Revealing the origins of old bordeaux wines using terpene quantification

Abstract

The overall quality of fine wines is linked to the development of “bouquet” during wine bottle ageing (1). Bordeaux red wine ageing bouquet is defined by the association of several odours including fresh and fruity notes sometimes related to specific compounds. Some of those molecules, such as thiols or DMS are issued from precursors produced by the grapevine (2–5). On the another hand, several compounds such as terpenes are produced by the grape as precursors (6) and released during ageing. The aroma of aged wines , the “bouquet” could originate directly in grapes thanks to flavour precursors (7). In this study we addressed the questions: What is the most important between vintage and terroir in wine identity? And is there a molecular signature in the aroma of old wines linked to grape origin and revealed during ageing?Over 80 volatile molecules including DMS, esters, terpenes, mint terpenes, C13-norisoprénoïdes, volatiles oak wood compounds and off-flavors were quantified by GC/MS in 80 red Bordeaux wines (7 domains x 12 vintages between 1990 and 2007). A statistical analysis was performed on the dataset. First, the presence of most of the targeted molecules were identified in the 80 wines and the link between their contents and the wines’ ages was evaluated. After that, the hypothesis of wine identity being linked to wood contact or off-flavors was rejected. Next, principal component analysis (PCA) on the data showed a separation between the 7 vineyards studied. Each Bordeaux area and domain could be represented by one or several molecules. Then, a discriminant factor analysis (DFA) showed the weight of each compound in the separation. The terpenes, in particular terpinen-1-ol, terpinen-4-ol and α-terpinene, were implicated to the partitioning of vineyards. A degradation of the separation of the wines is observed if terpenes levels are excluded from the data set. Nevertheless, the separation is not effective based on solely terpene levels. The profile of terpenes in the molecular signature of these Bordeaux old wines is important but the signature of studied domains is incomplete without the other compounds.These results highlight the specificity of productions areas and the existence of a molecular identity unique to each domain beyond the effect of vintage and the passage of years. The terroir and blending practiced in Bordeaux are probably involved in this singular molecular identity.