Stephan Sommer,* Faeth Anderson, and Fabian Weber
*California State University, Department of Viticulture and Enology, 2360 E. Barstow Ave. M/S VR89, Fresno, CA 93740 (ssommer@csufresno.edu)

Dark color is an important quality indicator for red wines and is associated with maximum extraction of grape components, long shelf-life, and increased perceived consumer quality. Increasing anthocyanin concentration alone has only a temporary effect, since large portions of red color are lost during winemaking due to oxidation, polymerization, and additions like sulfur dioxide. Some cultivars present additional challenges during red wine production due to their unique anthocyanin composition, low extractability of anthocyanins, lack of stabilizing factors, or predominant growing conditions like excessive heat. This study was conducted with Barbera as the main cultivar due to observed poor color retention in previous years. In addition to traditional strategies like co-fermentation with other cultivars (Syrah and Touriga Nacional) and extended maceration, the grapes were also subjected to polysaccharide ad- dition (pectin and mannoprotein), cold soak, and ripasso of Syrah and Touriga skins. Color extraction and retention was monitored throughout fermentation and maceration and after bottling. The phenolic composition, astringency, and polysaccharide profiles of all wines were determined using photometric assays and liquid chromatog- raphy. Results indicate that the addition of pure polysaccharides prior to fermentation affected color quality of red wines differently than extraction of polysaccharides from grape material during and after fermentation. Although the tannin concentration with pure polysaccharide addition was generally lower, the level of polymeric pigments showed no negative effect. Extended maceration clearly creates the most favorable environment for production of stable colored pigments, but also produces wines
that lean toward oxidation. A secondary polysaccharide extraction through a ripasso procedure shows that the right cultivar choice can improve the color and pigment composition of challenging grape varieties like Barbera.

Funding Support: n/a