# Oxygen Absorbing Caps



## JonnyAnchovy (28/4/10)

Hi All,

I'm interested in hearing people's opinions on the oxgen-eating bottle caps on the market - who used them? Any noticeable difference in shelf-life? 

Extra points for first-hand experience.


----------



## peas_and_corn (28/4/10)

I've never used them, but I really don't store beer for a long time.


----------



## Fourstar (28/4/10)

AFAIK Sierra Nevada have recently begain using them.

Anything to reduce oxidation especially with shipping your beer all over the universe is a good thing. They may also help the homebrewer who stores their beer in enviroments where the temperature can fluctuate quite a bit as O2 can be drawn in under the cap when this happens.


----------



## MHB (28/4/10)

There are two answers and they are both right
If you are packaging Filtered/Pasteurised that is to say sterile beer they are a great idea.
If your beer has live yeast they are a complete WOFTAM, the yeast will do a better job of scavenging any O2 than the caps ever will
As my beer has live yeast Bah! Hocus Pocus nonsence!





Fourstar said:


> AFAIK Sierra Nevada have recently begain using them.
> 
> Anything to reduce oxidation especially with shipping your beer all over the universe is a good thing. They may also help the homebrewer who stores their beer in enviroments where the temperature can fluctuate quite a bit *as O2 can be drawn in under the cap* when this happens.



Really, you must have interesting O2 at your place, stuff with a special exemption to the laws of physics, I never have any problem with gas leaking into a pressurised container.

MHB


----------



## bradsbrew (28/4/10)

I'll be using these after filling the bottles of my comp beers with my CPBF. Any other time I will be using normal caps.

Cheers


----------



## Kai (28/4/10)

MHB said:


> Really, you must have interesting O2 at your place, stuff with a special exemption to the laws of physics, I never have any problem with gas leaking into a pressurised container.
> 
> MHB



Any plastic is a semi-permeable membrane and O2 can transfer in against the pressure gradient just as easily as CO2 in the beer can transfer out with it. I never did physics at high school and university is too dim and hazy a memory to properly explain it, but 'strue. Same as why PET bottles aren't as good for long term storage; the CO2 inside wants to equilibrate with outside, and the O2 wants to do the same with what's in the bottle. It just happens a lot slower through a bottle top.

But, Sierra Nevada don't use oxygen scavenging caps. They use barrier seals, which will not scavenge oxy already present in the bottle but do reduce O2 ingress via the plastic under the seal when compared to normal or scavenging caps.

At home, just like HSA, I don't think there's any point using oxygen scavenging caps unless you can guarantee low DO levels in every other point of your process. By my reckoning if your beer has had too much exposure to oxygen before you bottle then your beer will continue to oxidise in the bottle regardless of what type of crown seal you use.


----------



## tallie (28/4/10)

I bought some of these recently for a Barley Wine that I'm planning on bottling and putting away for a few years.

Upon reading the replies above, I'm starting to wonder if it's worth it. Now I'm thinking of capping a couple of bottles with regular caps and trying them side-by-side in a few years time to see if there's any difference between the two.

Check back here in a couple of years and I'll let you know how it goes  

Cheers,
Kris.


----------



## zoidbergmerc (28/4/10)

Fourstar said:


> where the temperature can fluctuate quite a bit as O2 can be drawn in under the cap when this happens.



and fourstar's credibility does down, way way way down. 

Seriously? Air from the outside of a pressurised bottle getting into said pressurised bottle?


----------



## Kai (28/4/10)

zoidbergmerc said:


> and fourstar's credibility does down, way way way down.
> 
> Seriously? Air from the outside of a pressurised bottle getting into said pressurised bottle?



Not air, oxygen. Though temperature fluctuations have nothing to do with it.


----------



## /// (28/4/10)

Father-in-Law worked on the polymer for the oxygen scavenging caps in the late 70's (or was it 80's?) as an industrial chem with ICI .... can ask!

But, whats it matter with homebrew. Our left over yeasties and a bit of sugar are better than most a sucking up that oxygen!

Scotty


----------



## zoidbergmerc (28/4/10)

Kai said:


> Not air, oxygen. Though temperature fluctuations have nothing to do with it.



Care to share on how pure O2 manages to get into my pressurised beer bottles then?


