Jan-Peter Hensen,* Fiona Hoening, and Fabian Weber
*Rheinische Friedrich-Wilhelms-Universität Bonn, Friedrich-Hirzebruch-Allee 7, Bonn/ North Rhine-Westphalia/53115, Germany (hensen@uni-bonn.de)

Red wine sensory properties and quality largely depend on extraction of anthocyanins and tannins during winemaking and their interactions with other wine components. The climatic conditions in cool climate regions make it much more challenging to produce red wines with deep color and a full body, presumably because of the poor extractability of phenolic compounds. The high demand for those types of red wines necessitates the full use of the grape’s phenolic potential. There is, however, still a lack of knowledge regarding the mechanisms that change the extractability and the impact of polysaccharides. To further understand the correlation between grape maturity and polyphenol extractability, the influence of grape polysaccharides
was analyzed in microvinifications of Cabernet Sauvignon and Pinot noir in 2020. Grape polysaccharides extracted from differently ripe grapes were added to musts from three harvest dates (Cabernet Sauvignon: 17.1, 20.9, 21.8 Brix; Pinot noir: 16.7, 19.7, 21.6 Brix). The added polysaccharides were previously extracted as the alcohol-in- soluble residues at three different harvest points in 2019 from the respective berries from the same vineyard. The addition of these polysaccharides during maceration influenced tannin concentration in the resulting wine, while anthocyanin concentration was determined by actual berry ripeness. The observed effects were greater when polysaccharides from riper berries were added. Possible interactions with the polysaccharides stabilized or bound tannins in the must, which led to contrasting results in the different wines. While Pinot noir wines had more measurable tannin concentrations, addition of polysaccharides led to a decreased tannin concentration in Cabernet Sauvignon wines. The stabilizing effects could be based on protective reactions, with other wine components hindering those to bind tannins. The smallest impact of added polysaccharides was found in must from unripe grapes. Varietal and ripeness-specific effects highlight the diverse interactions of polysaccharides with polyphenols during vinification.

Funding Support: The German Ministry of Economics and Technology (via AiF) and the FEI (Forschungskreis der Ernährungsindustrie e.V., Bonn). Project AiF 20024N.