Propagating bad yeast

Back in September I made a beer with a packet of US-05, but the temperature got a little warm in my basement (around 74, so with fermentation, the wort might have been close to 80). I then pitched another beer onto this yeast cake and when that one was done, Next I made a 10gal batch and split the yeast cake between two fermenters.

After the first batch, the temps in my basement have lowered significantly and the beers have been fermenting in the lower 60s. I just got around to tapping the first beer which I fermented too high and it has a strong off flavor, I'd best describe it as a detergent taste. I attributed this flavor because of the high fermentation temperatures. I figured "time cures all", so I took this beer out of the kegerator and plan to let it age for a while. So I put the second beer on tap and it has a similar detergent taste despite fermenting in the mid to lower 60s.

So my question is, once the yeast is fermented at a high temperature, do the yeast mutate and should I not have used them in subsequent batches or could there be something else going wrong here?

Fermenting at high temperatures is IMHO the bigest problem for new brewers. The bugs can get going before the yeast does and once that happens "Game over". If you re-use that yeast then you doom the next beer too. It is only a couple of dollars for new dried yeast and temperature control is a must. Use a water bath in an ice cube (brand) name cooler. Yooper has a nice setup.

another idea: here

I'm usually pretty good about monitoring the temperature in my basement and putting it in a swamp cooler, but the weather caught me by surprise and we had a few days in the mid 80s in late September (rare for Minnesota).

Glad I dumped this yeast down the drain and got some new yeast this weekend. One bad part about filling your pipeline is that you won't know if the beer is good or bad for weeks or maybe even months.

drunkatuw said:

I'm usually pretty good about monitoring the temperature in my basement and putting it in a swamp cooler, but the weather caught me by surprise and we had a few days in the mid 80s in late September (rare for Minnesota).

Glad I dumped this yeast down the drain and got some new yeast this weekend. One bad part about filling your pipeline is that you won't know if the beer is good or bad for weeks or maybe even months.

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That's why it is so important to know the yeast is good (uninfected). If you taste the yeast slurry it is a good indication of it's integrity. To some this might seem taboo. I now have a 1000 X microscope so I can see the bugs (bad guys).