Silicone Corny Keg O-Rings

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f00b4r
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Re: Silicone Corny Keg O-Rings

Post by f00b4r » Fri Apr 27, 2018 4:47 pm

Sadfield wrote:
f00b4r wrote:Something that was mentioned by an Aussie seller of corny kegs was that, due to the oxygen permeability of silicon, you may want to be wary of aging beers in those kegs that have had silicone replacement o rings for the lids, for those it might be better to keep hold of nitrile o rings and use them for those particular beers.
Ha ha. I'm actually doing just that with oak chunks in the kegs, trying to replicate aging in an oak firkin. I purposefully didn't go for a 20L oak barrel as the surface area to volume is wrong and allows far too much oxygen pickup compared to a firkin. The news that I may still get some oxygen ingress using a Corny with silicone seal is actually music to my ears, a bit of oxygen never hurt the aging process. Thanks.
:) I guess it depends on what you are trying to achieve but it wasn't something I had thought of until I came across it.

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Re: Silicone Corny Keg O-Rings

Post by PeeBee » Fri Apr 27, 2018 6:05 pm

f00b4r wrote:
Fri Apr 27, 2018 11:50 am
Something that was mentioned by an Aussie seller of corny kegs was that, due to the oxygen permeability of silicon, you may want to be wary of aging beers in those kegs that have had silicone replacement o rings for the lids, for those it might be better to keep hold of nitrile o rings and use them for those particular beers.
Thanks for that.

I learnt silicone tubing was permeable to oxygen a while back (via unfortunate experience) and it hadn't even occurred to me silicone O-rings are going to be the same. I also learnt that acetic acid (vinegar) needs oxygen to form in beer. And that yeast is happy to metabolise alcohol to acetic acid if there's oxygen about - no need for nasty bugs. Basically an experience I don't want to repeat (the bulk of the beers was fine, but on a knife edge from then on).

I've ordered the fat soft O-rings "keith1664" linked - they are not silicone. Most people shouldn't concern themselves about silicone's oxygen permeability for O-rings because the surface area exposed is tiny (unlike tubing) but I can imagine long-term storage (a year plus?) is going to be an issue.

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Re: Silicone Corny Keg O-Rings

Post by Sadfield » Fri Apr 27, 2018 6:35 pm

Not convinced that is true. During normal fermentation conditions, yeast produce Acetic Acid, this reacts with ethanol to form Ethyl Acetate, a desirable fruity ester. In the presence of too much oxygen, yeast can metabolise glucose into C02 and water, but the Crabtree Effect usually prevents this and it would also require a higher glucose content than you'll find in a fermented beer. If yeast were to metabolise alcohol, it would be counterproductive to fermentation. To get considerable levels of acetic acid in beer I think you still require oxygen and Acetobacter.

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Re: Silicone Corny Keg O-Rings

Post by Mashman » Fri Apr 27, 2018 7:25 pm

Sadfield wrote:
Fri Apr 27, 2018 6:35 pm
Not convinced that is true. During normal fermentation conditions, yeast produce Acetic Acid, this reacts with ethanol to form Ethyl Acetate, a desirable fruity ester. In the presence of too much oxygen, yeast can metabolise glucose into C02 and water, but the Crabtree Effect usually prevents this and it would also require a higher glucose content than you'll find in a fermented beer. If yeast were to metabolise alcohol, it would be counterproductive to fermentation. To get considerable levels of acetic acid in beer I think you still require oxygen and Acetobacter.
I was just going to say that :shock:

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Re: Silicone Corny Keg O-Rings

Post by PeeBee » Fri Apr 27, 2018 8:43 pm

Sadfield wrote:
Fri Apr 27, 2018 6:35 pm
Not convinced that is true. During normal fermentation conditions, yeast produce Acetic Acid, this reacts with ethanol to form Ethyl Acetate, a desirable fruity ester. In the presence of too much oxygen, yeast can metabolise glucose into C02 and water, but the Crabtree Effect usually prevents this and it would also require a higher glucose content than you'll find in a fermented beer. If yeast were to metabolise alcohol, it would be counterproductive to fermentation. To get considerable levels of acetic acid in beer I think you still require oxygen and Acetobacter.
Beyond "Crabtree Effect". Fermentation is complete, the sugar is gone. The yeast is starving. But evolution gave yeast another trick. It is "diauxic"; it looks at its own waste and thinks "yummy"...

From https://www.morebeer.com/articles/how_yeast_use_oxygen:
The hazards of respiration: As a further testament to its flexibility, yeast is also diauxic, meaning the cells can use more than one carbon source for their energy needs. Under certain circumstances, yeast can respire ethanol as well as glucose, producing acetic acid (vinegar) as a by-product. This process can occur only in the presence of oxygen when no alternative energy source (that is, no fermentable sugar) is available. Fortunately, our yeast does not normally get the chance to oxidize ethanol to acetic acid because by the time all the sugar is gone and ethanol is available for respiration, no dissolved oxygen is left in solution.
I haven't dismissed "Acetobacter", it was my first conclusion, but I couldn't explain where it came from and might of expected other off-flavours. It was while exploring the possibilities that I came across this "dark side" to yeast. I finally concluded our naivety to silicone rubber was an opportunity for yeast to get on with its life.

