[kylekohlmorgen]

Off-flavors from settled yeast aren't a factor of time as much as they are yeast health. You can definitely buy a good amount of time if you pitched the right amount of healthy yeast to start, provided ample nutrients (O2, FAN, Ca, Zn, etc.), properly controlled the temperature of fermentation, and maintained controlled temp after fermentation is complete.

After a longer-than-normal primary (>2 weeks or so), I'm more concerned with the yeast slurry than the beer sitting on top.

I recently wrapped up an experiment that was supposed to gauge the repeat-ability of brewing the same beer with multiple generations of a sacch/brett mixed slurry.

Because the majority of the mix was Wyeast 3724, the first generation stalled and required about a month in primary at 75F.

Even though the 2nd and 3rd generations were ready for transfer much sooner, the damage was done. The 2nd gen beer is lovely but has the slightest hint of warmth from higher alcohols. The 3rd beer is a complete mess.

[Joe Sr.]

Even though the 2nd and 3rd generations were ready for transfer much sooner, the damage was done. The 2nd gen beer is lovely but has the slightest hint of warmth from higher alcohols. The 3rd beer is a complete mess.

To what are you attributing that differential in results?  Stressed yeast from sitting in the fermenter?  I'm not sure I buy that theory.  I've stored yeast for long periods and not had off flavors from subsequent generations.

Just off the top of my head I would think that repeatability with subsequent generations of a mixed slurry is difficult since you can't control the proportion of the components of the slurry.  I'm not intending to crap all over your experiment, so apologies if this comes across that way.  Quite the opposite, I think those sorts of experiments are important for each of us to better understand our ingredients and processes.

[kylekohlmorgen]

Even though the 2nd and 3rd generations were ready for transfer much sooner, the damage was done. The 2nd gen beer is lovely but has the slightest hint of warmth from higher alcohols. The 3rd beer is a complete mess.

To what are you attributing that differential in results?  Stressed yeast from sitting in the fermenter?  I'm not sure I buy that theory.  I've stored yeast for long periods and not had off flavors from subsequent generations.

Just off the top of my head I would think that repeatability with subsequent generations of a mixed slurry is difficult since you can't control the proportion of the components of the slurry.  I'm not intending to crap all over your experiment, so apologies if this comes across that way.  Quite the opposite, I think those sorts of experiments are important for each of us to better understand our ingredients and processes.

Definitely valid concerns, and I definitely jumped to this conclusion (which I just got done complaining about in another thread  )

I intend on repeating the experiment with a conical to eliminate this variable. The decline in yeast health could have been caused by something else I'm not accounting for. It was my initial conclusion because, in general, my yeast handling practices are pretty good.

If anything, the extended period in primary didn't help. In general, slurry viability will be higher when stored cold vs at fermentation temps. I just can't think of anything else that would have affected the viability so dramatically.

[Joe Sr.]

Cool.  I'll look for that thread.  I don't care for brett, so I may have skipped the thread if it was referenced.

FWIW, I typically build up a starter from my slurries so that may help reduce any impacts from older stressed yeast from the previous ferment.  But that would only further complicate your ability to gauge percentages.