isolates identified as S. cerevisiae during the 2009 and 2010 vintages. The amplified fragments from δ-PCR were run in capillary electrophoresis (Tristezza et al., 2009). A data elaboration was performed calculating the genetic similarity according to Dice´s coefficient (Dice, 1945). Dendrograms were constructed by the unweighted pair group method using arithmetic averages (UPGMA). During this study it was possible to create a collection of 492 yeast isolates from 24 vineyards belonging to 19 wineries among Oltrepo Pavese and Franciacorta areas. A total of 13 genus and 25 yeast species were isolated and identified during vintages for 3 years. 186 S. cerevisiae isolates were obtained during 2009 and 2010 vintages and from fingerprinting, a great genetic biodiversity was obtained among the analyzed patterns which presented a genetic similarity in a range of 0.2% to 95% by which…