Where There’s Smoke, There’s Tainted Grapes: How Researchers Are Trying to Remedy Smoke Taint

Chris Fladwood, head winemaker at Soter in Oregon’s Willamette Valley, expected 2020 to be one of the most incredible years the state had ever seen. It was dry, warm and consistent, with cool nights that ushered grapes to ideal ripeness.

But a pandemic hit. Then fires—larger than those that struck in the last 36 years combined—spread through the valley. For many winemakers, all was lost.

This event was far from unique. Extreme fires ravaged California in 2020. Australia suffered devastating blazes in 2019 and 2020. The Okanagan Valley burned in 2021 and 2023. Across the world, it’s resulted in lives lost and acres upon acres of land scorched. Winemakers have been forced to make tough decisions. When smoke hits a vineyard, volatile phenols bond with the skins of the grape and penetrate the fruit with persistent smoky flavors—sanguine and slightly charred in the best of cases, overtly ashtray in the worst. The resulting wine is often unsalvageable.

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As fires continue to threaten the world’s wine regions, researchers are working on ways to mitigate and remediate smoke taint. Oregon State University is testing barrier coatings that can be sprayed over vineyards to guard grapes against smoke. The University of British Columbia is experimenting with chemical markers to understand the extent of smoke damage. U.C. Davis is investigating predictive modeling.

As the climate continues to change and uncontrollable wildfires persist, can these potential solutions save the wine industry?

New Innovations

OSU researchers are testing a spray that provides a protective barrier from wildfire smoke—damage that resulted in more than $3 billion in losses in 2020 alone. Made from cellulose nanofiber, the spray can block many phenols (including guaiacol and syringol) and capture others, even after absorption. The product is expected to be available in the next several years, though there are a few hurdles to clear first, like finding a formulation that guards against all, not just some, of the more than a dozen flavor-impacting compounds in smoke.

This new technology offers hope, but U.C. Davis’s Anita Oberholster believes a “silver bullet” solution is far away. She points out that most smoke taint research is under five years old. “We only really started getting funding for this work after the 2020 wildfire,” she says.

In 2021, she applied 12 FDA-approved products on grapes to test their ability to reduce smoke damage. Only two had potential: kaolin, a clay-based product used to shade grapes from sunburns, and a powdery mildew spray.

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Neither are fail-safe—they’re a pain to apply. If you spray the products through the vineyards, coverage is spotty. “So, are you going to hand-dip every single bunch?” she says. “Maybe in high-end vineyards, but the labor and the cost would be prohibitive for most vintners.”

Expense and logistical issues aside, the use of these complex polymer sprays raises other questions for the vinification process. “There are issues of if these coatings will affect the winemaking process,” says Adam Casto, head winemaker at Ehlers Estate in Napa Valley. “I’ve farmed both organically and biodynamically and I’m not really into putting things on the grapes I’m unfamiliar with.”

He thinks it will take years for this new technology to get traction. “To gain the cultural penetration that would be required for this to be a large-scale deployment would take half a generation,” he says. “Think about it: Anytime there’s a shift in fermentation tank styles, yeast approaches, sulfur management protocols or any other developments, it takes a good 10, 15 years to be broadly absorbed and accepted.”

Playing Guessing Games

Why is smoke such a complicated topic? It’s unpredictable—its path is dictated by nature and even in a vineyard, location, elevation, climate and grape varieties can affect how much smoke phenols are absorbed.

“Just because smoke hits and the fruit smells and tastes of smoke, it doesn’t mean that smoke has impacted your fruit in a devastating manner,” says Casto. Luck is a large factor, but varietal choice and winemaking style can also influence the effects of smoke.

Different varietals respond to volatile smoke phenols in their own ways. Since smoke permeates the skin of the grape, thicker-skinned grapes like Chardonnay and Syrah are less susceptible to damage, while Pinot Noir’s delicate skins do little to protect the fruit. Minimizing extraction or cold maceration (a.k.a. cold soaking) can reduce some smoke flavors, though these processes limit the style of wines you can produce. The addition of oak, either through chips or barrel-aging, can mask some of the more unpleasant effects of smoke taint.

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“You can have two wines with the exact same smoke marker profile and they will seem different,” says Oberholster. A touch of smoke isn’t always bad, she adds. “These phenols are the same compounds that get released when you toast a barrel. At low levels, they’re actually a good thing—they’re pleasant, nutty, sweet, spicy and oaky. It’s at high levels that they become obnoxious.”

Oberholster is researching the difference in grape varieties and winemaking styles so she can set a standard for the upper limit of smoke infliction—in other words, when winemakers should call it. She’s also interested in predictive sensory modeling, which looks at the atmosphere, what plants and trees are burning, wind speed and movement and duration of exposure to understand the gravity of smoke damage.

“These technologies exist in other fields,” says Casto. “It’s just applying them to viticulture. There are challenges—how to get high-speed internet to remote areas, signal availability and electricity—but those are far more tangible challenges than predicting fire patterns.”

DIY Remedies

Because there are still no clear solutions, winemakers have been investigating potential fixes on their own.

