2008 - Smoke Taint Vintage?

We are experiencing a high pressure ridge here on the West Coast just now that is 1) baking us under a blanket of heat, and 2) wreaking havoc with our air quality.

After a cool-to-balmy weekend it really started to heat up Monday, when I saw the mercury at 106° F in the afternoon. Yesterday it was 108° and we are expecting 110° today and tomorrow.

Also since Monday we have had blood-red sunrises and sunsets again, as we did in the middle of June. Smoke from every fire between Shasta and Santa Barbara is trapped under this statewide temperature inversion. Here in Sonoma we just have hazy skies. Closer to the fires the air is thick with smoke and the smell of burning.

The million dollar question (literally) for winemakers this vintage is, "will the smoke affect the grapes?".

The issue is current, showing up in posts on Wines & Vines ("Dark Cloud Over California Growers", July 1, 2008) and Wine Spectator ("Northern California Vineyards Impacted by Wildfires", July 9, 2008).

My interest in this question started last Wednesday when Alex MacGregor, a winemaker friend of mine in Ukiah, called to ask me if I had any experience with smoke tainted wines. I had not, but he mentioned that he had, when he was working at a winery in the Okanagan Valley in 2003.

That year a large forest fire filled the area with smoke, and actually burnt through the ground cover of the vineyard where my friend worked, affecting their Merlot. Tom DiBello, winemaker at Cedar Creek Winery in the Okanagan Valley (and a former colleague at Stag's Leap Wine Cellars back in the day) mentioned in a 2005 interview with Appellation America that the fire affected their Pinot Noir in 2003.

That very afternoon last week I recieved an email from Arthur Przebinda, author of "Wine Sooth", asking for my take on smoke taint wines. I had already started some online research when Arthur emailed me a short list of references to brushfires in Western Australia and Victoria in 2003-04 and 2006-07 which caused substantial commercial losses due to smoke taint in wines (1, 2). I have cited some of the references Arthur provided throughout this post (thanks for the heads-up, Arthur!).

I have spent the last week reviewing references and talking to various people. The problem is real. The Australian Wine Research Institute (AWRI) has a current page on smoke taint on their website, which cites a seven-page Industry Report on the problem. The Victoria Department of Primary Industries (VDPI) presents a more detailed (bandwidth-choking) 59-page report. Kennison et al. report on smoke-derived taint in wine in J Agric Food Chem. 2007 Dec 26;55(26):10897-901 (abstract here).

Shorter references:
  • Smoke actually gets into the berries – not on the surface, dissolved in the waxy cuticle as I first presumed.
  • Ash fall does not contribute to taint, and washing the clusters before harvest or before crushing will not reduce taint.
  • The mode of entry appears to be transpiration through the leaves. It is presumed that the passive uptake of smoke-related compounds is blocked by the Casparian strip in the root structures.
  • The critical period is during rapid berry expansion around veraison, when the vines are translocating most into the berries.
  • The compounds that appear in tainted tissues, berries and wines are: guaiacol, 4-methylguaiacol, 4-ethylguaiacol, 4-ethylphenol, eugenol, and furfural.
  • These compounds don't appear to be metabolized once they are in the grapes – small decreases in concentration after exposure are attributed to berry expansion.
  • Some varietals are more susceptible than others: the VDPI report cites Sangiovese (most) > Cabernet Sauvignon > Chardonnay > Shiraz > Merlot (least); relative susceptibilities of other varietals were not mentioned.
  • Taint characters survive fermentation and most fining agents are ineffective, though carbon (OUCH!) will take some 4-methylguaiacol out.
  • Reverse osmosis treatment can be used to reduce taint in finished wines, just as it has been used to reduce the presence of similar compounds produced by Brettanomyces. Melbourne-based Memstar is already promoting their service on their website (if their warnings on the risk of taint seem a bit hyperbolic – um, they are selling a service after all) and Winetech is sure to follow.
I spoke with Sue Langstaff, sensory guru at Vinquiry Napa, to ask her about evaluation of smoke-tainted wines. She admitted to limited experience, but noted that the actual effects of taint can be slight, particularly in red wines.

In support, Rémy Charest, in a March 19, 2008 post to his blog "The Wine Case", noted regarding a smoke-affected wine that "the smokiness was noticeable by comparison with the other cuvées. I'm not sure anybody would have rated it a defect otherwise, or even noticed it as an external factor."

The Australian references also note that the effects of smoke taint are most problematic in white varietals. Nevertheless, I feel it would be unwise to underestimate the potential for damage to red grapes.

As I noted in an earlier post, we are mowing and discing more than usual at our Annadel Estate vineyard to minimize the risk of fire actually getting onto the property.

So far we have not had the kind of sustained, heavy, oppressive smoke that has impacted the Santa Barbara and Mendocino regions. But I will be taking precautions. I may have the grapes tested for taint compounds before harvest, especially if we have some serious smoke between now and then. I will work with the pickers extra hard to minimize leaf material in the lugs. I probably won't be doing any ferments on stems if there is a chance of taint.

And I'm thinking about maybe spraying the vines with Surround WP™. I spoke with Katie Madigan at St. Francis Winery, where they have been using this engineered Kaolin material to protect against sunburn and reduce transpiration. They have been very happy with the wines they have made with Surround™-treated grapes. I wonder if this material might reduce the susceptibility of the vines to smoke.

