Smoke was in the air — will it be in wine too?

What effect will smoke from the Napa fires have on Napa wine?
Smoke from the Napa Fires in September created huge banks of smoke that hung over the Winters area, seen here at the Turkovich vineyards on Highway 128. Photo by Debra DeAngelo

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Now that it’s cool and we’ve had rain, it’s hard to remember that October was hot, windy and filled with fires. The Atlas Fire southwest of Winters burned from Oct. 8-31 and consumed over 50,000 acres before it was contained.

Nearly 200,000 acres burned in Napa and Sonoma counties, prime wine country.

The good news is that most of the vineyards did not burn. An estimate is that about 90 percent of the vines in the fire-affected area are intact.

Also good news is that about 90 percent of the grapes had been harvested.

Mother Nature’s bad news is that unharvested grapes, still on the vine, can be strongly affected by “smoke taint.”

Smoke taint has been quaintly described by the Western Australia Agriculture Authority as giving wine a flavor of “smoked meat,” “disinfectant,” “salami” or “leather.” The most evocative descriptor is that the odor is like “smoldering cigar butts in an ashtray.”

Anita Oberholster, a UC Davis agricultural chemist, has said, “Even 30 minutes (of smoke) could affect grapes.”

Winters definitely saw and smelled plenty of smoke during the 2017 fires. The question is whether or not the wines will be affected.

Nicole Salengo, Berryessa Gap winemaker, said, “We got lucky this year. Our harvest was basically over before the fires came up.”

She said that in 2014, they had 60 acres of Malbec close to smoke. You can’t taste the smoke in the grape before harvest, but it will show up in the wine. Salengo said that Corinne Martinez, one of the owners of Berryessa Gap, actually liked the slight smoky flavor in the wine that year. It is common practice to age Chardonnays in oak barrels that have deliberately been charred on the inside, specifically to impart a smoky flavor to the wine.

The smoky flavors come from chemical compounds that are released from plants, particularly wood, when it burns.

The first most abundant natural polymer in the world is cellulose — the structural backbone of plants. Composed only of sugars, it does not contribute to smoke taint.

The second most abundant natural polymer in the world is lignin. Lignin gives rigidity to plant cell walls. It is formed by crosslinking chemical compounds called phenols. (The main ingredient in Listerine mouthwash is a phenol, to give you an idea of the odor.)

When lignin burns, as in wildfires, many different phenolic compounds are released. These compounds are volatile, and occur as gases that can be absorbed through the waxy skin of grapes. These phenolic compounds are responsible for smoke taint.

Salengo said the most common chemicals that can be tested for in the grapes,  juice or wine are guaiacol and 4-methyl guaiacol. They also occur in bacon, smoked fish, whiskey and roast coffee.

Once absorbed into the grape, they can chemically bond with sugars in the grape and lose their odor. That’s why tasting the grape may give you no idea of the smoke taint hidden in its juice.

Yet another trick of Mother Nature is that, while aging wine, the smoky phenol compound may be released from its bond with sugar and show up again as smoke taint in the wine. When you taste the wine, the smelly phenol has been released and you get smoke in the vintage.

Grapes are not equally susceptible to smoke taint throughout their growing season. In the shoot or flowering stage, grapes are less likely to absorb smoke. But once the grape starts to mature, after veraison when it starts turning color, until the time of harvest, the potential for smoke uptake is highest. The thicker the smoke and the longer it lasts, are factors that determine how much smoky flavor ends up in the grape and the wine.

One more complication that Mother Nature throws in is that different grape varieties have different susceptibilities to smoke taint. All varieties can have it. Australian researchers have determined that Semillon and Sangiovese are more sensitive than Cabernet Sauvignons. White wine varietals may be less susceptible only because they spend less time in contact with the grape skin that absorbs the phenol compounds.

Nichelini Winery, the oldest family-owned winery in California, was closer to the fires than either Berryessa Gap or Turkovich Family Wines. Doug Patterson, vice-president and director of marketing, said they were in the middle of harvest and production when the fires started. They have not lost any vineyards. In some of their vineyards, the winds actually blew the smoke away from the grapes.

They moved all their fermentation production to a site away from the wildfires, as a precaution.

Nichelini has sent samples off to be tested for smoke taint, but, at the time of the interview, did not have results back yet. Patterson said they had not yet formulated a plan of what to do if there were smoke chemicals in their grapes or fermentations.

He said, “It is almost impossible to get rid of them.”

Salengo said there were chemical treatments to remove the smoke taint, but they “beat up the wine.”

The local wineries have largely escaped damage from smoke taint this year.

Will we be as lucky next year to escape damage from wildfires?

Mother Nature will let us know.


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