Grapes Safe From Raging California Fires

August 19, 2015 – So far so good.  The fires raging in Lake County and on the northern border of Napa County are not threatening the grape crop.  As you can see from the nearby map, the inferno known as the Jerusalem fire is quite north of the grape growing area but the big concern that is being closely watched is smoke taint.

Until this weekend the smoke was blowing away from the Napa Valley but extreme temperatures over the last few days has resulted in smoky, hazy conditions.  With fires burning all over the state, these conditions prevailed even in areas well removed from the actual fire sites.  Fortunately, the temperature has dropped from triple digits to the high 80s to low 90s for the rest of the week.

So far there have been no reports of smoke taint, even in Lake County. The harvest has started early on the West Coast, including in Oregon and Washington where there have also been serious fires.

Red wine suffers more from smoke taint because the skins are an integral part of fermentation.  The juice for white wines is pressed off the skins reducing contact.  Smoke has large concentrations of phenol compounds that accumulate on the skins and even the pulp.  These phenols are released during fermentation imparting an ashtray flavor.

There are two ways to remove smoke taint.  Reverse osmosis has limited success by all accounts and research at Washington State University indicates that the smoke taint will return over time.  A newer method is called flash détente.  It involves boiling the skins and juice prior to fermentation to a temperature of 185 degrees then filtering through a vacuum chamber to extract the volatile compounds that cause smoke taint.  There are only a couple of machines capable of doing this available to winemakers in the Napa/Sonoma area and the inconvenience and cost would be considerable.

We can only hope and pray for cooler weather with a bit of moisture to bring relief to everyone, especially the thousands of firefighters battling the blazes.