Smoke hangs over Roots Vineyard the day after Labor Day, 2020. ##Photo by Hilary Berg

Realities of Smoke

A closer look at the potential impact

By Rusty Gaffney

Devastating wildfires in both Oregon and California have played havoc on the 2020 vintage. Not all wine grapes have been affected by the smoke, but those that have await the final word on the severity of impact. Depending on exposure of each vineyard site, volatile compounds in smoke can be absorbed by the grapes resulting in unsalvageable harvest or wines of unacceptable commercial quality.

Smoke damage to Oregon’s Willamette Valley and Southern Oregon vineyards is a certainty. Over one million acres of fires burned, nearly twice the average for Oregon. The forlorn words of the Baldwin Family, proprietors of De Ponte Cellars in the Dundee Hills, sound typical of many wineries at this juncture. In an e-mail to its dedicated fans, the winery stated: “Due to the tragic wildfires that are throughout our beautiful state, we have been under a heavy blanket of smoke for over a week. The air quality in our valley has ranked as the worst in the world day after day. Our enduring efforts at De Ponte center on the quality of our wine, and that principle is what guides our decision to not produce Pinot Noir from our estate vineyards in this vintage.”

Unlike Oregon’s wineries largely spared by wildfires, 19 Napa Valley wineries have been damaged or destroyed, and more than 200 wineries received evacuation orders. North Bay wildfires are estimated to cause $500 million in wine grape harvest losses. Claude Koeberle of Soliste Cellars in Sebastopol, California, noted, “Smoke is the elephant in the room with increasing frequency. Burgundy has hail that shatters their vineyards. Wildfire smoke is our invisible hail. It destroys a crop but seductively keeps the grapes on the vines.”

Research into the effects of smoke on wine grapes remains relatively recent, commencing in 2003 by Wine Australia as a result of the widespread fires in southeastern Australia. That research is ongoing. Additional information was gathered by California vintners and ETS laboratories as a result of the 800 lightning-caused Mendocino County fires that began the first day of summer in 2008 and infused many of California’s North Coast vineyards with smoke. In 2020, Oregon is launching its own inaugural research project at Oregon State University in an effort to alleviate the effect of smoke on this year’s harvest.

Gathering information from the Wine Australia reports; ETS Laboratories published research in 2018; experience related to me by noted vintner David Lloyd in Victoria, Australia (Eldridge Estate); the observations of vintner Ted Lemon (Littorai), whose Anderson Valley and Sonoma Coast Pinot Noir vineyards were significantly affected by smoke in the 2008 vintage; and my own experience on the front lines and tasting wines from the 2008 Pinot Noir vintage in California’s North Coast, I can summarize the generally accepted facts about smoke taint. Grape skins absorb volatile phenolic compounds such as guaiacol and 4-methylguaiacol. Smoke compounds minimally enter the leaves and stems of the vines and are transported to the skin of grapes. Very little smoke compounds reach the pulp of the grape. Smoke compounds do not enter the grape through the soil or roots.

