I go back and forth with this when saving my yeast slurry. Some say don’t save over a certain OG and some say over certain IBU matters also. What are some opinions on this?
~1.075 is about my upper limit for harvesting post-fermentation, but if top-cropping I don’t worry about the OG. No limit on IBUs and can’t think of any reason why it would matter as long as you rinse the yeast before pitching (if you’re going to use the yeast for something low-IBU).
It probably depends on the yeast strain, but with my main yeast I have saved and repitched parts of the slurry from batches (most recently) clocking in as high as 1.089, sometimes even over multiple brews. I’ve never experienced a problem with wonky fermentation or off flavors as a result.
Also, for whatever it’s worth, in the course of experimentation I have also had no issues whatsoever going from a high OG batch to a simple mild (and sometimes even back again). If I ever have a problem I may step back and reconsider the practice, but thus far (and for the 20 years or so I’ve been doing it) it hasn’t negatively affected the beers at all.
Lots of hops can hurt yeast health, but I don’t know if it’s the isomerized alpha acids that cause the trouble, or if it’s something else about them. If I want to reuse the yeastcake from a batch over about 1.070, I’ll do a starter to make sure my cells are happy and healthy; under 1.070, I’ll just rinse and repitch.
I don’t ever rinse my yeast but it is something I might start.
