I have a yeast cake that was born with an IPA and has since been used to make two more IPAs (dumping on top of the yeast cake). All three were middle of the road IPAs. 7ish ABV. I was going to pull a cup of slury from this cake and pour it into an Imperial Stout I'm about to brew (I'll calculate the pitch rate). Has anyone had issues with using the yeast this far out. For a 4th brew? Are there folks regularly re-using this many times? Most interested to hear from people who can speak from experience. Thanks!
I take my yeast 4-5 generations typically. The outcome of this beer is dependent on how well the yeast was treated during those 4-5 generations. If it were me, I'd probably pitch more than a cup of slurry (probably the whole thing) for an imperial stout. I would only pitch it if all beers in the previous generations were of moderate gravity, proper pitching rates and maintained good temperatures.
I likewise reuse yeast all the time, often over 4 or 5 batches, sometimes more. I've never had a problem doing 5. On the "sometimes more" I have noticed changes to the fermentation profile 1 time.
I'm not sure I ever used a cake four times, but I have definitely done it for three with no problems. How does your third beer taste? If it is what you expected, I would not have a problem using the yeast again. I would not use the whole cake but an appropriate amount based on a calculator as you mention.
Same as the rest, but I never used an apa or IPA cake for any stout. Not sayin it won't work, but I do tend to keep paler or darker beer yeasts separated.
I also take my yeast out at least 3 or 4 generations, and have never had a problem, as long as the jar holding the yeast slurry has minimal air space. The few times I had more than an inch or so head space, I've had mold develop. Now I fill them to the brim (since it cools down in the fridge, the water contracts a little, so there will no no spillage). Leave the lids slightly loose.
I routinely take my yeast through 5 or 6 consecutive brews, but have in the past routinely taken the yeasts through as many as 12 generations with no off flavors or other negative effects. On two occasions (around 35 years ago), I took my house yeast through 20 consecutive brews (of varying strengths)...again, with no adverse effects.
To clarify further...I never use the whole yeast cake from a prior fermentation...for most brews that would be far too much. Typically, only about 1/3 of the slurry from a previous brew would go into the subsequent fermentation (I'll usually measure that out first, and reserve the remainder to dump into the boil of the incoming brew to serve as 'yeast food' for the subsequent fermentation). I'll only use more of the old slurry for the actual fermentation if I'm pitching it into a higher gravity brew. I've been doing this with my 'house' yeast for more than 35 years now, and wouldn't do it any other way. I've also done it at times with commercial strains from both Wyeast and White Labs...how many generations you can take them through successfully and dependably depends upon the strain: some seem to lend themselves to this idea better than others. The best way to zero in on your preferred result is to experiment!
