Identification and characterization of indigenous yeast from priorat wine-making region

Identifier:  TFG:2195

Handle: https://hdl.handle.net/20.500.11797/TFG2195

Authors:  Figuerola Gatell, Pol

Abstract:
Currently, many wineries use indigenous yeasts for winemaking, due to their reproducibility of the geographical identity in the wine organoleptic properties. The objective of this work was to determine the biodiversity of yeasts of the Montsant Appellation of Origin (D.O.) and the Priorat Qualified Appellation of Origin (D.O.Q.), as well as to study their fermentative properties and compare them with commercial yeasts. The yeasts were isolated from the grape skin and from 3 points of the alcoholic fermentation of the different grapes: grenache from D.O. Montsant, carignan from D.O. Montsant and grenache from D.O.Q. Priorat. Seven species were identified using PCR-RFLP of the 5.8S-ITS region of ribosomal RNA and sequencing of the D1/D2 region of the 26S subunit gene of ribosomal RNA (Hanseniaspora uvarum, Metschnikowia pulcherrima, Starmerella bacillaris, Lachancea thermotolerans, Zygoascus meyerae, Candida californica and Saccharomyces cerevisiae). Seven different S. cerevisiae strains were also detailed by analysing delta elements. The fermentative properties of the indigenous strains and a commercial strain of S. cerevisiae were analysed, by performing microfermentations at laboratory scale. At the same time a study of imposition ability of the indigenous strains was carried out. Significant differences have been found in the fermentative kinetics between indigenous strains and some of them are similar with the commercial strain. Regarding chemical analysis, significant differences have been found in the production of glycerol and sulphur dioxide, and the final levels of acidity. To describe the microbiota of the wine-making region of the Priorat, further studies are necessary to identify and characterize the yeast population of the area during more vintages, by performing semi-industrial scale fermentations using the must of the grape variety studied. In this way, results will be confirmed and will allow the selection of specific yeast to produce wines with specific characteristics of the terroir.