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Just a simple question that I have never really got round to understanding properly…

Why does a Port [or any wine] not spoil when it is re-corked?
Surely some additional air gets into the wine that has been sealed for a good period of time and therefore it would be damaging. I know this is not the case as re-corking is quite common and can dramatically improve the potential life of a wine in the bottle but I am still in the dark as to how. What is the science behind this?

I think most people who do this (whether professionally or at home) take some steps to reduce the amount of oxygen that is admitted to the bottle when re-corking. This can range from just getting a spray can of something like Private Preserve (a mixture of inert gases) and spraying that into the neck after you have removed the old cork to doing the whole thing in a Nitrogen tank.

Also, more speculatively, I wonder just how much gas would get admitted to a bottle if you recork it whilst keeping it still and upright and how much impact that would have on the contents? Especially for Port which is, of course, a bit more robust then many table wines.

I guess it is the taking of steps to reduce oxygen that intrigues, as it does not eliminate completely the chance of oxygen entering the wine which therefore risks damaging it, albeit as your say, less likely with Port as it is more robust than unfortified wine.

Generally speaking. A needle is inserted into the old cork and a neutral gas is used to push out the old cork which also leaves a covering in the head space which prevents the introduction of oxygen. Then it’s recorked.

JacobH wrote: ↑11:57 Fri 01 Oct 2021 I think most people who do this (whether professionally or at home) take some steps to reduce the amount of oxygen that is admitted to the bottle when re-corking. This can range from just getting a spray can of something like Private Preserve (a mixture of inert gases) and spraying that into the neck after you have removed the old cork to doing the whole thing in a Nitrogen tank.

Also, more speculatively, I wonder just how much gas would get admitted to a bottle if you recork it whilst keeping it still and upright and how much impact that would have on the contents? Especially for Port which is, of course, a bit more robust then many table wines.

I’d like to work out the precise chemistry behind this, but presumably once a new cork has been driven in (even in the absence of an inert atmosphere) there would only be the amount of oxygen in the headspace between the new cork and the level of Port in the bottle to react (which may take however long) before before we return to the usual rates of gaseous exchange between the bottle of recorked Port and the atmosphere in which it’s stored.
Would this process of additional oxygenation, due to hypothetically recorking in a non-inert atmosphere, be observable by a taster in x years? Moreover, if the headspace were small and given the at least indirect antioxidant properties of ethanol, which is obviously at a higher concentration in Port, would the recorking of Port in particular reduce any perceptible difference for a given taster, relative to a non-recorked bottling? If any TPFers have any pointers to studies along these lines I’d be interested!

There have historically been problems with the recorking of table wine, which I do not think have universally been eliminated, given the small scale on which recorking is typically carried out. Air getting in is one risk (bear in mind the compression of gas into the wine under the new cork as it is pushed down, in anything other than the more sophisticated bottling lines which clamp the cork to allow it to escape, is going to have a fairly violent effect on the liquid in the bottle). The new corks going in having a fault themselves is another. There were a number of recorked burgundies put out by N Potel if I recall under the Bellenum brand which, I can attest, behaved very oddly.