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Grape researchers may have found way to detect smoke taint

Scientists are looking for a way to tell whether a crop has been ruined before it’s harvested and turned into wine
Cole Cerrato, a postdoctoral student, subjects vines to smoke at Oregon State University's Woodhall Vineyard. [Photo by Sean Nealon]

Wineries of the West are struggling against a growing problem — wildfire smoke, which has the power to spoil an entire vineyard full of grapes.

So far, there is no reliable way to detect ruin before harvest.

Dr. Elizabeth Tomasino, a food scientist and oenologist with Oregon State University’s Oregon Wine Research Institute, is the team lead for a series of smoke-exposure studies in Oregon and Washington. She and her colleagues believe they have finally discovered compounds that might reliably foretell the destruction of a harvest before it’s too late.

The only way to detect smoke-spoiled grapes has been to look for a collection of volatile phenols — guaiacol, 4-methyl guaiacol, o-cresol, p-cresol, m-cresol among others, Tomasino explained.

“We know when a smoke events happens, these phenols go up, but when you do sensory work with them, they don’t taste like smoke. So while they might be markers of smoke exposure, they’re not the things that are causing that ashy flavor,” she said.

Recent research from her team and others in the field have detected a new set of markers, smoke thiols, also known as thiophenols.

“If you add these new compounds, it tastes exactly like smoke taint, so essentially we’ve found new markers,” she said.

To confirm these new compounds are in fact the right markers of ruined crops, researchers subjected grapes to smoke, equivalent to a wildfire burning beside a vineyard, Tomasino explained. To do this, they covered some vines in a kind of plastic bubble and, through a hose hooked up to a tiny charcoal grill, fed smoke into the chamber.

Researchers have installed sensors in participating vineyards, searching for a reliable way to detect the presence of these markers before harvest. Detecting these smoke thiols early could save winemakers from investing in harvesting and processing grapes only to detect smoke taint six months into the fermentation process, she said.

Research is ongoing at vineyards throughout Oregon, in areas of the Applegate, Umpqua and Willamette valleys, as well as the Columbia Gorge. Eight vineyards in the Rogue Valley are participating.

The scientist wouldn’t reveal the names of the vineyards, saying it’s confidential.

Alec Levin, viticulturist and associate professor at Southern Oregon Research and Extension Center, said in an email that harvest has begun, and there’s plenty of work to do here.

“Southern Oregon is a very important research area for us,” he said.

The industry stands poised to absorb bitter losses without the tools this research could provide. The wildfires of 2020 cost the wine industry $3.7 billion, according to Oregon State University research. The university’s research is being funded by a $7.65 million grant from the U.S. Department of Agriculture.

Tomasino said the discovery of the compounds was only the beginning. Their volatility is a blessing and a curse. They’re hard to detect, and they could be destroyed in the winemaking process.

The thiols often are found in low concentrations, so researchers are hopeful their work with sensors will lead to the creation of some kind of detection tool. Tomasino envisioned an app or a device that could ping a winemaker with a warning.

The smoke chamber bubble is still a little wonky, Tomasino said. Another researcher is tinkering with it, but it’s been enough to start a secondary part of the research, addressing the question how much smoke is too much?

Not all grapes exposed to smoke are spoiled by it, she said.

“Everyone’s like, ‘Oh, there’s smoke; it’s going to be bad.’ No, it depends on the extent of the smoke exposure,” she said.

Sometimes a wine will fold the smoke flavor into its body and work with it, like a jalapeno pepper becoming a chipotle.

“There’s quite a range until you get to that taint level, where it gets to that old ashtray, campfire-smoke-in-your-mouth taste,” she said.

Through their experiments, she said, researchers are looking for that tipping point. Observational evidence seems to point to a cumulative effect.

A mild fire season may still destroy crops, she said. If smoke rolls in and lingers too many times, it seems to have the same effect, sometimes, as one major smoke event.

Some types of wine endure smoke better than others, she said. Whites, in general, survive better because the skins are removed in the winemaking process.

Pinot noir, pinot gris and petit verdot do poorly while cabernet sauvignon, merlot and syrah seem to fare better, she said. The reason for this is still mysterious, but researchers think it may have to do with the wines’ structure and phenolic content.

Tomasino and her colleges have been a nominated for the Innovator of the Year award in the annual Wine Star Awards organized by Wine Enthusiast magazine.

Reach Mail Tribune reporter Morgan Rothborne at mrothborne@rosebudmedia.com or 541-776-4487. Follow her on Twitter @MRothborne.