What contributes more to oxidised beer - Headspace or oxygen dissolving during transfer?

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Agentgonzo

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Re-reading this thread got me thinking about what is the major contributor to oxidation in the bottle (don't say "oxygen" :laugh8:) - oxygen that dissolves as you transfer, or oxygen in the headspace that dissolves during carbonation/conditioning/storage. Many homebrewers (especially new brewers) just syphon/rack directly into the top of the bottle, which splashes and can introduce oxygen, and other brewers use bottling wands. Obviously racking from a keg or with bottled CO2 is far better, but for many, this isn't an option. I figured I would just run some numbers and compare the two basic scenarios.

I just measured the amount of headspace in a fairly standard bottle by filling it with water to the 'normal' fill level, sticking it on some accurate scales, then topping up to the brim and seeing how much the extra water weighed.

Standard headspace (roughly) = 25g of water (=25 ml)
0.5cm headspace
(as in the above thread) = 1g water (=1ml)

Under standard conditions, 1L of air contains 0.0094 moles of oxygen, which equates to 0.15g of oxygen.
This gives us:
'Standard' headspace = 3.75mg oxygen
0.5cm headspace = 0.15mg oxygen


So how does this compare to what is dissolved when you fill the bottle.
I think it's a relatively safe assumption to say that using a bottling wand transfers the beer to the bottle with negligible dissolved oxygen (let's assume for now that there is no oxygen ingress into your fermenter/botting bucket - obviously your setup could invalidate this assumption).

It's hard to tell how much oxygen dissolves in the beer when you rack directly into the bottle from a siphon tube/spigot. I don't have a DO meter, but we can try to re-use the results from oxygenating wort. Various measurements have been made over the ages when comparing oxygenation techniques, mostly trying to focus on maximising (rather than our goal here to minimize) the amount of DO in wort (which may or may not differ from the beer you are racking). Anyway, racking directly into the fermenter without splashing can get you as low as 0.7ppm DO in the wort, and splashing with agitation (rigorous shaking, which we don't do when bottling!) can give you as high as 4ppm. (lots of sources, but here is one and here is another). So for this, let's assume a conservative range of 1-4ppm. In reality, it'll probably be at the lower range as when racking we try to reduce splashing and dissolved CO2 will come out of solution and help reduce oxygen entering solution.

So how much oxygen is actually in a 500ml bottle at concentration rates of 1ppm? I'll assume water for calculating this quantity, as beer is 95% water. 500ml water = 500g. 1ppm of this is 500/1,000,000g = 0.5mg.
A 500ml bottle with 1ppm DO contains 0.5mg oxygen, and at 4ppm contains 2mg dissolved oxygen.

(It's been two decades since I did my Chemistry A-level, so please check my numbers!)

So what can we conclude from this?

Your conclusions may vary, but for me, if you bottle without CO2 and without using a bottling wand, the major contribution to oxygen in the bottle is actually from the headspace, not from oxygen that dissolves in the beer as part of the transfer as the beer splashes into the bottle.

There are many other factors that go into the oxygenation of the beer that aren't discussed here. How quickly does the dissolved oxygen stale the beer? How quickly does it get scavenged by the bottle conditioning (if you do that). How quickly/slowly does the oxygen in the headspace diffuse into the beer and what effect does this have? Once conditioning has finished, is there residual oxygen in the headspace that will slowly diffuse into the beer and not be able to be scavenged by the yeast and will oxidise the beer?

The standard practise for using a bottling wand (without CO2) is to bottom fill (we can assume negligible DO in this beer), but as you pull out the bottling wand air will come in to fill the headspace (if you don't flush with bottled CO2) - Assuming (without any reasoning or evidence) that racking without a wand splashes the beer and gets CO2 to come out of solution, could it be possible that this CO2 fills the headspace to prevent air coming in and using a bottling wand actually introduces more oxygen into the bottle than just racking with a siphon tube and letting it fall into the bottle?

I don't have any answers to the above, but this was an interesting academic exercise for me to see what contributes to oxygen in the bottle and gives numeric data behind why (obviously) the smaller amount of headspace in @Neale 's experiment had a great effect on the outcome of the beers after prolonged storage.
 
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Water has got dissolved oxygen in it. When I worked for Coca Cola we removed the oxygen in a vacuum chamber and then carbonated the coke to 4 volumes. Without removing the oxygen we couldn’t consistently get 4 volumes.
 

