Polyphenol characterization of red wine from Germany's Wurttemberg region

Wurttemberg is Germany's fourth-largest winegrowing region and the only one with predominance of red varieties. To date, its wines have been poorly described with respect to physicochemical composition, including phenolic content, which has become of increasing interest to the industry, given the association of polyphenolics with desirable health benefits and the need for wine regions to identify points of differentiation. In this study, we sought to characterize a sample of commercial red wines from Wurttemberg with particular reference to their polyphenol composition. 37 red wines were assessed for general chemical composition (FTIR), mean degree of polymerization (mDP; HPLC), proanthocyanidins (HPLC) and total phenolic content (Folin-Ciocalteu). Large differences were found with regard to polyphenol content with wines made from V. vinifera L., cv. 'Trollinger' showing the lowest and cuvées showing the highest concentrations. Wines made from cv. 'Pinot noir' contained the highest concentration of monomeric tannins, which may account for the harsh and bitter sensations sometimes anecdotally reported for this variety. In contrast, Trollinger wines had the highest proportion of polymeric tannins (trimers and above). Despite these differences, the mean degree of polymerization was approximately 3 for all varieties. This finding agrees with the thiolysis results, which showed that the ratio between terminal and extension units of the tannins was around 1:2, confirming a medium chain length of 3. These results maybe used to inform production decisions, help optimize the quality of German wine, and assist in the branding and marketing of wines from Wurttemberg. Additionally, it may benefit longer-term goals of better understanding the key drivers of bitterness and mouthfeel sensations elicited by red wines.