The co2 "blanket"

[ericbw]

Then there's the issue of the purity of the CO2 source itself if you're using it to push the beer out. This has been covered in a few other threads here as well as on the German brewing forum, but food grade (99.5% pure) isn't good enough. Ideally the purity you want is 99.998% or better.

I see a lot of discussions about CO2 being food grade or pure. But where are people getting their CO2 from? Do the gas supply places have "food grade" CO2, along with "pure" CO2 along with "everyday" level of CO2?

Do commercial bottling facilities (soda and/or beer) have a special place they get their CO2 from?

Your post reads like kegging is bad for oxidizing beer, the CO2 isn't good enough, but bottling (which leaves the headspace full of more air than a QD pushes into the beer), and there's a seal that might or might not be O2-proof) is going to solve the problem? Are you fermenting in a sealed container and then bottling with a counter-pressure filler?

And as for the QD pushing beer into the keg - I vent frequently, which minimizes the exposure of beer to O2.

Think of how hard it is to aerate your beer before fermenting. It's not like it sees the air and instantly absorbs all the O2 it can. It takes time or effort (agitation) to get O2 in, right?

Of course, I am fully in favor of overthinking and over-engineering

 

[55x11]

You are absolutely spot on with respect to how little air/oxygen it takes trapped in the package to damage the beer, and you are also correct that naturally carbonating inside the keg is initially as good as carbonating in a bottle, perhaps even better if you've done a good job purging the keg first and performed a closed transfer.

The problem I have with corny kegs is the hardware we connect to them. Especially to the gas post.

Take a look at one of your grey quick disconnects. Turn it upside down, then fill it with water until the water level covers the poppet valve and reaches the o-ring. There's several ml there. When you connect the QD to the gas post, that space is filled with air which gets trapped by the o-ring, and enters the keg through the gas post once you force the disconnect on and the poppet valves open. Every time you disconnect or reconnect the QD, you are injecting several ml of air into your keg.

So why not just connect the gas once and leave it connected? Because your gas lines are oxygen permeable. To what extent depends on the material they're made of, but nearly all flexible plastic tubing has some oxygen permeability. It's not a fast diffusion, mind you, but a month or more is a very, very long time and your gas line has quite a bit of surface area. We are talking about 2 or 3 milligrams worth of oxygen being all it takes to damage the beer.

Then there's the issue of the purity of the CO2 source itself if you're using it to push the beer out. This has been covered in a few other threads here as well as on the German brewing forum, but food grade (99.5% pure) isn't good enough. Ideally the purity you want is 99.998% or better.

I think kegs are fine if you are running a bar or hosting a party or if you can empty them within 2 weeks or so of tapping them. Since I don't drink that fast, I'm considering going back to bottling.

Finally I want to emphasize that if you're happy with your beer, you don't have to go through all of this trouble. This stuff is really most important for extremely oxygen sensitive beers (like light lagers brewed with the low oxygen process from the paper I linked to, or a NE IPA whose hop character you want to last for more than 2 weeks).

All good points but I think you are over-estimating it.

well, so the inner diameter of the gray disconnect is about 16mm and the height from the middle of the o-ring where the seal is made to the top of the post is maybe 3mm or so, thats perhaps 0.5 mL, and majority of it, say about 90% or so (I would argue more) - will be "pushed out" by the post making a connection with the disconnect - the poppet is almost the same diameter and is sitting flush with the disconnect body. So let's say we are talking 1/10th of that, 0.05mL, or 50 uL of "dead air space" in between disconnect and the poppet (and I believe I am being generous, there's probably a lot less volume left there, depending on tolerances in manufacturing, wear-and-tear etc.), and I also believe that a great deal of this air will be pushed out by high pressure of CO2 once it starts flowing but before a good seal is made (sort of like mini-purge). Because when you re-connect a keg that is usually already under pressure, there will be high pressure on both sides, pushing air out until the good seal is established.

So maybe a few uL, maybe 10uL or even 20uL of air is trapped there - probably much less volume that is inside the volume defined by the bottle cap, but definitely not "several mL" of air.

