How do you know when your yeast has been through too many cycles?

[DVCNick]

I read a "rule of thumb" somewhere that you could use it about 6 times before starting from a new packet, but what specific signs would indicate the yeast has changed too much?

Attenuation, floc behavior, flavor, all of the above?

 

[kh54s10]

I have heard 10 generations, but I would say - all that you have mentioned. Change in flavor being the lead condition. I could handle the rest if the flavor remained the same.

 

[DVCNick]

I had a recent batch of a beer I've done several times and it is one of my favorites. It is a simple pale ale with all Citra.
Anyhow, this time the US-05, in addition to the cake a the bottom congealed into large (really large) chunks that mostly were floating near the top. I couldn't crash it since it was in a normal carboy type fermenter.

Some of this got into the keg, and I figured it would crash down there and be gone in the first couple pours.
Nope.
The entire keg, first pour to last, had little chunks of yeast in it. Didn't seem to affect the flavor and in an opaque glass I probably never would have been the wiser. I've seen commercial beers that seem to (intentionally) have this "chunks of suspended yeast" in it as well.

Bottled some of it as well trying out the new beer gun, and the chunks have collected near the bottom of the refrigerated bottles, but have not formed a cake ON the bottom.

Does this sound like yeast that is cycled too many times, or something else? I believe it was on its 6th or 7th generation.
I have one more batch going with yeast from that line, and will see if that behavior persists; if so I'll switch to a new packet and try again.

 

[Robert65]

Attenuation, floc behavior, flavor, all of the above?

Yes. Any change indicates, well, some change. But that may not be bad. Most yeasts take several generations to fully adapt from lab conditions to your actual brewery conditions and start performing at their best. But any change in performance that you find undesirable is reason enough to start with a new pitch. There is no number of cycles set in stone. I have taken yeast out past 25 generations and then started fresh only because I wanted to use a different yeast, though the same yeast could have kept on going. And then there've been times when yeast warranted replacement after less than 10 generations, especially if it was stressed early on. So if you're happy with your yeast, use it. If you're not, don't. That's all there is to it really. Just be sure to be rigorous about sanitation in your whole process.

 

[Calder]

There is no set time. Yeast will 'evolve' with repeated use, and the change will be influenced by how you handle the reuse. After a while the yeast will change; flavor, attenuation, flocculation, or other characteristic. 5 uses is the recommended number, but it will probably go many more batches unless it gets contaminated. I have run yeast for 10+ batches without going back to the original starter with no issues.

It is possible to change the yeast to the extent that it becomes so different from the original yeast that it becomes a new 'strain', and can become an exclusive yeast for you ...... whether it is still a desirable yeast to use is a different question.

Re-use of yeast is also affected by the gravity of the wort.

Re-using a starter is not considered as a re-use; the low OG of the wort does not affect the yeast as much as a regular gravity beer.

 

[InspectorJon]

I emailed Drake’s in San Leandro asking about what yeast they use and got this response:

Hello Jon,

Both 1500 and our Best CoastIPA use White Labs 001 yeast. Although we are unable to verify which generation the yeast may have been used for those particular beers, our lab ensures that each pitch has sufficient viability to fully attenuate without any risk for mutation or infection. Generally we use 001 to about 14 generations minimum before purchasing a fresh pitch.

 

[mashpaddled]

There is not a uniform answer. When you start to see changes in fermentation attributes then you've gone too far. Much of this depends on the strain and your brewing practices. If you pitch successively from one batch to the next your chance of introducing low level infections increases. If you harvest from the trub versus krausen you are selecting differently and will get cells with different properties that can change fermentation attributes. Successive harvesting can also invite selective pressures with gravity, finings, etc. Some strains are more easily selected by these pressures than others.

An easy way to avoid some of these issues is to save some of the original yeast or your original propagation and constantly use that as a base to get yeast for each batch rather than using cultures successively harvested from one batch to the next.

 

[DVCNick]

My normal procedure is to pour a little off the starter to use as the seed for next time, and then put about 1400ml worth of the starter into the 5gal beer. I figure that should keep from stressing the yeast with higher gravity wort, and also I don't have to worry about washing or other trub in the harvested part... does that sound good?

 

[Qhrumphf]

As others have said, there's no hard answer.

Different strains will also tough it out longer.

The principle things I notice when it's time to retire a culture and start over:

-rate of fermentation (takes longer to start and/or finish)
-level of attenuation (finishes higher or occasionally lower than expected)
-change in beer pH (doesn't drop as fast and finishes higher)
-poor character (by any definition)
-changes in flocculation (inverse correlation w/ attenuation changes)
-particularly with lagers, taking longer, or refusing to clear diacetyl/VDK precursors

I've taken Chico upwards of 15 generations before it starts to slow on me, and I see an upward pH drift. I usually cut that around 10 gens. Similar experience for most US and English typ3 yeasts I've used. I use Weihenstephan 34/70 for lagers and get 3-4 gens before diacetyl rest takes too long for my liking or fermentation in general slows, but could squeeze another gen or two out of it if I had to. Belgian and Hefe yeasts I don't usually even go to 3 gens (they stop attenuating fully and the character gets poor) but I knowingly abuse them to increase yeast character so that's not a shock to me.

