Still suffering from last year’s wrathful weather, West Coast winegrape-growing regions are casting fearful eyes toward a possible repeat of the wildfire-then-flooding scenario.

John Aguirre, president of the California Association of Winegrape Growers, speaking to the California Farm Bureau Federation, confirmed that winegrapes and wildfires were not a good mix.

“Winegrapes are at risk if exposed to smoke for a significant period of time – to the point of making those grapes potentially unusable for wineries” because of “smoke taint” where burning wood releases an oil (guaiacol) that permeates grape skins and gives wine the taste of a wet ashtray, he told the organization.

A Los Angeles Times report on the subject put it this way – “Smoke taint rears its head when grapes, kissed by environmental smoke as they’re growing, eventually yield a wine with unexpected smoldering flavors…, ‘like drinking from a well-used ashtray,’” using the words of University of California-Davis enology specialist Anita Oberholster. The story noted: “It’s a vintner’s worst horror movie nightmare – the smoke is coming from inside the grapes.”

Says Oberholster: “Compounds that are responsible for smoke taint are naturally present in grapes at low levels, they add complexity to the wine. Research into the subject is a slow process and to date, I can say there is very little you can do to prevent extracting smoke taint compound from grapes.  We are currently in the process of evaluating different amelioration techniques from finished wines and there is some promise there, but research is still on-going, and I have no data yet.”

It’s hard to detect taint initially as grapes that escape immolation from the flames themselves often mature normally with no odor from the vine at harvest, a pungency only discovered at fermentation when smoke molecules interact with enzymes and yeast.

‘The right kind of smoke’

And according to Washington State University (WSU) Wine Science Center professor Tom Collins, currently conducting research into how the timing of wildfire smoke affects grape berries, “the right kind of smoke with the right intensity (produces) some risk of smoke taint, both pre- and post-veraison.”

Collins has developed a portable smoke hoop house for smoke trials at WSU’s vineyard with the ability to control the amount of smoke to grapes, a project studying the timing of exposure and role of fuel source in taint. He is also working to develop analytical methods to accurately predict the potential for smoke taint in wines along with winemaking practices aimed at mitigating that taint.

Bloomberg News ran a recent story under the sub-head “Embracing Smoky Notes” that quoted Oregon Wine Board President Tom Danowski as saying: “Smoke compounds aren’t always negative. There’s some element of smoke-related compounds in some of the best wines that age in barrels that are slightly toasted.”

And as Jeff Bitter, newly-installed President of Fresno’s Allied Grape Growers notes: “We need to distinguish between smoke exposure and smoke taint and nobody really knows how to quantify when exposure becomes taint. As an industry, we need to fast-track that research.”

Toward a greater understanding of the problem, a multi-partner research project was launched in the fall of 2018 to focus on the effect of wildfire smoke on grapes and wines. “It’s our intent to support innovative new findings that will expand the understanding of impacts and to set a precedent for the importance of future research across Northern California,” says Debra Sommerfield, President of the Lake County Winegrape Commission. “We hope our collaborative project will develop a more precise understanding of wildfire impact on winegrapes.”

“The Lake County study will help obtain baseline data,” says Oberholster. “Because these compounds are naturally present in wine, we need to know what the ‘normal levels’ would be in grapes and wine for specific varieties. That data will give us a better idea about risk when growers and winemakers analyze grapes that have been exposed to some level of smoke.”

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Source: Lee Allen, Western Farm Press