Last year, I was celebrating my wife’s birthday at a restaurant in Napa. Among our guests was my longtime friend Pierre, winemaker at Signorello. Nobody was expecting that only a few hours later, the wine countryside of Sonoma and Napa was going to face those devastating fires. Pierre, armed with a couple garden hoses, battled the blaze at Signorello. He ultimately could not avoid the total destruction of his winery building. A year after the devastating wildfires that swept through our Valley, I would like to respond to few questions or concerns about smoke taint in wine and in the vineyards.
Smoke from the fires remained in the Valley for weeks. With prolonged exposure to smoke, vines can absorb unwanted flavors, which is passed on to the finished wine.
When wood burns, it releases aromatic compounds called volatile phenols. Berries are like small sponges. In the vineyard, these compounds can permeate the grape skin and rapidly bond with the sugars. This process renders the phenols no longer volatile, meaning their smokiness cannot be detected by smell or taste. Once the grapes are fermented, the acidity in the resulting wine will begin to break these bonds, rendering the phenols volatile once again.
Clove has a lot of volatile phenols like guaiacol. Clove is in the same family of smells found in smoke. Tests for smoke taint are done on the skin first to determine if the grapes are at risk to develop these smells later. Wines without oak treatment are easier to assess. Smoke taint can be described as “smoky,” “bacon,” “campfire” and “ashtray.” Smoke taint is long-lasting and can linger on the palate even after the wine is swallowed or spit out.
Smoke taint can ruin a wine. There’s no evidence it can make you sick, but the flavors associated with heavy smoke taint are enough to deter consumers from taking the risk on a wine that might be affected.
Fortunately for Northern California’s 2017 vintage, most of the grapes had been harvested before the fires had broken out. Only a few vineyards of Cabernet Sauvignon grown in higher elevations are in danger due to a later harvest. After the October fires, the air quality in California was poor but it did not affect wines that were already fermented or that had finished their primary fermentation. Indeed, they were saturated with carbon dioxide which acted as a protective blanket.
Smoke taint is largely a red wine issue. The skins are used during the fermentation for maceration. Whites grapes are simply pressed off and the compounds do not have time to be transferred into the grape juice. As for the smoke residue that sits on the grape skin–you can’t just rinse it off.
Research being done in Australia has not yet determined if one varietal is more susceptible than others. Cabernet, with its thick skin, seems to be the most sensitive. Researchers from UC Davis and Washington State University are currently investigating ways to evaluate risk of smoke taint. Winemakers can lower the exposure of the juice to the skin by using natural fining agents like activated carbon or by using a reverse osmosis filtration system. However, none of these methods are perfect, and seemingly eradicated taint can sometimes resurface.
The good news for affected vineyards is that the taint does not permanently stay in the soil structure or the plant structure. Our wine team is hard at work to evaluate each lot presented to us. The only “smokiness” you will get from a glass of WineShop At Home wines will be from a beautiful, medium to high-toasted oak barrel.