----------



## thelastspud (29/4/10)

yeah i thought positive pressure would keep o2 out, what happens? does a little bit leak out and that lets a little bit in?


----------



## Fourstar (29/4/10)

Im not going to go into depth about it as i dont know the science behind it. I heard/read about them some time ago, something todo with vacuum and temperature differentials of ambient and the contents of the bottle. I'd highly doubt the draw of O2 would be anything signifigant but for long term storage (including low O2 exposure up until bottling) they could be a good thing.

Thinking about it, i think it might have been during a Q&A with Charlie Bamforth although i cannot confirm. Heck i may even be confusing the use of vacuum to remove O2 during the bottling process before capping. But i definitly can remember something todo with temperature differentials and oxygen eating caps.


----------



## JonnyAnchovy (29/4/10)

lol @ poll results.


----------



## zoidbergmerc (29/4/10)

Fourstar said:


> Im not going to go into depth about it as i dont know the science behind it. I heard/read about them some time ago, something todo with vacuum and temperature differentials of ambient and the contents of the bottle. I'd highly doubt the draw of O2 would be anything signifigant but for long term storage (including low O2 exposure up until bottling) they could be a good thing.
> 
> Thinking about it, i think it might have been during a Q&A with Charlie Bamforth although i cannot confirm. Heck i may even be confusing the use of vacuum to remove O2 during the bottling process before capping. But i definitly can remember something todo with temperature differentials and oxygen eating caps.



i think you must be very very confused if you think just O2, not Air, not Nitrogen (which is smaller than Oxygen), just O2 entering a pressurised vessel.


----------



## JestersDarts (29/4/10)

Just popped over to DrKarls science forum and asked the quick question about oxygen permeating through the PET into the pressurised solution - 

From the answer I got back , it seems as though any oxygen in the solution can be at a different pressure than the other elements, and permeate out or in the bottle accordingly.

Although this process would be extremely slow.


----------



## Kai (29/4/10)

zoidbergmerc said:


> Care to share on how pure O2 manages to get into my pressurised beer bottles then?



I shared what I knew earlier in the thread.

Come to think of it, first year biology covered the concept too. Look up osmosis and diffusion.


----------



## zoidbergmerc (29/4/10)

I'm familiar with osmosis and diffusion but they just wont happen when the pressure in the bottle is much higher than the pressure outside the bottle. Look up Physics. All the pressure from the bottle would have to be released before anything else from the outside can get in.


----------



## felten (29/4/10)

4star said:


> Thinking about it, i think it might have been during a Q&A with Charlie Bamforth although i cannot confirm. Heck i may even be confusing the use of vacuum to remove O2 during the bottling process before capping. But i definitly can remember something todo with temperature differentials and oxygen eating caps.



yah Charlie Bamforth on the Q and A 30-11-09 ep says "air will creep between the bottle and the cap". They also mention temp fluctuations pull in air under the caps, but they don't elaborate on the science of it unfortunately.


----------



## Fourstar (29/4/10)

zoidbergmerc said:


> i think you must be very very confused if you think just O2, not Air, not Nitrogen (which is smaller than Oxygen), just O2 entering a pressurised vessel.



Errrr no, im not very confused. When did i say that? The topic is oxidation and the effect O2 has on beer stability. Not the effect of nitrogen, or the make up of our atmosphere on beer stability. Although im sure they could permeate into our beer with plenty of other things as well.



felten said:


> yah Charlie Bamforth on the Q and A 30-11-09 ep says "air will creep between the bottle and the cap". They also mention temp fluctuations pull in air under the caps, but they don't elaborate on the science of it unfortunately.



Yeah that must be it. Atleast somone has heard the same thing.


----------



## Kai (29/4/10)

zoidbergmerc said:


> I'm familiar with osmosis and diffusion



Then you'll remember that transfer through a semi-permeable membrane can go from an area of lower pressure to one of higher if the difference in osmotic pressure is greater.


----------



## zoidbergmerc (29/4/10)

No it's the other way around.

and while you 


Kai said:


> I never did physics at high school and university



my housemate and I are both currently doing it and you're wrong.


----------



## Kai (29/4/10)

zoidbergmerc said:


> No it's the other way around.



What's the other way round, specifically?



