The first materials oxidised include the phenolics to quinone these
further react to produce other products. But possibly even before
these is the oxidation of sulphur dioxide. When all the free SO2 is
oxidised further oxidation of SO2 releases acetaldehyde from the bound
SO2. This acetaldehyde reacts with phenolics producing brown coloured
resinous materials. The resins tend to precipitate and some also have
a bitter flavour.

Bob M
www.molab.co.nz

On Sep 21, 8:48 am, Dick Adams > wrote:
> Whan wine oxidizes, what is it that oxidizes?
> Is it the alcohol or the other ingredients?