[BrewBama]

When beer ferments, it is in a closed system expelling CO2 from an airlock of some sort. When that airlock is broken (say I pull the blow off tube out of the liquid solution in a jar) and the spigot at the bottom of the fermenter is opened, as the beer fills a CO2 purged keg it pulls air thru the tube into the headspace of the fermenter. This air mixes with the CO2 and begins to oxidize the beer. Here’s the question(s):

Is the top layer oxidize slightly at first, then gradually more and more saturated and begins to slowly work its way lower and lower into the beer? If so, how long does this take? Filling a keg with 5 gallons takes about 15 minute. If the fermenter was filled to 5.5 gallons will the oxygen have reached the half gallon depth (or more) in that 15 minutes or is the underlying 5 gal of beer protected by this top sacrificial half gallon layer resulting in a keg filled with near zero O2 beer?


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[RC]

Oxygen is not very soluble in water. In fact, it's far more insoluble than it is soluble. Given its lack of solubility, I can't imagine that it diffuses into the beer so quickly as to reach more than a centimeter or two below the surface during those 15 minutes. My take is thus that the beer is indeed protected by that top half gallon.

[Bob357]

I agree with RC. I did as you describe for several years and never saw any negative affect.

[majorvices]

i add a collapsable bag filled with Co2 on the top opening of the fermenter. the co2 displaces the air as the fermenter drains. not only does it displace the oxygen with Co2 but i feel it keeps the yeast more sanitary for rep itching.

Sometimes I get lazy and just rack the beer without the bag. Can't say i notice any difference except I feel better when the bag is used.

[denny]

i add a collapsable bag filled with Co2 on the top opening of the fermenter. the co2 displaces the air as the fermenter drains. not only does it displace the oxygen with Co2 but i feel it keeps the yeast more sanitary for rep itching.

Sometimes I get lazy and just rack the beer without the bag. Can't say i notice any difference except I feel better when the bag is used.

I think that last paragraph is a lesson.  FWIW, the GF fermenter I use accept a pressure fitting on top.  I pressurized when I cold crash and during the xfer.  I do not ferment under pressure.  I also remove the pressure fitt9ng when I dry hop.  I've timed it and I I've the fermenter open only 3 seconds during dry hopping.   No need to worry about gas mixing in that time.  Like you, I've compared doing things the more difficult way and can't see that it made any difference.

[narcout]

Filling a keg with 5 gallons takes about 15 minute. If the fermenter was filled to 5.5 gallons will the oxygen have reached the half gallon depth (or more) in that 15 minutes or is the underlying 5 gal of beer protected by this top sacrificial half gallon layer resulting in a keg filled with near zero O2 beer?

Wouldn't any staling compounds formed in that top layer of beer eventually diffuse to an even concentration throughout the entire volume?

[Richard]

Filling a keg with 5 gallons takes about 15 minute. If the fermenter was filled to 5.5 gallons will the oxygen have reached the half gallon depth (or more) in that 15 minutes or is the underlying 5 gal of beer protected by this top sacrificial half gallon layer resulting in a keg filled with near zero O2 beer?

Wouldn't any staling compounds formed in that top layer of beer eventually diffuse to an even concentration throughout the entire volume?

Yes, but the key word here is "eventually". If you finish your transfer in a time short compared to the time required to reach equilibrium then you can beat the system.

[goose]

i add a collapsable bag filled with Co2 on the top opening of the fermenter. the co2 displaces the air as the fermenter drains. not only does it displace the oxygen with Co2 but i feel it keeps the yeast more sanitary for rep itching.

Sometimes I get lazy and just rack the beer without the bag. Can't say i notice any difference except I feel better when the bag is used.

I think that last paragraph is a lesson.  FWIW, the GF fermenter I use accept a pressure fitting on top.  I pressurized when I cold crash and during the xfer.  I do not ferment under pressure.  I also remove the pressure fitt9ng when I dry hop.  I've timed it and I I've the fermenter open only 3 seconds during dry hopping.   No need to worry about gas mixing in that time.  Like you, I've compared doing things the more difficult way and can't see that it made any difference.

I do basically the sane thing as Denny and do not pressure ferment.  I put a tri-clover Tee on the top of the fermenter when I dry hop and have CO2 running through the side arm when dry hopping.  A funnel goes into the top of the Tee and I pour the pellets in while the CO2 is running through the side arm.  That way I get no O2 ingress when dry hopping.

