Oxygen in headspace from thermal expansión in bottle condition beer

[Alf34]

So far I have bottled dozens of ipa batches with relative success. I use ascorbid acid both in the mash and botteling day, and for a while I used to purge the headspace before capping. That seemed the work, but I'm always looking for new ways to improve my hoppy beers. I now bottle right to the brim, leaving no headspace, when the beer is warm, since I do not coldcrash. The beer carbonates with 0 headspace, never had any issues with carbonation or bottle bombs.

However, I am wondering what happens when the beer is done carbonating, and I put in the fridge. As it gets cold and liquid goes down, there is some small headspace created. My question is, do you think this headspace contains mostly CO2? Oxygen? A mix?

Btw I don't purge my bottles prior to filling, I tried for a while, and found no difference that I could detect compared to simply purge headspace or leave no headspace. I simply fill all the way up and then tilt the botteling wand to the side so I can fill it to the very top, and cap on liquid.

 

[Bobby_M]

As long as the bottles are filled in a controlled manor with limited splashing, only the remaining headspace prior to capping will have some trace of oxygen. During refermentation in the bottle, most of that O2 will get absorbed by the yeast leaving behind nitrogen. The rest of the gas is CO2 from the carbonation. Note, you do NOT want to fill all the way to cap on liquid. That is almost a guaranteed bottle bomb.

 

[MaxStout]

Assuming you purged all O2 at bottling and used AA to scavenge DO, I think the new headspace would be CO2 coming out of solution. I can't think of how O2 would get in at that point unless you have leaky caps.

Concur with Bobby. Just because you haven't had a bottle bomb yet, doesn't mean you won't. Leave a small headspace when bottling, maybe 1/4 - 1/2"

 

[Unicorn_Platypus]

If you bottled warm and placed in fridge afterwards then the headspace created is from thermal shrinkage. It could be a mix of a vaccum or CO2 coming out of solution.

I also try to limit headspace, but I bottle carbonated beer cold and cap on foam.

I ran a test by filling up bottles with hot tap water to the brim then stuck them in the fridge to see how much headspace was created from thermal shrinkage. See pictures below of how much headspace was created in a 16oz bottle and liter bottle. I don't bottle in 12oz, but you could run a similar test.

When I bottle (cold beer), I double this headspace. If you are bottling room temperature beer 1.5x the amount of headspace pictured here should be plenty.

 

[Broothru]

Although I seldom bottle, I’ve had a few bottle bombs nevertheless. Ninety-nine percent of the time I pressure transfer from a spunded fermentation to a CO2 purged serving keg. I also practice Yeast Oxygen Scavaging of brewing water prior to mashing-in. All of the above isn’t difficult and it ain’t rocket science, so I consider it “LoDO Lite” brewing.

Per your process of filling to the rim to displace O2 in the headspace, the never-to-be-mentioned website and former HBT members would suggest that even a capful of oxygen-containing air is enough to stale your bottled beer. I’m not totally convinced, but their data at least suggests a modicum of truth.

I found the Beer Gun to be mostly ineffective (though convenient to use), so when I do bottle I revert to my ancient DIY counter pressure bottler and purge, slowly fill, then quickly ‘cap on the foam’ to eliminate even that last capful of air by displacing it with evolved CO2. Plus, I still get the proper amount of ulege (head space) in the bottle and minimize the risk of bottle bombs. I also use oxygen absorbing caps, but I’m yet to see empirical data that suggests they actually work.

I’m glad your process works for you, but when you remove your fill device from the tipped bottle it’s physically impossible to be filled all the way to a meniscus above the rim. Liquid beer, unlike gaseous CO2 in the headspace is essentially not compressible, so at some point you almost certainly will experience the dreaded bottle bomb. I’ve had good luck with the messy but functional counter-pressure method. Prost!