Fermentation Temps & Flavor Profile

[kmos]

Hey folks,

I tried searching around the forum and couldn't find a good answer for this, but I apologize in advance if this has been beaten to death.

I have a clarification question regarding when the esters and other flavor components are "locked in" during fermentation. My understanding is that it happens in the first week or so -- I have heard everything from "first three days" to "the length of primary".

While I am not an advocate for lazy brewing, it is a real pain trying to keep my temps down in the swamp cooler this time of year. So I guess I'm wondering at what point can I be a little less anal about keeping the cool water temps from creeping towards ambient temp (or maybe I should just brew Belgians til the Fall). I imagine it probably depends on the yeast, the beer, etc., but if anybody has any insight I would be curious to learn a bit more about this aspect of brewing.

Cheers!

 

[jubelale]

After the bulk of vigorous fermentation. Basically when the ferment starts to slow is when you can be less concerned with rising temp. This is usually after the third day or so with ale yeast strains but can depend on yeast health, pitching size, pitching temp, aeration/oxygenation, lag time, and strain.

 

[diS]

As said, it depends on yeast health, pitching rate, temperature..
Generally, yeast produce minimal flavor compounds during lag phase (first 15 hrs), but some precursors like acetolactate (which creates diacetyl) can be produced in this phase, especially at higher temps.
Esters, fusel alcohols, sulfur and most flavor compounds are produced during growth phase (4-5 days after lag phase). Production of these compounds is in correlation with temperature, so first few days is critical. After that, during stationary phase yeast will reabsorb most of this compounds and higher temperatures will induce re-absorption.

If you can, keep temps low at beginning and after few days when you see that kraeusen is falling and yeast is starting to flocculate you can raise the temp. 4-10 F for next 1-2 days, so yeast can clean by them-self.