Smoke taint in the Vineyard
In the last 10 or so years, vineyards have been intruding into forested land, especially in the Northwest. Drought-like conditions and heavy, dry under-canopy areas have created ideal conditions for forest fires. Wine producers have been impacted by wildfires in British Columbia in 2003 and in Northern California in 2008. With more fires in California. Washington and British Columbia late in the growing season, smoke impacted grapes have become one more environmental condition that winemakers must overcome.
What can you do?
1. If your grapes have been exposed to wildfire smoke, collect a comprehensive sampling of berries or whole clusters for chemical analysis.
We do not have a complete understanding of the mechanism by which smoke taint precursors are incorporated into the grapes. My experience with the 2003 and 2008 fires suggests that the most vulnerable time for smoke impact is the weeks just before and after veraison begins. As the berries are going through this period, they take in more of these compounds than at any other time in the growth cycle. By convention, the industry standard is to use Guaiacol (G) and 4-Methyl Guaiacol (4MG) as indictor compounds for smoke. The analytical protocol to measure these compounds in a wine matrix was well documented before smoke taint became an issue, and there is no reason that these compounds should appear in juice or wine prior to intentional exposure to oak. Eric Herve at ETS Laboratories is “the guy” to talk to concerning analysis for smoke taint in wine or juice. ETS gained enough experience during the California fires of 2008 that enables them to loosely correlate levels of smoke taint indicators detected in grapes with levels of smoke taint indicators likely to be found in wine fermented from the grapes.
Information gathered from grape analysis will enable you to:
2. Plan ahead.
If you know that you will be bringing smoke-impacted fruit into your winery, do your best to segregate these lots. Some winemakers avoid enzyme treatments on smoke impacted fruit, as glycolytic enzymes have the potential to release smoke taint precursors that might otherwise remain bound to the skins. Research has shown that higher concentrations of the indicator compounds are found in the skins of smoke impacted grapes. Free run juice tends to have little measureable G or 4MG, while the harder press fractions have ever increasing levels of the compounds, so avoid hard pressing if possible. For whites, free run portions can be kept separate from different press fraction, which may reduce volume requiring treatment. For reds, skin contact is necessary and the uptake of the compounds increases over time of skin contact as well as through pressing off of reds.
Avoid fermentation methods that prolong skin contact. There is a new hope in smoke taint remediation: Carneros Vintners winemaker Dave Dobson shared some samples of wine from smoke impacted grapes at a seminar at UC Davis in July of this year. He compared wine vinted from grapes treated using his Flash Détente unit with wine from the same lot which did not receive this treatment. The difference in sensory expression in the two wines suggested that the Flash Détente process had eliminated precursors and prevented the formation of taint. No formal studies have been performed on this promising technique yet. Want to try it out? Several installed systems are available at California custom-crush facilities, and Winesecrets operates a portable unit.
Don’t Jump the Gun
3. Smoke-Impacted wines should be evaluated carefully.
Following the fires of 2008, more than a few winemakers followed some of the steps presented above, and when not able to detect the flavors or aromas in their wine, decided that they had dodged the bullet. Sadly, this was not always so. Smoke taint flavor and aromas become difficult to discern during and after fermentation. It is advised to wait for 6-8 weeks following final fermentation (primary or ML) before assessing the wines for treatment. Once the wines are past their post-fermentation reductive phase, it is time to taste. At this time, there is not a direct correlation to the sensory perception of the smoke components and laboratory measurements of the indicator compounds, so always use a combination of chemical and sensory scrutiny to confirm or deny the need for action. We do not really know what compounds cause the taste and sensation associated with smoke impact. If we did know what we were tasting, methodology for measuring it in a wine matrix could require years to develop. So it’s down to you and your wineglass. Many attempts have been made to describe the taste; my closest association is with burnt styrene or PVC. There has shown to be a quick “palate fatigue” when tasting smoke affected wines.
