Lik Xian Lim, Cristina Medina-Plaza, Ignacio Arías-Perez, Bishnu Neupane, Jean-Xavier Guinard, and Anita Oberholster*
*UC Davis, 595 Hillgard Lane, Davis, CA, 95616 (aoberholster@ucdavis.edu)

We investigated the impact of volatile phenols (VPs) released from burning wood (lignin thermal degradation) during wildfires on grape composition and that of the resulting wines. Wines made from these impacted grapes are characterized sensorially as smoky, burnt, ashy, barbeque, medicinal, and having a retro-nasal ashtray character. The study aimed to determine the baseline levels of VPs in grapes, to establish the sensory differences between smoke-impacted wines and non-smoke impacted wines, and to understand the drivers of smoke taint analytically. Descriptive analysis, multivariate statistics, and analytical measurements of the free and total VPs were used. The level of smoke impact depended on the concentration of free and total VPs present analytically. First, smoke-impacted, and non-smoke-impacted Cabernet Sauvignon wines from nine different sites across California were evaluated. Second, six other common California red wine varieties, Cabernet franc, Petite Verdot, Merlot, Syrah, Malbec, and Zinfandel, were studied. Analytical measurements gave varying concentrations of smoke marker indicator compounds present in the wine. The results show there are sensory differences between high-smoke impact wines and non-impacted wines. Wines which had low smoke impact, based on free and total VP concentrations, were not significantly different from the non-impacted wines when rated through descriptive analysis. Between the different varieties, some smoke-impacted varieties, such as Merlot, were similar in ratings to the non-smoke impacted varieties. Different wine matrices from the different locations and varietals play an important role in determining the level of smoke taint. The results of this study will contribute to our understanding of smoke taint and its wine quality impact by relating smoke marker indicator compounds to sensory attributes. It provides valuable insights for the wine industry and can inform future efforts to mitigate the effects of wildfire smoke on wine production.

Funding Support: Jackson Family Wines, USDA-ARS