> my housemate and I are both currently doing it and you're wrong.



So they taught you about beer caps then? 

Beer caps allow oxygen ingress, just like PET bottles do.


----------



## MHB (29/4/10)

One of the good things about AHB is that it makes me think.

As counter intuitive as it may seem after some further reading there is evidence that O2 can get into bottles via crown seals. If at what would appear to be very slow rates, I haven't really been able to find any evidence that it is going to be an issue � but it can happen.

The research I found mostly referred to Stelvin Closures on on wine bottles.

If anyone has a link to good quality research specifically on beer I would like to read more. Please note that sales brochures extolling the virtues of O2 scavenger caps, published by people who sell them aren't what I mean by research.

MHB


----------



## Fourstar (29/4/10)

MHB said:


> One of the good things about AHB is that it makes me think.



So the magical O2 at my place isnt so magical anymore?


----------



## MHB (29/4/10)

Perhaps not, temperature changes certainly aren't the issue, beer has been found that's over 100 years old, some of it was still quite drinkable, these beers were under cork that we know allows some gas exchange. So I seriously doubt that O2 uptake is a real issue.
What I can't figure is, when you think that the difference between the CO2 concentration in a bottled beer and the air outside the bottle and the concentration of O2 in the air, remembering that its concentration that provides the motive force to move gas through a membrane.

Let's say a beer is carbed to about 4.5 g/L. Air contains about 21% Oxygen, typically air at sea level weighs about 0.0012 g/L, so the Oxygen concentration in the air would be 0.000252 g/L.
So CO2 should be escaping 17,857 times faster than O2 is getting in. (rough as guts numbers not allowing for heaps of factors but still a huge difference)
I've drunk 20 year old home brew that was still well carbed and certainly wasn't oxidised.
So yes it's possible but I won't lose any sleep over it.

MHB


----------



## Benniee (30/4/10)

MHB said:


> So CO2 should be escaping 17,857 times faster than O2 is getting in. (rough as guts numbers not allowing for heaps of factors but still a huge difference)
> I've drunk 20 year old home brew that was still well carbed and certainly wasn't oxidised.



That's an interesting point. A lot of the discussion is centered around O2 getting into the container, but not so much on anything leaving the container. My understanding of the physical principal is that gas difussion is a two way street. So considering the greater pressure differential of CO2 between the container and the surrounding atmosphere you'd expect that to be leaving the conatiner faster than any O2 would be entering. I'm probably over simplifying things greatly.

You're right though Mark - gets you thinking...

Benniee


----------



## Kai (30/4/10)

MHB said:


> Perhaps not, temperature changes certainly aren't the issue, beer has been found that's over 100 years old, some of it was still quite drinkable, these beers were under cork that we know allows some gas exchange. So I seriously doubt that O2 uptake is a real issue.
> What I can't figure is, when you think that the difference between the CO2 concentration in a bottled beer and the air outside the bottle and the concentration of O2 in the air, remembering that its concentration that provides the motive force to move gas through a membrane.
> 
> Let's say a beer is carbed to about 4.5 g/L. Air contains about 21% Oxygen, typically air at sea level weighs about 0.0012 g/L, so the Oxygen concentration in the air would be 0.000252 g/L.
> ...



Very well said! That's what I've been trying to get at.


----------



## n87 (10/3/17)

tallie said:


> I bought some of these recently for a Barley Wine that I'm planning on bottling and putting away for a few years.
> 
> Upon reading the replies above, I'm starting to wonder if it's worth it. Now I'm thinking of capping a couple of bottles with regular caps and trying them side-by-side in a few years time to see if there's any difference between the two.
> 
> ...


So... might I ask how this experiment went?
Maybe a couple of years late....


----------



## Bribie G (10/3/17)

In view of your other thread, exactly what I thought as well when I saw this necro.


----------



## tallie (13/3/17)

n87 said:


> So... might I ask how this experiment went?
> Maybe a couple of years late....


Wow, how time flies. Funnily enough, I still have some of that beer, including two stubbies with the different caps. I'll try to remember to dig them out for an upcoming club meeting and see what a few people think.