The beer line "leaking in oxygen" effect can be estimated using Fick's diffusion law. I may try to do the calculation, but again, to make a strong argument one needs actual numbers, not just saying that the "surface area is large" and diffusion is very slow, but "the time is very long" - so where does this leave us? What is a very small diffusion rate times very long time - is that large or small?

The numbers quoted for oak barrel aging, which I suspect have a much higher oxygen permeability than polyethylene tubing, and have much greater surface area than the beer line (by about a factor of 10), by is about 2mL per liter of beer, per *month*. And this micro-dosing of oxygen is actually positive for many styles that benefit from long aging (imperial stouts, sours etc.)

The airlock, even when probably sealed, will let that much oxygen per day.

Again, I am not arguing these problems with kegging are nothing to worry about. But lets focus on areas where we let in a lot more oxygen - like during transfers (especially during bottling), cold-crashing or just letting the beer sit in a fermenter once fermentation is basically over. I still think transfers is the biggest area where most homebrewers oxidize their beers, followed by extended post-fermentation.

Unless one bottles from the beer gun from the keg, into a bottle that is flushed with CO2, with a beer that has been closed-transfered, cold-crashed under CO2, not dry-hopped past fermentation, not allowed to sit even for a few days after fermentation under airlock - I would argue it will have more chances to pick up large amounts of oxygen than a kegged beer. Even then, it could pick up more oxygen during bottle filling process.

And I would not try to age any beer that is not meant for aging (as in - high ABV>10%, dark style with no hops or other fleeting favors). I think even in complete absence of oxygen flavors of other beers undergo changes that are not desirable for most styles, so drinking a beer within a month or three of brewing/kegging is always a good idea.

 

[ferm.adventures]

This is either the best HBT thread I've read or the most terrifying. I'm not sure. But I think some day I may be obsessing about the amount of oxygen introduced by the poppets in my kegs too!

 

[p_p]

I don't buy that a small fermentation "erases" oxygen pick up. sure, the yeast may metabolize the 02, but the o2 has already been in contact with the beer and then it's too late.

I'm a long-time winemaker and one of the things we do as a matter of course is to use sulfites, around 50 ppm, in our wine. The s02 binds to the wine, so that oxygen cannot during transfers and bottling. This happens on molecular scale, and once the o2 is in there, a small bottle fermentation won't 'erase' it.

When I dryhop, I just do the best I can to avoid allowing too much oxygen into the vessel, either by transferring onto the dryhops or by quickly and gently opening the primary at the tail end of fermentation. It is not ideal, but I'm satisfied that I'm doing the best I can at this point without a way to do closed transfers. Others are more particular than I am; others may be less particular. My philosophy is to do the best I can and I'm satisfied with that. If I was doing a lot of aged beers, I may look at it differently but most of my APAs and IPAs are consumed rather quickly at my house.

Thanks for your reply.

May I ask if you add SMB to your beer in order to avoid oxidation as you do in wine-making?

I appreciate there is a long discussion on SMB that is being argued both ways, but I am asking you given your experience brewing IPAs and the like.

On my last hoppy ale I added a small douse of SMB (~6ppm) to the fermented beer, after dry hopping and before cold crashing. The beer carbonated in bottle. This beer seems to be holding ok after 6 weeks.

Do you think using SMB in this manner is helpful?

Thanks,
pp

 

[p_p]

What would adding sulfites to beer at dry hopping do? Would that help remove any O2?

Oh, I just realized I asked the same question. Apologies ..

 

[p_p]

from what I've read, yes. I added a bit of SMB to my beer while hop steeping and then added some dissolved DME to carb when I added my "keg dry hop". Fantastically hoppy IPA going on 6 weeks. Obviously a small sample size there, but the articles I've read back it up

Thanks for sharing your experience.

You mentioned that you added the SMB during hop steeping ... I guess you refer to flameout?

 

[NeoBrew]

All good points but I think you are over-estimating it.

I can see you did a lot of math, but I think you are forgetting some key parts of the system that negate or reduce them. I'm no scientist by a long shot, but...

1. When you push a gas line onto your keg, you should have the pressure on. The QD poppet will depress before the keg poppet that will purge the air out of that space in the QD.

