Smoke Taint

So far as we can confirm four wineries have suffered losses in the Northern California wildfires. 

 

1.         Signorello Estates (See photo left)

2.        William Hill Estate Winery

3.        Paradise Ridge Winery (facility burned down)

4.        White Rock Vineyards (Vandendriessche Family 1870).

 

Our thoughts and prayers for those in Napa and Sonoma, especially for the 13 people who have died. 

 

The question at last evening’s San Diego Wine Guild board meeting was “what impact does smoke taint have on the wines”?   Done some research and this is what I have found.  Smoke taint is at greatest risk during verasion, harvesting and fermentation.  The vineyards that have not yet harvested or haven’t yet crushed the grapes are most vulnerable.  In the fires happening now, there were power outages across the entire region so unclear as to whether the smoke got into the facilities to contaminate the free juice process.

 

What is smoke taint?

Smoke taint is caused by a wide range of volatile phenols found in wildfire smoke. These compounds are absorbed by vines and accumulate in berries. They eventually end up in wine where they can cause unwanted flavors. These off-flavors, described as “smoky”, “bacon”, “campfire” and “ashtray”, are usually long lasting and linger on the palate even after the wine is swallowed or spit out. (etslabs.com).  I would add “charry” as another off flavor for smoke tainted wines.  Also smoke taint characterized by being called “bandaid” taste.

 

Guaiacol and methylguaiacol are major components of smoke formed by burning wood.  Guaiacol (10-100µg/L) and methylguaiacol (1-20µg/L) also come from oak that is found in wine barrels.  Grapes depending on the varietal, some will have trace levels of phenols that is naturally present. Some varietals have more.  Taint usually effects red wine grapes more than white grapes due to wine processing and fermentation. 

 

Depending on the amount of saliva in a person’s mouth, some will not smell smoke but will taste it.  What you are tasting is the Free Volatile Guaiacol or m-Cresol that interacts with the enzymes in your mouth. The taste typically is a lingering sensation.  Wines with higher sugar concentrations may mask the m-Cresol.  (Smoke Taint by Adrian Coulter, Senior Oenologist).

 

The Australian Wine Research Institute believes that there are key factors whether smoke taint exposed grapes become in fact tainted.  The factors are grapevine growth stage, grape variety, smoke composition and the length of smoke exposure.  In the length to exposure should be an examination of proximity and intensity of the fire to the grape vines.  Radiant heat to the vines can cause smoke taint.

 

What can be done to reduce or eliminate smoke taint?

According to Kim Stemler, head of the Monterey County Vintners and Growers Association, she says “that there are technologies for removing smoke taint as well. They include reverse osmosis as well as something called “flash détente,” a fast-extraction process where the berries are essentially exploded through heat and pressure. On the other hand, Burns warns that rinsing the grapes at harvest or basic filtration and fining are not likely to fix the problem.”  We did find a list of possible reduction methods from the Australian Wine Research Institute. 

 

- Hand harvest fruit (Minimize breaking or rupturing of skins as long as possible)

Exclude leaf material (Leaf material can contribute smoke-related characteristics when in contact with fruit and juice)

-  Maintain integrity of harvested fruit (Avoid fruit maceration and skin contact with juice as this can lead to higher concentrations of smoke-related compounds.)

-  Keep fruit cool (Fruit processed at 10°C had less extraction of smoke-related compounds than fruit processed at 25°C.)

-  Whole bunch press (Whole bunch pressing has been shown to reduce extraction of smoke-derived compounds particularly in white grapes.)

-  Separate press fractions (Ferment free run juice and press fractions separately. There is less extraction of phenolic contaminants from smoke in the first 400 L/t fractions, especially when combined with fruit cooling.)

-  Conduct trials with fining agents (Fining with carbon is very effective especially in large concentrations although it is unselective and will have a negative impact on overall aroma and flavor.

-  Minimize fermentation time on skins (Fermentation that reduces skin contact time can reduce smoke aromas and flavors.)

-  Consider addition of oak chips and tannin (Oak chips can reduce intensity of smoke characteristics  through increased wine complexity.)

-  Reverse osmosis of wine (Reverse osmosis can be effective in removing smoke taint compounds; however, the taint might return in the wine over time.)

-  Market for quick sale Smoke-related characteristics can evolve in bottle as wine ages

 

What to do with vines possibly damaged by fire? 

John Whiting from the Department of Primary Industries (Bendigo DC, Victoria) breaks it down into three categories:

-  For low intensity fire damage (incomplete leaf desiccation, no trunk injury) there appears to be little impact on growth and fruitfulness in the following season – no post-fire pruning

needed.

-  For medium intensity fire damage (complete leaf desiccation, minimal trunk damage) there appears to be minimal impact on budburst but a reduction fruitfulness in the following season. Some vines may be more damaged than expected and collapse later. Consider pruning back to a cordon with short spurs or leave unpruned.

-  For high intensity fire damage (complete leaf desiccation, trunk damage) is usually sustained

where the fire front hits the vineyard, or from the burning of dense grass within the vineyard and/or mulch applied along the vine row. If a substantial amount of the trunk is damaged, the vines are unlikely to survive – no remedial treatment can be justified. If the trunk is partially damaged then consider pruning back to a cordon with short spurs or leave un-pruned and reassess after budburst in the following season.