Yeah, I’ve Got it. Now What?
4. Evaluate your treatment options.
Smoke in the Vineyard
At this time, Reverse Osmosis-based removal methods are the most effective means of reducing smoke taint. Our equipment restored over a million gallons of smoke impacted wines to sale-able and even award-winning condition in 2009. Other companies treated many thousands of gallons as well. There are some fining products and strategies that have been claimed as effective, though I have no personal experience with these. Remember, these are methods, not magic wands. Not all 2009 filtration services achieved the winemaker’s complete satisfaction, and there is information that suggests that both measurable indicator compounds and the perception of smoke can re-emerge as tainted wines are aged.
In 2009, winemakers learned that applying heavy oak to wines did not mask the sensory perception of smoke taint. Tannin additives and blending trials did not prove to be effective either, though these strategies may be employed after smoke taint removal to construct the flavor profile you desire. Winesecrets, offers RO-based smoke taint removal technologies as one of the many ways we help bring out the best in all wine. Cellar Dweller provides RO services in BC.
Knowledge is Power
5. Use a number of resources to gain expertise.
Talk to other winemakers who have encountered this problem. There is both good and bad info out there in the Cloud. Study up: I have enclosed a list of academic resources that was circulated by Professor Kay Bogart at UC Davis that can assist with informed decisions on what to do.
Be Patient, Do it Right
6. Ensure that your treatment method is effective.
Analytical measurements of G and 4MG serve as a starting point for predicting the duration of filtration required. However, final determination of completion of your treatment method needs to be determined with your trusty wine glass. Tasting the samples at regular intervals during the process is recommended. If you think you are done, come back and taste a day after processing (to counter-act the palate fatigue effect of the compounds). More than one winemaker quit early and had to invite the RO back to finish the job. The effect of palate fatigue is not to be underrated. My personal experience is that the perceived sensation resulting from smoke impacted wines will remain long after you have tasted. In 2009, I would drink a Starbucks Cappuccino after tasting smoke impacted wines to restore my gustatory equilibrium.
Finally, be confident. The Playbook is growing thicker as we collectively gain more experience in mastering this environmental condition.
For more information, please feel free to contact Winesecrets at 888-656-5553
Website at www.winesecrets.com
LINKS:
http://wineserver.ucdavis.edu/pdf/attachment/1173.%20Amelioration%20of%20smoke%20taint.pdf Review of an early research project by Dr Kerry Wilkinson
http://onlinelibrary.wiley.com/doi/10.1111/j.1755-0238.2011.00148.x/abstract Abstract concludes that RO initially worked to decrease the characters, but the taint slowly came back
http://ucanr.org/sites/Mendocino/files/17282.pdf Dr Kerry Wilkinson, again. This is a good slide presentation.
http://www.awri.com.au/wp-content/uploads/2013/07/jan-feb-2013-awri-report.pdf a 2013 report by the AWRI
http://onlinelibrary.wiley.com/doi/10.1111/j.1755-0238.2009.00056.x/full Drs Kennison and Wilkinson discuss the importance of the timing of the exposure of fruit to smoke. I’m hoping all can access this abstract.
http://onlinelibrary.wiley.com/doi/10.1111/j.1755-0238.2011.00137.x/full Drs Kennison and Wilkinson again……an updated review of the importance of the timing of the smoke exposure, this time in Merlot
http://onlinelibrary.wiley.com/doi/10.1111/j.1755-0238.2011.00128.x/full The abstract of an article on the importance of the precursors (glycosidic conjugates) found in grapes to the presence of the taint compounds in the resultant wine.
http://onlinelibrary.wiley.com/doi/10.1111/j.1755-0238.2011.00146.x/full Another good AJGWR abstract on the effect of winemaking on taint compounds.
http://onlinelibrary.wiley.com/doi/10.1111/j.1755-0238.2012.00200.x/full The impact of fining agents on smoke taint AJGWR