2. The diffusion of oxygen into a plastic line would only happen if they were at equal pressure. The CO2 is at a much higher pressure. The only thing that would be happening is CO2 leaking out of the line into the atmosphere.

 

[Yooper]

Thanks for your reply.

May I ask if you add SMB to your beer in order to avoid oxidation as you do in wine-making?

I appreciate there is a long discussion on SMB that is being argued both ways, but I am asking you given your experience brewing IPAs and the like.

On my last hoppy ale I added a small douse of SMB (~6ppm) to the fermented beer, after dry hopping and before cold crashing. The beer carbonated in bottle. This beer seems to be holding ok after 6 weeks.

Do you think using SMB in this manner is helpful?

Thanks,
pp

I don't use sodium metabisulfite at all, I use potassium metabisulfite (k-meta) in my winemaking.

I've never used it in beer, but I use it routinely in winemaking. I'm a somewhat lazy winemaker- I have three carboys in the living room behind a big chair that I put there in the fall of 2013. I don't have a single beer left from 2013! I just don't age beer like I do wine, and I make many beers like IPAs and APAs that are gone within a month or 6 weeks of brewday. I just don't feel the "need" to use k-meta with my beer.

 

[doug293cz]

I can see you did a lot of math, but I think you are forgetting some key parts of the system that negate or reduce them. I'm no scientist by a long shot, but...

1. When you push a gas line onto your keg, you should have the pressure on. The QD poppet will depress before the keg poppet that will purge the air out of that space in the QD.

2. The diffusion of oxygen into a plastic line would only happen if they were at equal pressure. The CO2 is at a much higher pressure. The only thing that would be happening is CO2 leaking out of the line into the atmosphere.

#2 sounds reasonable, but that's not the way diffusion works. Diffusion is driven by differences in the chemical potential of a species from one location to another. Diffusion direction is from higher potential to lower potential. For gases, chemical potential is approximately proportional to partial pressure, so that a difference in a gas's partial pressure will drive diffusion (again from higher pressure towards lower pressure.) The partial pressure of one gas is independent from the partial pressure of any other gases that it may be mixed with, so the fact that you have a very high CO2 partial pressure (chemical potential) gradient from inside the beer line to the atmosphere, doesn't affect the fact that you have an opposite partial pressure gradient for O2 from the atmosphere to the inside of the line. Thus O2 will diffuse from the atmosphere, thru the beer line wall, into the beer, in spite of the high potential of CO2 inside the line.

If you have a flowing gas, things get more complicated. Diffusion flow rates for gases are typically less than about 50 linear feet per minute. So, if you had a CO2 leak with a linear flow rate of greater than 50 ft/min, then O2 could not diffuse upstream and enter the vessel from which the CO2 was leaking. If the CO2 leak rate was less than 50 ft/min, then some O2 would be able to leak into the vessel against the CO2 flow.

Brew on

 

[NeoBrew]

:

I have no idea what you said, but it sure sounds science-y.

I defer to your expertise.

 

[doug293cz]

I have no idea what you said, but it sure sounds science-y.

I defer to your expertise.

Yeah, it is science-y. If you are interested, I can try to explain it in less technical terms.

Brew on

 

[55x11]

I can see you did a lot of math, but I think you are forgetting some key parts of the system that negate or reduce them. I'm no scientist by a long shot, but...

1. When you push a gas line onto your keg, you should have the pressure on. The QD poppet will depress before the keg poppet that will purge the air out of that space in the QD.

2. The diffusion of oxygen into a plastic line would only happen if they were at equal pressure. The CO2 is at a much higher pressure. The only thing that would be happening is CO2 leaking out of the line into the atmosphere.

If I understand your argument for #1, we are saying the same thing - much of minuscule amount of air trapped between QD and poppet, will be purged during connection. If so, I agree.

For #2, it goes both ways. It's about partial pressures on the two sides, so two gases basically don't care about each other. CO2 will leak out of the line, and the oxygen (and other gases present in air - nitrogen, argon, water vapor etc.) will diffuse into the line. It only matters what is the difference in pressure for each chemical species.

