How wildfire smoke put Bordeaux’s wine at risk

Winemakers in Bordeaux, France, set the standard for fine red wines—according to wine critics, at least. But the 2026 vintage could be the exception.

This July, massive wildfires ravaged much of southern France. In the Southwest, the fires reached Bordeaux’s city limits, forcing hundreds of thousands of citizens and holidaymakers to flee. Many of the region’s vines were spared from the flames, but the vast smoke plumes that billowed forth were seen and smelled hundreds of kilometers away. It remains to be seen if the smoke has tainted the grapes that weren’t burned.

Wildfire smoke contains volatile phenols such as guaiacol, cresols, and syringol, which are released into the atmosphere as plant lignin burns. Those compounds can penetrate grape skin and attach themselves to sugar molecules within the fruit, forming glycosides.

This process happens quickly. “Ten minutes after smoke exposure, and we see glycosides,” says Kerry Wilkinson, who researches ways to overcome smoke taint at Adelaide University.

Now that this year’s harvest is completed, Bordeaux’s wine industry is confronted by tough questions: Has smoke already interfered with the grapes’ chemistry? And if so, can the damage be reversed? Winemakers must decide whether to make the wine and hope for the best, blend it with unaffected wine, or just accept 2026 as a lost vintage.

Wine making is a billion-dollar industry

The answers to these questions are potentially worth billions of dollars: Bordeaux exported roughly €5.3 billion ($6.2 billion) worth of wine in 2024, according to a 2025 article in Decanter. The French Ministry of Agriculture and Food also forecasts that the country will produce one of the smallest amounts of wine in 3 decades because of the heat waves and droughts that plagued the country over the summer. In other words: the smoke-taint question couldn’t come at a worse time.

Early laboratory results offer some hope, however. Vincent Bouazza, who leads the fine analysis department at the wine science consultancy Laboratoires Dubernet, says initial testing suggests that only vineyards close to the fire’s epicenter appear to face a meaningful risk of smoke taint.

“We have analyzed a significant number of grape samples from areas affected or potentially affected by wildfires,” Bouazza says.

According to Bouazza, proximity to the fire and its intensity seem to be more important than the total time of smoke exposure. “A vineyard immediately adjacent to a fire for 15 min can be much more affected than a vineyard exposed to smoke for 2 days from a fire several kilometers away.” In fact, Bouazza’s team didn’t see any significant contamination in grapes growing farther than 2 km from a fire’s edge.

Bouazza’s investigations are immensely valuable to winemakers as they weigh their options, but these comforting results don’t rule out trouble further down the line.

Testing can often help catch what the nose misses

Smoke taint has a habit of hiding. Part of the uncertainty of smoke taint for winemakers comes from the question of what to measure. Free volatile phenols are what cause the unpalatable smoky and ashy aromas of smoke taint, so they are the logical things to track in grape samples. But they are often present only in low concentrations and only for a short while after smoke exposure because the compounds rapidly bind to sugars, where they are temporarily hidden as odorless glycosides.

These glycosides “act as a reservoir from which volatile phenols can subsequently be released during fermentation and aging,” Bouazza says. So in addition to testing for free phenols in grape samples, Laboratoires Dubernet tests for six glycosides. Bouazza says these are particularly useful to measure preharvest because they provide an idea of the size of the potential phenol reservoir. If the reservoir is significant, winemakers may not go to the expense of making the wine. Testing for free phenols during the wine-making process, on the other hand, helps gauge the extent of any damage in finished wine.

Wilkinson, who has spent years investigating the delayed emergence of phenols, advises winemakers to test their products repeatedly throughout production instead of relying on a single reassuring result. “I’d be cautious of saying ‘We’re safe; we’ve tested; we don’t see any of the smoke-taint marker compounds,’ ” she says. It would be wise for winemakers to test their wine before harvest, a couple of weeks after, and then, if possible, during the fermentation and aging processes, she says.

Even then, winemakers aren’t necessarily safe from smoke taint. Glycosides in a seemingly nonproblematic bottle of wine can break down and release their troublesome phenols even after the wine has matured and been bottled.

“Salivary proteins can break down some of those glycosides, and that will release some of the phenols in your mouth,” Wilkinson says. “It seems to vary from one person to another, so there’s a bit of physiological variation.”

Scientists are still searching for smoke-taint solutions

When test results do suggest smoke taint, winemakers have a few ways to mitigate the problem.

One idea is to mix the tainted wine with unspoiled wine. “If the taint is only minor, maybe you could blend it away. Although some of the work we’ve done suggests that you might have to blend with more than 50%, maybe even more than 75%, clean wine to hide those smoke characteristics,” Wilkinson says. At that point, however, she says it begins to feel like throwing good wine after bad.

In severe cases, it’s almost impossible to mask smoke taint. Wilkinson likens it to licking an ashtray. In those cases, “you’re better off just bottling your clean wine and not trying to blend it at all,” she says.

But there are other ways winemakers can limit the damage. Wilkinson says that using activate carbon to adsorb smoke-taint compounds is one of the best options, but this approach has a trade-off: the activated carbon doesn’t remove just the bad stuff. She says, “You might take out some desirable aroma and flavor compounds.”

Scientists are also working on more-selective treatments. For example, Devin Coleman-Derr, a molecular biologist at the US Department of Agriculture, and colleagues showed that bacteria can degrade guaiacol, one of the volatile phenols that can cause smoke taint (PLOS One 2025, DOI: 10.1371/journal.pone.0331854).

The researchers isolated two strains of the bacterium Gordonia alkanivorans from microbial communities that are naturally found on grapevines. In the lab, they gave the bacteria guaiacol as their only source of carbon. Both strains consumed enough guaiacol that the phenol was undetectable within 96 h. Furthermore, neither strain was able to grow when the guaiacol was replaced with six other phenols. That finding suggests that the bacteria’s chemistry is highly selective.

“If you can have a very targeted approach that can fine-tune the levels of individual compounds, you’re in a much better place from the perspective of preserving the compounds which give the beneficial flavors,” Coleman-Derr says. “That’s why we’re quite excited about this approach.”

But Coleman-Derr’s technique is still in the proof-of-concept stage. The bacteria haven’t been tested as a treatment for smoke-exposed grapes, and the researchers have yet to demonstrate that the bacteria can improve the taste of wine.

Winemakers are sure to welcome novel solutions to protect their vintages as climate change makes wildfires more commonplace. But it’s already too late for Bordeaux’s 2026 crop. Only time will tell if any bottles contain the taste of smoke taint.