The heightened risk of nighttime wildfires and how smoke damage decreases with drift were two of the topics four experts in the science of smoke exposure outlined during a seminar at the Unified Wine & Grape Symposium in January.

The forum, titled “Clarity in the Smoke: Integrating Wine Sensory to Chemical Analysis and Predictive Modeling for Wildfire Smoke Events,” was presented by the West Coast Smoke Exposure Task Force.

Santa Ynez Valley-based winemaker Alisa Jacobson, WCSETF research subcommittee co-chairwoman, moderated the event. Her label is Turning Tide Wines.

The task force was formed in 2019 in response to the devastating October 2017 wildfires on California’s North Coast. Its members include grape growers, research professionals and winery representatives from California, Oregon and Washington.

Smoke from wildfires can significantly impact the quality of wine grapes and the resulting wines, especially during the later stages of grape development. Grapes can absorb smoke compounds through their skins. The compounds — glycosides — bind with grapes’ natural sugars and remain undetectable until fermentation, when they break down, resulting in smoky or ashy flavors in the wine.

“Smoke taint costs the wine industry a lot of money (in a time) when we don’t have a lot of money to burn,” Jacobson told me during a subsequent interview in late February.

Since the task force’s formation, everyone with a hand in the West Coast wine industry is “collaborating more — it’s huge,” she noted.

On the January panel were Dr. Thomas Collins, assistant professor at Washington State University; Dr. Mark Krstic, managing director of the Australian Wine Research Institute; Camilla Sartori of Oregon State University; and Dr. Michael Kleeman, professor of civil and environmental engineering at the University of California, Davis.

Sartori, a sensory manager in the Oregon Wine Research Institute’s lab with Dr. Elizabeth Tomasino, filled in for the latter, a longtime task force researcher and advisory member who had a schedule conflict.

A key point: Smoke flavor in wine does not increase over time, as the chemical compounds do not, either. In very young wines, the natural fruit flavors often mask the smokiness.

Krstic, from the Australian Wine Research Center in Urrbrae, South Australia, opened with dark humor, noting that he traveled to Unified “straight from our fires back home.” January saw wildfires blacken hundreds of acres of vineyards and structures across southeast Australia.

The compounds in smoke are absorbed by the grapes, and then by the vine itself, he said. Smoke affects the hanging grape clusters and then the taint affects the wine.

Volatile phenols and their bound glycosides will not fade as the grapes ripen, but the ratio of free to bound VPs will decrease as ripening continues. The free VPs are glycosylated by grapes’ enzymes over time.

Research has proven that the smoke flavor in finished wine does not substantially increase over time, Krstic said: “The chemical compound is stable.”

Also less of a factor over time are the shifting winds that may blow smoke away from a fire’s point of ignition and then back again. As the smoke ages, its potential to damage decreases, he said.

Sartori shared the results of an Oregon State University consumers study in which participants tasted pinot noirs affected by smoke along with a control wine. The somewhat-heartening upshot: As many as 20% to 30% of participants “struggled to detect smoke taint in wines,” she said.

That taint typically tastes of band-aids, smoke, chemicals and ash trays, Sartori said.

The wines used in the study were Oregon pinot noirs that had been affected by the 2020 fires in both Northern California and Oregon, she said.

She cited the importance of labels, as some study participants “tasted smoke” when a sample in question wasn’t smoky, but a bottle name referenced “Smoke Stack.”

The research also identified a cluster of people who simply “were more accepting” of smoke-impacted pinot noir, she said.

Collins noted that while the WCSETF’s initial grant from the U.S. Department of Agriculture will end in August, members are confident that funding will continue: “Our website is up and we have newsletters available, as well as research bulletins.”

Continuing, Collins emphasized the goal of “prevention strategies for mitigation in both the vineyard and cellar.”

Equipment to measure smoke density in microns — particle counters — are in use in various vineyards in major grape-growing regions, he said.

PurpleAir makes sensors to empower communities who collect hyper-local, real-time, air quality data and share it with the public.

Jacobson later told me how vital PurpleAir is to growers: “We use it to determine if smoke is in the air,” especially when vineyards she or others might source from are located in other regions. 

However, she noted, these sensors do not detect volatile compounds (VOCs), only that there is smoke in the air. “This is why researchers are establishing their own sensor network to analyze potential smoke taint compounds,” she said.

Kleeman of UCD, who specializes in air pollution, noted that the timing of fires will determine smoke risk levels: “Ozone levels fall sharply at night, and without the protection of ozone, night-time fires are more dangerous (to wine grapes).”

Other factors include wind speed, the concentration of ozone and the distance from fires to vineyards and other crops. Most of the damage to date has occurred in the coastal range of Northern California, he said.

Panelists agreed that as smoke from fires lingers, it becomes less of a risk. Collins noted that aerial sprays to help protect vineyards are in the works, and that timing of fires ignition is key. Kleeman suggested that “strategic prescribed burns around vineyards” would be beneficial.

In February, Jacobson described the WCSETF as a “resource for the industry, especially regarding crop insurance and during the need for micro fermentations when faced with the risk of smoke taint.” (Micro fermentations utilize small equipment — think picking buckets — in order to test the level of possible taint before one processes an entire lot of fruit).

 “We are a one-stop shop,” Jacobson said. “If we can learn from one another, then (our education) will be faster.”

She emphasized the big role the USDA has played in the funding of the task force; in addition, “two dedicated USDA researchers” are members of the WCSETF committee.