CO2 may diffuse through most substances more slowly than oxygen - it depends on porosity and size/shape of the molecule (for example, CO2 will leak from bike tubes much faster than air, if you ever used CO2 cartridges to fix a flat tire). But nonetheless, if the permeability of beer gas lines was sufficiently high, we would see it as a "slow leak" every time we disconnected our gas tank and see the pressure slowly dropped. I did it for a few weeks at a time on my system (consisting of 9 beer lines) - when I went on vacation last month, and didn't see a very significant pressure drop. So I doubt it's a significant effect.

My broader point is that often we are paranoid about nanoliter-sized air leaks, while missing a bigger problem - like oxygen getting into our fermenters during cold-crashing, which is on liter scale. Or dry hopping, adding sugar, etc - which is on tens of mL scale or so. And sure, yeast can clean some of it up - but how much and over what timescale?

I think someone should work out a ranking of various potential contribution of oxygen to the beer.

PS: I guess doug beat me to it with the partial pressure explanation. Somehow I missed the whole exchange.

 

[p_p]

You are correct that yeast cannot "erase" oxidative damage once it has happened, but how fast the damage happens depends a lot on temperature. At mash temperatures, the oxidation of malt compounds happens within seconds to minutes, whereas at fermentation temperatures it's more at the scale of several hours to days. I actually do use about 50 ppm sulfite in my mash water which has already been preboiled to drive off the dissolved oxygen that was already present; if you haven't seen this yet, I would encourage you to read it (I'm one of the authors):

http://www.germanbrewing.net/docs/Brewing-Bavarian-Helles-v2.pdf

Even a small amount of yeast + sugar will metabolize free oxygen extremely fast, on the order of minutes. Check this out:

http://forum.germanbrewing.net/viewtopic.php?f=50&t=355

As long as beer is not exposed to oxygen for more than a few minutes before fresh sugar/yeast is added, the free oxygen picked up during bottling will be scavenged by the yeast much faster than it can react with the beer itself.

Hi, I read your paper a couple of weeks back and am slowly chewing through the rather extensive thread. The more I read, the more confused I get.

For someone brewing in a non-LoDO system who cares only about preserving hop flavour and aroma and perhaps extending shelf life altogether, what kind of SMB additions you would recommend?

I've taken on your 4ppm addition at bottling time but I still have to deal with a couple of weeks primary in a bucket which may or may not be leaking air plus the point at which the bucket is open to add dry hops.

I am not sure what is the mechanism by which the SMB stops oxygen from binding with the compounds we care about, so I don't know if adding it when the bucket is open to add hops is just too late ...

Thanks,

 

[KimJohansen]

My experience is that dry hopping is the biggest problem. My lagers stay fresh (also the very hoppy Kellerbiers/Pilseners) a lot longer than my heavily dry hopped APA's/IPA's.

My scheme for APA's & IPA's is usually:

7 days primary -> Drop the yeast & add dry hops
7 days with the dry hops -> Graviity kegging from Conical.

From what I read here (https://byo.com/stories/issue/item/3187-advanced-dry-hopping-techniques) 3 days of dry hopping should be enough to extract the oils. Also a bit of active fermentation should help get rid of O2 introduced by the dry hops. That leads me to the following scheme change:

Primary 5 days, drop yeast and then add dry hops
4 days with dry hops then pressurized transfer to a Co2 purged keg.

What do you guys think?

 

[KimJohansen]

By the way, in the pursuit of as little O2 as possible it would be nice to be able to measure it.

Would this do as an instrument? https://www.aliexpress.com/item/Pro..._4&btsid=934dd111-d3d7-4798-a9d8-44dedd858f16

 

[techbrau]

Hi, I read your paper a couple of weeks back and am slowly chewing through the rather extensive thread. The more I read, the more confused I get.

For someone brewing in a non-LoDO system who cares only about preserving hop flavour and aroma and perhaps extending shelf life altogether, what kind of SMB additions you would recommend?

I've taken on your 4ppm addition at bottling time but I still have to deal with a couple of weeks primary in a bucket which may or may not be leaking air plus the point at which the bucket is open to add dry hops.

