Letting wine "breathe" (aerate)

[OregonYeti]

I have noticed that some wines, at least, taste better after they "breathe". I was wondering what the science is behind this. I did a little research but didn't find a satisfactory answer; in fact I found conflicting answers.

Can anybody explain what happens with aeration? I've done some research on liquor distilling in the past and the "lightest" (first) little bit of condensate is usually rejected since it has some adverse flavor. I was wondering if maybe aerating wine is for the same reason, since those lightest elements would vaporize first? Or does it have to do with oxygen dissolving in it? Just a couple of guesses.

[Luc_H]

OregonYeti,
I am convinced this will be a very controversial and possibly heated thread. Let me through my hat in the arena first.

In chemistry there are 2 VERY common chemical reactions that are very difficult to ignore.
Oxidation which is chemically attaching an oxygen atom to a chemical molecule. Rust is the result of oxidation of iron. Fe reacts with air and water to become FeOx (many Oxygen can attach to 1 Fe).
Reduction, the opposite, meaning tearing an oxygen atom from a chemical molecule. Iron ore is always rust (FeO2). Smelting strips away the oxygen ending up with reduced iron. In the body reducing agents are often called antioxidants (opposite of oxidant).

When yeast ferments wine, dissolved oxygen and chemical oxygen is consumed and taken out by the fizz which is CO2. Once the fermentation has ended, residual chemicals interact with any free dissolve oxygen. Once all the dissolved oxygen has been consumed the wine chemicals play a oxido-reduction tug of war. Chemicals get reduced others oxidized. this process is quick in the beginning then slows down with time because certain chemicals react more slowly. Light, shock, air infiltration, temperature fluctuations can disrupt this tango. The final result is a stalemate of highly reduced and oxidized chemicals.
reduced sulphurous chemicals taste bad and others as well (like tannins and phenols).
Letting a wine breath reincorporates oxygen gas to oxidize highly reduced yet reactive chemicals like tannins, phenols and sulphurous compounds. These will taste better which adds freshness.
If air is left too long then it will oxidize slower reacting chemicals that taste bad when oxidized. Timing is crucial.

Luc H.

[OregonYeti]

I like the "oxido-reduction tug of war" phrase

[Grumio]

me too - good one

"reducti-ox?"