[BrewBama]

Filling a keg with 5 gallons takes about 15 minute. If the fermenter was filled to 5.5 gallons will the oxygen have reached the half gallon depth (or more) in that 15 minutes or is the underlying 5 gal of beer protected by this top sacrificial half gallon layer resulting in a keg filled with near zero O2 beer?

Wouldn't any staling compounds formed in that top layer of beer eventually diffuse to an even concentration throughout the entire volume?

Yes, but the key word here is "eventually". If you finish your transfer in a time short compared to the time required to reach equilibrium then you can beat the system.

This depends on how deep those staling compounds penetrate within the time it takes to complete the transfer. Hopefully, it is slow enough that I can beat the clock.

If it’s a few centimeters no problem. That top layer is sacrificial. It never makes it into the keg. It ends up going down the slop sink drain.

If it’s inches deep it could pose a problem. That’s why I asked the question(s). How deep is the O2 reaction diffusing into the beer within a given transfer time?

I do believe the reaction is slow. …but how slow?



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[denny]

i add a collapsable bag filled with Co2 on the top opening of the fermenter. the co2 displaces the air as the fermenter drains. not only does it displace the oxygen with Co2 but i feel it keeps the yeast more sanitary for rep itching.

Sometimes I get lazy and just rack the beer without the bag. Can't say i notice any difference except I feel better when the bag is used.

I think that last paragraph is a lesson.  FWIW, the GF fermenter I use accept a pressure fitting on top.  I pressurized when I cold crash and during the xfer.  I do not ferment under pressure.  I also remove the pressure fitt9ng when I dry hop.  I've timed it and I I've the fermenter open only 3 seconds during dry hopping.   No need to worry about gas mixing in that time.  Like you, I've compared doing things the more difficult way and can't see that it made any difference.

I do basically the sane thing as Denny and do not pressure ferment.  I put a tri-clover Tee on the top of the fermenter when I dry hop and have CO2 running through the side arm when dry hopping.  A funnel goes into the top of the Tee and I pour the pellets in while the CO2 is running through the side arm.  That way I get no O2 ingress when dry hopping.

I don't go that far.  I just open the fermenter and drop them in.  I've timed it at 3 seconds.  I'm not worried about O2 pickup in that amount of time.

[erockrph]

There are quite a few variables here. My gut reaction is to say that the effect on flavor in the finished beer would be negligible given the amount of time and mixing, but I think everything is just conjecture without some actual measurements.

Couldn't you just rig up a connection to your airlock hole and run some CO2 in at a low PSI?

[majorvices]

Couldn't you just rig up a connection to your airlock hole and run some CO2 in at a low PSI?

This is what i did until i came up with the "bag" solution. It's difficult to get the gauge to dial in and match the flow of the beer. I had to degas it regularly.

The bag trick works great! If this is something that concerns you you should just try it and stop fussing about it. 

[majorvices]

here's the bag -- https://www.usplastic.com/catalog/item.aspx?itemid=122655

here's the spigot that fits -- https://www.usplastic.com/catalog/item.aspx?itemid=136411

[tommymorris]

Couldn't you just rig up a connection to your airlock hole and run some CO2 in at a low PSI?

This is what i did until i came up with the "bag" solution. It's difficult to get the gauge to dial in and match the flow of the beer. I had to degas it regularly.

The bag trick works great! If this is something that concerns you you should just try it and stop fussing about it. 

I use a bag also. I capture the co2 from the fermentation.

[lupulus]

First a solution.

To any fermenter blowoff system you can attach two ball lock connectors with an interconnection.
When you break the connection, no air will get in. Then you can connect a tank and fill the space with CO2 as you drain the fermenter.
You can also use this system to purge a keg with CO2 during fermentation.

You can use sulfites to minimize the damage as well.

Keg conditioning can also take care of minor oxygen pickup at transfer.

Best approximation of the damage you did would be to measure TPO in the final container, but it's impossible to quantify the exact damage. There are too many oxidation reactions occurring, many not involving oxygen directly.

I don't mean to scare you. My guess is that it's not a lot and it's up to you and your taste buds whether you can live with it or not.

Cheers!




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