AROMA ASSESSMENT OF COMMERCIAL SFORZATO DI VALTELLINA WINES BYINSTRUMENTAL AND SENSORY METHODOLOGIES

Abstract

Sforzato di Valtellina DOCG is a special dry red wine produced from partially dehydrated Nebbiolo wine-grapes growing in the Rhaetian Alps valley of Valtellina (Lombardy, Italy). Valtellina terraced vineyards are located at an altitude of 350–800 m according to ‘heroic’ viticulture on steep slopes. The harvested grape bunches are naturally dehydrated indoors, where a slow and continuous withering occurs (about 20% w/w of weight loss), until at least 1st December when the grapes reach the desired sugar content and can be processed following a normal winemaking with maceration. The wines can be marketed only after 20 months of aging, of which at least 12 in wood. Despite the increasing economic importance, few studies have been published on Sforzato di Valtellina wine and to our knowledge none on volatile organic compounds (VOCs).

In this study, VOCs of Sforzato di Valtellina wine were determined by HS–SPME–GC–MS. Sensory analysis was also performed by QDA and CATA methodologies with the aim of establishing correlations between VOCs content and perceived aroma intensity and descriptors. Thirty-two wines were analyzed in 2021 from two consecutive vintages (17 wines of 2016 and 15 wines of 2017), representing wineries producing 90% by volume of this denomination.

In addition to fermentative VOCs (mainly ethyl esters and some acids), terpenes and norisoprenoids were found in contents that could potentially contribute to the aroma of Sforzato di Valtellina wines. The 2016 wines were significantly richer in total VOCs than 2017 ones, particularly regarding total norisoprenoids and fermentative esters. This result was confirmed also in sensory analysis, with 2016 wines having higher aroma intensity than 2017 ones. Despite the variability found among the wines analyzed for each vintage, some differences were reported in the contents of single compounds: vitispirane and TDN (norisoprenoids), β-pinene and linalool (terpenes), diethyl malate, ethyl hexanoate, ethyl octanoate and methyl octanoate (esters), and hexanoic and octanoic acids (volatile acids). During aging, some compounds can be formed through chemical reactions depending on wine composition and storage conditions. These reactions include ester hydrolysis and formation (associated to fruity-related descriptors), hydrolysis of non-volatile glycoside precursors and chemical rearrangements of norisoprenoids and monoterpenes promoting balsamic-type descriptors, associated here mainly to vitispirane and β-pinene. Acknowledgments: Funded by PSR 2014-2020 Regione Lombardia (Italy) project no. 201901320242. We thank the Consorzio di Tutela dei Vini di Valtellina and Coldiretti Sondrio (Sondrio, Italy) for supplying the wines.