Copper Pennies from Heaven

I’m a stress eater.  To be fair, so are Kim Kardashian and supposedly Reese Witherspoon.  Under the guise of anxiety and extreme neurosis, I have been known to down an entire pint of ice cream in a single sitting.  The unflattering consequences extend below my waistline since I’m also lactose intolerant. Yeast, like people, also release gas when stressed.  (Yes, I just joked about my own flatulence.  The thud that followed was me displacing Charlie Sheen from rock bottom).  Most often, the noxious gas in question is H2S, hydrogen sulfide.  Obviously, this sulfur-y, rotten egg/cooked cabbage/onion-y smell detracts from the perfumed, fruity aromatics we desire.  Wines with low levels of sulfur are referred to as “reduced.”  In this case, the “rotten egg” is less obvious, but the nose seems sharp, less bright or lacking fruit.  It’s a sign H2S might be afoot.

H2S is a normal byproduct of alcoholic fermentation.  Elemental sulfur (the “S” of H2S) is an essential building block of protein synthesis.  For yeast to successfully multiply during the so called “exponential” phase, they’ll require lots of protein precursors.  Proteins are part of their internal machinery, and each organism has identical innards.  The H2S generated during…er…yeast sex, is usually blown off with carbon dioxide and volatilized into thin air.  However if H2S production exceeds what the yeast require to multiply, the extra sulfur gets dissolved in the wine.  And you can smell it.

Please let me reiterate that H2S production is a normal by-product of fermentation.  Everyone who makes wine has it.  (Just like everyone poops).  Only the amount varies.  And like most great mysteries in life, we don’t know exactly why.  The volume of H2S depends on yeast strain, physiologic status, and metabolic deficiencies.  In other words, during fermentation if yeasts lack certain essential nutrients, they’ll get stressed and burp out H2S.  Vagaries of yeast protein degradation, fermentation rate (either too fast or too slow), fermentation temperature (either too hot or too cold), and metal ion concentrations have also been implicated.  Both residual sulfur from vineyard pesticides and too little nitrogen in vineyard soil also shift the sulfur balance from imperceptible blow off to detectable stench.  For yeast it’s more complicated than adding LactAid to your morning cereal.

At least in wine, detectable H2S is an easy fix.  It’s mopped up by copper cocktail chemistry.  When you add copper sulfate, the Cu and the S hook up and precipitate into a solid.  You just rack your sweet smelling wine off of the gunk at the bottom of the barrel and move on.  But there are no gimmes in life.  You can’t shower your wine with pennies from heaven (pennies, copper, get it?) since there’s a legal threshold for copper additions.  First you’ve got to do a copper trial to determine the absolute lowest amount of copper that will brighten up the bouquet.  Plus excess copper has been known to cause a haze (called a “casse”) or mop up proteins (called “flocculate”).  In the video below, you’ll see me working through a copper trial for one of our 2010 pinots.  Can you guess which of our three pinot lots was the stressed out, neurotic one? 

If you can't see the video below, please click here.