Assessing the Effect of Different Percentages of Red Blotch-Affected Fruit on the Composition of Cabernet Sauvignon Wine
Sean Eridon, Raul Girardello, Larry Lerno,
Monica Cooper, Charles Brenneman, Hildegarde Heymann,
Martina Sokolowsky, and Anita Oberholster*
*Department of Viticulture and Enology, University of California,
Davis, CA 95616 (aoberholster@ucdavis.edu)
As Grapevine Red Blotch-associated Virus (GRBaV) has only recently (since 2011) been identified as the causal agent of Red Blotch (RB) disease, there is a general lack of scientific knowledge regarding how grape and wine composition and quality are affected. RB can severely affect sugar accumulation and color development in red grapes. To deal with RB, growers and winemakers must react based on the severity and incidence of the disease. Possible actions include selected harvesting or replanting the affected vineyard. The objective of this study was to provide the industry with some insight into how inclusion of RB-affected grapes will impact wine quality. Cabernet Sauvignon grapes from infected (RB(+)) and uninfected (RB(-)) vines were harvested separately from a vineyard in Rutherford, CA, in 2015. Wines were made in triplicate from fruit containing different percentages of RB(+) fruit (0, 5, 15, 25, or 100%) by mass. Basic wine chemistry (ethanol, volatile acidity, titratable acidity, pH, and free and total SO2) and phenolic profiling of the wines was performed by ETS Laboratories to determine the impact of including RB(+) fruit on wine composition. Phenolic profiling showed significant differences between RB(+) and RB (-) wines in the concentration of many phenolic compounds, including monomeric flavan-3-ols, anthocyanins, and polymeric pigments, but no significant difference in tannin concentration. Wines will also be analyzed by phloroglucinolysis to investigate potential differences in tannin composition and by HS-SPME-GC-MS to determine the aroma profiles. Formal descriptive analysis of the wines will commence shortly. Preliminary evaluation of the wines indicated clear differences among wine treatments in both flavor and mouthfeel.
Funding Support: American Vineyard Foundation, the Louis R. Gomberg Scholarship, the Adolf L. & Richie C. Heck Research Fellowship, the Horace O. Lanza Scholarship, the Orange County Wine Society Scholarship, the Vernon and Kathryn Singleton Award, the Wine Spectator Scholarship, the Margrit Mondavi Fellowship
