Bottle Carbonation When Filling From Keg

Typically I will bottle a few beers from a keg if I want to cellar them, or just finish off and free up a keg. My process is to cool the clean bottles in the freezer, spray some sanitizer in, drain (sometimes some sanitizer remains in the bottle), turn keg pressure down to 1-2, bleed excess pressure, and fill the bottle from the faucet (very slowly). Usually I will have minimal foam, but enough (maybe 1/2 inch) to cap-on-foam. I use O2-absorbing crowns.

More often than I would like, my bottles will have excessive carbonation months later. The carb level in the keg is dialed in to where I want it. I have not been able to detect any off-flavors in the bottles, which would SEEM to rule out infections in the bottle.

Is there anything else that could be happening? Maybe its an infection, but the bug hasn’t had enough time to work on the sugars and create enough off-flavor for me to perceive it?

My filling process is essentially the same, and I often have the same exact thing happen. Their definitely not infected, as some of mine have been 8 or 9 months in the bottle and they taste fine. They just seem to be a bit more carbonated somehow, or at least more prone to foam more than usual when poured.

Interesting…I opened a Belgian Dark Strong that I bottled off the keg in the same manner about a year ago. It was slightly under-carbonated.

One thing I left out, I typically store them at cellar temps, then if drinking, will cool them back down. I wonder if it has to do with the storage temp being higher (and thus less gas-soluble) than the bottling temp? Still doesn’t make sense to me. There is a finite amount of gas in the bottle. Some in the liquid, some in the headspace.

I may put one of these blonde ales in the fridge tonight and open it on Friday/Saturday to see if it something stupid with the temp and the chilling.

That’s strange. I always thought that a primary problem with bottling from the keg was undercarb since you lose some carbonation in the transfer. Was there any residue in the bottle indicating that there was natural bottle carbonation happening?

The yeast will drop out of suspension whether there were sugars to ferment or not. Not sure how residue would be a sign of more C02 being produced by the yeast. Unless I’m missing something

The yeast will drop out of suspension whether there were sugars to ferment or not. Not sure how residue would be a sign of more C02 being produced by the yeast. Unless I’m missing something[/quote]

I’m transferring clear beer from the keg to the bottle, so there’s usually no sediment in the bottles, even after extended aging. The “overcarbed” ones are still crystal clear and there’s no sediment. I’m thinking its more to due with a foamier pour than actual over carbonation. The beer’s carbonation just seems a little more “lively” than it was coming from the keg.

I need to try cooling the bottles next time. Sounds like a good idea. I have one of the growler fillers, that attach to the faucet, with a piece of tubing that then runs into the bottle. Seems to work, but there are still times that I get foam.

I typically bottle some if I am going somewhere or plan to give some to a friend to try, but I’ve never tried to keep for an extended period of time. I never thought that they’d last quite as long, but I might do an experiment soon.

You could try sanitizing the faucet and the tubing to see if that makes a difference. It might not help, but it lessen the infection probability.

Matt, here’s my philosophy. Keep in mind I’m still rather new to brewing. When we bottle condition we add sugar to the beer and then bottle. There are some yeast still in suspension in the beer. I assumed that when you add the sugar and then bottle the yeast resume reproduction while there is food to consume and that increased the amount of yeast that will then drop out of suspension and create the sediment in the bottle.

If the beer is in the keg for a period of time and kept cold then the yeast would presumably stop their activity. If the beer was bottled and stored back in a not so cold environment, and if there were some degree of unfermented sugars in the bottle then might the yeast start doing their thing again and producing CO2? Causing reproduction and more yeast to drop out of solution? Just taking a shot at an answer.

It’s clear that if the bottles are more carbonated after transfer from a keg and then stored that the yeast must be consuming sugars. Otherwise there is no source for the additional carbonation.

Honestly, I think its relatively simple as to what’s going on. When you pour a pint from tap you are getting turbulence/ head (like you should) which is releasing CO2, thus making it less carbonated. When you are bottling from the tap with very little foaming, the CO2 is remaining in solution, thus causing a sensation of over carbonation.

If you open a bottle from one of these batches like a week or two after bottling from the keg, and it’s fine, but then months later, it foams, then you are seeing fermentation in the bottle. It might be an unwanted organism (brett or even a more attenuative sacc strain) or it could mean that your initial batch was not fermented all the way out and over time your primary yeast worked away at some of the sugars in the beer.

Sounds like you have some experimenting to do.

So it turns out I did have a old barleywine bottle sitting around in the fridge. It was bottled off the keg six months ago and has been in the fridge for at least a few weeks. I compared it with another bottle of the same, which had been resting in the cellar since being bottled. I put in the fridge for a day just to get it cold.

The bottle that spent a few weeks in the fridge poured with less head and I was able to pour it pretty aggressively without creating a half glass of foam. The cellared bear, however, was quite a bit foamier. I had to rather gently pour it down the sides to keep it from being too foamy to get the whole beer in the glass. However, once all the foam died down both beers tasted pretty much identical. Neither was overcarbed.

I think the issue is that the higher pressure and co2 concentration in the headspace of the cellared beer just causes it to release more co2 when opened, causing a foamier pour and the appearance of overcarbonation. Allowing it time to reabsorb co2 in the fridge seemed to mitigate this. (caveat: I’m in finance, not science so it’s a definite possibility I have no idea what I’m talking about).