Oxygen Absorbing Caps

[AnOldUR]

Is there any way to visually tell the difference between oxygen absorbing caps and non oxygen absorbing caps?

 

[MaxStout]

I've used both and could not tell the difference by looking at the cap liners. But maybe there is something subtle about them to look for. I too would be interested to know if anyone has an answer to this.

 

[orangehero]

I'm sure there are different manufacturers but mine have a dark grey liner and "OXYCAP" on the side. The regular and oxygen barrier caps I have contain a translucent liner.

I suspect maybe some retailers, whether knowingly or not, sell the oxygen barrier caps as "oxygen absorbing".

 

[AnOldUR]

I suspect maybe some retailers, whether knowingly or not, sell the oxygen barrier caps as "oxygen absorbing".

This is probably the answer I was looking for. I was at Keystone Homebrew in PA and asked a new guy for oxygen caps. I may have left out the "absorbing" part.

I thought all caps were on there as an oxygen barrier. :cross:

 

[MaxStout]

One guy at my LHBS claims that all their caps are O2-absorbing, even though only some of the packages are marked as such. But this guy will say anything to make a sale, so I take his advice with a grain of salt.

I prefer the O2-absorbing caps (I want all the help I can get), and only buy the ones clearly marked as O2-absorbing.

 

[kh54s10]

I have a bag of LD Carlson Oxygen Barrier Crown caps. There are no markings on the cap. It has a grey liner that seems thicker than my regular caps that have a translucent liner with the number 22 on it.

I have no idea if they really do anything better than regular caps.

 

[AnOldUR]

One guy at my LHBS claims that all their caps are O2-absorbing, even though only some of the packages are marked as such.

I was back to the same homebrew store yesterday and tried to clarify this. I tried to get them to distinguish between what was "barrier" and what was "absorbing", but didn't get far. One guy was still going with the "all their caps are O2-absorbing" story that a different employee had given me earlier. A second guy behind the counter didn't look convinced, but seemed to not want to disagree.

Just now looking at hops on-line at Farmhouse Brewing Supply and thought I'd check out their caps. I couldn't find anything with the oxygen absorbing claim, but all their cap were "oxygen barrier" with the explanation quote below. The part I put in bold indicates to me that none of these are oxygen absorbing caps. (Although probably very good caps.)

Oxybarrier is a higher end PVC free liner which totally seals off the bottle. This means, what's in it stays in and nothing comes in or out; leaving the beer fresh for about 3 months longer than a regular PVC free liner. This liner is commonly used for lower rotation, high end beers which are bottled in a near perfect environment. In a nutshell, if you have a good filler and the oxygen is near 0 when the cap goes on, then this liner is the best of the best.

Edit to add:
I emailed Farmhouse to confirm and got this back:

I had a long discussion about this with my rep and yes these are apparently just barrier caps. I can't get the absorbing caps any longer but I've been looking. Sorry buddy.

John

 

[MaxStout]

Interesting twist of words in that trade name "Oxybarrier." Yes, it's a "barrier" to oxygen only insofar as its ability to seal up. So, in other words, it's just another crown cap, an invention that's been around since the 1890s.

Here's an open challenge: Can anyone--manufacturer, retailer, brew experimenter, etc.--substantiate the so-called "oxygen-absorbing" cap? What's inside the cap liner that purportedly absorbs O2, and how does it work? Is there empirical data showing a reasonable reduction of O2 versus ordinary caps? Or is this just another sleight-of-hand trick to re-package and mark up ordinary crown caps by a buck? Show us the science.

 

[orangehero]

Search "iron oxide oxygen scavenger" and you'll find more than you wanted to know.

Apparently it's also sometimes used on the bottom of aluminum cans.

From THE USE OF OXYGEN SCAVENGERS AND ACTIVE PACKAGING TO REDUCE OXYGEN WITHIN INTERNAL PACKAGE ENVIRONMENTS:

"Beer crowns containing immobilized SmartMix® have been used commercially on 12 ounce beer bottles by a number of smaller brewers such as G. Heileman Brewing Co. and tested by major brewers such as Anheuser-Busch and Miller. AOT reported that after the first 24 hours, the oxygen concentration was reduced to less than 50 ppb from an initial concentration of over 2000 ppb.

The experiments demonstrated that when the oxygen scavenger is not in direct contact with the beer, it is effective in removing oxygen from the beer. As the oxygen is removed from the headspace, which accounts for about two-thirds of the total small quantity of oxygen in the bottle according to AOT, dissolved oxygen vaporizes from the liquid into the headspace to re-establish equilibrium. This additional oxygen was then scavenged, and this process continued until only a trace amount of dissolved oxygen, less than 50 ppb, was left."

