Aroma chemical signatures of wine geographical origin in relationship to grape variety, sensory characteristics, and technological factors. A case study on Valpolicella red wines

The connection between a wine and its geographical origin is of great relevance in the context of wine production and marketing. Notions such as wine typicality and identity (at the foundation of Protected Designation of Origin), cru and terroir, all of great importance in the wine market, are based on the ability of a wine to express a ‘sense of place’. The relationship between a wine and its geographical origin is in large part associated with distinctive sensory characteristics, aroma in particular, characterizing wines from specific areas. From a chemical point of view, this implies the existence of unique and specific chemical profiles underlying recognizable sensory features of wine identity and typicality. In spite of the many studies aimed at characterizing the wines of different wine regions, the chemical bases of such aroma typicality are still poorly understood. The main aim of this study was therefore to investigate the existence of unique aroma signatures of Valpolicella Corvina and Corvinone wines from specific geographical origin. For this, grape from five different vineyards were harvested and vinified during three consecutive vintages, and the wines obtained were submitted to chemical and sensory analyses aimed at identifying quantifiable chemical markers and sensory parameters. Although large quantitative differences exist across different vintages, results highlighted the existence of clear chemical patterns distinguishing the wines from each vineyard. We define these aroma chemical signatures of geographical origins. The main drivers associated with these chemical signatures were terpenes and norisoprenoids, but also compounds mostly associated with fermentation, such as branched chain ethyl esters and acetate esters. The fact that the drivers of distinction were deriving both from grape and fermentation imply that the link between a wine’s composition and its geographical origin is the result of complex interactions between grape composition and yeast response to grape related factors. Among these, grape concentration of aroma precursors and YAN play a central role. The work also allowed to highlight patterns of odor similarities across the wines, providing evidence also for a sensory dimension of wine geographical identity. Evaluation of the impact of different S. cerevisiae strains on aroma signatures of geographical origin indicated that area of origin has a greater impact than yeast. In fact, from a chemical point of view, most volatile compounds that are thought to influence wine aroma were primarily affected by grape composition. Sensory analysis confirmed that grape composition induces greater differences than yeast strain too. Lastly, since a period of ageing is mandatory for most Valpolicella wines according to the product specification, the influence of aging on the aroma chemical signatures of the different wines was studied. Despite strong transformations of volatile chemical profile, aged wines retained an aroma chemical signature that was characteristic of their geographical origin. The results of this part of the work also allowed to clarify the role of different possible precursors in the formation of the potent balsamic/minty odorants 1,4- and 1,8-cineole during wine aging.