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Old 01-08-2013, 04:56 AM   #1
Arrheinous
 
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So I'm brewing a Scottish ale tonight and I have had plenty of time to think.

If I were to ask about how to properly aerate wort in a big carboy with plenty of exposure to the air, people wouldn't recommend that I simple shake the carboy - swing that thing around like I'm a Lord of the Rings movie extra - because they would say that is barely effective.

However, if I were to ask about shaking a rather sealed carboy during fermentation to agitate settled yeast, people will openly worry about oxygen getting in! I've read some people don't even so much as touch the fermenters during this phase for fear of oxidation.

Which way is it?

 
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Old 01-08-2013, 05:12 AM   #2
Zamial
 
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I believe you are confusing oxygen, which is vital for yeast reproduction, often called aeration for an off flavor called oxidation. Oxidation can happen with very little oxygen present.

FWIW I NEVER recommend picking up a carboy full of anything, you are an accident waiting to happen. Get an airstone and O2 tank or a pump and save yourself and the carboy.

It doesn't matter if you venturi, shake, whisk, aerate with a stone and pump you will only ever get 8ppm into solution. Yeast prefer 10ppm at a minimum. 60 seconds of pure o2 with a stone will get you 12ppm.
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Old 01-08-2013, 05:23 AM   #3
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It's both. There is no contradiction.

 
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Old 01-08-2013, 05:25 AM   #4
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Edit. What zamial said.
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Old 01-08-2013, 01:13 PM   #5
hogwash
 
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Yeast need oxygen to do their thing, so before fermentation = oxygen good. After fermentation, exposure to oxygen can lead to oxidation and cardboard-y off flavors, so after fermentation = oxygen bad.

And also what zamial said.

 
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Old 01-08-2013, 05:46 PM   #6
Arrheinous
 
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Quote:
Originally Posted by Zamial View Post
FWIW I NEVER recommend picking up a carboy full of anything, you are an accident waiting to happen. Get an airstone and O2 tank or a pump and save yourself and the carboy.
I use plastics ones and I haven't actually lifted them up to aerate them - done more of a vortexy rotation while it sits on the ground. Performing a pseudo hammer-throw with the carboy was just for example. I try to splash it around in the kettle after cooling or during the pour into the fermenter. I'm working on putting together an aquarium pump setup but it's either that or a propane burner setup for now.

My major issue is that imparting air isn't said to be effective when you can shake up an unpitched wort however you want but then the effect of air becomes an issue after fermentation and people worry about the slightest introduction of air at that point.

But if even shaking the thing up isn't going enough to impart air then why is it going to be a problem for something less intense like trying to agitate settled yeast?

Maybe I'm not splitting enough hairs when it comes to taking about oxygen vs. air but oxygen is the only thing I can think of in air that will be reactive.

 
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Old 01-08-2013, 05:49 PM   #7
hoppyhoppyhippo
 
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While I don't think it would be a massive problem, the primary reason is that yeast need oxygen to do their job, as more yeast settle to the bottom they aren't active anymore, even rousing them may not get them active, so if you introduce more oxygen to inactive yeast, you're in trouble.

 
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Old 01-08-2013, 06:35 PM   #8
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Quote:
Originally Posted by Arrheinous View Post
But if even shaking the thing up isn't going enough to impart air then why is it going to be a problem for something less intense like trying to agitate settled yeast?
you're missing the point. while shaking it may not provide as much air into solution as the yeast would like, it imparts way more than enough to oxidize a beer. oxygen is used for yeast reproduction, once they stop reproducing any more oxygen exposure leads to oxidation.

 
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Old 01-08-2013, 07:57 PM   #9
shyanny
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It always annoys me when i see posts that say you have to do this or that in order to make good beer. As in the case for using an oxygen tank to aerate the wort, i dont and i'm quite certain that good beer has been made throughout history without the use of an O2 tank and oxygen stone. The truth is you're beer will be fine using agitation method of aeration. Will your fermentation be more vigorous with pure O2? Maybe but doubtful. Ive made lotsa batches using the agitation method and have great results. As for oxidation after fermentation, i transfer my beer manually into a bottling bucket. I am careful not to splash the beer around but im not fanatical about it. Again, ive never had an issue with oxidation either. Relax... Hav a home brew.

 
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Old 01-08-2013, 08:22 PM   #10
bovineblitz
 
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Shaking is quite effective in oxygenating the wort. I use O2 but there was a pretty nice article comparing shaking vs using an aquarium pump (pumping ambient air into the solution). They found that the pump didn't do much and the shaking was quite effective, it was capable of infusing a good amount of O2. Using pure O2 is more effective, but shaking is sufficient in most cases.

 
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