 

[FarmerTed]

Interesting twist of words in that trade name "Oxybarrier." Yes, it's a "barrier" to oxygen only insofar as its ability to seal up. So, in other words, it's just another crown cap, an invention that's been around since the 1890s.

Here's an open challenge: Can anyone--manufacturer, retailer, brew experimenter, etc.--substantiate the so-called "oxygen-absorbing" cap? What's inside the cap liner that purportedly absorbs O2, and how does it work? Is there empirical data showing a reasonable reduction of O2 versus ordinary caps? Or is this just another sleight-of-hand trick to re-package and mark up ordinary crown caps by a buck? Show us the science.

I've measured O2 uptake with some that I purchased. I think I got ~0.3 mL of O2 per liner. It was a slow process (took a week or more; I used a gas burette in my lab for the measurements, and measured the uptake of 10 liners at one time). They aren't designed to absorb a ton of O2, but are rather designed to scavenge O2 as it passes from outside the bottle through the liner. There are patents out there with info on how some are designed, and I cannot remember where I read it, but I did find that most are designed to scavenge about 0.4 mL of O2.

As far as what the scavenger is, I think it differs per the manufacturer. Some are ascorbic acid, and I believe others have iron in them. A patent search will give you some ideas. They do work, but like I mentioned above, if you bottle your beer with the headspace filled with air (~15 mL total), you will totally overwhelm the O2 scrubbing capacity of the cap. I'd love to know how well yeast absorbs O2 during bottle conditioning, but it's tough to find info that is relevant to bottle-filling on the homebrew scale.

 

[MaxStout]

I've measured O2 uptake with some that I purchased. I think I got ~0.3 mL of O2 per liner. It was a slow process (took a week or more; I used a gas burette in my lab for the measurements, and measured the uptake of 10 liners at one time). They aren't designed to absorb a ton of O2, but are rather designed to scavenge O2 as it passes from outside the bottle through the liner. There are patents out there with info on how some are designed, and I cannot remember where I read it, but I did find that most are designed to scavenge about 0.4 mL of O2.

As far as what the scavenger is, I think it differs per the manufacturer. Some are ascorbic acid, and I believe others have iron in them. A patent search will give you some ideas. They do work, but like I mentioned above, if you bottle your beer with the headspace filled with air (~15 mL total), you will totally overwhelm the O2 scrubbing capacity of the cap. I'd love to know how well yeast absorbs O2 during bottle conditioning, but it's tough to find info that is relevant to bottle-filling on the homebrew scale.

Interesting, thanks. I've never seen the actual numbers put out there before on this.

Based on a typical 15ml headspace volume, there would be ~3ml O2. If the cap scavenged 0.4ml, that's about 13% of the O2 inside. One would need to fill bottles to within 2ml of the top for the caps to remove (theoretically) all of the O2. Filling that high is probably not a good idea.

Now, to determine if the caps touted as "oxygen-absorbing" are indeed that, or something an unscrupulous (or ignorant) vendor has merely repackaged and labeled as O2-absorbing. My spidey senses tell me that not all caps are O2-absorbing, despite the claims made by some vendors.

I just assume they are not, unless I have reason to believe otherwise. But with an absorption effectiveness somewhere around 13%, it seems like a minor advantage to me anyway.

 

[FarmerTed]

They may absorb more, but the ones we buy could be 10 years old for all we know. The ones I tested did not burn through the oxygen very fast, but maybe if they were fresh and packaged under argon in a well-sealed container, they would work better. I'm sure the ones breweries use are much better than ours. I know that the caps are moisture-activated, but still, if they are years old and have been sitting in a plastic bag, I'm sure some of the capacity is gone.

The one thing I'll say in their favor is that they seem to be higher quality than a lot of the crappy caps you can buy in bulk at a shop. Some of those caps are really flimsy.

I just assume they are not, unless I have reason to believe otherwise. But with an absorption effectiveness somewhere around 13%, it seems like a minor advantage to me anyway.

Well, the way I use them is that when I fill the bottles and cap them, I immediately shake the bottle, then store it sideways a few days. The goal is to have the yeast absorb the headspace O2 during the early stages of conditioning, and to have the beer cover the cap liner to prevent it from being oxidized immediately after filling. After a few days, I shake the bottles again and then stand them upright. Does it work? Hell if I know, but it makes sense to me to do, and isn't a hard thing to do.