Agentgonzo

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Water has got dissolved oxygen in it. When I worked for Coca Cola we removed the oxygen in a vacuum chamber and then carbonated the coke to 4 volumes. Without removing the oxygen we couldn’t consistently get 4 volumes.
But I think we can safely assume that the beer you are transferring out of the fermenter starts out with zero dissolved oxygen? (I was only using water for calculating molarity/mass from volumes)
 

MickDundee

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Many homebrewers (especially new brewers) just syphon/rack directly into the top of the bottle, which splashes and can introduce oxygen,
Is that right? Before I kegged I only ever used a bottling wand so I genuinely don’t know, but I was of them impression that those using a syphon put the tubing right to the bottom of the bottle?
 

Agentgonzo

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Is that right? Before I kegged I only ever used a bottling wand so I genuinely don’t know, but I was of them impression that those using a syphon put the tubing right to the bottom of the bottle?
When I started, a bottling wand wasn't in the standard starter kit. You'd get siphon tubing and a tap for the end of it that you would hold at the top of the bottle. If you put the tubing all the way to the bottom of the bottle, you couldn't stop the flow. Maybe things have moved on now and a botting wand is standard practise? 🤷‍♀️ I'll admit I'm assuming what others do and going on what I saw when I started. I know bottling wands are common, but not necessarily universally used.
 
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Sadfield

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Feels like you've decided on the conclusion and are making many assumptions about negligible DO uptake, to fit. Only a DO meter will answer the question.
 

Agentgonzo

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That wasn't the intention. There are many things I don't know about DO uptake, so I have to assume them. I don't own a DO meter. It would be interesting if someone did own one to measure it. To my knowledge, this hasn't been done. The best I can do is make the most basic assumptions and work with that to get the most basic conclusion. If any of my assumptions are wrong, let me know thumb. .
 
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My recent experience with using a tapcooler counter pressure bottle filler is that removing a wand/filling stick definitely causes O2 to be sucked back into headspace causing very quick oxidation.
I now remove the filler. Flick the tap to release a small amount of beer to cause foaming. Slightly less headspace and capping on foam has cured my previous oxidation issues.
I didnt have any issues previously using a tube on the end of a growler tap as there was always plenty of foam when bottling as no counter pressure.
Cap on foam, less headspace definitely less oxidation when bottling off keg.
 

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This is a subject near to my heart and the physics and biology involved are fascinating. I’ve written before on consumption of oxygen in the head space - which is in minutes not hours. The time taken for darkening is the subsequent cascade of oxidation related to free radicals. This means it is not just about DO levels, as the oxygen will be consumed over the time of exposure and will not show as being dissolved.
I agree with all the comments about capping on foam and preferably purge the bottles with CO2 before filling.
The temperature issue needs more investigation, filling using v cold beer will slow the oxidation process, but makes it far easier for oxygen to dissolve quickly. There’s a good reason why the gold standard for commercially bottling is vacuum purged twice before filling with CO2 and only then counter pressure filling with beer.
 

Agentgonzo

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I’ve written before on consumption of oxygen in the head space - which is in minutes not hours.
When you say 'consumption' what's doing the consumption here? Yeast/solution/staling reactions/ascorbic-acid/going-into-solution?
I've read the previous thread about ascorbic acid and have been trying it lately to try to make the beer in minikegs last a little bit longer.
 
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chthon

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I think that what one should do is bottle beer, take taste and colour notes (perhaps photos with a calibrated color next to it), then keep a bottle for a year and then compare.

I certainly have no problems keeping my beer for a year, and I don't notice oxidation, off-taste or darkening, and I brew many blond beers.

What I do when bottling is adding the cap immediately (be it crown cap or flip top bottle) but not fasten it. Let the CO2 dilute and drive the air above it for 15-20 minutes, then close them completely. The head space is the volume of the bottling wand that is immersed.

Apart from avoiding splashing and keeping outlets of racking cane and bottling wand immersed, I don't to anything special. I rack from the fermenter into a bottling bucket, and then fill bottles from that.
 

Nicks90

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What I do when bottling is adding the cap immediately (be it crown cap or flip top bottle) but not fasten it. Let the CO2 dilute and drive the air above it for 15-20 minutes, then close them completely. The head space is the volume of the bottling wand that is immersed.

That's exactly what I do, but I didn't start that for any o2 expulsion, it just seemed sensible to put a cap on to prevent any dust or nasties falling it.
However it was only after watching the bottles that you see the beer off gassing after being put in that I realised it was co2 coming out of suspension and that would partially 'purge' the headspace.
No idea how much off gassing occurs or how much it expels oxygen, but every little helps right?
 
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Yeast in the bottle will only consume the priming sugar, not the oxygen as they are in their anaerobic stage.
A good article here by a home brewer who is also a biochemist.


