Oxidation

[adyb]

Can a keg get oxidised through the beer line / tap?

I've been trying to track down the cause of oxidation. Last brew was fermented in a fermzilla, i didn't dry hop, just large whirlpool addition. Keg purged from fermentation, closed transfer. After 2 weeks connected to my beer line and tap and the beer was amazing. 10 days later the hop flavour had pretty much gone. Then a week later I poured a beer and the first beer was horrendous, tasted really badly oxidised, sherry like flavour(this would have had a large portion off beer from the line in). I braved another and this was no where near as bad, just seemed lightly oxidised and lack of hop flavour. I didn't think it could oxidise through the beer line or tap back into the keg?

I use eva barrier.

Any thoughts?

 

[Conehead]

Cherry like flavour to me means some sort of infection. I do experience the hop flavour going away after a few weeks or so. I wonder if it is the water profile that causes that? What water profile did you use?

 

[AlexKay]

The beer sitting in the beer line absolutely goes off, and relatively quickly, even if you're using barrier tubing. So yes, the hoppy beer left sitting the line for a week may not be good anymore. Sounds like that's exactly what happened here.

Does the oxygen in the line get back into the keg and stale the beer? In my experience, not very quickly. I haven't had trouble keeping my IPAs hooked up for a month or a little more, though that's usually my limit.

Are you using EVA for the gas lines, too? Someone will come on to post that oxygen ingress through the gas lines is just as bad as through the beer lines. There's some theoretical basis to think this, though my assessment is that the science doesn't point to a clear answer. It has not been my experience that a PVC gas line causes significantly more oxidation than a barrier gas line (I have one keezer plumbed each way.)

As you troubleshoot, it's worth considering that when you're observing the oxidation (after a few weeks) does not necessarily correlate to when the oxygen pickup is. If you let a lot of oxygen in at transfer, for instance, it could still take several weeks for staling to show up, if the beer is kept cold.

Are you force carbonating? Small amounts of oxygen in your CO2 supply could be a culprit.

Are you particularly sensitive to hop staling? A beer that still tastes hoppy to me could be unacceptably stale to you.

 

[adyb]

Cherry like flavour to me means some sort of infection. I do experience the hop flavour going away after a few weeks or so. I wonder if it is the water profile that causes that? What water profile did you use?

I used the Pale Ale profile from Bruin Water.

 

[adyb]

The beer sitting in the beer line absolutely goes off, and relatively quickly, even if you're using barrier tubing. So yes, the hoppy beer left sitting the line for a week may not be good anymore. Sounds like that's exactly what happened here.

Does the oxygen in the line get back into the keg and stale the beer? In my experience, not very quickly. I haven't had trouble keeping my IPAs hooked up for a month or a little more, though that's usually my limit.

Are you using EVA for the gas lines, too? Someone will come on to post that oxygen ingress through the gas lines is just as bad as through the beer lines. There's some theoretical basis to think this, though my assessment is that the science doesn't point to a clear answer. It has not been my experience that a PVC gas line causes significantly more oxidation than a barrier gas line (I have one keezer plumbed each way.)

As you troubleshoot, it's worth considering that when you're observing the oxidation (after a few weeks) does not necessarily correlate to when the oxygen pickup is. If you let a lot of oxygen in at transfer, for instance, it could still take several weeks for staling to show up, if the beer is kept cold.

Are you force carbonating? Small amounts of oxygen in your CO2 supply could be a culprit.

Are you particularly sensitive to hop staling? A beer that still tastes hoppy to me could be unacceptably stale to you.

I use EVA barrier on my entire set up now.
So this beer was carbonated by a mixture of pressure fermenting(spunding with about 8gravity points left) and the topped up by force carving.

I'm now thinking on my next beer which I kegged yesterday to just serve with a picnic tap and disconnect after every session. At least this way it will confirm if the problems there or earlier in the kegging process.

 

[AlexKay]

I use EVA barrier on my entire set up now.
So this beer was carbonated by a mixture of pressure fermenting(spunding with about 8gravity points left) and the topped up by force carving.

I'm now thinking on my next beer which I kegged yesterday to just serve with a picnic tap and disconnect after every session. At least this way it will confirm if the problems there or earlier in the kegging process.

Sounds like the right thing to do from a troubleshooting perspective.

 

[tracer bullet]

I'll agree that the EVA Barrier has helped overall, but that beer in the line even overnight will taste different than the rest of the keg. Closed transfers upped my game significantly, that was the biggest change for me, filling keg with water and pushing it out with CO2, then using a bit of leftover keg pressure to purge my transfer lines as well (I do a true closed loop where gravity puts the beer in the keg and the CO2 which comes out of the keg goes back to the fermenter).

