Friday, August 23, 2013

Oxidation, Friend or Foe?

The process of oxidation contributes to some of the world’s great wines, yet most of the time it is considered a fault.  Here’s a primer on what it is, how to recognize it, and when you might want some!

As the name suggests, oxidation happens when wine is exposed to oxygen.  Oxidation can happen slowly or quickly, depending on how much oxygen is in contact with the wine.  Oxidation causes wine to turn a brownish color and creates nutty, sometimes caramelized aromas.

If you open a relatively young wine (less than 5 years old), and it looks like this picture, it is oxidized.  See how brown it is?  When I opened this 2-year-old wine, I noticed that the cork was protruding slightly from the bottle.  This is generally not a good sign, but you never know until you open the bottle.  Sure enough, the wine was oxidized due to a bad cork seal, which allowed far too much oxygen to circulate into the bottle.  If this happens to you, I have good news and bad news.  First the bad news:  this wine is officially “faulted” and will not taste the way it should.  The good news:  if you like the way it tastes, you can still drink it.  It won’t hurt you or make you sick.  (I drank some from my oxidized bottle, just to notice the changes in flavor.  It wasn’t terrible.)

Many wines are partially oxidized on purpose.  This happens in a slow, gradual, controlled way when wines are aged in oak at a winery.  It also happens very slowly as wines are aged in the bottle, since the cork allows a small amount of air into the bottle.  (More about aging wine here.)  If the picture above had been a 10+ year old wine, there would have been no problem.  Part of the allure of older wines is that they take on different characteristics through slow, gradual, oxidation.  If you use a wine aerator, you’re increasing the wine’s exposure to oxygen just before drinking it, to mimic a bit of that aging effect.  (More on aeration here.)  But wines that have oxidized at a young age due to improper bottling or storage are not better for it.  Storing bottles on their sides helps to keep the cork moist, maintain a good seal, and prevent unwanted oxidation.  

A few wines are heavily oxidized on purpose.  The most famous of these are Oloroso Sherry, Tawny Port, and Madeira.  These are sweet, fortified wines that are aged in oak until they take on a brownish hue and nutty, caramel-like aromas.  They are delicious, and you should try one!

Have you ever opened a young wine that had turned brown from oxidation?  Did you taste it anyway?  Did you like it?

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