From vineyard to bottle. Rationalizing grape compositional drivers of the expression of valpolicella aroma ‘terroir’

Abstract

AIM: Valpolicella is a renowned Italian wine-producing region (Paronetto, 1981). Wines produced in its different sub-regions 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 (Kotseridis, et al., 1999), 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 wines obtained from grapes harvested in selected vineyards during three consecutive vintages, assess the existence of recurring patterns that could represent unique aroma chemical signatures and to identify key grape compositional features underling such aroma signature.

METHODS: Corvina and Corvinone grapes were harvested from five different vineyards located in two sub-regions within Valpolicella during three consecutive vintages. Winemaking was performed under standardized conditions. Free volatile compounds and glycosidic precursors were analysed with GC-MS analysis co. Sensory characteristics of the wines have been investigated through sorting tasks performed with semi-trained panel.

RESULTS: Application of multivariate data analysis techniques allowed to identify volatile chemical patterns representing the unique aroma chemical signature of the geographical origin of each wine regardless of vintages. The main drivers associated with these chemical signatures were terpenes (linalool, α-terpineol), norisoprenoids (vitispirane, TDN, TPB), and, unexpectedly some fermentation derived esters. Wines’ terpenes content was related with grapes terpenes pool. In particular variations in wine linalool content were strongly associated with the grape content of different linalool forms. Finally, in the case of esters, a strong correlation between grape content of yeast assimilable nitrogen (YAN) and wine ester content was observed, further broadening the boundaries of vineyard factors able to influence wine aroma. Patterns of odor similarities were observed during sensory evaluation, indicating a recurring association between geographical origin and occurrence of aroma compounds such as linear and cyclic terpenes, esters or norisoprenoids. 

CONCLUSIONS: 

This study provides evidence for the existence of volatile chemical signatures that are representative of geographical origin. Identification of grapes compositional characteristics related to the main drivers of wines chemical signature provides clues to support producers in identifying and managing appropriate vineyard and/or winemaking practices, in the quest of producing wines expressing their sense of place and ‘terroir’