I am not sure what is the mechanism by which the SMB stops oxygen from binding with the compounds we care about, so I don't know if adding it when the bucket is open to add hops is just too late ...

Thanks,

If you only care about hop flavor and aroma then skip the SMB. Dry hop during the last 3 days of active fermentation, and keg/bottle before the yeast have completely gone dormant. Add enough sugar when you package to naturally carbonate in the keg/bottle, and make sure to fill your packages as completely full as possible. If you are kegging you can try to first purge your destination keg by filling it to the brim with sanitizer and then pushing it out with co2, then doing a closed transfer of the beer into that keg.

The single biggest factor is to avoid any contact with oxygen post-fermentation. The easiest way to do that is natural carbonation in your bottle/keg.

 

[techbrau]

My experience is that dry hopping is the biggest problem. My lagers stay fresh (also the very hoppy Kellerbiers/Pilseners) a lot longer than my heavily dry hopped APA's/IPA's.

My scheme for APA's & IPA's is usually:

7 days primary -> Drop the yeast & add dry hops
7 days with the dry hops -> Graviity kegging from Conical.

From what I read here (https://byo.com/stories/issue/item/3187-advanced-dry-hopping-techniques) 3 days of dry hopping should be enough to extract the oils. Also a bit of active fermentation should help get rid of O2 introduced by the dry hops. That leads me to the following scheme change:

Primary 5 days, drop yeast and then add dry hops
4 days with dry hops then pressurized transfer to a Co2 purged keg.

What do you guys think?

That won't work because you've just added an enormous amount of oxygen when you plonk in your dry hops, and you have no actively fermenting yeast to mop it up.

The technique we reccomend on the GBF is to dry hop during the final few days of primary fermentation, and then add priming sugar when you're ready to rack to your keg. Purge the keg before transferring by filling it to the brim with sanitizer and then pushing it out, and do a closed transfer from the fermenter to the purged keg. Fill the keg as full as possible with beer - cutting the gas dip tube shorter will allow you to do this. Let the beer naturally carbonate inside the keg.

 

[KimJohansen]

That won't work because you've just added an enormous amount of oxygen when you plonk in your dry hops, and you have no actively fermenting yeast to mop it up.

The technique we reccomend on the GBF is to dry hop during the final few days of primary fermentation, and then add priming sugar when you're ready to rack to your keg. Purge the keg before transferring by filling it to the brim with sanitizer and then pushing it out, and do a closed transfer from the fermenter to the purged keg. Fill the keg as full as possible with beer - cutting the gas dip tube shorter will allow you to do this. Let the beer naturally carbonate inside the keg.

But that's what I tried to describe. Adding the dry hops 2 days before my primary would normally finish.

 

[wishingiwasfishing]

The technique we reccomend on the GBF is to dry hop during the final few days of primary fermentation, and then add priming sugar when you're ready to rack to your keg.

What methods do you use when adding sugars, for moving to a keg? any concerns on the methods you use?



Thanks!


I really like where this discussion is going. Even if I don't implement every single detail, I'll adopt the concerns into my methods. Hopefully this will improve my beer over time.

Dan

 

[p_p]

If you only care about hop flavor and aroma then skip the SMB. Dry hop during the last 3 days of active fermentation, and keg/bottle before the yeast have completely gone dormant. Add enough sugar when you package to naturally carbonate in the keg/bottle, and make sure to fill your packages as completely full as possible. If you are kegging you can try to first purge your destination keg by filling it to the brim with sanitizer and then pushing it out with co2, then doing a closed transfer of the beer into that keg.

The single biggest factor is to avoid any contact with oxygen post-fermentation. The easiest way to do that is natural carbonation in your bottle/keg.

Thanks for that. I've been reading in this forum for abut a year and I the more I read, the more I realize that I have only scratched the surface.

We know that during fermentation the yeast will take on O2. In a previous post you mentioned it takes a small amount of sugar (~1 gravity point). Others believes that only vigorous fermentation has the ability to rapidly consume the O2 (?)