Fladwood has only had one year of experience with a smoke-affected vintage. When multiple fires emerged from the Cascade Range and Chehalem Mountain in 2020, California winemakers he spoke to warned him to give up hope. “That doesn’t sound like a winemaker,” he says. “Whether it’s smoke, rain, heat, birds, mildew, botrytis or frost, every year is marked with hurdles. Some are harder than others, but they’re all challenges.”

He tried everything—spraying the vines with water to wash off the sulfur and ash. They pulled leaves off the west side of the canopy, which would usually cause sunburns, to let rain clean the grapes. Instead of picking early to avoid smoke, he let his grapes ripen as normal. With so much unpredictability, he at least wanted the correct tannins and fruits in his wine.

As he racked the wines from fermenter to tank, layers of ash appeared in the bottom of the tank. “It was completely alien,” says Fladwood. He cooled, resettled the wine and added yeast, which has a propensity to absorb odiferous compounds, repeatedly until the ash disappeared. “It was like whack-a-mole: smoke would pop up and we’d hit it with yeast.”

That harvest was debilitating, filled with evacuation and overtime. But for small wineries, he sees no other solution. “We’re not owned by a billionaire,” says Fladwood. “We can’t just throw things out.”

In the end, however, Fladwood was proud of the wines he made in 2020 and they ended up being a success. “None of the wine club members wanted to order this vintage,” he says. “But once they came and tried it, they were sold.”

Castro had another approach to the 2020 vintage. His crop was unsalvageable, so he used the opportunity to experiment, employing every method of smoke mitigation he could access. He tried ozone gas, washing the grapes, activated carbon fining, reverse osmosis treatments, molecularly imprinted polymers and food-grade fining resins.

He wasn’t impressed with the results. Some—specifically carbon fining and reverse osmosis—added a little relief, he says, “but it’s just hard to make 10,000 cases of killer wine with these hurdles.”

Chelsea Barrett, director of winemaking at Materra in Napa Valley, tried bentonite clay in the past, primarily for sunburns, but found it needed to be sprayed and completely dried well before it’s needed. If not, it can actually make smoke taint or sunburns worse. Her advice is to experiment with different techniques during the winemaking process. “The best tool that anyone has is a five-gallon bucket for micro-ferments—that way, you can really taste what you’re up against,” she says.

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Many of these methods, such as flash detente, are pricey and, aside from sprays, few are specific to removing smoke compounds. “They’re not laser focused,” explains Oberholster. “You can end up with a lower-quality wine by accidentally removing positive phenolics and tannins.”

This leaves winemakers to face big questions. Do you let the vintage (and the investment) go up in smoke? Do you damage your brand by releasing a potentially imperfect wine? Do you raise the prices of old wines as a cushion? Do you lower the price of a smoky wine? Do you follow Bordeaux’s lead and release a third label?

“There are a number of approaches, and all are complicated,” says Castro. “Ultimately, someone is going to be unhappy.”

Even more uncertain is how these compounds could impact wines as they age. Winemaker Rob Mondavi first dealt with smoke in the early 2000s. While he didn’t see much of an impact in the initial ferment, “eight months later, we started to pick up smoke taint,” he says. “We had forgotten that there were fires in Mendocino. We had to throw the baby out with the bathwater.”

The issue is especially pertinent in pricier bottles that are intended to age and evolve for years. “These are $200 bottles of wine—will they go the distance?” asks Mondavi. “Will the smoke emerge years down the line?”

In 2017’s Atlas Peak fire, they tried spraying the vineyards with water to try and rid the grapes of ash. “It had no impact,” says Mondavi. They tried flash detente, a process that heats grapes then drops the temperatures rapidly in a vacuum chamber. “I guess if you’re making a highly quaffable table wine, it’s not a problem to use flash detente. But with luxury-tier wines?”

So, he relies on crop insurance to help ease the financial burden of skipping entire vintages—he’d rather bow out of a bad year than release a fire-kissed wine and risk brand damage.

“I hate to say it, but the best way we can future-proof is with insurance—ensuring we don’t put out an inferior product,” says Mondavi. “It breaks the promise a winemaker makes to a consumer that they’re buying a quality product.”

Moving Out of the Vineyard

Outside of new vineyard technologies and changing winemaking techniques in the cellar, some winemakers are adapting to a future of wildfires by overhauling production from the start. Barrett is eyeing white varietals like Sauvignon Blanc, Albariño and Semillon and offering rosé as a fallback when heat waves hit.

“It makes sure I have options in years when things don’t go well,” says Barrett. That said, “there’s only so much rosé that people want to buy.”

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Castro has seen a trend of earlier picking. “It guarantees a bit of cash flow and ensures that grapes come off the vine before heat waves and the smoke that follows,” he says. It also falls in line with the current move towards lighter, fresher wines in Napa. “It’s a climactic and cultural shift; moving away from big, over-extracted Cabernets and towards harvesting at lower Brix to make lower-alcohol, brighter wines.”

Even with these moves, winemakers are still holding out that researchers will discover long-term solutions to growing wine grapes in a changing climate. “If we could find something that works really well, it would be a huge advantage and would save the industry a lot of money,” says Oberholster.

Published: April 12, 2024