PORTLAND — Smoke isn’t an equal opportunity offender for wine grapes, with flavor impacts depending on the varietal as well as the fire’s proximity, experts say.

Reverse osmosis filtration and other processes can mitigate the smoke’s effects, though they come with their own costs for the finished wine, according to speakers at the Oregon Wine Symposium in Portland on March 8.

“We took a wine that would not be usable and made it usable,” said winemaker Brian Gruber. “The biggest drawback is we made a wine that would not stand on its own.”

Gruber worked at a custom crush wine facility in 2020, when more than 1 million acres of Oregon forestland were consumed by fire and smoke blanketed the state’s Willamette Valley.

The consequences of smoke exposure were immediately noticeable in the grapes, Gruber said. “This tasted like cherry barbecue sauce in the bin, before we even started fermenting.”

Pinot noir, Cabernet franc and Grenache appear to suffer from the most noticeable effects of smoke taint, though it can affect any varietal, he said.

Smoke that recently originated from a nearby fire is more damaging than older smoke from a more distant blaze, he said.

It’s also more likely to harm flavors in grapes that are nearing harvest than those that are immature, he said.

Through the reverse osmosis process, Gruber separated the water and alcohol from the other elements that impart flavor, texture and aroma to wine.

That water and alcohol were then run through a carbon filter to reduce the effects of smoke taint, he said.

“It’s a gentle way of splitting your wine and just treating the part that’s a problem,” he said. “You’re breaking it apart, so you’re trying not to touch the good stuff.”

During the process, some of the tannins and other positive elements are lost, resulting in a less robust wine that tasted “thinner,” Gruber said.

However, the when blended at a rate of 5% with wine that wasn’t harmed by smoke, the treated wine was successfully salvaged, he said.

“Wildfires aren’t going away, so it’s just how we’re going to deal with them in the future,” said Brandon Moss, a winemaker in the Walla Walla region of Washington.

Moss said he encountered grapes in 2020 that didn’t come into contact with smoke as dense as that in Oregon.

The impacts from smoke taint didn’t become apparent until near the end of fermentation, he said. “It was pretty promising at first and went downhill quickly from there.”

That wine was also filtered with reverse osmosis, resulting in an “innocuous” red wine that had lost some of its character, Moss said.

“Some people are more sensitive than others and I err on the side of making the wine clean,” though as a “blender,” the treated wine “100% works,” he said.

While all smoke contains compounds that are harmful to wine, the fumes from “cars and buildings” are particularly “gross,” said Elizabeth Tomasino, associate professor and sensory analyst who studies wine at Oregon State University.

Isolating which types of smoke are especially damaging is under study at OSU, she said. “We’re looking to track which compounds are really the problem.”

The university is also examining films that can be sprayed on grapes to resist smoke taint, which imparts the taste of an ash tray, she said.

A method of testing for smoke taint that doesn’t require fermentation would benefit the wine industry, Tomasino said. To that end, OSU is searching for “markers” that would indicate grapes are impacted.

The university is renovating a laboratory to specialize in smoke analysis and expects to learn a lot more about smoke taint in the next two to three years, Tomasino said.

“All this goes into risk management,” she said.