Wildfire smoke may have tainted wine grapes

Wildfire smoke may have tainted wine grapes

19 September 2008

published by www.pressdemocrat.com

USA — Three months after smoke from wildfires carpeted California’s vineyards, some winemakers in the thick of harvest are reporting grapes giving off unusual odors that may be signs of smoke taint.

Smoke from wildfires makes the sun look red as it sets over a vineyard off Geysers Road in June.

While it’s too early to generalize about the scope of the potential problem, some troubling reports are filtering in from Mendocino County, which earlier this summer endured some of the fiercest wildfires and worst air quality in memory.

“Winemakers are saying that they think stuff is smelling funny to them, and they want to know what’s going on,” said Glenn McGourty, viticulture adviser for the University of California Cooperative Extension in Mendocino.

While worrisome for winemakers, consumers may not need to worry about tasting smoke instead of oak in their favorite chardonnay because winemakers have sophisticated filtration tools to remove offending flavors.

To help winemakers understand their options, McGourty hosted a workshop last week in Ukiah to share some Australian research on the subject.

About 20 people, mostly winemakers, attended, he said. Not all were reporting problems. Many were there to educate themselves as a precautionary measure given the scope of the fires, which broke out on the North Coast after a June 21 lightning storm.

Some took more than a month to extinguish.

“There were 120 fires in Mendocino County, and there were fires on all sides of our wine grape areas,” McGourty said.

Laboratories, such as Vinquiry in Windsor, are seeing a stream of grapes and juice samples coming in for tests that can identify smoke taint.

“We’re definitely getting a few samples here and there that are tainted by smoke taint,” said Michelle Bowen, director of laboratory operations at Vinquiry.

The aroma “is kind of smoked salmony and fishy, and people are picking it up in the juice right now.”

Bob Kreisher, president of Santa Rosa-based wine filtration company Memstar North America, said many winemakers he speaks with report test results confirming smoke taint.

“It’s really hard to say how widespread it is at this point,” said Kreisher, whose company removes the compounds that produce smoke-tainted wine. “I would say it’s widespread and common but not ubiquitous.”

Not everyone agrees with that assessment.

Sonoma County, where skies turned hazy, did not have a major blaze itself this summer and appears to have been spared.

Nick Frey, president of the Sonoma County WineGrape Commission, said he’s heard no concerns here.

“Certainly, a lot of grapes have been tasted by now, and lots of fermented product has probably been tasted as well, and there’s not been a peep from anyone that I’ve heard of in this county,” Frey said.

His counterpart in Lake County, Shannon Gunier, had a similar reaction.

“We’re not really seeing the same problem Mendocino is,” Gunier said. She pointed out that many of the county’s fires were on the eastern edge of the county, east of most of the grape-growing areas.

Gordon Burns, president of ETS laboratories in St. Helena, said he receives about 1,500 samples a day from wineries this time of year, and only a small fraction this year are requesting smoke taint tests.

No one in the industry can yet say just how big a problem exists, Burns said.

One reason for the uncertainty is that some research suggests taint can’t necessarily be detected from tasting grapes or unfermented juice. Studies have shown the compounds that cause smoke taint—guaiacol and 4-ethylguaiacol — bind to sugar and aren’t fully released until fermentation, Burns said.

McGourty doubts Mendocino County is unique in being affected by the phenomenon. The problems are turning up “all over the North Coast,” but McGourty thinks “nobody wants to own up.”

Some winemakers are concerned but also have reason to be cautiously optimistic.

Sarah Bennett, research enologist and co-owner of Navarro Vineyards, said she and winemaker Jim Klein have been keeping a close eye on the grapes as they move through the earlier stages of harvest.

Fires were all around their 90 acres of Anderson Valley vineyards in the early summer, as the grapes were growing rapidly.

One blaze came within about 1½ miles of a vineyard.

Firefighting helicopters took a million gallons of water from the winery’s Boonville irrigation pond, she said.

While there were some days when it was too smoky for workers to spend much time outside, the Anderson Valley’s proximity to the coast helped, she said.

“We definitely had some days where it cleared out,” she said. As a precaution, they are regularly sampling grapes in the vineyard to see if they can detect funky flavors. So far, everything seems fine. So they wait and hope and educate themselves as best they can.

Some of their preliminary research suggests the gentle way they make their wines — mostly pinot noir, gewurztraminer, riesling and chardonnay — may minimize any problems that could arise.

Some harvesting methods the winery uses may reduce the amount of taint that makes it into the wines, Bennett said.

Research suggests that when the grapes get warm or when they get mushed during harvest, as with mechanical harvesters, the skins can get broken.

Because offending smoky compounds concentrate in the skins, this can exacerbate the problem, she said.

But Navarro picks its grapes by hand at night, which may reduce problems.

Research also shows that gently pressing grapes may reduce the amount of compounds squeezed out of the skins, she said. But Navarro already uses settings more gentle than suggested maximum levels, she said.

Another way to manage problem grapes may be to segregate them from the rest of the crop, but that won’t be terribly difficult either, because the winery already tends to pick grapes in small batches and keeps them in different tanks, she said.

Whatever the scale of the problem, McGourty is confident winemakers will be able to muddle through.

“The good news is that there seems to be the technology to fix things if something is wrong,” McGourty said, referring to filtration companies that specialize in removing the compounds. “Winemakers are wizards at taking problems and turning them into drinkable products.”

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