Author Topic: Oxygenation and Fermenter Head Space  (Read 1283 times)

Offline flbrewer

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Oxygenation and Fermenter Head Space
« on: March 03, 2016, 04:30:30 PM »
In thinking about reducing oxygenation, I started thinking about my almost 8 gallon Speidel that normally is only filled with about 5.5-6 gallons of beer. Is this a potential issue during the ~2 weeks my wort/beer sits there?

Secondly, what about kegs in the same situation? Here I will purge so in guessing it's not a problem.


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Offline dilluh98

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Re: Oxygenation and Fermenter Head Space
« Reply #1 on: March 03, 2016, 04:42:15 PM »
Impossible to know for sure but I've made 1 gal and 2.5 gal batches in a 3 gallon carboy of the same recipe (both APAs). I did not pick up on any oxidation issues with the 1 gal batch. On top of that I almost always just put a loose piece of foil over the top for the first few days of fermentation followed by a simple airlock for the remainder of the fermentation. Again, I'm not picking up on off flavors or dull hop flavor due to any oxidation. CO2 being heavier than air is a very fortunate thing for beer.  ;)

Offline flbrewer

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Re: Oxygenation and Fermenter Head Space
« Reply #2 on: March 03, 2016, 04:50:02 PM »

Impossible to know for sure but I've made 1 gal and 2.5 gal batches in a 3 gallon carboy of the same recipe (both APAs). I did not pick up on any oxidation issues with the 1 gal batch. On top of that I almost always just put a loose piece of foil over the top for the first few days of fermentation followed by a simple airlock for the remainder of the fermentation. Again, I'm not picking up on off flavors or dull hop flavor due to any oxidation. CO2 being heavier than air is a very fortunate thing for beer.  ;)
Why the foil?


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Offline Bob357

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Re: Oxygenation and Fermenter Head Space
« Reply #3 on: March 03, 2016, 04:53:04 PM »
Oxygen is a good thing prior to active fermentation. Once active fermentation begins, the CO2 produced will effectively purge any air out of the fermentor. CO2 is heavier than air so will do a good job of blanketing the beer even after active fermentation is complete.
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Offline narcout

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Re: Oxygenation and Fermenter Head Space
« Reply #4 on: March 03, 2016, 05:02:56 PM »
In thinking about reducing oxygenation, I started thinking about my almost 8 gallon Speidel that normally is only filled with about 5.5-6 gallons of beer. Is this a potential issue during the ~2 weeks my wort/beer sits there?

Aren't you using an airlock that lets gas out but not in?
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Offline flbrewer

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Re: Oxygenation and Fermenter Head Space
« Reply #5 on: March 03, 2016, 05:07:12 PM »

In thinking about reducing oxygenation, I started thinking about my almost 8 gallon Speidel that normally is only filled with about 5.5-6 gallons of beer. Is this a potential issue during the ~2 weeks my wort/beer sits there?

Aren't you using an airlock that lets gas out but not in?
Of course! I just thought that more open surface area in the fermenter would be not as ideal.

Offline 69franx

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Re: Oxygenation and Fermenter Head Space
« Reply #6 on: March 03, 2016, 05:22:16 PM »
It may not be ideal, but as long as you get active fermentation, the CO2 offgassing will displace the O2, just may take longer. I just used my 30L speidel for the first time, and it took an extra 24 hours to see airlock activity, though I could see the wort level rising in the fermenter( krausen that is not wort). Its just a lrger amount of O2 to displace than in a more normal scenario
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Offline dilluh98

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Re: Oxygenation and Fermenter Head Space
« Reply #7 on: March 03, 2016, 05:26:54 PM »
The foil is just to keep dust or anything else from falling into the fermentor while not putting pressure on the yeast initially (this is a know issue with some saison yeasts (WLP565 in particular)).

Regarding surface area, this is something to think about I suppose. It's not as if the CO2 blanket on top of the fermenting beer is an impermeable barrier that O2 absolutely cannot cross, it's just that the rate of O2 getting to the beer is likely quite low along with the fact that yeast can actively scrub O2 from your beer. 

Offline narcout

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Re: Oxygenation and Fermenter Head Space
« Reply #8 on: March 03, 2016, 05:31:58 PM »
Once you pitch your yeast, they take up any available oxygen in the wort (beer now I guess) pretty quickly.  Any additional O2 in the headspace that dissolves into the beer (if any) before it is displaced by CO2 from active fermentation will also be taken up by the yeast.  It's not going to cause you any problems.

Some small amount of O2 will probably make its way into your fermentor post fermentation, but I don't see how using a smaller fermentor would change that, and it's not an issue anyway.
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Offline HoosierBrew

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Re: Oxygenation and Fermenter Head Space
« Reply #9 on: March 03, 2016, 05:56:36 PM »
Agreed with the above advice. Justin - Basically all my beers are 5.5 gallon batches in 8 gallon buckets. Zero oxidation issues. Once the O2 is purged through the airlock by the CO2, it stays purged until you open to rack. Picture a nice, warm, fuzzy blanket of CO2 covering your beer.   ;)
Jon H.

Offline Hand of Dom

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Re: Oxygenation and Fermenter Head Space
« Reply #10 on: March 03, 2016, 06:18:27 PM »
I often make small batches (10/15L), and ferment them in my 30L bucket.  Never had any issues with oxygenation, and I tend to leave it for 3 weeks before I bottle it.
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Offline reverseapachemaster

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Re: Oxygenation and Fermenter Head Space
« Reply #11 on: March 03, 2016, 08:28:30 PM »
I've fermented as little as one gallon in an eight gallon bucket. It's not really an issue on headspace unless you are aging that beer for a considerable period of time (months, minimum). Eventually oxygen is going to make its way into the headspace in any fermentation vessel but it's not going to be enough to stale the beer unless given too much time. The homebrewing belief that CO2 forms a permanent barrier is not accurate. Atmospheric air, with it's oxygen content, makes its way in and the gases mix. If that didn't happen then all oxygen respiring life would die due to the blanket of CO2 hugging the planet.
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Offline HoosierBrew

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Re: Oxygenation and Fermenter Head Space
« Reply #12 on: March 03, 2016, 08:44:40 PM »
I've fermented as little as one gallon in an eight gallon bucket. It's not really an issue on headspace unless you are aging that beer for a considerable period of time (months, minimum). Eventually oxygen is going to make its way into the headspace in any fermentation vessel but it's not going to be enough to stale the beer unless given too much time. The homebrewing belief that CO2 forms a permanent barrier is not accurate. Atmospheric air, with it's oxygen content, makes its way in and the gases mix. If that didn't happen then all oxygen respiring life would die due to the blanket of CO2 hugging the planet.



Agreed. There will be gradual mixing of gases over a long period of time, for sure. I just meant that over the course of my normal brewing (ie., beer in fermenter not over a month), I haven't experienced that to any degree that my beer showed oxidation.
Jon H.