Apart from Belgian/Hefe yeasts, I get the best performance from yeast 2nd and 3rd generation, and then from the 4th gen on it starts declining at varying rates.

 

[CascadesBrewer]

I strongly suspect that the risk at the homebrew level (for most people) is contamination or the risk of contamination over mutations.

People have different reasons for reusing yeast. I mostly use very common yeasts. I do it partially because I am frugal (why pay $8 per batch vs $2 per batch) and partially because I feel I get better fermentations with a healthy pitch of harvested yeast vs a single new pack. It it also nice to harvest small jars of yeast to use in 1 gal batches.

If I get to the point where I am questioning my yeast, I will just grab a new pack. I tend to get several batches out of a pack (got a bunch of batches out of a pack of WLP001) but then at some point I don't use a yeast for several months or I use up all my supply in high gravity beers or heavily dry hopped beers, and I start over with a new pack. (I have harvested from heavily drop hopped beers, but I am starting to think that is a bad idea.)

 

[Qhrumphf]

I think people confuse/conflate "mutation" with selective pressure. If you harvest only the first yeast to drop, you'll be pushing the most flocculant (and almost always least attenuative) yeast. If you only harvest late yeast (or especially bottle harvest if the original wasn't re-yeasted), you'll be selecting the least flocculant (and almost always most attenuative) yeast. The more the cycle repeats, the more pronounced the effect.

It's simply evolution at work.

In other words, how and when you harvest has a big impact.

Not to minimize the contamination part either.

 

[ChaosB]

I had a recent batch of a beer I've done several times and it is one of my favorites. It is a simple pale ale with all Citra.
Anyhow, this time the US-05, in addition to the cake a the bottom congealed into large (really large) chunks that mostly were floating near the top. I couldn't crash it since it was in a normal carboy type fermenter.

Some of this got into the keg, and I figured it would crash down there and be gone in the first couple pours.
Nope.
The entire keg, first pour to last, had little chunks of yeast in it. Didn't seem to affect the flavor and in an opaque glass I probably never would have been the wiser. I've seen commercial beers that seem to (intentionally) have this "chunks of suspended yeast" in it as well.

Bottled some of it as well trying out the new beer gun, and the chunks have collected near the bottom of the refrigerated bottles, but have not formed a cake ON the bottom.

Does this sound like yeast that is cycled too many times, or something else? I believe it was on its 6th or 7th generation.
I have one more batch going with yeast from that line, and will see if that behavior persists; if so I'll switch to a new packet and try again.

Why can't you crash a carboy? I have plastic carboy fermenters which I drop down to 30 some degrees all the time.

How do you like the beer gun? I've been eyeing those for awhile.

 

[DVCNick]

I don't have a way to keep air out of my regular carboy type fermenters for crashing, and I use a chest freezer, so no room for a spiderman balloon that you see in one of the popular threads on the topic.

Beer gun... its a little bit of a pain to set up, but once you are going, it is easy to use. Got to say it isn't quite as foolproof as I was lead to believe before using it for the first time; I find that you do have to chill the bottles and keep the keg pressure very low to avoid too much degassing. My first session with it I lost more gas than I would have liked. Second session with a different beer I believe went much better... actually need to pop one of those to be sure.

I really like that it has a full C02 purge ability can easily be fully disassembled for a thorough cleaning.... I've bottled right off the tap for drinking same day, but I would think the risk of oxidation and infection would be far, far greater doing that if you expected to need any kind of shelf life out of the bottles.

 

[ChaosB]

I don't have a way to keep air out of my regular carboy type fermenters for crashing, and I use a chest freezer, so no room for a spiderman balloon that you see in one of the popular threads on the topic.

Beer gun... its a little bit of a pain to set up, but once you are going, it is easy to use. Got to say it isn't quite as foolproof as I was lead to believe before using it for the first time; I find that you do have to chill the bottles and keep the keg pressure very low to avoid too much degassing. My first session with it I lost more gas than I would have liked. Second session with a different beer I believe went much better... actually need to pop one of those to be sure.

I really like that it has a full C02 purge ability can easily be fully disassembled for a thorough cleaning.... I've bottled right off the tap for drinking same day, but I would think the risk of oxidation and infection would be far, far greater doing that if you expected to need any kind of shelf life out of the bottles.

I'm also using a chest freezer. I don't use the giant helium balloons, just the regular size party balloons, a step up from water balloons size but same style. It doesn't have enough room to be fully upright but I can place it over the top of an S style airlock with the balloon slightly folded off to one side and the gas still reaches the fermenter. The jury is still out on if this actually prevents any oxygen from getting in though. I still never have the same aroma and flavors on the nose as commercial hoppy beers but I'm not ready to concede that my other methods aren't too blame or that I simply can't get as high a quality of hops as the professionals.

I actually just read an article about the beer gun and needing to drop the pressure on the keg, that isn't very appealing to me considering the struggle I have obtaining co2 overseas but maybe I'll look into it when co2 is a less painful commodity to acquire.

 

[DVCNick]

In that case you might want to bottle condition as much as not, at least for beers where a yeast layer in the bottom adds to the flavor.