Last night I made a starter for some US05 that was harvested back in September. When I opened the mason jar, I caught a sour odor. This is my first time harvesting 05 as I usually jut throw a pack of the dry stuff in. However this weekend I am planning a few brew sessions and will need extra.
Is this a sour smelling yeast or did it probably go bad? It had been sitting with about a half cup of left over beer on top from when I harvested it after fermentation.
[quote=“Roddy”]Last night I made a starter for some US05 that was harvested back in September. When I opened the mason jar, I caught a sour odor. This is my first time harvesting 05 as I usually jut throw a pack of the dry stuff in. However this weekend I am planning a few brew sessions and will need extra.
Is this a sour smelling yeast or did it probably go bad? It had been sitting with about a half cup of left over beer on top from when I harvested it after fermentation.[/quote]
You’re pushing the limit reusing yeast that is 6-7 months old. After 6 months the viability is questionable. It may work out fine but you may also be under-pitching quite a bit. There is no sure way to tell without a microscope.
I harvest and reuse yeast quite a bit, but if I catch a bad smell when I open the jar, I toss it. If it isn’t very strong, you might get away with it, but why take the chance?
Sounds like I will be throwing it. I have used 8 month old yeast before that has taken of quite well with a starter, but with this odor, I don’t think I will chance it.
I’ve used yeast that sat in my fridge for over a year (with a bunch of step-ups before it was healthy enough to pitch). And I have tossed jars that were only a few months old. Just have to deal with what you have.
When in doubt throw it out.
