Ignacio Arias Perez, Yan Wen, and Anita Oberholster*
*University of California Davis, 595 Hilgard Lane RMI North 1139, Davis, CA, 95616 (aoberholster@ucdavis.edu)

The increasing incidence of wildfires in grape-producing regions has highlighted the need to develop mitigation strategies to manage the impact of smoke and volatile phenol exposure on grapes and the resulting wines. Smoke taint can reduce product quality and cause financial losses for grapegrowers and wine producers. This experiment compared the effects of different materials applied to grape bunches in reducing absorption of smoke marker compounds in a simulated wildfire scenario. The experimental design involved applying 12 different treatments to individual grape bunches on four Cabernet Sauvignon vines close to harvest time. Three bunches from each vine were treated per treatment. Treated vines were exposed to intentional smoke using a smoke tent for two hours. Control samples were taken before smoking and from control vines on either side of the structure. Smoke-exposed control (no barrier applied) grapes were sampled at different time points after exposure. Air parameters were monitored using a Thingy sensor and atmospheric samples were taken during smoke exposure. The free and acid-labile forms of volatile-phenols in grape were analyzed by GC-MS and the individual glycosylated forms by UHPLC-qTOF-MS. There was strong stratification in the distribution of volatile phenols within the structure. The heterogeneous distribution of smoke is reflected in the different levels of uptake of volatile phenols in the grapes. We observe that glycosylation begins to occur within a few hours, with significant increases in almost all glycosylated compounds within four hours of smoke exposure over the non-smoked controls. However, variation in smoke exposure could affect the glycosylation kinetics of volatile phenols. Some potential barrier sprays lowered the amount of volatile phenols in the grapes during smoke exposure under these conditions. However, some applied materials seemed to aggravate the absorption of smoke volatiles.

Funding Support: USDA-ARS