Naomi Kampen, Cristina Medina-Plaza, Yan Wen, Chris Alaimo, Guillermo Garcia-Zamora, Ignacio Arias-Perez, and Anita Oberholster*
*UC Davis, 595 Hilgard Lane, Davis, CA, 95616 (aoberholster@ucdavis.edu)

The impact of wildfires on winegrape growing regions has increased. Wildfire smoke contains high concentrations of volatile phenols (VPs) that can absorb into grapes and negatively impact grape and wine quality. A few investigated barrier sprays have shown some efficacy in decreasing grape VP absorption from smoke. However, quantitative data regarding application methods is lacking. Two different industrial sprays (Kaolin and GM3-E) were selected for further study, as they showed promise in prior tests. The sprays were applied at two time points prior to intentional smoking, 10 and 21 days, to establish the most efficient application interval for regular protection. Each spray was applied using two different applications: only to the bunch zone, or to the bunch zone and the canopy, to determine the potential for VP translocation from leaves to grape bunches. Additional control samples (no smoked exposure) were taken before smoking. Intentional smoking was accomplished by constructing smoke tents, followed by overnight application of smoke with commercial smokers and hickory pellets. VP concentrations in the tents during smoking were monitored by TD-GC-MS. Samples were taken pre- and post-smoking from treated, untreated, and control (no smoke exposure) grape bunches. At maturity, the grapes were harvested and again split into two treatments: 50% of the grapes were washed with tap water and 50% were left unwashed. All grapes were then fermented in benchtop microferments. The wines from these ferments, berries from the smoked vines, and air samples taken from the smoking tents were analyzed using gas chromatography mass spectrometry (GC-MS) to quantify VP marker compounds in both the free and acid-labile forms. Analysis is ongoing and the results will indicate which treatment could be the most effective, as well as optimal application method and rate.

Funding Support: USDA NIFA SCRI grant