Author Topic: racking to limit attenuation  (Read 2159 times)

Offline mmitchem

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Re: racking to limit attenuation
« Reply #15 on: March 12, 2013, 09:55:38 AM »
The yeast will clean up, or take back up, things like diacetyl at the end of fermentation. The thing is...to do so, the yeast have to be active and in suspension. Since you cold crashed your secondary and sent your yeast to the bottom (dormant), they will not have the chance to do so.
I am not convinced that this is 100% the case - I believe it will slow, but not stop the process.  I think it comes down to surface area and availability.  By cold crashing you massively reduce the surface area of yeast exposed to the beer.  You also drastically reduce that yeasts' exposure to compounds that need to get cleared up.  During an active or semi active fermentation the CO2 bubbling out is constantly mixing the beer, so the non-flocculating yeast and the compounds like diacetyl are being mixed throughout.  When the beer has been chilled and CO2 is no longer coming out, the compounds have to diffuse through the beer to come into contact with the yeast, which is now mostly at the bottom.  So I think it is these two factors, combined with the lower yeast activity due to the cold, that keep the yeast from cleaning up the beer.  And I don't mean to minimize the decreased activity due to the lower temperature, but it is not zero.

Solid theory there if I understand it correctly...What you are saying Tom is that the yeast are still able to take up diacetyl that they are in contact with, but that amount decreases as they pile up at the bottom of the fermenter, hence the surface area reduction. Am I reading that correctly?
« Last Edit: March 12, 2013, 09:58:56 AM by mmitchem »
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Offline tschmidlin

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Re: racking to limit attenuation
« Reply #16 on: March 12, 2013, 10:12:28 AM »
Tom - do you think this is why you don't need a diacetyl rest with more powdery yeasts like WLP001/1056? Or is it that some yeasts are just better at completing fermentation in less-than-ideal conditions?
I'm sure flocculation and strain variability lays a role.

Solid theory there if I understand it correctly...What you are saying Tom is that the yeast are still able to take up diacetyl that they are in contact with, but that amount decreases as they pile up at the bottom of the fermenter, hence the surface area reduction. Am I reading that correctly?
Yes, exactly.  Although their ability to do so is still reduced by the lower temps.
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Offline mmitchem

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Re: racking to limit attenuation
« Reply #17 on: March 12, 2013, 10:24:09 AM »
Tom - do you think this is why you don't need a diacetyl rest with more powdery yeasts like WLP001/1056? Or is it that some yeasts are just better at completing fermentation in less-than-ideal conditions?
I'm sure flocculation and strain variability lays a role.

Solid theory there if I understand it correctly...What you are saying Tom is that the yeast are still able to take up diacetyl that they are in contact with, but that amount decreases as they pile up at the bottom of the fermenter, hence the surface area reduction. Am I reading that correctly?
Yes, exactly.  Although their ability to do so is still reduced by the lower temps.

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Offline ynotbrusum

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Re: racking to limit attenuation
« Reply #18 on: March 12, 2013, 06:52:51 PM »
Tom - do you think this is why you don't need a diacetyl rest with more powdery yeasts like WLP001/1056? Or is it that some yeasts are just better at completing fermentation in less-than-ideal conditions?
I'm sure flocculation and strain variability lays a role.

Solid theory there if I understand it correctly...What you are saying Tom is that the yeast are still able to take up diacetyl that they are in contact with, but that amount decreases as they pile up at the bottom of the fermenter, hence the surface area reduction. Am I reading that correctly?
Yes, exactly.  Although their ability to do so is still reduced by the lower temps.

I rarely do D-rests, but I leave my lager beer in the primary for around a month for this reason.
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Offline pinnah

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Re: racking to limit attenuation
« Reply #19 on: March 13, 2013, 06:36:34 AM »
AHA Forum Baby! Spreading the knowledge and making better brewers one post at a time! Woooo!!!

Amen brother.  I really appreciate the knowledge and experience.

I got both  8) and  :-[ !


Soooo, next obvious question for me is:
if I am destined for a green apple sulfuric butter honey lager

how soon might these off flavors develop?  Are they already present?  Develop over time?

Offline Jeff M

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Re: racking to limit attenuation
« Reply #20 on: March 14, 2013, 09:30:53 AM »
if i understand all of this correctly they are already present.

Couldnt he add some more fermentables and remix the yeast and have them complete the process to save his beer?
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Offline garc_mall

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Re: racking to limit attenuation
« Reply #21 on: March 14, 2013, 09:37:32 AM »
AHA Forum Baby! Spreading the knowledge and making better brewers one post at a time! Woooo!!!

Amen brother.  I really appreciate the knowledge and experience.

I got both  8) and  :-[ !


Soooo, next obvious question for me is:
if I am destined for a green apple sulfuric butter honey lager

how soon might these off flavors develop?  Are they already present?  Develop over time?

They should already be present, and dissipate over time (as yeast cleans up their by-products). If you don't taste it currently, you should be fine.
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Fermenting: Flanders Red, Saison