To what degree is carbonated beer protected from oxidation

[RichB1]

As a wine maker, I feel confident that my fermenting wine is protected from oxidation by the heavy production of CO2 and the continued release of CO2 from the wine even after fermentation is complete. I pressure ferment beer using a corny keg in primary (actually after SG gets below 1.030 so technically secondary). I connect gas line of primary to liquid line of serving keg, add a spunding valve to the serving keg set at 12 psi, and let the co2 purge the serving keg. After 10 days of conditioning I cold crash the kegged beer, at which point the pressure drops maybe from 12 psi to 8 psi upon full CO2 absorption at low temp. I would have thought that the now fully carbonated beer, similar to the fermenting wine, would be fairly well protected from oxidation (assuming I then opened the keg and exposed the beer to oxygen for whatever reason), but I could find zero articles on the subject. What do you think?

 

[doug293cz]

If you open a keg to the atmosphere, you will get enough oxygen in the headspace to oxidize the beer to some extent. There is no such thing as a CO2 "blanket" that keeps out O2. How bad the effect will be depends on beer style (hoppier beers are affected more readily than other styles), how long the keg was open, how much headspace there is in the keg when opened, the temperature of the beer during storage, and how soon the beer is consumed.

Brew on

 

[AlexKay]

To the extent the carbonated beer foams up it can expel oxygen from the headspace. If you can fill the headspace with foam, the remaining oxygen exposure can be quite low.

 

[RichB1]

Yes if I were talking about a "blanket" of CO2 by spraying CO2 over the beer, it makes sense that there would be minimal protection. I am thinking that 10-12 psi of CO2 in the beer at, say, 34 degrees F would steadily release CO2, similar to the what occurs in fermentation but to a far less degree of CO2 production, and the steady release would provide temporary protection until the amount of CO2 remaining in the beer dropped significantly (I appreciate this occurs fairly rapidly). What I am considering are cases like adding a gelatin fining solution (<1 minute of exposure) or using an autosiphon (open transfer) to rack to a serving keg (10 minutes), before then sealing the keg and purging with CO2. In an attempt to minimize oxygen exposure I have been adding gelatin solution with a plastic hypodermic needle through the gas QD and racking by closed transfer with pressure differential, but it would be easier without trying to maintain closed system.

 

[Bobby_M]

It's impossible to know how much oxygen makes it in without testing DO with a meter or more pragmatically by determining with your own senses how damaged beer may be getting after some time. I'll say that there are other ways to get small solutions of fining into kegs without any exposure. I use a syringe that has a leurlok end on it and it makes a perfect seal on 5mm ID EVA tubing. That then easily connects to a Duotight gas QD. You can push the solution into the keg even with a couple psi in the headspace.

Wine is primarily protected by the thick cap of skins floating on top during primary.

 

[whattabrau]

As a wine maker, I feel confident that my fermenting wine is protected from oxidation by the heavy production of CO2 and the continued release of CO2 from the wine even after fermentation is complete.

I don't think that premise is true. During fermentation, yes and to no small part due to yeast consumption, but after fermentation not really. The off-gassing may evacuate some air after racking, but you top-up for a reason. Also, keep in mind that tannin-heavy wines need to oxidize to age and soften. Non-tannic wines (whites) are usually pressed before fermentation and subsequently handled with much more care.

Most beer is better if you keep all oxygen out after the fermentation starts to dwindle. There are some exceptions, such as barley wines, where the oxidized flavor is part of the expectation. Some people also don't mind stale beer. I guess it's a matter of personal preference.

Yes, you'll probably get less damage with carbonated beer, but I'd figure out a way to not have to do damage at all. Specifically for gelatin, given that the functional benefit of crystal clear beer is better shelf life, is it all that necessary for your homebrew?

 

[mac_1103]

In an attempt to minimize oxygen exposure I have been adding gelatin solution with a plastic hypodermic needle through the gas QD and racking by closed transfer with pressure differential, but it would be easier without trying to maintain closed system.

I guess I'm not seeing what's so hard about doing closed transfers since you're already set up for them. It sounds like you've got a process worked out that lets you do what you want with minimal oxygen exposure. Why change it?

 

[Bassman2003]

As a wine maker, I feel confident that my fermenting wine is protected from oxidation by the heavy production of CO2 and the continued release of CO2 from the wine even after fermentation is complete. I pressure ferment beer using a corny keg in primary (actually after SG gets below 1.030 so technically secondary). I connect gas line of primary to liquid line of serving keg, add a spunding valve to the serving keg set at 12 psi, and let the co2 purge the serving keg. After 10 days of conditioning I cold crash the kegged beer, at which point the pressure drops maybe from 12 psi to 8 psi upon full CO2 absorption at low temp. I would have thought that the now fully carbonated beer, similar to the fermenting wine, would be fairly well protected from oxidation (assuming I then opened the keg and exposed the beer to oxygen for whatever reason), but I could find zero articles on the subject. What do you think?

To better understand, what is your base premise of thought? That the amount of CO2 occupying the beer would be inverse to the amount of O2 that could interact and harm the wort? More CO2 dissolved = less O2 that can be dissolved = less oxidation?

Basically what was posted above and other things. Gas laws and mixing is something I am try to know more about because they are complex and simple at the same time. The way I have learned to think about anything O2 ingress related is that gases are kind of like sound. They go everywhere. The only way to stop them is complete separation. Trying to force its movement or direction is a fools errand. If there a slight opening, oxygen will find a way in.

With regards to any kind of purging, it only works with an overwhelming amount of purge gas flow combined with a small outlet opening. Basically this means the only way to purge effectively is to push and keep on pushing with only one small exit pathway. Because even as you are pushing the O2 is still mixing. You can't separate it, so just push the whole mess out this tiny opening so no new outside oxygen can get in. Which takes time. Slower flow is better as it promotes less mixing. Opening something like a keg lid lets so much in that running gas through at the same time does not do much.

Hope this helps set the scene. It is a losing battle outside of a few proven techniques.

 

[DavidWood2115]

I use a syringe that has a leurlok end on it and it makes a perfect seal on 5mm ID EVA tubing. That then easily connects to a Duotight gas QD.

Sounds like a nice kit…(hint, hint).