When I prime bottles I reckon I am adding 1 - 1.5 points but I have no idea how much oxygen is taken in in the process and how much is left in the head-space. What makes you say it only takes ~1 gravity point?

Looking at the bottling process itself (no beer gun). What is the best technique? I usually use a wand and try to do it gently, where possible capping on foam. But when I see the beer swirling on the bottle as it gets filled up, I get the shivers.

Finally, in your post you mentioned to dry hop at the tail end of active fermentation, which is fair enough. If for whatever reason that is not possible, for example I have a beer that was 1°P away from finishing last night and I will not get to it until tonight) would you recommend to add some sugar (1 point presumably) along with the dry hops to get the fermentation going again and help mop up?

Why in your reply you decided not to recommend the use of SMB for those that cannot do LoDO but wish to extend hop aroma and shelf life? In your paper you recommend 4ppm at bottling time. Would it be wise to drop those 4ppm or more at the same time we dry hop hoping to help the beer after fermentation has complete?

Lots of questions, lots of answers.
Hats off to all of you sharing your experience, awesome generosity.

 

[ferm.adventures]

Stumbled on this video of John Kimmich talking about drinking Heady Topper in the can, and he made a couple of statements that are off to me.

First, he said that pouring the beer to a glass will expose the beer to plenty of oxygen (true), but after 20 minutes will taste very different due to oxidation. I'd think the change in flavor is more due to beer warming and the co2 coming out of solution. But he then said that the co2 blanket in the can will protect the flavor. Uhm, ok, but I can't see that much oxidation occurring while one drinks the beer via either method and the can will drastically restrict the aroma.

Second, he talks about storing Heady for months or a year, and pours and obviously very oxidized old Heady and then says it tastes great. Am I missing something here? Why be concerned about oxidation in the glass, while thinking it perfectly fine for it to deteriorate over months.

http://youtu.be/amgfgU5-lhs

 

[ericbw]

Stumbled on this video of John Kimmich talking about drinking Heady Topper in the can, and he made a couple of statements that are off to me.

First, he said that pouring the beer to a glass will expose the beer to plenty of oxygen (true), but after 20 minutes will taste very different due to oxidation. I'd think the change in flavor is more due to beer warming and the co2 coming out of solution. But he then said that the co2 blanket in the can will protect the flavor. Uhm, ok, but I can't see that much oxidation occurring while one drinks the beer via either method and the can will drastically restrict the aroma.

Second, he talks about storing Heady for months or a year, and pours and obviously very oxidized old Heady and then says it tastes great. Am I missing something here? Why be concerned about oxidation in the glass, while thinking it perfectly fine for it to deteriorate over months.

http://youtu.be/amgfgU5-lhs

First, I hear people talk about oxidation in the glass, and I think, "hmmm...."

But remember that a can of beer from the brewery shouldn't have any oxygen in it. It's canned in a factory that can limit it for this very reason. Just like tomatoes in a can.

If they flush the cans with CO2, then fill in a way that doesn't expose it to O2, there is no need for a CO2 blanket to protect it. It's all CO2.

I also think it is the warming that changes the flavor of the beer. I have an Irish Red that should probably be served warmer, but it's impractical to keep the kegs at 45+ degrees. So you pour it and it tastes one way, but in about 5-10 minutes, it has warmed up and tastes even better.

Some beers are better colder, so when they warm, they taste different/worse.

Probably the same thing here.

 

[ferm.adventures]

Agreed. I guess my main question is, is in glass oxidation a bigger concern than long term oxidation in the can?

The screen cap I can see with the video, the beer on the table on the left has suffered obvious oxidation due to the color darkening. Yes, they've certainly minimized it, but haven't completely eliminated it.

 

[mongoose33]

I also think it is the warming that changes the flavor of the beer. I have an Irish Red that should probably be served warmer, but it's impractical to keep the kegs at 45+ degrees. So you pour it and it tastes one way, but in about 5-10 minutes, it has warmed up and tastes even better.

Some beers are better colder, so when they warm, they taste different/worse.

Easy enough to test w/ cans or bottles. Chill one, keep the other warm, pour both at the same time, taste.