To our employees, friends, customers and vendors impacted by the recent wild fires, we are grateful to be part of such a strong and unified community.  The losses incurred by some are unimaginable and our hats go off to the outpouring of help, love and support from all during these difficult times. As a company involved in the removal of taints from devastating events such as these, we want to make sure that the information that you are seeking is relevant and honest.  If you have any questiosn at all related to smoke taint, please do not hesitate in calling on us. 

SMOKE TAINT

This article serves to present the facts regarding smoke taint and offers potential solutions for dealing with this problem based on the most recent information available to the industry. For those wanting more information on the exact mechanisms of smoke taint adsorption, detection and handling of the fruit, there are some great links at the end of this article. 

What is Smoke Taint?

Smoke taint is made up of numerous compounds present in smoke that in simplistic terms enters the fruit/wine via the skin. The historical markers for smoke taint were generally Guaiacol and 4-Methylguaiacol. Guaiacol, however, is naturally present in some grape varieties, especially Syrah (8), and 4-methyl guaiacol is also present in wines aged in oak barrels, which complicates their use as markers for smoke taint potential. Latest research suggests other components being present including o-cresol, m-cresol, p-cresol, syringol, 4-methyl syringol, 4-ethylguaiacol and others (Hayakasa et. al. 2010, J. Agric. Food ; Parker et. al. 2012, J. Agric. Food). These compounds are now also monitored as additional indicators of smoke taint risk. It must be noted, however, that these markers do not necessarily indicate the extent of the problem but are used to identify a potential issue with the fruit. Often smoke taint isnot detectable based on a sensory evaluation of crushed fruit. 

Smoke taint compounds are bound to the glycosides within the juice via a glycosidic bond. During fermentation and aging, these gycosides break down and relaease the volatile smoke taint phenols into the wine, which are then easily identifiable via a sensory evaluation of the wine. Interestingly enough, if one was to take a measurement of the guaicaol concentration before, during and after fermentation, one would see a steady rise in these volatile phenolics. This was evident in 2009. These glycosides also continue to break down through hydrolysis at wine pH as the wine ages. This is one of the suggested reasons as to why the taint comes back when a wine is processed too soon for phenolic taint removal. 

The levels of taint are typically much higher in red wines than in white wines. The evidence points to a concentration of the smoke compounds within the skin of the fruit. Since red wine requires extended skin contact, it is reasonable that these wines would see higher levels of taint. 

Treatments for Smoke Taint in wine

It has been shown that membrane treatment in combination with adsorption is an effective means of dealing with smoke taint – see Fudge, A. L.; Ristic, R.; Wollan, D.; Wilkinson, K. L. (2011) Amelioration of smoke taint in wine by reverse osmosis and solid phase adsorption. Aust. J. Grape Wine Res. 17 (2): 41-48. 

The experience gleaned by VA Filtration USA from 2009 fires was invauable in dealing with the issue of smoke taint. At one facility, where over 500,000 gallons was treated in multiple lots of wine, approximately half of the wine treated showed no sign of smoke taint within one year of processing. The other half showed smoke taint at levels that were a lot lower than the original levels but were still detectable! There is also anecdotal evidence that indicates treatment is more effective later in a wines life. This might be due to a slow-down in glycoside breakdown as the wine ages. Theoretically at that point, the process of smoke taint removal would be more effective and limit the chance of a reoccurrence. There is no hard evidence to back this theory, but it was definitely a trend when dealing with the 2008 harvest smoke taint issues. 

Some Suggestions regarding aging

If you want to barrel age the wine, I strongly suggest using neutral oak barrels for aging purposes. Toasted oak barrels add a smoky component to the wine that exacerbates the perceived levels of smoke taint.  We do not have any evidence or knowledge of barrels being contaminated with smoke related phenolics.

For those of you with no alternative but to get the wine to bottle and on the shelf, treatment will be necessary early in the wines life and bottle aging might not be possible if this is the case. 

The Treatment Process

The most effective process of treating smoke tainted wine involves the use of VA Filtration patented nanofiltration membrane in combination with adsorption process. Typically the wine needs to be passed through this process at least 2-4 times, depending on the severity of the problem. In 2009 wine required an average of 3 passes through the system, although some wines took 6 or 7 passes to reach undetectable levels. 

References and further reading material related to smoke taint

http://wine.wsu.edu/extension/viticulture-enology-news-veen/

http://www.awri.com.au/information_services/current-topics/smoke-taint

http://onlinelibrary.wiley.com/doi/10.1111/ajgw.2011.17.issue-2/issuetoc

http://vafiltration.com/usa/services/mobile-smoke-taint-reduction/