Biproducts of Temperature vs. activity

[bovinejony]

Hey good people,

My question is regarding the affects that temperature has on undesirable biproducts of fermentation, especially how they may develop over their range of activity. Put in lamen terms: does biproduct production occur most during the yeast's peak activity levels of fermentation (0-120 hours), and less in the post-peak activity period (~120 hours-month), where the temperature of the fermentation during the latter period is less influential?

A piggy-back question to the one above would also ask; (assuming the yeast become dormant/inactive after first week of fermentation or so) do dormant yeast still produce biproducts where a high temperature could lead to off-flavors even after most of the wort has been converted?

I live in SoCal and have struggled to keep my swamp coolers in the low 60's. My first few beers have all had a hot alcohol taste due to high fermentation temps, which I'd like to correct for.

Do dormant yeast require as good of conditions as the peak-state yeast?
(please assume in all answers that the FG has been reached before the yeast's state is considered "dormant")

Thanks in advance.

 

[ASantiago]

1. I understand that the vast majority of the byproducts are created during the lag phase, which is basically the initial phase which includes respiration and reproduction. There may be byproducts created at other stages though. But temp control at the very beginning seems to be, if we were to assign degrees of importance, relatively more important than at other times, understanding of course that temp control throughout, from starter to natural carbonation, is all important.

2. Re: the piggy back question, I'm not sure how to answer that. I don't think the yeast go dormant after the first week of fermentation. You may see less activity and for sure some (maybe most?) of the yeast may start flocculating, but they are very much active. In fact, that's when they start cleaning up the byproducts they created in the first place. At this time, you want a slightly higher (5-10F) temp than fermentation in order to encourage higher activity for the clean up job.

3. I'd say that dormant yeast still should be kept at an "agreeable" temp (whatever *that* means) if they are going to be in contact with the beer. Else, you are either throwing them out, in which case you don't care, or you are keeping them for reuse, in which case you need to drop the temp to as cold as possible until reuse in a starter.

BTW, the recent book "Yeast" is a phenomenal source for this kind of info. I'm in the middle of reading it and finding it very informative.

 

[bovinejony]

Thanks for the thorough answer.

Your answer to the second question raises another question in my mind: does the temperature difference in the fermentation vessel from ambient temperatures remain the same (5-10degF + ambient) post primary activity? Example: during the first week of fermentation I kept my ambient temps ~60degF hoping that the fermentation temps were around 65-70F. After the first week is it safe to assume that the temperature caused by active fermentation is lower, and the increase from ambient temps is only say 2-5degF?