Atlas Fire, 2017 (copy)

Smoke from the Atlas Fire in October 2017 hung heavily over vineyards in Napa County, where a trio of wildfires in the North Bay disrupted harvest for the wine industry. Scientists say they're researching ways to quantify the impact of smoke taint on wine grapes.

Smoke taint is a phenomenon dreaded by the wine industry, and one scientists say they’re researching at length.

The term came to the consciousness of the North Bay wine industry following wildfires in 2017. In Napa Valley, a thick, creeping blanket of smoke coated vineyards and homes alike. The smell of wildfire smoke is especially penetrating: it’s acrid, heavy and tends to linger. Under the right circumstances, smoke exposure gives the wine grapes residual, undesirable smoky characteristics — smoke taint.

Those “smoky characteristics” have a scientific name — volatile phenols — and they’re produced from burning lignin, which is present in wood and straw, according to Eric Herve, a research and development scientist at ETS Laboratories in St. Helena.

ETS Labs began researching smoke taint in 2008, Herve said, after the Australian Wine Research Institute proposed two volatile phenols could be “markers” of smoke taint. ETS, in its own research, “improved their detection and quantification in grapes and wines,” Herve added. Testing for the markers in grapes ultimately proved a way of predicting whether or not smoke characteristics would develop in wines.

“Part of our vocation is to do applied research, serving as a bridge between research organizations and the wine industry,” Herve said. “Of course, at the time, we didn’t anticipate that so many catastrophic wildfires would occur in the next decade in our part of the world.”

As harvest after harvest is plagued by evacuations, power shut-offs and smoke, wildfires in wine country have become an increasingly pressing concern for the industry. Vintners, growers and residents alike commonly face extreme fire danger following California’s lengthening dry season, a kind of new normal, they say.

In Australia, wildfires in wine country are no longer new. The country has been weathering “very bad fires” since the early 2000s, according to Dr. Anita Oberholster, an enology specialist at UC, Davis. She began researching smoke taint after the 2017 wildfires in California.

“Australia has at least fifteen years of research on us,” Oberholster said, speaking after a panel on smoke taint at the WIN Expo in Santa Rosa this month. There’s an incredible amount of research to be done on the subject, she added. “Think of it this way: Australia still doesn’t have the solutions, either. But we’re using everything that they’ve learned, and we’re building on it.”

Oberholster, at Davis, does research similar to ETS in St. Helena. She cites “predictive power” as the most important tool for growers and vintners with product potentially impacted by smoke taint. ‘Potentially’ is the key word: how can we know for absolutely certain, using scientific research, whether or not grapes are smoke impacted?

It has to do with volatile phenols, which can be markers for smoke taint in wines. After all, Oberholster emphasized, the presence of smoke itself does not necessarily make for smoke tainted grapes. It depends largely on how old the smoke is and how long it lingers.

“There’s a lot of people that see the smoke, and say — there’s a vineyard, there’s smoke. I’m not buying those grapes,” she said. “That’s totally wrong.”

When grapes absorb volatile phenols, they’re odorless in the fruit. It’s the fermentation process that releases the smoke odor and flavor in wine, according to Herve. That makes wine grapes a crop uniquely susceptible to damage from wildfires, although parallel industries — cider, for instance — could hypothetically suffer similar consequences.

“We haven’t run into it yet: the timing of the wildfires has been thankfully post- (apple) harvest,” said Ned Lawton, founder of Sonoma County-based Ethic Ciders. “I think with apples, we have a couple advantages — the skins are thicker, and we don’t press skins.”

It’s something Ethic has discussed internally, though, and Lawton has considered strategies, like using chemicals to reduce impact. Research on mitigation methods is being done, according to Oberholster, but there is no quick solution for banishing smoke taint. Methods that do exist are each “tools in the tool belt” of the wine industry.

But knowing definitively if product is impacted, and to what extent — are invaluable tools, Oberholster said.

“(The industry) could make more empowered decisions based on real information, not just gut feeling or personal preference,” she added.

When wildfires tore across Napa County in 2017, it was already late into harvest. Most of the year’s crop was in, except for some Cabernet and Petit Sirah, according to Don Clark, a vineyard manager with Nord Vineyard Services. Nord was concerned with its hillside fruit, especially exposed to smoke, Clark said.

A 20-year veteran of vineyard management, Clark added that smoke taint “wasn’t even in my vocabulary” in 2008, following those wildfires. The industry’s attention wasn’t fixed upon the phenomenon then, at least that he was aware of.

In 2017, though, one client did ask for a discount on grapes it had purchased, saying they were detectably smoky. Others, Clark said, couldn’t detect any smoke in tasting the wine, but turned to testing just in case — only to find that some of the markers for smoke taint were indeed present. In the end, Clark said, “people were gun shy about” using the grapes.

“It is clearly a concern within the industry — (in 2017), people dealt with it in different ways,” Rex Stults, director of industry relations for the Napa Valley Vintners, said. “Our encouragement was not to put wines on the market that may have been impacted by smoke.”

In her research, Oberholster aims to eliminate that conditional gray area– no more “may” or “may not” when it comes to impact.

“Napa wineries, especially, are so sensitive — they’re sitting on wine that I think has nothing wrong with it, but that they’re too scared to release,” she said, adding that that is understandable.

“If you’re a consumer, you don’t know that much about wine, but somewhere you heard that winery ‘X’ has a smoke taint problem … for the next five years, when you see that label, you’ll just pick the bottle next to it,” she said.

The industry, recognizing what’s at stake, has acted accordingly. Wineries have willingly provided Oberholster with samples, labs provided access to their technology free of charge, industry has united to lobby for research dollars — all in pursuit of gathering new, accurate information.

“So many people spend thousands of dollars on analysis to maybe or maybe not learn anything. It may or may not be necessary, and it uses techniques that may not work,” she said. “When you don’t have information, it’s like the blind leading the blind.”

As many regions that make wine increasingly find themselves wildfire territory, Oberholster is collaborating with researchers in Oregon, Washington state, Canada and Australia.

“We’re all talking to each other,” she said. “We’re working on so many levels at the same time, and that’s a great thing.”

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You can reach Sarah Klearman at (707) 256-2213 or