British Columbia

'Like drinking an ashtray': Why scientists and winemakers are fighting smoke taint from wildfires

Annual forest fires fed by climate change are dragging winemakers and scientists into a high-stakes game of hide-and-seek to find and eliminate offensive aromas in vintages caused by smoke taint.

Wineries can take precautions to mitigate contamination in vintages

Thick smoke from wildfires engulfs the city of Kelowna and its surrounding vineyards on July 30. (Tom Popyk/CBC)

Salami. Barnyard. Ashtray. They're not the flavours you'd expect in fine wine, but annual forest fires fed by climate change are dragging winemakers into a high-stakes game of hide-and-seek to find and eliminate those offensive aromas.

They come from a contamination known as smoke taint, and unlike the peaty aromas scotch lovers lust for, or the oak flavours in wine that are intentional, smoke taint is the last thing winemakers want in a glass.   

As its name suggests, the culprit is airborne compounds from burning trees and soil that settle on grapes still on the vine. The wildfires don't have to be close to the vineyards. And it doesn't take much smoke on the grapes to ruin a batch of wine. 

Wesley Zandberg, an assistant professor of chemistry at the University of British Columbia's Okanagan campus, has been studying smoke taint and how to prevent it for six years. The contamination he's looking for is measured in amounts as small as just 10 parts per billion.

"So you take a teaspoon of smoky aroma and stir it into an Olympic pool and now you've got a perceptible level of smoke," Zandberg said. 

Smoke and flames from the Nk’Mip Creek fire near Osoyoos, B.C., threaten nearby vineyards on July 21. (Maggie MacPherson/CBC)

That amount would be unmistakable in a glass.

"If you actually get a tainted wine, it's like drinking an ashtray. It is obvious very quickly. The intensity of that taint starts to build up after that second or third sip."

Wineries around the world have been swallowing the bitter reality of smoke taint for years now. 

Financial losses

Reports of financial losses vary. Wine Australia pegged the cost of smoke taint from fires in 2003 at more than $275 million Cdn. 

In California's Napa Valley last year, producers took a hit of nearly half-a-billion dollars, based on crush reports from the California Department of Food and Agriculture.

B.C.'s wine industry generates $2.8 billion annually, when things like tourism are factored in, according to industry group Wine Growers British Columbia. More than 85 per cent of the province's wineries — there are nearly 200 — are in the famed Okanagan Valley, or the "Smokenagan" as some have come to call it after fire seasons have grown year after year.

It's easy to understand why something as insidious as smoke taint is being taken seriously.

It doesn't commonly show up in a bottle because in an industry for which success or failure is based on taste and smell, producers aren't likely to let it get to anyone's table.

Still, for sommeliers like Mike Wong at Vancouver's Chambar restaurant, the potential of smoke taint in wines from regions subject to wildfires is a concern.

"Sometimes smoke taint is not always obvious when you first taste the wine, say in March," Wong said. 

"Then you commit to buying a case of wine — and we taste in September, and it's a lot more prevalent. We don't know what happens long term in the bottle if over time it dissipates."

'Part of the story'

A large part of wine's allure is the mythos, Wong said, or the story of how each bottle came from a specific vineyard in a certain part of the world and was made under unique conditions.

"For better or for worse, smoke taint is now going to be a part of that story, too."

But it's a story winemakers would rather not have to grapple with.

UBC chemistry professor Wesley Zandberg uses smoke tents, like this one, to analyze the effects of smoke exposure on grape vines. (Submitted by Wesley Zandberg)

Ross Wise, chair of the British Columbia Wine Grape Council, is also winemaker at Black Hills Estate winery in Oliver, which was under an evacuation alert until last week. Wise takes the challenge in stride.

"We're learning to adapt," he said about the potential for smoke taint.

"It's another thing ideally we wouldn't have, but at this stage, it's just a matter of adaptation and learning to work with it."

Labs capable of testing for the unwanted smoke molecules have never been busier. Wise said wineries can also take extra precautions to mitigate contamination.

"It might mean hand-harvesting the grapes [as opposed to mechanical methods] so that the berries are intact when they come to the winery. They've got less time exposed to the juice. I think that's probably the biggest way to mitigate it."

Leaves may also be involved

The ultimate goal, however, is to prevent smoke molecules from getting into the fruit in the first place. That's what Zandberg is working on, with the backing of the B.C. Wine Grape Council.

"Direct entry into the berry is a major route and it may be the major route," Zandberg said, noting that science hasn't entirely settled the question of how smoke taint finds its way into the fruit. The leaves may also be involved, he said.

"Clearly understanding how the smoke gets in is kind of a prerequisite for informed crop protection."

To that end, he and a team of students are experimenting with a variety of agricultural sprays, coating grapes that are then placed inside tents filled with smoke from burning pine needles and soil. 

An experimental smoke tent used by Zandberg in his research is shown at a vineyard near Kelowna, B.C., in 2018. (Submitted by Wesley Zandberg)

Zandberg then hunts for contaminants in the fruit using a mass spectrometer. This coming winter, he'll use store-bought table grapes to carry on his research when the vines are bare.

But smoke taint is vexing for both winemaker and scientist alike, largely because the grape itself aids and abets the felonious smoke molecules.

"When those compounds go from the smoke into the grape, the grape immediately uses enzymes to chemically attach these smoky aromas to sugar," Zanderberg said.

"These things are hiding out in grapes where you can't taste them. You can't smell them. There is no obvious fault in the grapes until you add the yeast and then the fermentation process starts."

Yeast unmasks taint

It's the yeast that effectively unmasks the grape's smoky intruder, releasing it into the fresh wine.

Shortening fermentation can help, but it's not a solution.

"It really does come down to the timing of the smoke in relation to the grapes ripening," Wise said. "And also the concentration of the smoke in the air."

Wise said the fire situation has improved near Oliver, where Black Hills Estate vineyards are located. He's optimistic that smoke in the area won't be a factor in his winery's vintage this year.

However, just a few minutes drive north, at Nk'Mip vineyards, the owners are less certain. They say it's a relief that the fires appear to have moved away from their grapes.

"It's too early to determine if there are any impacts from the fires/smoke on our grapes," a spokesperson for the winery said via email.

Grapes seem to be at their most susceptible to smoke taint during what's known as veraison, when the fruit changes colour and the berry essentially closes up to preserve its sugars and juices.

In the Okanagan, that's happening now.


Curt Petrovich is a journalist and author with more than three decades of national, international and investigative reporting experience.