Paul Mawdsley and Federico Casassa* 
*Wine and Viticulture Department, Cal Poly San Luis Obispo, 1 Grand Avenue, San Luis Obispo, CA 93407, San Luis Obispo, CA 93407 (lcasassa@calpoly.edu)

Cofermentation is an established practice within certain regions and areas of the wine industry and is speculated to improve wine color stability. The hypothesized reason attributed to Viognier cofermentation with red-skinned grape cultivars, most notably Syrah, is copigmentation (and thus color enhancement) resulting from a higher concentration of certain cofactors, primarily skin flavonols, which are potentially introduced by the Viognier grapes. In this study, a control wine (100% Syrah; Sy) and five cofermented Syrah blends consisting of additions by weight of 10% pressed solids of Marsanne (Mr), Roussanne (Rs), Viognier (Vg), Picpoul blanc (Pc), and Grenache blanc (Gb)) were made in triplicate 60 L fermentors (n = 3). In addition, prior to bottling of the finished wines, a portion of the 100% Syrah wine was blended with 10% (by volume) of Mr, Rs, Vg, Pc, and Gb wines (postfermentation blending). It was hypothesized that adding white grape solids would result in color enhancement and different phenolic profiles relative to 100% Syrah as opposed to postfermentation blending. At pressing, wines were analyzed by HPLC for phenolic content and by UV-Vis spectrometry and CIELab tri-stimulus colorimetry analysis to quantify wine color. Tannin and polymeric pigments were not significantly affected in any cofermentation treatment, but catechin and anthocyanin content were, with Sy-Vg and Sy-Mr showing higher anthocyanin content than other cofermentation treatments, but still lower than the Sy control. There was a statistically significant reduction in color amongst cofermented wines relative to the 100% Sy control, with Sy-Gb showing statistically larger reduction in color (chroma, a*) than other cofermentation treatments. Further color testing will be performed to evaluate color stability and sensory analysis of the wines will be performed to fully evaluate the effects of white cultivar cofermentation and postfermentation blending additions of Rhône white varieties on Syrah wines.

Funding Support: Wine and Viticulture Department – Cal Poly San Luis Obispo