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Ferment Temperature Change

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elollerenshaw

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I have read in a book 'New Brewing Lager Beer' by Noonan that you shouldn't change the ferment temp by more than 3 degrees per day.

E.g. when increasing temp for a diacetyl rest or reducing temp for lagering.

Has anyone found this to be true?
I assume 'cold crash' means dropping temp very quickly.
 

Wolfy

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A similar subject is covered in the 'Yeast' book, where they essentially say that yeast does not like quick temperature changes, however if you are chilling it to low temperatures it does not really matter very much because the yeast is essentially pushed into dormancy.
 

glenwal

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if you are chilling it to low temperatures it does not really matter very much because the yeast is essentially pushed into dormancy.
Correct me if i'm wrong Wolfy (you know alot more about yeast than I), when lagering (in the true sense of the word, not as in leaving beer in the fermenter for an extra week or 2) you generally want to chill to low temperatures very slowly since you want the yeast to actually stay just on the verge of being going to sleep (ie. still on the awake side) for the lagering stage, where as crash chilling will pretty much shock the yeast to sleep

like putting a frog in a pot and bringing it to the boil (it'll happily sit in the nice warm bath till he's boiled to death) vs throwing a frog in a pot of boiling water (and he'll jump right back out of the pot).
 

kevin_smevin

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I have read in a book 'New Brewing Lager Beer' by Noonan that you shouldn't change the ferment temp by more than 3 degrees per day.

E.g. when increasing temp for a diacetyl rest or reducing temp for lagering.

Has anyone found this to be true?
I assume 'cold crash' means dropping temp very quickly.
Chilling beer at the end of fermentation shouldn't be done too quickly - it can result in stressing yeast out which cause them to do all kinds of crazy things like spew out all the esters and things they have sitting happily inside their cell walls. I cant remember how quick is too quick though. It's in the yeast book by jamil and chris white though
 

Yob

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I quite habitually raise temps toward the end by small increments (0.5'c a day or so) but when it comes to CC'ing, turn it down to 2'c and walk away..

I dont remember reading not to, by belief is it's the raising of temps significantly that is not good to do.

Unless you are using liquid nitrogen to crash, it all happens relatively slowly doesnt it? I know my fridge takes at least 12-18 hours to bring it down from 19-20'c.

Yob
 

Wolfy

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Correct me if i'm wrong Wolfy (you know alot more about yeast than I), when lagering (in the true sense of the word, not as in leaving beer in the fermenter for an extra week or 2) you generally want to chill to low temperatures very slowly since you want the yeast to actually stay just on the verge of being going to sleep (ie. still on the awake side) for the lagering stage, where as crash chilling will pretty much shock the yeast to sleep

like putting a frog in a pot and bringing it to the boil (it'll happily sit in the nice warm bath till he's boiled to death) vs throwing a frog in a pot of boiling water (and he'll jump right back out of the pot).
You're analogy is spot on.

Information is on page 114-115 of the Yeast book.
What I was talking about above is Cold Crashing (which I thought was what the OP was asking about) where they say that below 4C not much happens nor does it make much difference if it's done quickly (negative impact on some esters and yeast repitching if it's crashed in less than 6 hours).

When lagering the temperature is reduced slowly (1C per day) to avoid sending the yeast into dormancy, is generally kept just above 4C and requires precise control.

Two different processes and you're correct with both.


I quite habitually raise temps toward the end by small increments (0.5'c a day or so) but when it comes to CC'ing, turn it down to 2'c and walk away..

I dont remember reading not to, by belief is it's the raising of temps significantly that is not good to do.

Unless you are using liquid nitrogen to crash, it all happens relatively slowly doesnt it? I know my fridge takes at least 12-18 hours to bring it down from 19-20'c.
You've been told now (less than 6 hours can be bad for esters and repitching), but - like yours - my fridge is old and can only bring the temps down slowly anyway.
 

elollerenshaw

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Thanks for the advice. I will stick to a slow rate of change, to be safe.

Sounds like the yeast book is really good. I better get myself a copy
 

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