Dissolved CO2 in frozen beer

[BPal75]

Hi All,

For the first time recently I had a newly filled keg freeze on me in the beer fridge. It was the one stuffed furthest in the back up against the coils and I guess there wasn't sufficient air flow so it froze. I took it out and tried to vent the CO2 through the pressure release valve to take a look inside and foam exploded out of the valve all over the place. I disconnected the gas ball lock QD and beer/foam had backed up into the CO2 line.

Since this had never happened before I'm at a loss about what is going on here. Is it the case that when a beer freezes the co2 is forced out of solution and thus the head space was drastically over pressurized, causing the forceful explosion? If I let the beer thaw (which I'm doing today) will the co2 dissolve back into the beer and equalize the pressure in the keg? Just trying to get a grasp on what's going on here so would appreciate any and all feedback.

 

[helterscelter]

If it froze while under pressure you likely are way over carbed. As liquid cools or can dissolve more co2. When liquid freezes it also expands. Effectively decreasing the available head space in the keg. I suspect your keg isn't solid but rather a bit slushy on top.

If you let the keg warm, co2 will come out of solution. Causing more excessive foaming when your release pressure.

I don't think you have any good options here. You need to vent it to decarb some or you'll only pour foam. I would let the keg warm to a little warmer than your normal serving temp, (say 45f) but no warmer. Take it out side, away from everything and open the prv. Let it foam out all over the place. Once it stops, you can try opening or re venting a couple times with a rest in between. Once vented. Chill back to normal and vent after a day or so. It shouldn't foam out (much )

Try not to freeze it again. Lol

 

[BPal75]

Thanks for the helpful info. I think you were spot on and after thawing and venting the keg is back in the fridge and back under pressure and beer tastes ok. It tastes a bit sweeter than before which is interesting, almost like some of the hop bitterness fell out because of the freeze. Drinkable though just more of a dessert beer now!

 

[helterscelter]

Thanks for the helpful info. I think you were spot on and after thawing and venting the keg is back in the fridge and back under pressure and beer tastes ok. It tastes a bit sweeter than before which is interesting, almost like some of the hop bitterness fell out because of the freeze. Drinkable though just more of a dessert beer now!

Strange. It shouldn't have sweetened from a freeze/thaw. Do you have it fully recarbed yet? If it is a little flat the amount of carbonic acid present might be low which can affect taste some.

 

[BPal75]

It's possible it's not back to full carb. It has only be back in the fridge under pressure for 2 days. Just hard to tell how much co2 was still in solution from before. I didn't end up fully venting the keg. Just let enough out so it was no longer explosive, but there was still co2 in there. I'm just glad it's still drinkable. I was worried I'd lost close to a full keg of delicious schwarzbier!