Fodder Family! There was a time, not too long ago, when California wine growers and geeks scrunched up their nose and asked "Smoke taint, is that really a thing?" Back before the 2013 Rim Fire (257,314 acres burned), the 2014 King Fire (97,717 ac), the 2015 Rough Fire (151,663 ac), the 2016 Chimney Fire (46,344 ac), the 2017 Thomas Fire (281,893 ac), the 2018 Mendocino Complex (459,123 ac), the 2019 Kincade Fire (77,758 ac), and most certainly before this horrific year of wildfires-SCU, LNU Lightning, North and August Complex Fires (over 2 million acres burned). Back before Purple Air was on everyone's phone like the weather and when home air purifiers were still on the shelf at the local big box store. Back before Napa's ETS labs had a 40 day backlog for processing smoke taint samples and the term "smoke" was associated with a pleasant tobacco like character picked up in complex red wines. But, like climate change, smoke taint has been creeping in as an issue we can no longer ignore. The Aussies knew it first, of course. And now, armed with $2 million of newly awarded research funds, West Coast USDA and University researchers have added winegrape smoke taint to their list of critical wine industry issues to address. Anita Oberholster, our UCCE Enology Specialist at UCDavis, is one of the researchers doing just that. Anita recently shared some critical information on smoke taint during the California Alliance of Winegrape Growers (CAWG) hosted webinar on Wildfire and Smoke Exposure Events.
The 2018 Mendocino Complex Fire burned 459,123 acres. 2020 wildfires have burned over 2 million acres to date.
Smoke taint in wine is defined as a lingering retro-nasal character (some describe as licking an ashtray-yeck!) and is not to be confused with “tobacco” flavors some grapes and wines may impart. White wines, which are less complex than reds, often show smoke compounds more since the offending smoke cannot "hide" in the oak or wine matrix. When you taste a wine, saliva picks up the smoke compounds with the other flavors. Interestingly, approximately 20-25% of wine drinkers can't pick up smoke in a tainted wine.
How does smoke taint a wine? When lignin, found in woody plants, is burned, volatile phenols (VPs) are released that absorb to grapevine leaves and berries. The VPs are absorbed through the berry skin and become BOUND inside. So, there are both FREE and BOUND volatile phenols in grapes affected from smoke exposure. For the wine industry, predicting smoke taint is tricky. The amounts of VPs present in smoke affected grapes are not related; there may be little to no
FREE VPs and a lot of BOUND VPs. The BOUND VPs are extracted and released during winemaking and can not be detected before wine is made. This is why it is recommended that winemakers concerned about the possibility of smoke taint make a small micro-fermentation batch of wine and test that, as well as testing berries, for volatile phenols of smoke taint. There are seven FREE VP compounds available for testing in berries and six BOUND VP precursors. While Anita's research has shown good correlation between guaiacol, one of the VPs found and tested for in berries, and full smoke VP panels, she cautions that this work is based on a small number of samples and more research is needed.
Many foothill vineyards are in close proximity to forests. The 2013 Rim Fire in Tuolumne nearly burned this vineyard at Yosemite Cellars.
What's a grower to do? While washing ash off of fruit may help with flavors directly from ash, washing will not reduce smoke taint. And, so far, there are no known vineyard treatments (sprays) that have been shown to reduce taint. Spraying anything with a spreader/sticker adjuvant, even oil, during a fire event may even increase smoke taint uptake. Possibly the best thing a wine grape grower can do is get clear on their winery contract with relation to criteria for rejection, and insure their crop against possible losses, from smoke taint.
So far, most of the 2020 wildfires are far from foothill vineyards. And, since most of the taint research is related to "fresh" smoke (in close proximity to an active fire), I'm hopeful that 2020 foothill wines will escape with little smoke taint. Years ago, after the 2013 Rim Fire that burned in Tuolumne County, I visited Yosemite Cellars owners Cheryl and Ron Harms. They boldly made a Rim Fire Red with smoke tainted fruit from that vintage. Cheryl said for a time, it was a favorite with young wine drinkers. They loved the smokey flavor, reminiscent of an expensive Scotch, she said.