Also agree that a sherry flavor is not oxidation, it's some sort of infection. My guess is wild yeast, I've had it as well. I do my best but on rare occasion have it happen in an Imperial Stout. But it's garage brewed instead of inside the house, and sits far longer than any IPA's and such, and so I suppose it's more likely to show any imperfect sanitation practices.

 

[DBhomebrew]

Sherry is a classic descriptor of long-term micro oxidation. Some beers such as English barleywines and imperial stouts can benefit from it, almost count on it.

 

[tracer bullet]

Sherry is a classic descriptor of long-term micro oxidation.

That is a really good point.

When I've had it, twice ever, once was accompanied with the gravity beginning to drop again (Imp St went from high 1.020's to the low 1.010's and was continuing to go, and creating pressure in the keg), and the 2nd time it was accompanied with some awful smells coming out of the headspace (not exactly sulfur, I've smelled that, but still a rotten, farty kind of smell).

But, yeah you're right, more info would be needed before assuming it's spoiled.

 

[Bilsch]

I use EVA barrier on my entire set up now.
So this beer was carbonated by a mixture of pressure fermenting(spunding with about 8gravity points left) and the topped up by force carving.

CO2 sources vary wildly in the amount of O2 they contain. Even with spunding and adding minimal gas if your carbon dioxide came from a trash gas source you could still be doing damage. You also might want to evaluate your hot side ingress.

 

[adyb]

CO2 sources vary wildly in the amount of O2 they contain. Even with spunding and adding minimal gas if your carbon dioxide came from a trash gas source you could still be doing damage. You also might want to evaluate your hot side ingress.

Gas is from a reputable seller, and is sold as food quality beer/bar gas

 

[Broken Crow]

Just to dismiss a couples basics and make sure we're not missing anything; When you say;

Gas is from a reputable seller, and is sold as food quality beer/bar gas

..is this Beer Gas or CO2?
Also; I've had a couple occasions when I got lazy and didn't clean my tap for a few days and the first pour tasted like vinegar...my bad.
Last question to help us help you if we can; How long have you been kegging? Just wondering if this is atypical and I couldn't find any mention of that.

 

[adyb]

Just to dismiss a couples basics and make sure we're not missing anything; When you say;

..is this Beer Gas or CO2?
Also; I've had a couple occasions when I got lazy and didn't clean my tap for a few days and the first pour tasted like vinegar...my bad.
Last question to help us help you if we can; How long have you been kegging? Just wondering if this is atypical

Just to dismiss a couples basics and make sure we're not missing anything; When you say;

..is this Beer Gas or CO2?
Also; I've had a couple occasions when I got lazy and didn't clean my tap for a few days and the first pour tasted like vinegar...my bad.
Last question to help us help you if we can; How long have you been kegging? Just wondering if this is atypical and I couldn't find any mention of that.

It's CO2.
Tap and line were cleaned with purple line cleaner.

I've not been kegging long. I use to use plastic pressure barrels where I'd use sugar.to carbonate and never use to have any issues.

 

[KegLand]

Can a keg get oxidised through the beer line / tap?

I've been trying to track down the cause of oxidation. Last brew was fermented in a fermzilla, i didn't dry hop, just large whirlpool addition. Keg purged from fermentation, closed transfer. After 2 weeks connected to my beer line and tap and the beer was amazing. 10 days later the hop flavour had pretty much gone. Then a week later I poured a beer and the first beer was horrendous, tasted really badly oxidised, sherry like flavour(this would have had a large portion off beer from the line in). I braved another and this was no where near as bad, just seemed lightly oxidised and lack of hop flavour. I didn't think it could oxidise through the beer line or tap back into the keg?

I use eva barrier.

Any thoughts?

What type of o-rings are you using on your kegs. If you are using silicone o-rings I would watch this video we made some time ago:



Silicone allows oxygen to freely pass through the seals in the keg and many customers think because the keg is under pressure oxygen can't get in but this is completely incorrect which is why we found this video to be important.

I would not worry too much about the fermenter as small amounts of ingress of oxygen in the fermenter can get soaked up by the active yeast. With that said once you clarify and chill it's really important to make sure your storage vessel contains no silicone seals.

 

[Bobby_M]

Was the fermentation purge just running through an empty keg or did you fill it with starsan first and use fermentation to push it out?

 

[adyb]

Was the fermentation purge just running through an empty keg or did you fill it with starsan first and use fermentation to push it out?

