From vineyard to bottle. Rationalizing grape compositional drivers of the expression of “Amarone della Valpolicella” terroir

Abstract

Valpolicella is a famous Italian wine-producing region. One of its main characteristic is the intensive use of grapes that are submitted to post-harvest withering.  This is rather unique in the context of red wine, especially for the production of a dry red wine such as Amarone. Amarone wines produced in Valpolicella different geographic origin are anecdotally believed to be aromatically different, although there is no systematic study addressing the chemical bases of such diversity. Aroma is the product of a biochemical and technological series of steps, resulting from the contribution of different volatile molecules deriving from grapes, fermentations, and reactions linked to aging, as well as one of the most important features in the expression of the geographic identity and sensory uniqueness of a wine. The aim of this study was to investigate the volatile chemical composition of dry red passito wines obtained from withered grapes from different origins and vintages, and assess the existence of recurring patterns that could represent unique aroma chemical signatures. Comparison between wine volatile profiles and grape compositional data allowed to identify some key grape compositional features underling such aroma. Corvina and Corvinone withered grapes were harvested from five different vineyards located in two sub-regions within Valpolicella during three consecutive vintages (2017-2019). Winemaking was performed under standardized conditions Free volatile compounds and glycosidic precursors were analysed with GC-MS analysis.

Sensory characteristics of the wines have been investigated through sorting tasks performed with semi-trained panel. PCA analysis techniques allowed to identify volatile chemical patterns representing the aroma chemical signature of the geographical origin of each wine. Terpenes and norisoprenoids were the main drivers of vineyards aroma chemical signatures, but many other compounds such as vanillates, branched chain ethyl esters and acetate ester contributed significantly. The contribution of certain fermentative compounds to chemical signatures, like isoamyl acetate was also important. Patterns of odor similarities were observed during sensory evaluation, even if they were not always associated with geographical. Variations in wine terpenes content were associated with the grape content of different forms, mainly free. Finally a good correlation between grape content of yeast assimilable nitrogen  and wine isoamyl acetate content was observed, further broadening the boundaries of vineyard factors able to influence wine aroma.This study provides evidence for the existence of volatile chemical signatures that are representative of geographical origin even in wines from withered grapes. Azienda Agricola F.lli Tedeschi is acknowledged for financial support