Smoke Taint a Concern in Northern California Vineyards

Initial findings show that some wine grapes may be affected by midsummer wildfires
Sep 30, 2008

As harvest switches into full gear in California, vintners are finally able to assess the impacts of the wildfires that swept across the state earlier this summer. Although the fires have long been extinguished, concerns still linger over how the smoke, which blanketed many Northern California vineyards in late June and early July, might have affected the grapes.

The wildfires reportedly did not damage any wineries or vineyards when they hit Northern California after a June 20 thunderstorm system hit the state. But they did raise concerns in Mendocino County, where thick smoke covered vineyards and many winemakers made it mandatory for their workers to wear facemasks while working outside. "[The smoke] was dense for three solid weeks," said Zach Rasmuson, winemaker at Goldeneye. The Mendocino fires lasted for about a month before they were fully contained.

Now that the smoke has cleared and the harvest has started, winemakers are trying to determine if any smoke compounds are still lingering in the grapes. Studies done by the Australian Wine Research Institute found that wine grapes can be tainted by smoke. The two most prominent compounds that contribute to smoke taint, guaiacol and 4-methylguaiacol, can absorb into a grape's skin and impart flavors into the grape juice during maceration.

The issue of smoke taint is a hot topic among winemakers this year, but many Mendocino County winemakers are not concerned. Even if the smoke compounds are present in some of the grapes it does not necessarily mean that they will impart any perceptible flavors.

The Australian Wine Research Institute determined that the intensity of the taint is strongly correlated to the amount of the compounds in the grape skins and whether or not they are above sensory threshold levels. How far away a vineyard is from the fire, the density of the smoke and how long it is in contact with the grapes determines how much of the compounds may be absorbed. "The question is whether it's going to be there in detectable amounts," said Jason Drew of Drew winery in the Mendocino Ridge AVA.

Some winemakers say they have found smokiness in their grapes. "[We are] picking up some smoke nuances in the red grape musts," said Brad Holstine, winemaker at Husch Vineyards. But Holstine pointed out that the taint is showing up in the unfermented grape juice. Rasmuson has detected slight char notes in some of the harvested grapes at Goldeneye but the notes were less apparent after fermentation. "There is going to be something distinct in the 2008 vintage," he said, however, he doesn't believe that any flavors imparted by the smoke will have a detrimental effect on the finished wine.

Laboratory tests have confirmed that the chemicals from the smoke are still present in some grapes. "We have seen samples that show smoke taint," said Jerome Lillis, a chemist at Vinquiry Laboratories in Windsor. While the samples have shown perceptible notes of taint above sensory threshold, Lillis cautioned that the methods of detection are still being validated. He also said that smoke taint has only appeared in a handful of wines so far.

That appears to be the case, as many vintners are reporting no signs of smoky grapes. Milla Handley, of Handley Cellars, who has been testing the grapes personally and sending samples to be lab tested, said that all the grapes coming through her winery have been clean. Even though the fruit doesn't appear to be tainted, the winery will still be taking precautions. "[We're] going to be a little more conservative in our winemaking techniques this year," said Handley.

Whether or not smoke taint is an issue, many winemakers are taking steps to mitigate any possible effect on their wines. Drew is decreasing the maceration time of his grapes and using a shorter cold soak and a gentle punch down to limit the amount of contact the skins will have with the juice.

Winemakers outside of Mendocino County are less concerned with the issue. Monterey County and Lake County were also hit by wildfires but the grapegrowing areas appear to have been too far away from the fires for the smoke to cause a problem. "I have talked to several growers and winemakers and no one is aware of any smoke taint," said Shannon Gunier, executive director of the Lake County Winegrape Commission.

It's too early to tell what kind of effect the smoke taint may have on the finished wine. Paul Ardzrooni, who manages vineyards in Anderson Valley, said that since the taint is site specific, no generalizations can be made about the smoke's overall effect. He also notes that while the concern exists, it has not kept winemakers from buying the grapes.

Winemakers will have to wait until spring when the wines are being bottled to see if the smoke taint is an issue. If any of the smokiness persists, some winemakers say they may look into taint-removal systems. "It may be a lot of worry over nothing or it could be a stamp of the vintage," said Holstine.

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