The Flavor of wine is like delicate poetry
-Louis Pasteur

Two thousand eight was a challenging year for vintners in the Napa Valley. The late frost decreased the yield of many vineyards in the valley, followed by wild-fires-a-plenty throughout Northern California.  Here at Hess Collection Winery (USA) grapes are purchased from a number of grape producers located in a number of areas which were the hardest hit by the smoke from the wild fires.

The smoke from these fires is composed of many volatile aromas that can be integrated into the grapes.  The grapes are most adversely affected just after veraison; therefore, when anthocyanins are being produced in the grape skins the vines integrate these volatile chemicals into them.  The largest constituents of the smoke are two related molecules, Guaiacol and 4-methylguaiacol.  These two molecules are less soluble in water than in alcohol so the grapes and juice generally smell smokier than wine. They are easier to smell in juice than finished wine.

When wines are affected by smoke, we can use a process called reverse osmosis to remove the smell.  Reverse osmosis works as a three part process.  First, the wine passes through a reverse osmosis machine.  This is essentially a wine pump with a selective membrane attached to it.  The membrane is semi-permeable, only allowing molecules of a certain size to pass through.  Water, alcohol, the smoke taint molecules and a number of other small compounds may pass through the membrane.  This fraction of the wine is called the permeate.  Anthocyanins, tannins, large aroma compounds and other large molecules do not pass through the membrane.  This fraction of the wine is called the retentate. 

 The permeate, in the second phase of this process, passes through a series of activated charcoal filters.  This is not a very selective procedure. The activated charcoal binds many of the smoke taint compounds, but, it also binds other flavor profile compounds. This procedure would not be used injudiciously.  We would only use this procedure if the process will improve the resulting wine.

The final phase of the process, is the return of the permeate and retentate to the tank it came from.  This process occurs in a continuous loop.  The Guaiacol, 4-methyguaiacol and the myriad of other smoke taint compounds are removed until the impact on the palate is minimized.  When the final treated wine is put into the master blend, with other wine that has not been smoke tainted, the smoke is difficult to notice at all.  It becomes an interesting flavor component as opposed to overwhelming the palate.