Author Topic: Stirring the fermenter  (Read 509 times)

Offline majorvices

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Re: Stirring the fermenter
« Reply #15 on: Today at 05:57:42 AM »
I'd be concerned with bad effects of keeping the yeast in a growth phase for that long. You may want to reinvigorate yeast growth with some o2 for super high gravity beers but for anything under 1.100 a healthy dose of aeration and an adequate pitch of viable yeast and a good should do the trick.

Be aware that excessive yeast growth in beer can cause problems with head retention and solventy flavors.

Offline santoch

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Re: Stirring the fermenter
« Reply #16 on: Today at 08:48:53 AM »
yeast produce ethanol and co2 when they go into anaerobic fermentation (e.g. without oxygen).  To keep adding oxygen is counter to that end.
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Offline narvin

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Re: Stirring the fermenter
« Reply #17 on: Today at 09:16:47 AM »
I thought the crabtree effect meant that all growth in regular gravity wort was due to fermentation, and O2 was just used for building ergosterol and other during the process.  AKA there are no actual phases in fermentation unless you're propagating yeast at a very low gravity (< 1.010).
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Offline denny

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Re: Stirring the fermenter
« Reply #18 on: Today at 10:51:34 AM »
I thought the crabtree effect meant that all growth in regular gravity wort was due to fermentation, and O2 was just used for building ergosterol and other during the process.  AKA there are no actual phases in fermentation unless you're propagating yeast at a very low gravity (< 1.010).

AFAIK, you are correct.
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Offline santoch

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Re: Stirring the fermenter
« Reply #19 on: Today at 01:20:47 PM »
I thought the use of O2 indicates respiration as opposed to fermentation, with no ethanol production during that time, due to the different pathway.

If I am wrong, I apologize.

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Offline denny

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Re: Stirring the fermenter
« Reply #20 on: Today at 01:40:51 PM »
I thought the use of O2 indicates respiration as opposed to fermentation, with no ethanol production during that time, due to the different pathway.

If I am wrong, I apologize.

The O2 is to synthesize sterols to keep cell walls flexible for budding.  And the Crabtree Effect states that in the presence of a >.05% glucose solution, like wort, fermentation begins immediately.  As Narvin pointed out, there are no distinct phases.  It all happens at once.
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Offline santoch

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Re: Stirring the fermenter
« Reply #21 on: Today at 04:06:40 PM »
Ok, thanks for the correction.
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Offline drgmg

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Re: Stirring the fermenter
« Reply #22 on: Today at 05:18:25 PM »
Great conversation!