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Re: Silicone Corny Keg O-Rings

Post by Sadfield » Fri Apr 27, 2018 9:48 pm

Fair point, but given how insufficiently homebrewers aerate wort despite our best efforts, thrashing and shaking, I'm still extremely sceptical transfer through silicone would provide sufficient dissolved oxygen. Highly permeable oak casks have been used for centuries without issue, often for aging ales for more than a year. Wouldn't most brewers report the result of respiration, instead of symptoms of oxidation?



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Re: Silicone Corny Keg O-Rings

Post by McMullan » Sat Apr 28, 2018 12:34 am

:lol:

Edit: There's probably more data on cock rings, but, here we are, stating 'facts'. Bogosphere!

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Re: Silicone Corny Keg O-Rings

Post by PeeBee » Sat Apr 28, 2018 9:39 am

Sadfield wrote:
Fri Apr 27, 2018 9:48 pm
Fair point, but given how insufficiently homebrewers aerate wort despite our best efforts, thrashing and shaking, I'm still extremely sceptical transfer through silicone would provide sufficient dissolved oxygen. Highly permeable oak casks have been used for centuries without issue, often for aging ales for more than a year. Wouldn't most brewers report the result of respiration, instead of symptoms of oxidation?
Okay, let me explain what I was doing and see if I can change your opinion. Firstly, silicone isn't just a bit permeable to oxygen, it is very permeable. I understand this feature is used in medical equipment, but I couldn't find any examples.

A year ago I decided to improvise some fermenter temperature control. I had a shelf cooler which I used to get the cooled wort's temperature down (the CFC would only get it down to 25-30C in quick time). So I connected the shelf cooler (product coils) to the fermenter with silicone tube. Out via the fermenter's racking arm (its a conical) and small pump, in via the sample port (so all completely submerged, no splashing, the product coils and connections all sterilised with hot VWP and rinsed). The setup worked great, controlling the fermentation temperature and for dropping the temperature rapidly at the end. I left the recirculation plumbing attached during 1 week maturing (no transfer, beer now under airlock, no oxygen ingress from these).

The sampling tap was still attached, sharing the port with the recirculation plumbing. And I of course had the occasional sample. I soon began to notice an "acetic" taint to the samples. Panic. By the time it was casked the samples were very acetic. But the beer being casked seemed fine. After casking I removed the silicone tubing and what came out of them was no less than vinegar you could put on chips.

Two brews affected before I dismantled the recirculation system for good. One brew is drunk, the other, an "old ale", is still being drunk (8-9 months maturing). No hint of acetic. There was a third, but the recirculation failed when yeast clogged up the racking port. The ample oxygen must have encouraged enormous yeast growth (I remember discussing this wayward yeast with you back then).

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Re: Silicone Corny Keg O-Rings

Post by Sadfield » Sun Apr 29, 2018 3:39 pm

PeeBee wrote:
Fri Apr 27, 2018 8:43 pm
I haven't dismissed "Acetobacter", it was my first conclusion, but I couldn't explain where it came from and might of expected other off-flavours.
So we agree on something, respiration may not be the cause of your issue. Given that we sanitise and not sterilise, the usual sources of contamination apply. Under normal conditions, acetobacter are denied the oxygen needed to grow. Getting back to the original topic of Silicone o-rings, I would imagine it would be near on impossible to get the levels of oxygen required for respiration or acetobacter growth, in a static liquid under a co2 headspace of higher pressure than the external environment. Oxidation may occur as it does in wooden barrels and corked or crown capped bottles, but that's part and parcel of developing aged flavours.

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Re: Silicone Corny Keg O-Rings

Post by PeeBee » Mon Apr 30, 2018 12:42 pm

Sadfield wrote:
Sun Apr 29, 2018 3:39 pm
... So we agree on something, respiration may not be the cause of your issue. ...
Yeap. I can't prove either way. But yeast's "dark side" was an interesting find. And wouldn't Acetobacter add other off-flavours? The taint was purely acetic acid (there is no mistaking "vinegar").

But I was hoping to forward the dangers of using silicone polymer (especially tubing, but perhaps O-rings too?) with fermented beer. And I don't seem to be making headway there. And I neglected to outline another point where this affected beer would go "acetic" because that was an un-necessary extra factor - a few mils in the tap (free-flow, not hand-pump) would turn acetic between sessions. "Tap must leak air in" I'd tell myself, which is of course nonsense because the beer is under pressure.

By one of those coincidences I started dismantling my dispensing setup yesterday ahead of finishing my "bar" area. Hidden behind the facia was the pipes connecting the taps to the beer-line enabling valves tucked away in the corner. Part of the project I started last year. The taps were connected with very flexible tubing in such a tight space - silicone tubing!