Just an empty keg, does it need to be filled with starsan first? I didn't think it mattered due to the large volume of co2 produced?

 

[Bobby_M]

Just an empty keg, does it need to be filled with starsan first? I didn't think it mattered due to the large volume of co2 produced?

I know that's the theory but I have to wonder if there's still residual O2 left. As the CO2 enters (through the liquid port I presume), it causes gases to vent out of the gas port (into a blowoff bucket or airlock I presume), it's a mixture of CO2, Nitrogen and Oxygen. The assumption is that after a while, all the nitrogen and oxygen will be gone. I'm just not 100% confident.

 

[Beerstein]

I know that's the theory but I have to wonder if there's still residual O2 left. As the CO2 enters (through the liquid port I presume), it causes gases to vent out of the gas port (into a blowoff bucket or airlock I presume), it's a mixture of CO2, Nitrogen and Oxygen. The assumption is that after a while, all the nitrogen and oxygen will be gone. I'm just not 100% confident.

Hypothetically speaking, an empty keg full of atmosphere will slowly diffuse with the co2. There should be residual oxygen left. How much . A star san fill is the only way to drastically decrease the amount of gaseous oxygen.

Now I'm wondering how much dissolved oxygen in the starsan could evaporate within the keg? Can't be much. Dependent on the temperature swings? More questions than answers.

 

[Bassman2003]

With a cut gas dip tube, the CO2 comes in low and the only exit is the high gas out. The key is the slow and steady flow of CO2 over days that makes it work. We want the gasses to mix and then get ushered out together. Eventually, there will be nothing left to mix with and be pure CO2. I do not think this would work as well if the the same amount of CO2 created by an entire fermentation was run through the keg at a faster clip. Then you would have less mixing and more pass through going on. I think you can trust it.

 

[adyb]

I'll try a filled keg next time.

 

[Bassman2003]

Are you going to push the sanitizer out with fermentation gas or pressurize the keg with tank CO2 and push it before hooking up to the keg?

 

[adyb]

Are you going to push the sanitizer out with fermentation gas or pressurize the keg with tank CO2 and push it before hooking up to the keg?

My aim would be to use fermentation gas, as this is what I've been doing, i haven't used sanitizer before, I've just used an empty(clean) keg.

 

[Bassman2003]

Others say this works but I would be concerned with the amount of sanitizer left behind. When I purged kegs with tank CO2, the end of the sanitizer was helped greatly by the pressure. I have some floating dip tubes in service as well. If you are fermenting at atmosphere, it seems everything below the dip tube level would stay in the keg. Dip tube lengths vary though.

In my mind, the dry purge has been proven enough to use it. And it is very easy!

 

[day_trippr]

it seems everything below the dip tube level would stay in the keg. Dip tube lengths vary though.

An oem diptube properly installed will leave roughly a teaspoon of fluid behind, be that beer or Star San.
A solid reason not to ever shorten an Out dip tube...

Cheers!

 

[Brewer Mike]

Now I'm wondering how much dissolved oxygen in the starsan could evaporate within the keg? Can't be much. Dependent on the temperature swings? More questions than answers.

I would think that would be minimal, considering it's fighting the positive pressure of the incoming CO2. And, once the Starsan is evacuated, you can let it continue pushing the CO2 into the keg and further purge.

 

[Beerstein]

I would think that would be minimal, considering it's fighting the positive pressure of the incoming CO2. And, once the Starsan is evacuated, you can let it continue pushing the CO2 into the keg and further purge.

That's what I'm leaning towards too. I did enough fluid dynamics in college to know that what you think "should" happen isn't always the case. There is gas exchange even when the pressure differential is large. I don't think it's enough to matter here.

 

[Broken Crow]

My aim would be to use fermentation gas, as this is what I've been doing, i haven't used sanitizer before, I've just used an empty(clean) keg.

I'm kinda surprised everyone has been so 'polite' so far and not dog-piled on you for not using sanitizer. It's not just O2 that is a threat to good beer, but the organisms that feed on O2 as well. A 'sherry-like' taste could well be just the beginning of it turning into malt-vinegar owing to airborne contaminants supplied with O2.
There's a lot good threads on here on sanitizing kegs such as this: Feedback on keg sanitizing method?
Oxydation still shows up sometimes for other reasons, but starting with a filled-then-purged, fully sanitized keg usually gets rid of the most basic culprit.
Just a suggestion to avoid waste: If you're gonna dump the remains, use some of it first to soak chicken or pork destined for the BBQ...works great for that!

