Purging oxygen from keg with shaking

[trustyrusty]

Hi I am just curious, I have just kegged a beer. I am going to let it stand before I put in fridge as I add 3 tablespoons of sugar to start carbonation and let it mature more, while I am drinking others. I have shaken keg and let out gas a couple of times. I assume the gas is co2 coming out of the beer and there seems a bit of pressure - would this be ok while pressure builds or do you think I still have to add co2? Thanks

 

[klangers]

Are you shaking immediately after adding sugar? Or are you talking about after the sugar has fermented? Either way there's not a lot of point to shaking a keg that you're intending to naturally carb.

3 tablespoons in a 20 L keg may not be enough to carb up the beer fully. I don't know as I've never naturally carbed a keg.

I'd suggest that you should just leave it be, until after at least 2 weeks to give it time to naturally carb up.

 

[mtb]

There should be no need to release gas from the keg if you've added a calculated dose of sugar to carb naturally. There are plenty of calculators online to tell you exactly how much to add to achieve your desired level of carbonation. If you've simply dumped in some sugar without measuring.. don't. Take the extra step to do it properly.

 

[trustyrusty]

Thanks, I am talking about now as I filled, instead of adding co2 to purge oxygen.

Using co2 in beer to purge.

*I have carbed this way before, even putting in keg at 1014 gravity and finishing off.

 

[mtb]

Ohh gotcha. One possible issue there is that, by shaking, aren't you mixing the O2 in the headspace into your beer?

 

[trustyrusty]

Guys just wondering if there is enough pressure to seal the keg and purge with gas inside.

I have calculated sugar before 3 tablespoons is about 80 grams that I need, but not the point of this post, thanks

 

[trustyrusty]

Thanks mtb.. I have shaken and burp a few times would the o2 not have come out, co2 being heavier and replacing o2?

 

[mtb]

Smarter individuals than I on this forum and beyond believe that CO2 doesn't form the "blanket" we think it does, rather, it simply mixes with the O2 and if present at all in the headspace of a keg it'll oxidise beer. Also, when you shake it, any "layering" of gases would come unstuck and any O2 sitting above the CO2 would be mixed right back in.

Nothing to be quoted on, but this is a general opinion I've seen around the traps and it seems to hold mostly true.

 

[trustyrusty]

Ok I won't be lazy and hook up the bottle

 

[trustyrusty]

Gassed the keg, btw there was actually about 8 psi from shake...

 

[Black Devil Dog]

I wouldn't be shaking it. You're likely to oxidise your beer.

A better idea would be to use your co2 to purge the air out of the head space and also to give the keg a good seal so as to prevent any gas leaking out.

 

[wynnum1]

If you put dry sugar in the keg that releases the co2 try putting dextrose into a fermenter it just keeps foaming up will not do that again

 

[goatchop41]

Smarter individuals than I on this forum and beyond believe that CO2 doesn't form the "blanket" we think it does, rather, it simply mixes with the O2 and if present at all in the headspace of a keg it'll oxidise beer. Also, when you shake it, any "layering" of gases would come unstuck and any O2 sitting above the CO2 would be mixed right back in.

Nothing to be quoted on, but this is a general opinion I've seen around the traps and it seems to hold mostly true.

This is true mtb. It's physics. You can form a very temporary CO2 'layer', but with time all gases in the headspace will simply mix throughout the space that they have available.
Here is a very good explanation.

 

[Grott]

But by purging the head space are you say the O2 mixes with the CO2 being put in rather than the O2 being forced out?

 

[mtb]

But by purging the head space are you say the O2 mixes with the CO2 being put in rather than the O2 being forced out?

No, this was before extra CO2 was being added to purge the headspace. OP was suggesting that he pull the PRV then shake the beer to force more CO2 out of the beer and into the headspace, allowing him to purge again. The problem there is that O2 would be in the headspace at the time of the shaking.

 

[Quokka42]

No, this was before extra CO2 was being added to purge the headspace. OP was suggesting that he pull the PRV then shake the beer to force more CO2 out of the beer and into the headspace, allowing him to purge again. The problem there is that O2 would be in the headspace at the time of the shaking.

You are correct again, and thank you for posting it. I'm on my final warning for suggesting the most important thing in home brewing is producing a beer you enjoy drinking. In fact I will probably be banned just for saying that and this post deleted.

They can't stop me reading it, so keep up the good work.

 

[Lionman]

You should always purge the headspace of keg, even if carbing with sugar.

put sugar in bottom of keg
rack beer into keg
put lid on
pressurise keg
vent keg a few times
disconnect gas line
leave keg to ferment out

After another week or so at room temp it should be good to stick in the fridge. By pre pressurising the keg, the CO2 produced by fermentation will go directly into solution rather than pressuring the headspace.

You shouldnt need to shake it at all.

If you don't purge the headspace then you will have more O2 in the beer and it wont last as long/taste as good.

 

[motman]

Won't the yeast chew through the o2 left in there anyway?

 

[mtb]

Won't the yeast chew through the o2 left in there anyway?

I doubt it. Yeast consumes oxygen during fermentation, yes, but mostly during primary fermentation.. there's probably a more science-y explanation about

 

[captain crumpet]

Just thinking about the co2 blanket with logic. If c02 infact was heavier and sat like a blanket what does that mean for us oxygen breathers? Its been a while since i was at school but our air comprises mostly of oxygen nitregon and co2.