It's been one or two years since I've tried a beer from that batch. From memory it had aged quite significantly, developing the sherry-like oxidation qualities you'd expect. Some bottles had taken on a bit of clove/spice phenolic flavour, I guess due to picking up some wild yeast while bottling. It might be a bit difficult to see through all of that now to find any differences between the caps.


----------



## n87 (13/3/17)

tallie said:


> Wow, how time flies. Funnily enough, I still have some of that beer, including two stubbies with the different caps. I'll try to remember to dig them out for an upcoming club meeting and see what a few people think.
> 
> It's been one or two years since I've tried a beer from that batch. From memory it had aged quite significantly, developing the sherry-like oxidation qualities you'd expect. Some bottles had taken on a bit of clove/spice phenolic flavour, I guess due to picking up some wild yeast while bottling. It might be a bit difficult to see through all of that now to find any differences between the caps.


Look forward to hearing the verdict.


----------



## tallie (29/3/17)

tallie said:


> I'll try to remember to dig them out for an upcoming club meeting and see what a few people think.





n87 said:


> Look forward to hearing the verdict.


TLDR; No noticeable difference in this particular case

Last night I took the two stubbies to the Merri Mashers club meeting. The beers were presented in a blind triangle test among 7 members who had a mix of levels in brewing and judging experience. The tasters weren't told anything about the beer (including the style or age) and asked to identify the different beer, and what their preference was. Only one taster correctly picked the different beer out of the three samples, and out of them, preferred the non-oxygen absorbing cap sample.

Obviously this is a very small sample size, and due to the size of the bottles, tasters only had a small amount to compare, so take it with a grain of salt.

In terms of the beer itself, as I mentioned in my previous post, it has developed quite a lot of complex flavours over the years. A few of the tasters thought the beer was a strong Belgian ale, giving weight to the possibility of a wild yeast contribution. The phenol was more minty to me than what I remembered as spice/clove. The beers also had a noticeable autolysis flavour in the aftertaste (vegemite/meaty). Once I noticed how much yeast and other material had dropped to the bottom of the bottles, this made sense. I think I was more surprised about how much there was of it in the bottle considering that it wasn't bottled conditioned.


----------



## Lyrebird_Cycles (29/3/17)

Since this has been resurrected and since oxygen diffusion through polymers was a research interest of mine (some years ago I patented a wine technology which exploited this) I thought I'd add a couple of points to the above.

It is in fact possible to have a polymer barrier which allows oxygen ingress into the container whilst not allowing significant CO2 pressure loss. The two important factors are the relative permeability of the two gasses and the relationship between concentration gradient and the concentration difference which will have a perceptible effect on the beer.

On the first topic, the permeablity of a gas through a polymer depends on the solubility of the gas in the polymer which in turn depends on the polarity of the gas. For a typical non-polar polymer like polythene the solubility for a non-polar gas like O2 is much greater than that for a polar gas like CO2 and thus the permeation rate is also much higher, a ratio of 5:1 is typical.

On the second topic, although the pressure gradient for CO2 is about 10 times higher than that for O2 and thus the CO2 transfer rate would still be twice the oxygen transfer rate given the 5:1 permeablity ratio cited above, a 20 ppm decrease in CO2 concentration would be difficult to detect where a 10ppm increase in O2 concentration would be catastrophic.

Hope this clarifies things a little.


----------



## Zorco (29/3/17)

That's amazing LC


----------



## n87 (30/3/17)

Lyrebird_Cycles said:


> Since this has been resurrected and since oxygen diffusion through polymers was a research interest of mine (some years ago I patented a wine technology which exploited this) I thought I'd add a couple of points to the above.
> 
> It is in fact possible to have a polymer barrier which allows oxygen ingress into the container whilst not allowing significant CO2 pressure loss. The two important factors are the relative permeability of the two gasses and the relationship between concentration gradient and the concentration difference which will have a perceptible effect on the beer.
> 
> ...



Thanks LC,

Do you have an opinion (researched or otherwise) on the oxygen scavenging polymer used in the caps?
Would be really interesting to see how much oxygen it actually takes out of the equation, and how fast as I have worked out that if you have a perfect (home brew level) bottling process, you are still likely to have ~7ppm oxygen in the headspace
http://aussiehomebrewer.com/topic/94479-how-much-o2-does-the-yeast-actually-consume-in-bottle/


----------