 

[adyb]

I'm kinda surprised everyone has been so 'polite' so far and not dog-piled on you for not using sanitizer. It's not just O2 that is a threat to good beer, but the organisms that feed on O2 as well. A 'sherry-like' taste could well be just the beginning of it turning into malt-vinegar owing to airborne contaminants supplied with O2.
There's a lot good threads on here on sanitizing kegs such as this: Feedback on keg sanitizing method?
Oxydation still shows up sometimes for other reasons, but starting with a filled-then-purged, fully sanitized keg usually gets rid of the most basic culprit.
Just a suggestion to avoid waste: If you're gonna dump the remains, use some of it first to soak chicken or pork destined for the BBQ...works great for that!

The keg was cleaned and sanitized, sorry probably didnt make that clear.
I just didn't completely fill it and then push it out with co2. I just used the large amount of co2 produced during fermentation to purge it as this should in theory work.

 

[doug293cz]

I know that's the theory but I have to wonder if there's still residual O2 left. As the CO2 enters (through the liquid port I presume), it causes gases to vent out of the gas port (into a blowoff bucket or airlock I presume), it's a mixture of CO2, Nitrogen and Oxygen. The assumption is that after a while, all the nitrogen and oxygen will be gone. I'm just not 100% confident.

Hypothetically speaking, an empty keg full of atmosphere will slowly diffuse with the co2. There should be residual oxygen left. How much . A star san fill is the only way to drastically decrease the amount of gaseous oxygen.

Now I'm wondering how much dissolved oxygen in the starsan could evaporate within the keg? Can't be much. Dependent on the temperature swings? More questions than answers.

With a cut gas dip tube, the CO2 comes in low and the only exit is the high gas out. The key is the slow and steady flow of CO2 over days that makes it work. We want the gasses to mix and then get ushered out together. Eventually, there will be nothing left to mix with and be pure CO2. I do not think this would work as well if the the same amount of CO2 created by an entire fermentation was run through the keg at a faster clip. Then you would have less mixing and more pass through going on. I think you can trust it.

The full analysis of purging an empty keg with fermentation CO2 was done here. This is a "worst case" analysis, in that it assumes that the incoming CO2 completely mixes with the existing gas in the keg before any gas exits. The residual O2 in the purged keg finishes at around 5 parts per Billion (0.005 ppm.) In the real world, the incoming CO2 does not completely mix with the existing keg atmosphere, so the gas pushed out of the keg has more O2 than in the case of complete mixing. This means actual results of purging with fermentation CO2 are much better than the calculation estimates. This has been verified by people with O2 meters that can measure in the ppb range ($$$$$), but the results are behind a paywall.

Brew on

 

[KegLand]

I know that's the theory but I have to wonder if there's still residual O2 left. As the CO2 enters (through the liquid port I presume), it causes gases to vent out of the gas port (into a blowoff bucket or airlock I presume), it's a mixture of CO2, Nitrogen and Oxygen. The assumption is that after a while, all the nitrogen and oxygen will be gone. I'm just not 100% confident.

Lets say you push 2000Litres of carbon dioxide through a 19L keg that atmospheric 21% oxygen concentration will be diluted to about 0.2%

This is still quite high with respect to oxygen concentration in CO2. Normally for oxygen concentration we would aim to have be 0% to at least 2 decimal places. The ISBT specification for oxygen concentration in beverage grade gas is sated to be 30ppm.

If on the other hand you fill the keg with liquid firsts and displace with CO2 then you should get below the 30ppm threshold.

 

[doug293cz]

Lets say you push 2000Litres of carbon dioxide through a 19L keg that atmospheric 21% oxygen concentration will be diluted to about 0.2%

This is still quite high with respect to oxygen concentration in CO2. Normally for oxygen concentration we would aim to have be 0% to at least 2 decimal places. The ISBT specification for oxygen concentration in beverage grade gas is sated to be 30ppm.

If on the other hand you fill the keg with liquid firsts and displace with CO2 then you should get below the 30ppm threshold.

Read this post above, and the linked post. The theory has been presented and verified experimentally. Your math is for mixing 2000 L of CO2 with 19 L of air all at once. The fact that the dilution takes place gradually, over time, makes a huge difference.

Edit: The fact that the final volume is 20 L, rather than 2020 L, and most of the gas gets pushed out of the keg is also a big part of the difference. (Actual enclosed volume of a corny is closer to 20 L than 19 L.)

Brew on

 

[IslandLizard]

Your math is for mixing 2000 L of O2 with 19 L of air all at once.

I think you meant to write CO2, not O2...

 

[doug293cz]

I think you meant to write CO2, not O2...

Yes indeed. Corrected. Thx.

Brew on