Questionable yeast starter - how to evaluate it?

[timsch]

Here's a picture of a starter for I made about a week ago from some frozen vials I had harvested from some unfiltered IPAS a while back. It fermented for at least 3 days at ~75F, and then I put it into the fridge, leaving the magnet in it to break up the yeast cake before pitching. When I pulled it off the stir plate, there was no more foam/krausen.

Tonight I put it back on the plate to break up the cake, and after an hour it had about a 1.5" head of foam - not what I expected. It smells not great, but I've second guessed myself in the past about starter smells. I wish there were a more certain way to evaluate the health of my yeast before pitching. I'd hate to wind up with another batch that the only thing I can say is that it's not bad enough to pour out.

Why would It have apparently finished prevously and then wind up with such a head now?

 

[dmtaylor]

You've likely either got more than one different yeast strains in there, or...

If there was any dry-hop residue in your yeast that originated from your previous unfiltered IPAs... hops contain enzymes, so the fact that you brought frozen yeast from IPA back out of the freezer and up to 75 F *might* have allowed those enzymes to break down more sugars, which the yeast can then eat. This is known as "hop creep" and is typically experienced after dry hopping late in the main fermentation, but seems hypthetically possible from dry hopped yeast samples as well if there was still a good amount of hop residue remaining in your frozen yeast.

But the simplest answer is usually the correct one. So, I am leaning towards, you might have more than one yeast in there.

 

[timsch]

Interesting. If so, I hope they get along together, and if not, I hope the best one wins.

 

[day_trippr]

WLP002 is famous for its "chunky style" appearance, and WLP007 is often described as chunky as well...

Cheers!

 

[frithy]

https://www.mbaa.com/publications/t...esent,enzyme levels over a period of 28 days.