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?
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.
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.
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.
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.
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?
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?
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.
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.
The only problem with using a tank to replace the headspace is that you have to have an extremely sensitive gauge to match the flow of the beer from the FV unless your FV can handle pressure. That’s why the bag works so well. You can literally walk away without worrying about over pressurizing the FV. If you have a pressurizable FV then using a tank is a no-brainer.
One cool thing about the siphon less FVs such as the Big Mouth Bubblers is that the valve has a hole in it that will allow Co2 gas to escape through your racking hose. I usually use a “IN” black QDC connected to the FV valve with tubing then I leave some pressure on the corny I plan to rack to. The keg depressurizes through the line and out the small hole on the FV valve, purging the tubing (obviously you have to vent the keg while racking). Then I close transfer with the bag attached to blow off.
The keg purge with sanitizer and remaining in keg connection through to racking works really well (especially with a cold crash). I always use that method when pressure fermenting due to its simplicity. I use a 14 gallon kegmenter and a 7 gallon Fermzilla All Rounder as my pressure fermentation vessels usually. The CO2 “catch bag” approach seems fine as to cold crashing - but with spare kegs and pressure fermenting, I don’t run into an implosion issue on cold crash.
Alternatively, (or in addition) you can simply hook up CO2 to the fermenter (or purged keg) and push beer to receiving keg through purged lines. I use a spare keg to pressurize with CO2 and purge all lines before racking with those tubes. It isn’t perfect and I have no way of knowing/measuring the extent of minimal O2 ingress (indeed some would say the use of packaged CO2 is not pure enough relative to O2 ingress and staling over time), but it is close enough to low ox as I am willing to get on the cold side.
I moved to keg priming and/or spunding and it makes things even easier as I don’t mind transferring with the lid open and letting the fermenter backfill with air at the tail end of primary fermentation. The reason was less about concerns while kegging, and more displeasure with the results I get when force carbonating. The difference between homebrew and commercial brew is that commercial breweries bubble CO2 through with minimal head pressure, while at home we inject in a closed system and all the oxygen impurities in your CO2 stays in the beer.
I got this from the LODO folks but I think it makes a bigger difference in shelf life than almost all of the other tricks combined.
