Author Topic: factors contributing to diacytel  (Read 1539 times)

Offline astrivian

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factors contributing to diacytel
« on: July 08, 2011, 12:09:31 PM »
What are the factors that can contribute diacytel (butter flavor) in beer? I know the yeast strain and infection are two of them. Would high fermentation temperature also result in diacytel?
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Offline tom

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Re: factors contributing to diacytel
« Reply #1 on: July 08, 2011, 12:55:42 PM »
Not unless it stressed the yeast.  Sometimes a "diacetyl rest" is done to lower the diacetyl by raising the temperature toward the end of fermentation.
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Offline mabrungard

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Re: factors contributing to diacytel
« Reply #2 on: July 08, 2011, 12:58:05 PM »
High fermentation temperature is less likely to cause diacetyl production.  Prematurely dropping your fermentation temperature before the yeast have reassimilated the diacetyl is a much more likely cause.
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Offline bonjour

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Re: factors contributing to diacytel
« Reply #3 on: July 08, 2011, 02:11:19 PM »
Oxidation can also cause it by oxidizing diacetyl pre-cursors post ferment.
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Offline bluesman

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Re: factors contributing to diacytel
« Reply #4 on: July 08, 2011, 02:16:33 PM »
High fermentation temperature is less likely to cause diacetyl production.  Prematurely dropping your fermentation temperature before the yeast have reassimilated the diacetyl is a much more likely cause.

Jamil Z says the opposite. He believes an initial high ferm temp will potentially produce a higher level of diacetyl than a cooler start.

Reducing diacetyl near the end of fermentation can be accomplished by raising the beer temp to 65F or thereabouts for a couple of days.

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Offline astrivian

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Re: factors contributing to diacytel
« Reply #5 on: July 08, 2011, 03:07:59 PM »
This is interesting. I did a batch the way i did it before, which i know is wrong, just to see. The fermentation temperature varied between 60 and 80 degrees (night and day). I wont do that again, but i was curious.

I did do a diacytel rest but maybe should have done it a few days longer. I read that highly flocculant yeast are not as good as absorbing diacytel as well, but the yeast i used (WLP400 - Belgain wit ale) says it is low flocculating.

Maybe a higher fermentation temperature causes the yeast to speed up too much and die off before they get a chance to mellow and absorb some of the butter?
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Offline zorch

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Re: factors contributing to diacytel
« Reply #6 on: July 08, 2011, 03:22:30 PM »

I think the fluctuating temperatures are the real culprit.  Many yeast strains will respond to a 'sudden' drop in temperature by dropping out.

I am assuming that the temperatures you gave were the ambient temps, and not the actual fermentation temperatures, but even so I would suggest you'll have much better results if you can find a way to keep the temperature in a more narrow range.

Offline tom

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Re: factors contributing to diacytel
« Reply #7 on: July 08, 2011, 08:09:42 PM »
High fermentation temperature is less likely to cause diacetyl production.  Prematurely dropping your fermentation temperature before the yeast have reassimilated the diacetyl is a much more likely cause.
Jamil Z says the opposite. He believes an initial high ferm temp will potentially produce a higher level of diacetyl than a cooler start.
Reducing diacetyl near the end of fermentation can be accomplished by raising the beer temp to 65F or thereabouts for a couple of days.
Diacetyl is a natural part of fermentation.  Alpha-acetolactic acid is transformed into diacetyl by an oxidation reaction.  This is absorbed into the yeast cell and metabolized into 3,2-butanediol which has a much higher taste threshold than diacetyl.  The taste threshold of diacetyl is in the ppb (parts per billion) range.  Both of these reactions are increased proportional to the temperature.  So the usual plan is to ferment cool to decrease diacetyl formation, then increase the temperature (about 2/3 of the way through the fermentation) to increase diacetyl metabolization.  So don't chill the fermentation too quickly.  And different yeasts will produce and remove diacetyl at different rates so these are all yeast specific.
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Re: factors contributing to diacytel
« Reply #8 on: July 09, 2011, 09:23:23 AM »
Jamil Z says the opposite. He believes an initial high ferm temp will potentially produce a higher level of diacetyl than a cooler start.

I'd have to hear an explanation for that....
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Re: factors contributing to diacytel
« Reply #9 on: July 09, 2011, 09:55:36 AM »
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Re: factors contributing to diacytel
« Reply #10 on: July 09, 2011, 10:47:46 AM »
Life begins at 60.....1.060, that is!

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Offline astrivian

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Re: factors contributing to diacytel
« Reply #11 on: July 09, 2011, 05:45:54 PM »
Hmm. That article was interesting. I still think a fermentation temperature of close to 85 degrees had something do to with it:

Quote
Diacetyl production and reduction are strongly influenced by temperature, and the rates for both increase as temperature increases. Thus, an ale fermented at 20 degrees C (68 degrees F) typically has a higher diacetyl peak than, say, a lager fermented at 10 degrees C (50 degrees F).

My thinking is that the extraordinary temperature caused a spike in diacetyl that the yeast was simply not able to keep up with. I wonder if the temperature fluctuation between 55 and 85 degrees caused the yeast to flocculate early (or just plain die), resulting in an inability to convert diacetyl after fermentation.

Like i said though, that was my last haphazard brew. Going forward i am paying far closer attention to details like temperature.
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Offline bluesman

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Re: factors contributing to diacytel
« Reply #12 on: July 09, 2011, 07:13:38 PM »
High fermentation temperature is less likely to cause diacetyl production.  Prematurely dropping your fermentation temperature before the yeast have reassimilated the diacetyl is a much more likely cause.
Jamil Z says the opposite. He believes an initial high ferm temp will potentially produce a higher level of diacetyl than a cooler start.
Reducing diacetyl near the end of fermentation can be accomplished by raising the beer temp to 65F or thereabouts for a couple of days.
Diacetyl is a natural part of fermentation.  Alpha-acetolactic acid is transformed into diacetyl by an oxidation reaction.  This is absorbed into the yeast cell and metabolized into 3,2-butanediol which has a much higher taste threshold than diacetyl.  The taste threshold of diacetyl is in the ppb (parts per billion) range.  Both of these reactions are increased proportional to the temperature.  So the usual plan is to ferment cool to decrease diacetyl formation, then increase the temperature (about 2/3 of the way through the fermentation) to increase diacetyl metabolization.  So don't chill the fermentation too quickly.  And different yeasts will produce and remove diacetyl at different rates so these are all yeast specific.

Well said Tom...I couldn't have said it any better myself.  ;)

Jamil Z says the opposite. He believes an initial high ferm temp will potentially produce a higher level of diacetyl than a cooler start.

I'd have to hear an explanation for that....

JZ says that a higher ferm temp produces more of the precursers that are responsible for diacetyl formation and visa versa. Therefore he recommends pitching low to supress the precursers and ultimately produce a beer with miminal diacetyl.
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Offline astrivian

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Re: factors contributing to diacytel
« Reply #13 on: July 10, 2011, 09:11:07 AM »
JZ says that a higher ferm temp produces more of the precursers that are responsible for diacetyl formation and visa versa. Therefore he recommends pitching low to supress the precursers and ultimately produce a beer with miminal diacetyl.

For pitching low, what sort of temperatures are we talking about?

Also, i notice it says raising the temperature to around 65, which is way lower than i can achieve in the hot Denver summers. The lowest i can get is 72. What sort of techniques to you all use to lower fermentation temperature in the summer?
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Online denny

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Re: factors contributing to diacytel
« Reply #14 on: July 10, 2011, 09:20:13 AM »
For me, pitching low means in the 62-65 range.  That's my standard practice.
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