  • The volatile smoke compounds permeate the waxy cuticle of grape skins and enzymatically become bound to sugars forming glycosides (“glycosylated”). The glycosides are not readily detectable to smell or taste and analytical analysis. During fermentation, the phenolic glycoside compounds are freed from their sugar attachment leading to release of volatile phenols that lead to smoke taint in the finished wine.
  • Risk of smoke taint is greatest close to harvest with only a low-to-medium risk up to the point of veraison.
  • The fuel source of the smoke is of unknown significance. Some researchers have said it does not matter while others have stated that the various fuels can result in a different expression of smoke taint due to different absorbed smoke-related odor and flavor compounds.
  • The closer the vines are to smoke the greater the risk of smoke taint; but fires do not have to be close by to impact fruit quality. Other risk factors include the age of the smoke (fresh smoke is much worse than weeks-old smoke), length of smoke exposure, geography and weather conditions.
  • Repeat exposure to smoke during the growing season has a cumulative effect.
  • There is no carry-over effect on grapes exposed to heavy smoke between growing seasons, but the growth and yields of vines may decrease the following year.
  • The aromas and flavors of smoke taint have been described in words like as phenolic, smoked meat, burnt, charred, charcoal, campfire, barbecue, tar, burnt rubber, char, ashtray, ashy, gamy, spicy, medicinal and cigar box.
  • Pinot Noir is more susceptible to smoke taint than Chardonnay, Syrah or Cabernet Sauvignon. Pinot Noir clusters have thin, delicate skins (the source of the wine’s complex and exotic flavors), making smoke exceptionally damaging.
  • Individual tester thresholds for smoke taint vary due to DNA-determined taste sensors and the mouth microflora. Up to 20% of people cannot taste smoke flavors in wines others find unpalatable.
  • A wine containing smoke taint can be subtle initially but stand out over time. Usually, the longer the wine is in the bottle the more likely it will show smoke taint. A major concern for winemakers is that a wine may seem fine when bottled, but can develop noticeable smoke taint features as it ages.
  • Washing grapes and reducing maceration time for red wines do not reduce smoke taint. Oak can sometimes help mask some of the smokiness.
  • One winemaking option to salvage at least some of the smoke-tainted Pinot Noir is to minimize grape skin contact by opting to make rosé or white Pinot Noir where skin contact can be minimized or avoided. White grapes such as Chardonnay are less impacted by smoke exposure and during white winemaking, very gentle whole cluster pressing leaves the skins behind.

Lab tests (GC-Mass Spectrophotometry) have been available by ETS Laboratories and others over the past decade to assist winegrowers and winemakers in identifying and quantifying volatile compounds and glycosidically bound counterparts that create smoke taint. These methodologies have focused on identifying two markers for smoke taint compounds: total guaiacols and 4-methyl guaiacol. This approach, while helpful, is not entirely reliable as these markers for smoke taint can be absent in wines thought to be exposed to heavy smoke and non-smoke tainted wines can have these markers present. Besides, this type of testing gives only an approximation of the volatile compounds relative to a standard.

It has been recommended that in the short term, at the time the grapes are tested, micro-ferments should be done and a sensory evaluation performed by a group of tasters before committing to winemaking. The problem with this approach is that bound smoke compounds may appear in the wine until long after bottling. To mitigate this situation, smoke-affected lots have been blended with clean lots of wine.

Remedial work on finished wines has been approached using multiple methodologies, including reverse osmosis, carbon fining, flash detente and enzymes. Unfortunately, these treatments do not remove all the smoke taint while deleting delicate aromas and flavors that are part of great, ultra-premium wines. In other words, some of the good is removed along with the bad.

ConeTech, with headquarters based in Santa Rosa, California, long a recognized world leader in de-alcoholization technology, launched a proprietary process for smoke taint removal in late 2018. It has since processed more than 1 million gallons of smoke-impacted wines. Using a new GC-Mass Spectrophotometry method, the true concentrations of multiple volatile phenolic and glycosidically bound compounds can be determined.

Then, using this analysis, and a process that begins with low-temperature distillation, the offending free and bound compounds can be targeted for permanent removal.

ConeTech’s experience to date indicates that smoke compounds can be removed while preserving over 95% of desirable flavor and aroma compounds. To date, the offensive compounds have not returned during observation periods. ConeTech’s experience will be greatly expanded with the fire-ravaged 2020 vintage.

Winemakers are involved in the entire ConeTech process and have three options at the conclusion: bulk the wine out, blend the wine, or bottle it as a marketable wine. For high-end Pinot Noir, any remedial smoke taint removal on finished wines will probably destine them for lower-priced cuvées.

The challenge is immense for both growers and winemakers dealing with smoke exposure since each wildfire will have a different impact on individual vineyard sites. Vintner Ted Lemon points out, “Smoke taint numbers are general guidelines, and they are not particularly accurate in depicting what is going on with any individual lot or vineyard.” The total smoke damage to the 2020 crop in Oregon has yet to be determined.

Lemon’s simple advice to vintners: “Blind hope is your enemy. Realism is your friend.” This could equally apply to wine lovers who will face the reality of a reduced number of enjoyable 2020 vintage red wines. That said, there will surely be many superb Oregon red wines produced from the 2020 vintage. Be sure to support your favorite wineries during this difficult time.

Oregon Wine Press does not necessarily share the views of commentaries.


Web Design and Web Development by Buildable