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Old 09-18-2009, 03:59 PM   #1
AdamCanFly
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Default Weird question about yeast and oxygen

I'm new to the hobby and have done a fair amount of research, but still have a lot to learn. I'm on brew #2 and really enjoying it.
Heres my question. I've read that yeast requires oxygen to live, breed, and ferment. If thats the case, then why do we lock them in and air tight container? Wouldn't it be better to provide them with an oxygen rich environment? When I say that I realize that would be very hard to do, and avoid infection.

Humor me here. Lets say we have a room that is completely sterile, and a fermenter right in the middle. Now lets say that fermenter is a contraption that keeps the wort very aerated. Wouldn't the yeast go crazy and ferment a lot quicker?



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Old 09-18-2009, 04:05 PM   #2
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Quote:
Originally Posted by AdamCanFly View Post
I'm new to the hobby and have done a fair amount of research, but still have a lot to learn. I'm on brew #2 and really enjoying it.
Heres my question. I've read that yeast requires oxygen to live, breed, and ferment. If thats the case, then why do we lock them in and air tight container? Wouldn't it be better to provide them with an oxygen rich environment? When I say that I realize that would be very hard to do, and avoid infection.

Humor me here. Lets say we have a room that is completely sterile, and a fermenter right in the middle. Now lets say that fermenter is a contraption that keeps the wort very aerated. Wouldn't the yeast go crazy and ferment a lot quicker?
If you want to drop 20 grand on a sterile room and maintain it knock yourself out.

I just bucked up 50 bucks for an oxygenation system and it works great


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Old 09-18-2009, 04:18 PM   #3
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If you want to drop 20 grand on a sterile room and maintain it knock yourself out.

I just bucked up 50 bucks for an oxygenation system and it works great
So your saying it would work? Would it make the yeast do their job quicker?
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Old 09-18-2009, 04:26 PM   #4
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Pumping the wort full of oxygen before pitching allows the yeast to use this oxygen to reproduce to the levels needed to ferment your batch. After this, it is essential to keep your batch away from oxygen as much as possible. Introducing oxygen after the start of fermentation can cause oxidization in your final product, resulting in off-flavors.

One thing to think about regarding open fermentation vessels is that they are not really "exposed" to oxygen like you'd think. There's going to be a layer of CO2 over the beer keeping the oxygen out of the batch. Open fermentation by no means introduces oxygen to the beer in the same way using an air stone would.

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Old 09-18-2009, 04:30 PM   #5
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S. cerevisiae are actually very unique in that they function both aerobically (reproduction) and anaerobically (fermentation). During this latter process, you do not want to introduce oxygen in the system.
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Old 09-18-2009, 04:37 PM   #6
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Quote:
I've read that yeast requires oxygen to live, breed, and ferment.
No
Yes
No

As PseudoChef says, with oxygen you get growth, without it you get beer.
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Old 09-18-2009, 06:13 PM   #7
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S. cerevisiae are actually very unique in that they function both aerobically (reproduction) and anaerobically (fermentation). During this latter process, you do not want to introduce oxygen in the system.
+1 perfect simplified explanation!
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Old 09-18-2009, 06:17 PM   #8
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The main thing is that when there is oxygen, the yeast will not produce alcohol.

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Old 09-20-2009, 05:43 PM   #9
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so let me get this strait, starting off with a good airated batch will promote good growth of the yeast, but less alcohol in the brew.
or not airating the batch and letting the yeast ferment normally and produce more alcohol....or did i misunderstand somthing

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Old 09-20-2009, 08:34 PM   #10
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so let me get this strait, starting off with a good airated batch will promote good growth of the yeast, but less alcohol in the brew.
or not airating the batch and letting the yeast ferment normally and produce more alcohol....or did i misunderstand somthing
Close. You want aerated wort, so the yeast will reproduce. Eventually the oxygen runs out, and your now large quantity of yeast will ferment. If you didn't aerate, you won't have enough yeast to ferment the beer fully, and if you continuously aerated you would produce a lot of yeast but probably not much alcohol.


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