The Extraction of Condensed Tannins in Red Wine Fermentations

The first year of this project was designed to survey the effects of a large number of different pomace maceration practices in commercial-scale fermentations on the extraction of anthocyanins and tannins. This year of the project focused on Pinot Noir and observed variables included cold soak, manual vs. mechanical punch down, and pump over vs. punch down. The wines were prepared at a cooperating winery according to an agreed-to protocol. The phenolic composition of the musts/wines were analyzed using both spectral (at the cooperating winery) and chromatographic methods (at UC Davis and ETS), including a new Silica gel based procedure which separates phenolics based on size. Five analyses were carried out on 9 wines although the focus was on 5 Pinot Noir wines from the Widoe’s Vineyard. The major difference was that the treatments of both mechanical punch down and pump over increased both colored and uncolored tannin, while the cold soak decreased these components. The pump over regime also increased monomelic color. The goals in this project included the following: 1) Develop a method for sample preparation and an HPLC method for the determination of condensed tannins. 2) Assist in the production of four lots of wine in each of two wineries. Production lots will include four fermentations each of a single vineyard Pinot Noir and Cabernet Sauvignon (fermentation conditions to be decided at a later date and with input from each winery.) 3) Through the course of each fermentation, pull samples and analyze condensed tannins by HPLC and information on color colorimetrically. Additional analyses (acetaldehyde, sugar, SO2) will be performed at the principal investigators’ discretion. 4) Conduct tastings of finished wines with production staff to associate style preferences with chemical data.