by Sally Colby
Winemakers work hard to tweak each vintage for flavor and special notes that make it consistent yet unique. However, smokiness is not one of the aromas or flavors winemakers seek to set their wine apart.
This year’s fires on the west coast, most recently in the wine country of California, have caused great concern for growers and winemakers. For some, the loss of established vineyards is a devastating economic loss while others will deal with the potential of smoke taint.
“The good thing is that Napa and Sonoma had a great vintage, and they’ve harvested early,” said Dr. Anna Katharine Mansfield, associate professor of enology at Cornell’s NYSAES in Geneva, NY. “A lot of areas were completely finished with harvest. All the whites should be in, but some grapes are still on the vines, like Cabernet Sauvignon, Merlot, Petit Verdot and Cabernet Franc — the reds that are typically used to make the heartier, more full-bodied wines.”
Mansfield says the wines at highest risk for smoke taint are reds because they’re typically fermented on the skin. This increases the level of phenols, the volatile compounds in smoke that potentially end up in wine and affect wine flavor and quality. These compounds are very tiny and are difficult to pull out of solution. Mansfield says that options for masking a smoky flavor are limited but winemakers can use oak chips, process batches differently or avoid skin contact. The fact that whites are already harvested and made without skin exposure means less potential for smoke taint than with reds.
But wine flavor is complex, and the potential for any added and undesirable flavors make the winemaking process more complicated. “If you taste a grape and then taste wine, you realize the wine has so much more flavor than the grape,” said Mansfield. “That’s because most of the things you can smell are bound up in the sugars in the grape. During fermentation, those compounds break apart; things that didn’t smell are released into the wine matrix and develop odor. That can happen during fermentation because there are acids that are breaking compounds apart in the heat of fermentation. Then during aging, reactions continue and slowly release these compounds. Some can come out quite early in fermentation, and some can show up later over the course of aging.”
Mansfield explains that some of the phenols (such as guaiacol) affect wine in much the same way as the presence of Brettanomyces. “Is it complexity, or is it a flaw?” she said. “It depends on the style and who’s drinking the wine. A little bit is potentially complex, which is why if you’re barrel aging and you don’t have a lot of smoke taint, you might just have a different aroma profile in that wine. But if there’s a lot, and it distracts from the other elements of the wine, it’s a problem.”
Part of the issue with smoke taint is that although scientists may have some level of understanding of how smoke affects grapes, smoke composition is inconsistent. “There are so many fuels burning,” said Mansfield. “It seems like wood smoke is one of the worst culprits, but there are also plastics and vinyl siding burning. I don’t know what kind of volatile compounds are being released and how they might be taken up (by grapes). We’ve mostly looked at forest fires, and this fire is more of an urban and rural fire with a mix of fuels.”
How soon will the winemaker know there’s a problem? If they know the vineyard from where the grapes originated experienced smoke, the answer is obvious but it might be more difficult to determine the level of smoke damage in vineyards in outlying areas. “If you just see a mild haze like on mild, smoggy day in your vineyard, visual inspection is a big deal,” said Mansfield. “If you haven’t observed a lot of smoke in your vineyard, there’s much less chance it’ll be a problem. You can see the level of smokiness and the amount of particulate in the air when there’s a problem. A vineyard that’s far enough away from the fires and the wind [where] someone can walk outside and not see smoke in the vineyard is probably okay.”
Mansfield explains that there are some marker compounds that can be used as an early warning system for smoke taint and lab tests might be useful to determine whether smoke taint will be an issue. But she noted that the Australian Wine Research Institute (AWRI), which has done significant research on smoke taint, suggests also doing mini fermentations because it’s too difficult to predict the levels of compounds.
A mini-fermentation will help determine, at least for the short term, if smoke is easily detectable. However, if chemistry is used to reduce or eliminate taint in the finished product, smoke taint could still return. Mansfield says that’s because some of the compounds bound up in the wine matrix are mute when they’re bound, and over time either turn into other compounds or are released from the chemical complexes they’re in.
Despite research into smoke taint, Mansfield says there are still many unknowns. “It’s a combination of science and art, and in this case we only know so much of the science,” she said. “For a long time, we weren’t exactly sure how smoke compounds influenced the grape. Was exposing the leaves enough that it would be taken in and metabolized? It seems like it’s actual contact with the grape skins that causes the most intake. We’re learning, but it’s a lot of steps and a lot of tiny chemistry.”
The potential upside, at least for California winemakers, is that most wines in America are not aged. “But if we assume that some of the grapes that are still hanging are the ones they’re using to make premium reds, those are the wines they’d be aging,” said Mansfield. “They’ll have to consider whether they want to make the wine in a style that would be suitable for long-term aging or if they want to rethink their stylistic goals for a particular wine so they can circumvent the issue.”
Should wineries with tasting rooms in affected areas be concerned about guests’ possible perceptions of off-odor when tasting previous vintages due to lingering smoke odor in or around affected areas? “If you’re smelling a background aroma all the time, your brain shuts that off,” said Mansfield. “That’s why if you’re smelling or tasting wine and you get nasal fatigue, they tell you to smell the inside of your elbow or your wrist because you’re adapted to your own smell.” Mansfield added that even if there’s a lingering odor present, the odor will retreat to background for anyone who’s in an area for more than a couple of hours.
“The wine industry is pulling together so quickly,” said Mansfield as she discussed the most recent fires in California’s wine country. “It’s a nice reminder of how tight the community is.”