Currently fermenting a Pilsner with a 3rd generation of Imperial Harvest (Augustiner yeast, WLP860). As I ponder my next couple brews I’m curious to what people have found as indicators that it’s best to dump the yeast rather than try and reharvest…
I’m on my 5th gen of 34/70 with no perceivable changes. I will harvest this again and use it until I notice any difference. Thats probably the only way to know.
First would be a macro/microscopic inspection; if the yeast morphology is off in any way (size, shape, flocculation, obvious contaminants, etc.) then it’s probably time to toss it.
Generally, though, you’ll see indications that performance is falling off in the fermenter. Lag time, attenuation rate, and flocculation rate will all drift over time. With some strains I’ll see actual attenuation start to drop off after a few generations.
Good to know, I’ll look for those changes…I’m hoping to avoid a crappy 5 gal of beer at the sake of saving a few $$ but I do enjoy the productivity and performance of generations 2 & 3 of this yeast so far
I’ve found lager yeasts don’t hit their stride (adapting from lab to brewery conditions) and start performing optimally until the third to fifth generation, and I’ve had lager yeasts out past 25 generations with no change in performance and only started anew because I wanted to switch strains. But the advice holds, when you no longer like what it’s doing, time to change it out.
How do you store your yeast?
Under the beer it made, in a loosely covered Mason jar, in the fridge.
If you are fastidious in your process, you can achieve 25 generations. I have done so with an American lager yeast, adding yeast nutrient and storing slurry in sanitized plastic containers under the beer. Solid pitches to prevent stress was all that I did over that many generations. No fall off and no adverse mutation that I could detect from flavor or fermentation time. But maybe I got lucky, at least in part.
My experience is about the same as Robert, although the farthest I taken a yeast is 13th generation US-05. Last evening I did a starter of 9th gen. 34/70 for the Chili Lager I’m brewing today, I had bubbles every 4 seconds 4 hours after pitching. I usually only dump a harvest when it gets autolytic, had to dump 2 jars of 05 last night that were only a couple months old.
Update. FWIW I had to dump the last 2 jars of harvested 05 yesterday because they were showing definite signs of autolysis, one was only 3 weeks since harvest. Could be coincidental but all of the harvests from the most recent generations started getting autolytic in a fraction of the time I would normally expect from 05, but could also be a result of serial re-pitching. Anyone else have this experience this?
That is not entirely surprising. When I took that yeast out 25 generations, I serially repitched on a week or two basis, typically going from harvest to repitch on the same day as brewing. I was brewing similar beers, too and no big ABV beers. Yeast nutrient each time. Even with best practices, we are dealing with live cells and they have the final say…cheers.