Stirred Fermentation

I guess it could also be there was some settling as you were transferring the wort to the respective containers. Do you use a hopback? just trying to think of other things that may have contributed to a different wort profile in different containers.

mightynintendo said:

I guess it could also be there was some settling as you were transferring the wort to the respective containers. Do you use a hopback? just trying to think of other things that may have contributed to a different wort profile in different containers.

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Nope, no hopback.
Thinking back now though, I remember one of the unstirred carboys had a longer lag time than the other; maybe it had something to do with a difference in oxygen levels. The two unstirred carboys were just shaken for a few minutes each. I wasn't the one who did the shaking though, so maybe one got less time than the other.

was the carboy with the diacetyl flavors the one that lagged longer?

I think we may be on to something with the oxygen levels.

mightynintendo said:

was the carboy with the diacetyl flavors the one that lagged longer?

I think we may be on to something with the oxygen levels.

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At this point, unfortunately, I can't say with certainty which one it was.

Sulli said:

At this point, unfortunately, I can't say with certainty which one it was.

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Bottom line is you didn't get the oxidation flavors the naysayers always said would happen even though the brew was airlocked? Never understood that reaction.

Hermit said:

Bottom line is you didn't get the oxidation flavors the naysayers always said would happen even though the brew was airlocked? Never understood that reaction.

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He also only kept it under stirred fermentation for four days.

Keeping it stirred beyond some arbitrary fermentation activity level would increase the risk of oxygenation if you were opening the container for reasons like checking gravity and what-not.

I agree that there should be little reason for concern as long as there is active fermentation going on and there is no chance outside air is getting inside the container.

mightynintendo said:

He also only kept it under stirred fermentation for four days.

Keeping it stirred beyond some arbitrary fermentation activity level would increase the risk of oxygenation if you were opening the container for reasons like checking gravity and what-not.

I agree that there should be little reason for concern as long as there is active fermentation going on and there is no chance outside air is getting inside the container.

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Letting air in shouldn't be any different, stirred or not. But, yeah. For purposes of this experiment I can see where it would be a problem.

Hermit said:

Letting air in shouldn't be any different, stirred or not. But, yeah. For purposes of this experiment I can see where it would be a problem.

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Why wouldn't it be different? A stirred fermentation would have a higher gas exchange rate and would result in increased oxidization if there wasn't adequate yeast activity to consume any oxygen that wandered into the beer.

mightynintendo said:

Why wouldn't it be different? A stirred fermentation would have a higher gas exchange rate and would result in increased oxidization if there wasn't adequate yeast activity to consume any oxygen that wandered into the beer.

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That's another thing I've wondered about. As long as you have active yeast, how much do you have to worry about oxidation anyhow? I bottle condition, generally after three weeks in the primary, and it isn't an issue then. I have some beers over a year old. Chris White seems to think the yeast scavenge available oxygen pretty rapidly.

Hermit said:

That's another thing I've wondered about. As long as you have active yeast, how much do you have to worry about oxidation anyhow? I bottle condition, generally after three weeks in the primary, and it isn't an issue then. I have some beers over a year old. Chris White seems to think the yeast scavenge available oxygen pretty rapidly.

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As long as the yeast is active I think the risks of oxygenation are low. I can't speak with too much authority here as I am by no means a mycologist. However, you really don't want to introduce oxygen to your beer at any point after you pitch yeast early on. Alcohol is only created under anaerobic conditions. Like I said before with an active fermentation I don't think oxygen would have the ability to get into a well-sealed container with or without a stir bar. Once the activity level decreases and the yeast stop producing as much CO2, the chances of introducing oxygen to a stirred fermentation, especially after breaking the seal to check gravity, are probably higher than if it was not being stirred due to the increased gas exchange capacity.

Bottle conditioning has no problems with oxygenation if you're careful not to splash or otherwise aerate the beer.

I wouldn't want to introduce any O2 during a stirred ferment if it were me. The initial O2 for aeration is all you want, unless you are making a starter.