A s devastating wildfires continue to blaze in the heart of Northern California’s wine-growing country, wreaking catastrophic destruction on the industry, vintners can take a bit of comfort knowing that most of their grapes already have been harvested. But vineyard owners in other places haven’t been so lucky.
Smoke-infused wine has become both an aesthetic and economic problem for wineries in recent years as dry conditions and high temperatures driven by climate change have fueled destructive wildfires near their facilities or vineyards. Winemakers, who traditionally take great pride in the quality of their products, have had to cope with smoke-contaminated wine, much of which is not always salvageable.
We’re not talking about the delicate smoky-like aroma of fine wines that have been aged in oak barrels. Those scents often are described as smelling of “caramel,” “spice” or “clove.” Rather, this is nasty, an odor variously called “campfire,” “burnt,” “bacon,” “ash” or “ashtray.” Not surprisingly, they often are unpalatable and difficult to market.
It’s an issue that extends beyond Northern California, where vineyards in Napa, Sonoma and Yuba are still under siege from fires. There’s no indication yet that the flavor of California wines will be affected. But wines produced in Australia and Southern Italy have been affected when forest fires have erupted in the past.
“I think that many wineries in Oregon may have some issues from wildfires and smoke,” said Sara Gorr, national sales manager for Cliff Lede Vineyards in the Napa Valley. Even in areas where most of the grapes have been collected, “any fruit that is still on the vine might be smoke-tainted, and wineries might decide not to use it,” she said. “It could negatively affect the vintage.”
Her company and others encountered this problem in 2009 after buying a winery in Anderson Valley in Mendocino, a region where wildfires had struck several months earlier. “The pinot noir grapes that the winery had harvested that year were exposed to the smoke from the fires,” she said. “In an effort to remove the smoke taint from the wines, many winemakers tried to filter the wines, but it did not help. The wines tasted like smoked pinot noir, a character described as “campfire.’”
When grape vines are exposed to fires, they absorb the smoky aroma via their leaves and fruit. In the plant, chemicals in the smoke known as phenolics bind with sugar. But during fermentation, the smell is released “and the resulting wines are spoiled,” said Wilfried Schwab, a scientist at the Technical University of Munich who recently published a study in the Journal of Agricultural and Food Chemistry describing what happens within the grapevines after they are exposed to wildfire smoke.
“We have clarified how the grapevine plant attaches sugars to the phenolics and keeps them stored in the plant cells,” he explained. “Grapes produce a natural plant protection agent called resveratrol. This natural product is structurally similar to the phenolic compounds contained in smoke. We found that the [same enzyme] which [processes] resveratrol, also binds the phenolics to sugars.”
When wine yeast is added during fermentation, sugar molecules separate and the smoky odor develops. Sometimes winemakers are unaware that their vineyards have absorbed wildfire smoke. “Therefore it only becomes apparent in the finished wine that the vineyard was exposed to a fire and the final product is of poor quality,” said Katja Härtl, the paper’s lead author.
There is some good news, however. Now that scientists know what happens at the molecular level in the plants, it might be possible to find ways to prevent smoke-permeated wines in the future, especially as wildfires continue to increase under conditions provoked by climate change. “Since we now know the mechanism of the reaction, we can take counteractive measures,” Schwab said.
These include cultivating grapevines with less of the enzyme which binds phenolics to sugars, or adding an additional sugar during wine-making that would result in blocking the release of the smoky smell, he said. “Alternatively, yeasts that are not capable of releasing the smoke aromas could also be used during fermentation. The gene responsible for this could also be removed.” The latter might work in the United States, where genetically altered foods already are in use, but wouldn’t play well abroad. “Genetically modified foods are not accepted in Europe, and in particular Germany,” he said.
Interestingly, there may be one additional option the scientists haven’t yet considered: patience. In 2009, Cliff Lede Vineyards sold wines made from the 2008 vintage at a discount, because it was considered flawed. But Gorr saved a few bottles, and opened them several years later. “I found them to be unique and interesting,” she said. “The fruit flavor that had been overpowered by the smoke flavor in the beginning now was integrated, and the smoke flavor was no longer overpowering. By then, the fruit was really coming through with just a hint of smoke. I found some of the wines to be delicious.”
As rising temperatures and extended drought drive up the risk of wildfire, however, that strategy could prove untenable. Future blazes could ruin the flavor of many California wines or, as happened this week, set vineyards aflame. “That’s the way it is with a warming climate, dry weather and reducing moisture,” said California governor Jerry Brown about the ongoing wildfires. “These kinds of catastrophes have happened and they’ll continue to happen.”
Marlene Cimons writes for Nexus Media, a syndicated newswire covering climate, energy, policy, art and culture.