Clustering wine aromatic composition of Vitis vinifera grapevine varieties

Abstract

Context and purpose of the study

Climate change is likely to impact wine typicity across the globe, raising concerns in wine regions historically renowned for the quality of their terroir. Amongst several changes in viticultural practices, replacing some of the planting material (i.e clones, rootstocks and cultivars) is thought to be one of the most promising potential levers to be used for adapting to climate change. But the change of cultivars also involves the issue of protecting the region’s wine typicity. In Bordeaux (France), extensive research has been conducted on identifying meridional varieties that could be good candidates to help guard against the effects of climate change while less research has been done concerning their impacts on Bordeaux wine typicity. Thus, the present study aims to characterize the aromatic composition of a large pool of Vitis vinifera cultivars through the analyses of some impacting aromatic compounds. Then, aromatic composition of traditional-Bordeaux varieties and non-Bordeaux varieties are compared.

Materials and Methods

A 2-hectares plot of 84 cultivars was planted in 2013, in the Médoc wine region (Bordeaux, France) within the vineyards of a wine estate. Amongst this very large collection of cultivars, a pool of 25 red varieties was isolated, including traditional Bordeaux varieties and potential candidates for introduction in the Bordeaux varietal mix. Each of those varieties has been separately vinified since 2018 in 2hL stainless steel tanks, close to commercial wine production conditions. 41 major aroma compounds were then quantified in each variety for each vintage (from three to five vintages per cultivar) by gas chromatography and mass spectrometry (GC-MS). Statistical analyses, including hierarchical clustering analysis (HCA) and principal component analysis (PCA) were then performed on this unique dataset for aroma profile characterization and to discriminate and isolate varieties according to their aromatic profile.

Results

As expected, analyses resulted in a strong varietal characterization of the different wines with a significant vintage effect on some of the aroma compounds. Of the 41 aroma compounds analyzed, a subset appears to explain a large part of the Bordeaux wines aromatic composition. Clustering of cultivars was possible, and Bordeaux cultivars grouped well together into a unique cluster. Interestingly, a few non-traditional Bordeaux cultivars were close to some of the classical Bordeaux varieties in both the HCA and PCA analyses. These results enhanced the idea that some non-native cultivars could be introduced in the Bordeaux cultivar mix while maintaining global wine typicity. This methodology could help other established wine regions to identify varieties that could be potential candidates for adaptation to climate change.