When does kegged beer become vulnerable to oxygen?

[Bristol D]

So it seems to be fine to open your fermenter and check gravity readings, grab a sample, whatever, right up until fermentation has finished.

Then, let's say, you transfer to a pressure barrel.

The internet is of the opinion that the moment a bit of air gets into that barrel, your beer is dead, within a couple of days.

So, at what point does the beer become so vulnerable to contact with air? Clearly nothing has changed when you first transfer it. After a couple of weeks, once it's fully primed, is it susceptible to staling then? If so, what has changed during conditioning to make the presence of air so bad, when it didn't do any harm before?

I've got my first pressure barrel batch priming at the moment. I haven't got any way of adding C02 yet, but I've caved into temptation and tried a few pints before it's fully primed. There's been a bit of glugging, so a bit of air has got in.

Is the whole beer-going-stale thing a myth? Or should I panic and drink this whole barrel full of beer as fast as I can?

Cheers for any thoughts

 

[mongoose33]

Your beer is vulnerable as soon as yeast is no longer actively converting oxygen.

How much is too much oxygen depends on style, a person's ability to perceive oxidation, and time.

Things take time. Hoppiness is one variable that is affected by oxidation, which is why people sometimes advise to drink an IPA when fresh.

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If I read your situation correctly, you're using priming sugar in the keg? If that's so, a little air getting in isn't going to be the end of the world. That's one of the things people note about bottle conditioning--whatever oxygen is getting in there is going to be scrubbed by the yeast, minus whatever oxidation occurs.

But it doesn't happen immediately. In your case, you have a terrific opportunity to test what the effect might be. Let the priming sugar run its course, then drink it as normal. Take a few notes as you go along.

I wouldn't expect huge effects, so see what happens.

 

[Bobby_M]

So it seems to be fine to open your fermenter and check gravity readings, grab a sample, whatever, right up until fermentation has finished.

Not really even that. Can you get away with it? Sometimes, if you can't pick up slight oxidation. Once the yeast is in there, I don't open the fermenter. When I have to dry hop, I purge the fermenter out with CO2 after. When I transfer the beer to the keg, it's completely isolated from air. CO2 purge in both containers. IMHO, it's one of the many differences between good beer and great beer.

 

[Vale71]

So, at what point does the beer become so vulnerable to contact with air?

The moment your wort turns into beer, i.e. as soon as yeast starts working its magic. You don't even have to wait for fermentation to be complete.

 

[Bristol D]

Thanks for all this. I'll just have to see whether I'm one of the unlucky ones who can taste oxidation!

 

[JohnSand]

Opinions vary widely on how quickly beer oxidizes under various conditions. There is a vigorous debate over LODO brewing, which tries to reduce oxygen exposure at every step. That is an advanced method. If you are a newer brewer, there are many things to learn and improve. For kegging, I highly recommend CO2 for serving pressure.