CHARACTERIZATION OF PROSECCO VINEYARDS (VENETO REGION, ITALY) USING SR-ISOTOPE DATA FOR THE GEOGRAPHICALORIGIN ASSIGNMENT

10.1474/Epitome.04.0507.Geoitalia2011 CHARACTERIZATION OF PROSECCO VINEYARDS (VENETO REGION, ITALY) USING SR-ISOTOPE DATA FOR THE GEOGRAPHICALORIGIN ASSIGNMENT PETRINI Riccardo1, AVIANI Umberto1, SLEJKO Francesca1, SANSONE Luigi2, TOMASI Diego2, VACCARO Carmela3 1 - Università di Trieste 2 - CRA-VIT Conegliano (TV) 3 - Università di Ferrara Presenter e-mail: umberto.aviani@phd.units.it Key terms: food safety; stable isotopes; plant-soil interaction. The realization of models of traceability that allow to go back to the origin of a product, protecting food safety, is an issue that has been affecting the wine production sector and the scientific community for a long time. This work aims at defining a reliable and repeatable operating protocol at a regional scale, that allows to confirm the geographic and varietal origin of grape and wine Prosecco CDO (QWPSR) in order to preserve their uniqueness and quality that underlie success recognized by all. Analysis of stable isotope abundance ratios proved to be quite successful in determining the geographical origin of agricultural products; in particular, the Sr isotopic systematics is increasing applications to verify the authenticity of wines, since every isotopic fractionation occurring during the biological transfer from soil to plant and grapes is in-run corrected during mass-spectrometry data acquisition. The 87Sr/86Sr ratio in grapes hence reflects the isotopic signature of soils from the different geological environment of growth and can also discriminate wines from different origins, provided that no changes occur during vinification. In the viticultural areas of Controlled Denomination of Origin, of the provinces of Treviso, Padova, Vicenza, Belluno and Venezia, some zones characterized by homogeneous pedo-climatic environment have been identified: clayey soils and climatic variables comparable with the exception of rainfalls that show a positive gradient of 150 mm, by moving from south to north of the entire area selected. In each of these areas more vineyards planted with Prosecco were selected, differing by type of conduction and pruning systems adopted, as Guyot, Sylvoz, spur pruned cordon, Geneva Double Curtain (GDC) and pergola, in order to check possible interference of these factors on the dynamics of absorption in addition to the role of soil composition. To this aim, from each site a representative number of soil samples was collected, 3 depths for each site, interesting a total thickness of 60cm, corresponding to the soil layer more explored by roots; moreover, at the ripening, samples of grape consisting of a significant number of bunches have been taken. The production activity, recorded over a significant number of vines, and in each vineyard, was assessed through the quantity of grapes per plant, number of bunches per vine and the average bunch weight; on obtained musts, conventional qualitative parameters such as, soluble solids content (° Brix), total titratable acidity and real acidity (pH) were evaluated. Successively, on wines obtained from every vineyard under investigation, the main aromatic precursors will be analyzed. Samples of vineyard soil were dried in oven and the Sr isotope-ratio was measured on the exchangeable fraction of Sr, the carbonate fraction and by the total soil digestion. The Sr isotopic composition was also measured on crushed and homogenized grape skins, seeds and grape stalks and on carefully extracted grape juice by both nitric acid and hydrogen peroxide and oxidative calcination procedures, to highlight possible experimental bias. Sr was separated from the chemical matrix by ion-exchange and the isotopic composition determined by TIMS. The results indicate Sr-isotopic equilibrium between grape stalk, seeds and juice, supporting the hypothesis that the isotopic signature is not altered during biochemical reactions in the plant. A slightly lower isotopic composition is observed for grape skin, possibly reflecting the effects of an aerosol component