So my attention turned to the hand-pumps. I knew these had silicone hose to the nozzle, but as the nozzle is wide open to air that's no concern. Except: I'd installed the same beer-line enabling valves into the outlet (behind the nozzle) to help prevent the pump cylinder contents turning bad between sessions. I was partly successful, but bemused by the first few mils (of any beer) having turned to vinegar 'tween sessions (the whole cylinder would turn in a week). What would also bemuse me is the beer in the cylinder would totally degas between sessions so the cylinder would always end up half full (even hand-pumped beer often contains 1-1.2 volumes CO2) (EDIT: That gives the impression I think one volume of beer plus one volume of CO2 equals two volumes; which it doesn't as the CO2 dissolves in the beer. So where's the beer gone? No, no, no, I don't want to go there just now). It seems that just a few hours was enough time to equalise the gaseous component in the beer (100% CO2) with air (350ish ppm CO2; and 19% oxygen) via that short length (75mm) of silicone tube. Any other leaks in the hand-pumps would have shown up with beer on the floor.

So, am I convincing you? Finished beer and silicone polymer (tubing, and after time O-rings too) must not mix! The oak casks mentioned must have a permeability to gases that is a minute fraction of the permeability of silicone polymer.

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Re: Silicone Corny Keg O-Rings

Post by Sadfield » Mon Apr 30, 2018 3:30 pm

Acetobacter is used to make vinegar, and will convert ethanol into Acetic acid, if it threw off other flavours vinegar would also have other characteristics.

There is a world of difference between beer in a tube (low volume, high surface area, in contact with beer, flexible tube) to a seal on a keg (large volume, low surface area, not in contact, compressed silicone).

In my experience silicone seals on kegs don't appear to drop pressure, indicating co2 permeability over time isn't that high. Therefore it is fair to accept oxygen permeability the opposite way would be similar.

For aging beer there is a need for some oxidation in order to promote the correct flavour profile.

Whilst there may be scientific milage in not using silicone tubing and the 'dark side' of yeast, let's have some common sense and see that your issue is a world away from the subject of the thread.

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Re: Silicone Corny Keg O-Rings

Post by PeeBee » Tue May 01, 2018 12:33 pm

I've done my bit - hi-light what f00b4r mentioned about using silicone O-rings. But I accept my comparisons are taking the thread well off-track: I'll continue to purge the silicone tubing I'm using for dispense and may put the outcome up in a separate thread.

There's loads of stuff written (WWW) about O-ring gas permeability for anyone to read more, but I'll take Sadfield's view that silicone O-rings may well offer a benefit to maturing beer long-term: I'll just be slightly cautious of a potential to "over-do" it (I'll cry if a beer I've been maturing for 18 months starts oxidising).

But I'm not going without a parting shot!
Sadfield wrote:
Mon Apr 30, 2018 3:30 pm
... There is a world of difference between beer in a tube (low volume, high surface area, in contact with beer, flexible tube) to a seal on a keg (large volume, low surface area, not in contact, compressed silicone). ...
All very good, volume and surface area ought to be important factors. But contact (or lack of)? At the scales being discussed, solids and liquids are just busier gases.

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Re: Silicone Corny Keg O-Rings

Post by PeeBee » Thu May 31, 2018 11:54 am

Sadfield wrote:
Sun Apr 29, 2018 3:39 pm
So we agree on something, respiration may not be the cause of your issue. ...
You were right.

Different beer. There is no sign of acetic taint after leaving the hand-pumps idle for a day or two. After three days there was an unpleasant taint, but not acetic, to the first few millilitres of beer which could well be the beer in the silicone having oxidised. So seems that both beers I'd previously discussed had got a dose of Acetobacter which took advantage of silicone's oxygen permeability, and it was not yeast respiration. Interesting that you can have beer infected with Acetobacter but notice no ill effect until the beer is exposed to oxygen for a while.

Anyhow, I purged the Silicone hose from my keg dispensing setup and hand-pumps and replaced it with PVC.

As for O-rings: I accept your arguments that silicone in this situation can't be responsible for excessive oxygen ingress. But the fatter, softer, nitrile O-rings discussed earlier are working fine, so I'll be sticking with them.

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Re: Silicone Corny Keg O-Rings

Post by PeeBee » Sat Jun 09, 2018 3:56 pm

PeeBee wrote:
Thu May 31, 2018 11:54 am
… But the fatter, softer, nitrile O-rings discussed earlier are working fine, so I'll be sticking with them.
Spoke too soon. The keg I (think I) bought the fatter O-rings for still failed to seal. New lid, even newer, and now fatter, O-ring for lid, and still the keg leaks like a sieve. No obvious damage to the keg, what's going on?

I tried (thinking it will be in vain) to dismantle the PRV on the shiney new lid (from China - bought a pair). And... there's no flippin' O-ring!

Found an O-ring that seemed to be right, re-assembled the PRV and the keg now seals fine.

The one thing that can really mess up any attempt at fault-finding is... COINSIDENCE!


These nitrile O-rings really pong despite soaking them - I going to regret not getting the silicone ones now.

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