Luk wrote:
> Michael Pronay ha scritto:
> > Luk > wrote:
> >
> >
> >>>>The refrigerator, as Mark will confirm, will increase the
> >>>>oxidation risk.
> >
> >
> >>>Sorry Mike, but this is contrary to common wisdom, my
> >>>experience, and chemistry. Cool temperatures slows down
> >>>oxidation.
> >
> >
> >>It results that at 5 °C the oxigen content into water (or wine)
> >>is twice than at 20°C
> >
> >
> > So what? Oxidation is the reaction of wine with oxigen, not
> > the content in itself. Reaction *is* much slower at cooler
> > temperatures.
> >
> > M.
>
> IMHO it is disputable if oxidation occurs at the wine surface because of
> enviromental oxygen or inside the wine when it absorbs oxigen. You are
> right, but it is also true that cooling wine it absorbs oxigen.
>
> Luk

Pardon me Luk, but this does not hold water. Solubility of gases in a
liquid does decrease with temperature (all other things being
constant), but the rate of oxidation of an organic molecule increases
with temperature (all other things being constant). One does not offset
the other - the oxidation rate increases in spite of higher solubility.

And what we are discussing is oxidation of, not dissolution of oxygen
in, the wine. Cooling wine (or any organic chemical) will make it less
likely to oxidise - whatever be the solubility of oxygen in it.

Cooling will also make the mixture less volatile and certain "light"
hydrocarbons in the mixture will not evaporate so easily. Depending on
the wine in question, this may be a good or a bad thing of course, but
is usually a good thing.

Also, the difference of solubility at 20 % degree Centigrade is
probably 3 mg for half a bottle of wine. This small quantity is not
going to oxidise the wine so very appreciably. I do not have a model
which estimate oxidation rates of any organic chemical at various
temperatures, but the impact oxidation has on the wine (reflected by
change in odour, taste and sedimentation) is more in the deci- or whole
grams order of magnitude.

Difficulty in oxidising hydrocarbons at low temperature is why one
needs all manners of efforts to ignite car engines on cold morning.

Cheers