Wednesday, October 20, 2010

Wine Please, Hold the Eggs

With how much we've mentioned the huge time commitment and work schedule of vintage, it would be natural to wonder exactly what there is left to do in the winery after we harvest, crush, (punch down), and press the grapes.  Obviously there is nothing quite as urgent and time consuming in the coming weeks, but there is a lot that goes into making sure our new wine is staying happy and healthy.  Primarily this means we will all be checking sugar levels, temperatures, and looking/tasting for overall health in our wines every day at least until the fermentation process is complete and the yeast frozen out. 

In the immediate future, however, we are preparing to feed our yeast so they keep working without complaint.  After the yeast has fermented about 1/3 the available sugar into alcohol in wine ferments they begin to run out of necessary nutrients other than sugar that they are unable to make for themselves.  As they enter this period they start "stressing;" a unique piece of jargon which has nothing to do with a teenager cramming for an exam the night before... unless that teenager also starts to emit hard boiled egg aromas as they get more stressed out.  When we smell the beginning of these stressed aromas (variously described as hard boiled egg, scrambled egg, or sulfurous), or the fermentation has went through a third of the total sugar, we know it is time to feed our yeast the nutrients they need.

With white wines, those where the fermentation is occurring after pressing and therefor without skin contact, we feed our yeast a mixture of diammonium phosphate and a mixture known as Fermaid-K.  The former is to provide the crucial missing ingredient of nitrogen back to the yeast, the latter provides much smaller amounts of various other pieces the yeast and juice lack.  With red wines, where the fermentation is occurring with skin contact, we only worry about adding diammonium phosphate for nitrogen; as the skins and stems often provide the other components the yeast desire.  The result of this is, to an extent, distinctly new world insofar as our aim is to produce wines that are immediately "clean" (filled with aromas and flavors of fruit) and easier to control (not smelling of eggs).

All in all it is a straightforward process that is easy to predict the start of and even easier to carry out.  The only trick is making sure to be careful when adding anything to a white fermentation.  Since the fermentation is occurring in a large, stainless steel tank without interference, there is a large amount of dissolved CO2 that is ready to burst out of solution if given the opportunity.  Many are the stories of someone adding a granular slurry of diammonium phosphate or Fermaid-K to a white fermentation too quickly, only to end up covered in wine a few moments later.  No such luck this year at Fox Run, but we'll make sure to grab a photo of it if it happens.

By: Kelby Russell, Winemaking Team

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