And an excellent website with a terrific library here.
Methods of the Modern Brewhouse - The Modern Brewhouse

I don't worry about oxidised beer, my beer doesn't move around until I pluck it from its resting place and is kept below 20C. We all drink beer relatively fresh, if the beer is kept in a static and cool environment then there is no need to worry as long as bottlining was carried out in a careful manner.
 

DocAnna

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When you say 'consumption' what's doing the consumption here? Yeast/solution/staling reactions/ascorbic-acid/going-into-solution?
I've read the previous thread about ascorbic acid and have been trying it lately to try to make the beer in minikegs last a little bit longer.
The paper in the thread referenced which is relevent is here - https://www.agraria.com.br/extranet...ovas_abordagens_oxidacao_da_cerveja_-_ing.pdf

It is a well written paper with recognition of the experimental limitations, of relevance to this thread is below, consumption in this context is about removal of oxygen from the headspace into solution and reaction to start oxidation of the beer.
Thus, it appears that oxygen in the bottle is consumed in a few minutes, whether the bottle is shaken or not. Nevertheless, although the calculations appear to show that the beer may be protected from the first moments of its entry into the bottle, too great a significance should not be attached to the actual figures now presented, as the presence of foam at the gas-liquid interface could be responsible for a reduction of the rate of transfer and thus affect the oxidation kinetics.
This initial rapid oxidation is dependent on the concentration of antioxidants, which in the case of a dry hopped beer will be much higher than one that has not been dry hopped since many of the hop compounds are 'reductones' which means they are very quick to oxidise. This then sets of a cascade of oxygen free radicals which oxidise further compounds. The use of vit C is a bit controversial but the principle is that it is sacrificial as a highly reactive reductive compound but one that doesn't generate the oxygen free radicals that go on to cascade further oxidation.

The lines above from the paper are another case for capping on foam too.
 
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The paper in the thread referenced which is relevent is here - https://www.agraria.com.br/extranet...ovas_abordagens_oxidacao_da_cerveja_-_ing.pdf

It is a well written paper with recognition of the experimental limitations, of relevance to this thread is below, consumption in this context is about removal of oxygen from the headspace into solution and reaction to start oxidation of the beer.

This initial rapid oxidation is dependent on the concentration of antioxidants, which in the case of a dry hopped beer will be much higher than one that has not been dry hopped since many of the hop compounds are 'reductones' which means they are very quick to oxidise. This then sets of a cascade of oxygen free radicals which oxidise further compounds. The use of vit C is a bit controversial but the principle is that it is sacrificial as a highly reactive reductive compound but one that doesn't generate the oxygen free radicals that go on to cascade further oxidation.

The lines above from the paper are another case for capping on foam too.
Papers are generally for the benefit of commercial breweries. While the home brewer is at a disadvantage when it comes to preventing oxygen ingress into their beer and the limited options they have, they are also at an advantage in it isn't going to be shipped either interstate or all over the world.
For the home brewer oxidised beer would be fairly rare, it is only when introducing tish loads of dry hops where it becomes a problem.
 

Sadfield

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For the home brewer oxidised beer would be fairly rare, it is only when introducing tish loads of dry hops where it becomes a problem.
Totally disagree. It's the same argument that crops up regarding microbial contaminations, that if a beer isn't completely ruined or have a glaringly obvious flaws, then it's not an issue for homebrewers. That there's no grey area in between. All homebrew gets oxidised and affects the overall freshness and clarity of flavour do varying degrees. It's a staling process.
 
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Totally disagree. It's the same argument that crops up regarding microbial contaminations, that if a beer isn't completely ruined or have a glaringly obvious flaws, then it's not an issue for homebrewers. That there's no grey area in between. All homebrew gets oxidised and affects the overall freshness and clarity of flavour do varying degrees.
I have had one oxidised beer, It was around 2.5 years old, no cardboard taste, just sherry like.
If a home brewer takes care in transfers from fermenter to bottling bucket, or transfers from fermenter to keg then there should be little or no problem with oxidisation. I believe Wolfe has done another thesis on the subject.
As home brewers we are safe from the fact that our home brews remain in one place and hopefully at a temperature favorable to the beer.
 

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The use of vit C is a bit controversial but the principle is that it is sacrificial as a highly reactive reductive compound but one that doesn't generate the oxygen free radicals that go on to cascade further oxidation.
Have you come across any research regarding ascorbic acid's rumoured ability to become a "super oxidiser" under some circumstances? I see it mentioned on forums as some sort of hand-wavey-bogey-man thing but can't find any actual research that describes how it happens and at what dosing rates one should be concerned, if at all.
 
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