Safeguarding US Vines and Wines from Wildfire Smoke
By Arran Rumbaugh, USDA Agricultural Research Service
As the severity and frequency of wildfires increase globally, the grape and wine industry faces the risk of smoke exposure in its vineyards. Researchers across grape-growing regions are dedicated to elucidating the complex impacts of smoke exposure on grapevine physiology, grape chemistry and wine quality. While it is well known that vineyard smoke exposure can lead to smoke taint in wine—characterized as smoky and ashy flavors—it is unknown how much smoke is too much. Therefore, USDA-ARS partnered with NGRA, with support from the West Coast Smoke Exposure Task Force, to organize a two-day workshop in November 2024 to sift through the “smoke signals” to find solutions. More than 50 university researchers, ARS scientists and industry members met in Corvallis, OR, for two days of structured discussions across five topic areas: detection and monitoring, establishing thresholds and baseline values, prevention in the vineyard, mitigation in the winery, and utilizing atmospheric modeling to assess risk.
There are many factors that determine whether a wildfire event will affect vineyards, such as distance from fire, duration of smoke exposure, and vineyard topography. When smoke lingers in vineyards, grape berries absorb volatile compounds in smoke that are then metabolized to form odorless compounds, sequestered in the grape skin and pulp. However, during fermentation, and even during consumption, these compounds are released back into their odor-active form. With high enough concentrations, this process leads to smoky, ashy and medicinal flavors on the palate that can obscure a wine’s intended profile. Not all smoke-exposed fruit yields smoke tainted wines, which is why ongoing research aims to identify the threshold at which exposure results in grapes unsuitable for quality wine production.
In addition, researchers are working to establish best practices that will enable growers and winemakers to detect smoke impact early, even before any sensory changes are apparent in the wine. Analytical tools like gas and liquid chromatography (done at a lab), alongside small-scale fermentations, known as nanofermentations (that winemakers can do themselves), can measure key chemical markers of smoke taint. Among them are compounds like guaiacol, cresols, syringol, and their glycoconjugates, as well as a newly identified group called thiophenols, which may be specifically responsible for that lingering ashy aftertaste.
Yet detection alone is not enough. The industry needs actionable guidance on prevention and real-time decision-making. Growers want to know: Is my fruit even worth harvesting? What treatments in the winery work? Can we anticipate (e.g., via modeling) smoke impacts that may be incurred during a fire event?
A roadmap to guide this research resulted from the November smoke workshop, viewable on the West Coast Smoke Exposure Task Force website. In it, ongoing research priorities include:
- Building a baseline database of smoke compounds in grapes and wines, understanding that not all varieties are affected equally—and some, like Syrah, naturally exhibit compounds related to smoke exposure
- Developing quick, affordable testing tools for vineyards and wineries
- Using atmospheric models to predict vineyard-level risk when smoke events happen
- Exploring prevention strategies like barrier sprays or breeding smoke-resistant vines
- Designing techniques winemakers can use to reduce smoke compounds in finished wine
The Task Force will be rolling out information from the roadmap in digestible sections.
Scientists from across the country—often joined by colleagues around the world—meet quarterly to collaborate, share their findings and keep the drumbeat going. While progress is being made, many knowledge gaps remain. Grapevine physiological responses are still being investigated to properly develop prevention and mitigation tools. As mentioned above, grape varieties may react differently to the same level of smoke exposure. Complicating matters further, variables such as environmental conditions, vineyard management practices, and winemaking styles make it unlikely that a universal solution will emerge. Instead, future strategies will need to be flexible and based on regional conditions.
Ultimately, researchers hope that, by better understanding the science of smoke taint, the industry can make more informed choices during fire seasons and preserve the quality, identity, and economic viability of American wines. This work is about safeguarding a tradition rooted in the land, the fruit, and the people who cultivate it.
Arran Rumbaugh is a Research Chemist at the USDA-ARS Crops Pathology and Genetics Research Unit in Davis, CA. She leads the ARS smoke exposure research program.