" a few months ago" is a LONG time to save reused yeast. That's enough time that you'll get autolysis & its byproducts in the starter material. Bare minimum, you're getting excess potential for mutations.Seven said:
Experimenting with my first yeast harvest/yeast starter. I saved some Nottingham yeast from my last blonde ale a few months ago and decided to do a trial run at a yeast starter.
If your concern is the cost of yeast, just buy S-05 a pound at a time; It's $80 a pound, but that's only $1.60 per batch of beer. It will last 2-3 years in the fridge, with decreasing efficacy over time. There is no benefit to reusing yeast so the risk isn't worth it to save less than $2 per batch.
I say this as a guy that bought a conical fermenter so I could harvest yeast, and then after several times of reusing yeast my quality suffered.