8 Comments:

At 4:45 PM, Anonymous Arthur, winesooth.com said...

Hi John,

Well done (and thanks for the kudos)! I knew you'd be better poised to do this piece.

I am curious 1) if using less toasted/older barrels may help with any juice that may be affected, and 2) if some kind of grape/cluster washing regimen at the time of crush could help?

 
At 8:38 AM, Anonymous Arthur, winesooth.com said...

D'oh!

Scratch question #2.

 
At 12:14 PM, Blogger John M. Kelly said...

Thanks, Arthur. I will take a whack at the first question at least, starting and ending with caveat after caveat.

Will less toasted/older barrels help? Depends on what you mean by help. Depends on the wine. Mostly I think it depends on how much smoke effect is measurable in the grapes.

Posing a hypothetical, I am thinking of smoke taint the same way I think of Brett affected wine. Given identical levels of 4-EP and 4-EG in two Bretty wines, the defect stands out more in the lighter wine than in the more-extracted one. To me this would argue for more new wood, not less. I do agree with the thinking that light toast rather than med+ might be in order.

Were I to confirm by lab analysis before harvest that I do actually have smoke taint in my fruit, I think I would probably make the wine as normal, but without any stems (in the varietals where I might otherwise consider fermenting on them). Note that I am only talking about reds.

I saw in the VDPI report that lees fining decreases levels of 4-methylguaicol. So after pressing I would thoroughly settle and rack clean. Then I would add neutral lees to the receiving tank, Guth-mix and settle clean again before another racking. After clean racking I would bring in the RO service and take out as much smoke as possible. And after the RO treatment I would add more neutral lees back to the wine before inoculating for ML.

My philosophy is that if you have to beat up a wine, do it as early in life as possible and hope that longer gentle treatment after helps it to forget.

 
At 10:00 AM, Anonymous Arthur, winesooth.com said...

Looks like there is more talk about this topic, although it seems some people are having a hard time admitting that smoke taint happens: http://www.pressdemocrat.com/article/20080717/NEWS/807170377/1036/NEWS07&title=Will_smoke_taint_wines_

 
At 11:13 AM, Blogger John M. Kelly said...

Thanks for the link. I was wondering how the Memstar representative would be recieved at the Wine Tech group presentation - it seems to have gone down about like I thought it would.

Yes, Kreiser wants to play up the potential for smoke taint to be a problem. It will bring in more business for his company.

Growers and wineries want to play down the potential for it to be a problem, because the last thing we need from a sales standpoint is to have the vintage trashed in the media even before the wines are tasted.

The reality is that (absent a lot of research) we have no tools to prevent smoke getting into the fruit.

We do have tools to assess whether or not the grapes have picked up smoke compounds - the same analyses we use to assess Brett impact.

I expect that some wineries are already considering this, and that some growers are going to have to discount their selling prices if taint is found.

For those like me that grow our own grapes, pre-harvest testing is probably a good idea. Forewarned is forearmed. And at least we do have tools to minimize the impact in the wine.

 
At 1:12 PM, Anonymous Wm. Buck said...

I am a complete rank amatuer so I'll apologize up front. The other day I had a Burrowing Owl 2004 Cab and it was delicious. My host advised that it was due to the effects of the forest fires in 2003 up in the Okanogan of Canada. Specifically that the soils were made more acidic by the heavy smoke. In doing a quick internet search and seeing your posting, it appears as though that is not the case. If the smoke effect is beneficial, it would suggest a difference in how the smoke effect is brought into the fruit; via the leaves and grape skins - not good, via the roots - good. Regadless, you might speak with the Burrowing Owl vintners to sort out the urban legend.

Best wishes with your harvests.
Wm Buck
wm.buck@verizon.net

 
At 10:52 AM, Blogger John M. Kelly said...

Wm Buck: Hmmm... Far be it from me to criticize another winery for engaging in a little marketing hype. I don't have specific knowledge about the pH of soils in the Okanagan, but IIRC they are mostly alluvial/glacial deposits of decomposed basaltic lava, grantie and gneiss. These soils should already be pretty acidic.

It takes a lot of input to change soil pH. I can tell you from experience that some vineyard guys will add many TONS per acre of potash to the soil before planting in order to move the pH UP just a few tenths, to improve fruit quality (personally I consider the "improvement" debatable, and the resource and effort wasted, but that's antoher story).

In an earlier post I mentioned the 1996 Cavedale Fire in the hills above Sonoma Valley, which burnt up Carmenet's vineyards and damaged Martini's Monte Rosso. I don't recall anyone mentioning that the 1997 vintage wines from Monte Rosso were especially good. It took years to reestablish the Carmenet plantings; IMO the wines were no better than before the fire. Overall I believe there is no benefit to fire in or around vineyards, though I am open to enlightenment or correction.

Maybe 2004 was just a good vintage for Burrowing Owl Cab.

 
At 11:50 AM, Blogger John M. Kelly said...

OK. To the guy who wants to use my blog to market his "magic" process to clean up smoke taint? Um.... that would be no.

 

Post a Comment

<< Home