Ethanol oxidation

Hi folks,

I was wondering if ethanol could be oxidised if it gets in contact with dissolved O2 into the brew ?

In other words, I was wondering if the oxidation of ethanol
(which leads to acetaldehyde being created and further acetic acid creation) could happen at the surface in contact with the air; or into the brew in contact with dissolved O2.

If somebody could give me a scientific evidence that Ethanol can oxidise in presence of dissolved O2 into water, I'd be grateful

Thanks!


Cheers

Scientic evidence? probably not, but if you tasted one, that would be sufficent to be 'proof'.

Of hand, I'm going to say 'yes it will oxidize' but the 'how fast' comes into play. First it will depend on the O2 levels of the cider and second the transfer rate from air into liquid (in the case of contact). Lastly are the yeast active or not.

If there are still live yeast, then I'd expect oxidation/consumption of the ethanol until all that was left was water and co2.
Ethonal has a 'flash point' of 13-14 C (meaning with a spark at 13-14C you coul dignite it), but this also means the chemical could become unstable in the presence of O2 at this time. Doesn't mean it will, just that it could. This in turn means that it could convert from Ethonal to something else.

Again this all takes time, which is why we generally cap our beer or cider or wine, and keep it that way, and even pasturized wine flavor changes (or so I've noticed) when the bottle is opened and fridged and drunk over a few weeks.

Thanks for answering my post.

Apparently, the only way ethanol could oxidise to Acetaldehyde is through alcohol dehydrogenase, which is handled by enzymes;
in our liver and in yeast for instance.

I cannot think of another chemical reaction happening in a bottle of wine which could induce ethanol oxidation to acetaldehyde.

So, the explanation for ethanol oxidation (in wine oxidation):
some yeast is still alive and has metabolized ethanol into acetaldehyde.

Or in presence of some residual sugar, some yeast has metabolized sugar into ethanol; in presence of O2 around, that might have gone wrong (O2 binding with a degraded ethanol) and ethanol turned into acetaldehyde or another nasty thing.

That kind of mess could probably happen in a fermentation too;
in bad winemaking practise: like exposure to oxygen during fermentation (when it's not done at purpose).


In a nutshell, that's got to be at enzyme level.
Therefore, not a "natural" chemical reaction.


Does that make sense ?


Cheers.

That makes sense to me. I understood the inital post as a 'could' rather than a 'how'. I was considering activation energies as I was writing.

Frankly even after I've racked and stablized, I'd expect yeast, or yeast emzymes to still be in my cider/wine failing a filtering. While some commerical (but not nesc all) are filtered, most homevint isn't, so I'd expect there to be more yeast in home stuff than in comercial. But I'd not rule it out of either. One of the early experiements (about 1900) was taking trub, destroying living objects, and then presenting it to a sugar solution, which feremnted. This lead them to emzynes (literally 'out of yeast' in greek I think). So while the trub had no viable yeast, hit still had working emzymes. I suppose heat could denature/destroy them, but that might also alter the wine.

I would presume that if there was an open o2 source, the wine over time will obtain saturation. I wouldnt' expect it to be instant, but hours? days? weeks?