Wine, with time, will turn to vinegar. o L'Ortolan
As common as corkage, and almost impossible with screw cap or alternative closure, is when the wine is oxidised.
Oxidisation occurs when too much air has got into the bottle. Now, the whole point of a cork is to allow some transit between the outside of a bottle and the inside. However, this transit is designed to be over many years, it is very controlled very slow oxidation, and it is equally important that what is inside the bottle is allowed to get out, as what is outside is allowed to get in.
A lot of producers have actually gone back to cork for their top wines to allow this controlled oxidation to occur - the screw cap was actually a too good a closure, and so the atmosphere inside the bottle was quite literally 'getting stuffy', like when you don't ventilate a room properly. This is known as reduction in the trade, and can be detected on tasting. Older wines are intended to expand, contract, escape and breathe in this way.
But when you get a faulty cork, and too much air is allowed to enter your bottle, the wine is ruined. If you've ever opened a bottle and been hit with that sharp twang of acidic vinegar, then you know what to expect from a wine that has become oxidised. That smell is not healthy. As with detecting a corked wine, the best way to detect an oxidised wine is to smell to wine itself.
Always aim to pour the wine gently with no glugging, and then lift the glass up to your nose to just let the fragrance of the wine come up and reach your nostrils. Do not stir the wine in the glass, as this will get all the tones in the wine going, and this could mask any unhealthy scents.
If there is no smell at first then this is actually better - the wine is probably healthy - but if straight away you get something you weren't expecting, this suggests that you've got a fault.
The vinegary taste and smell you get with an oxidised wine is caustic, sharp, basic and deeply unpleasant.
It is particularly noticeable on softer reds and whites, as sharper wines may cover partial oxidisation. But even if you are serving something like a Sauvignon Blanc just on the top of that pleasant fruitiness there will be a kind of lingering bitter, acrid tang.
If the wine is badly oxidised, along with the bad smell it will start to change colour, and this is more noticeable in whites than in reds. In whites the wine will move towards the more yellow/orange/brown spectrum, and will take on a muddier colour, where as younger reds will darken, often moving from a bright fresh ruby colour to a deeper garnet.
There is a way to tell, just by looking at the cork, that there may be a risk of your wine being oxidised. If you can see wine veining up the side of the cork, then you can assume that the cork has failed. If it is only a small amount then it may not be enough to compromise the wine, but what it does mean is that the mischievous wine has found a way through the cork and that air will be able to find its way back in again.
It doesn't even matter how much you've spent on the bottle; I've seen this happen in really fine wine, even some of the top stuff that has a cost price well over £100 has developed this ribbon of wine up the side, and that really makes your heart sink.