Question about yeast generations.

My guess is that you would keep building starters from the current generation you have. I think it's much simpler to keep using the yeast (generation after generation) until it starts developing flavors that you don't care for. I doubt most breweries are even doing what you are describing of using a specific generation of yeast for this amount of time. On probrewer I routinely see brewers saying they use "X" strain for "Y" amount of pitches and then restart fresh.

 

The answers to your questions are "maybe" or "sometimes" or "could be but unlikely". Not trying to be funny, but there's a lot of variables involved here. In the most strict terms, any time a strain is started (or re-started) you have new growth which by definition is a new generation. Do they mutate or evolve between generations? . . . of course they do. How much they change is another complex set of variables and although I'm not into the science at the micro-level this has to be strain-related.

More variables: when you harvest/rinse/reuse you potentially change the strain's characteristics. If the "quick floc'cers" and "top crop'ers" are not homogeneously collected you change what's going on. This can be tricky to always get perfect. Sanitation really matters. Let some tiny wild strain in and you have a game-changer. Randomly I've had a strain actually improve with re-starts, most likely a result of something being introduced. Normally I find multiple re-starts tend to mute desirable characteristics and end up with higher than expected attenuation. But it all depends.

A suggestion is to look into making more than you need before pitching and save the excess for the future; i.e. if you need 200B then make a starter with 250-300B and pour off the extras for the next brew. I've found this is overall easier and eliminates some of the problems of sanitation/harvesting/rinsing. I've personally never gone past 7 generations, currently working on 1318 that's a 4th gen. I doubt whether this makes it to 7 re-starts. It's pretty easy to know when you've gone one re-start too far.

 

Chris White has said that they work hard to maintain consistency. The whole lab is primarily about making the identical identical, year after year after year. Clients have commented that they can detect some characteristic changes when moving from the White Labs strain to the original commercial strain. Dr. White points out that the commercial brewers yeast is in fact mutating, not the yeast lab strain.

Point being, some of the most famous breweries on the planet can sometimes experience yeast drift. Our chances in a humble homebrewery are mighty slim.
Cheers.

 

Unless you are abusing your yeast, I would not be very concerned about mutations over a few or even a few dozen generations.

But I would keep in mind that with each batch, you're selecting individual cells over others (due to flocculation characteristics, or survival under your brewhouse conditions, or whatever) for survival and thus replication. (@PortLargo talked about this.) So eventually your strain will perform differently than it did when you started, even without any mutations per se.

 

Yeast goes through a number of stresses throughout the brewing process. For example, during fermentation the yeast will initially be subjected to oxidative & osmotic stress and later in the fermentation process nutritional & ethanol stress.

You can read more on this topic in this presentation:

http://youngscientistssymposium.org/YSS2016/pdf/Lawrence.pdf

Cheers!

 

Basically.... say goodbye to what you love about generation 7 and embrace what generation 8 brings to the table.

 

You're really not thinking about this right. You will get x amount of mutations after x amount of replications, so it not only has to do with which generation of yeast, but how large your initial sample size was, how many times you stepped up that sample, and how large your main beer was, as yeast replicate to volume.

All you have to do is get a sample of it and use a sanitized (or possibly sterilized, which would be ideal) container as a yeast brink. Whenever you want to brew, you just pull a small volume of the sample and grow it up into a volume that is enough to pitch. Kinda like growing yeast from dishes or slants, but without all the fancy equipment.

Lots of advanced information regarding isolating, storing, and regrowing yeast on, where else, the MTF wiki:

http://www.milkthefunk.com/wiki/Laboratory_Techniques

 

Although this is all very true as they are propagating from isolates from their yeast banks, White Labs has had . . . well . . . some very public issues with sample purity for a while now. I don't buy their products, as I've had issues in the past, and I know that if I was a commercial brewery I wouldn't bother with them.

 

I have been using the “same” yeast for the last 2 years and I brew at least once a week, so it’s hundreds of batches old.

I do not wash, but I am fanatical about clear wort at all steps of the brewing process, so that when I harvest I get pure yeast back. Since I spund when I reclaim my slurry it still has sugar left in it. So when I put them to sleep in the fridge they are not void of food. This also cold conditions the yeast. My pitch rates basically use 50% of the slurry harvest (I pitch at 2.5ml). This means I get 50% new growth every batch so technically after 2 generations they are “new” again.

Also my frequency of brewing keeps them fresh and healthy. I ferment at 45f and day 5 ready for spund( and slurry harvest) day 7 at fg.

I would love to post a link to my processes, but “some” folks are butthurt and report it as spam. So you will have to google it.

 

@TheBeerery
I would argue that your processes are much more sterile then most and like you mentioned you aren't getting trub with your yeast. I can't see the average homebrewer going above 3-5 generations and not noticing a difference. You are kind of perfectly set up to reuse yeast as you seem to operate close to or in many case above brewery standard.

 

This it?

 

I went as high as 10 generations with no trouble. Usually I get 1-4 now before using new yeast. Just because , I guess.

 

Probably a stupid question but I store a portion of my starter in a sanitized ball jar whenever I use liquid yeast. I don’t screw the lid on all the way because there’s still sugars being consumed and I don’t want a ball jar to blow up in my fridge. Is this normal practice?

 

Yes although at fridge temps I'm sure they would flock out anyway. I degas mine once and a while.

 

Top cropping strains can go hundreds of generations. The art is in knowing when to crop the best yeast.

 

If you haven't installed a Burton Union in your basement brewery you ain't shit.

 

That's pretty overrated.