Valpolicella chemical pattern of aroma ‘terroir’ evolution during aging

Abstract

Valpolicella is an Italian region famous for the production of high quality red wines. Wines produced in its different sub-regions are believed to be aromatically different, as confirmed by recent studies in our laboratory. Aging is a very common practice in Valpolicella and it is required by the appellation regulation for periods up to four years. The aim of this study was to investigate the evolution, during aging, of volatile chemical composition of Valpolicella wines obtained from grapes harvested in different sub-regions during different vintages.

Wines were produced with a standard protocol with Corvina and Corvinone grapes, the two main varieties of Valpolicella appellation. Grapes were harvested from five different vineyards located in two sub-regions within Valpolicella during three 2017, 2018 and 2019 vintages. Wines were submitted to accelerated aging treatment at 16°C and 40 °C for 30 days in epoxy resin sealed vials. Free volatile compounds and glycosidic precursors were analysed with gas chromatography mass spectrometry (GC-MS) analysis coupled with SPE and SPME extractions techniques.

Application of multivariate data analysis techniques to young wines allowed to identify volatile chemical patterns representing the unique aroma chemical signature of the geographical origin of each wine, regardless of vintages. In the case of aged wines, aroma signatures of individual geographical origin were preserved to a good extent after aging. In the case of Corvina, ageing slightly reduced the diversity associated with vineyard signature, conversely in Corvinone it seemed to have enhanced it. Terpenes were at the same times among the main drivers of vineyard signatures of both young and aged wines but also among the compounds most affected by ageing treatments. Highly relevant correlations were found between the decrease of some of the terpenes, mainly linalool, geraniol, β-citronellol and nerol, and the occurrence or increase of others like p-menthane-1,8-diol, 1,4- and 1,8-cineole. A significant influence of pH was found in the accumulation patterns of 1,8-cineole. These transformations involve odor- active compounds with implications for floral and balsamic attributes. Despite the deep changes occurring during aging, aged wines retained an aroma chemical signature that was characteristic of their geographical origin.