Tony501 said:
I am interested in maturity. Why by leaving a liquid completely enclosed, airtight and in a cool place, does it improve the flavour? Is it the cork that adds flavour or the tiny bit of air or just the fact that that is able to rest after working hard to produce alcohol?
Well if you find a simple answer to that, please let us all know.
On face value, yeast turns sugar into alcohol plus carbon dioxide, you start with a C
12 sugar, that gets broken into two C
6 sugars, each of those gets broken into two C
2 alcohols plus two C
(1)O
2s, so 12 carbons in, 12 carbons out, and the hydrogen and oxygens all balance too. However, on the way they make aldehydes and all sorts of other crap. In simplistic terms, let's say that most of the alcohol production is done in the first couple of weeks, but it can take those yeasties the next couple of weeks to finish tidying away all of the aldehydes, so that's why it's a mistake to rush fermentation, stabilise and add finings before the yeasties have finished their job. But, you can reckon that after a month you've got something which should be quite good and perfectly safe to drink.
There are other changes which will go on over a period of months with things like esters, tannins and tartrates, but my wines will usually be left in demijohns, still under airlock, topped up to within about 3cm of the bung, so at this point the airspace is minimal and there is no contact with a cork. However, if you can bring yourself to leave some of your wines alone for 6-12 months, it does make a massive difference.