Pitching yeast from the top of an ongoing fermentation??

I've been taking yeast straight off the top of the last batch (during high krausen) and adding it to the next batch of fresh wort, to ferment that.
Anyway, I've been doing this for 6 batches now, kind of as an experiment, and it's been working fine.
But, I would like to know a little bit more about what I'm doing--like "why(in long, elaborate terms) is this wrong?"-and "how long can I do this before my yeast get mutated"--things like that.

Now, please, lets just assume that I am sanitizing properly, pitching the right amount of yeast to the new batch, and not breaking through to the fermenting beer while im harvesting the krausen. Please. Because I'm not trying to get yelled at for basic/common sense things. I really just want to know the science end of, or at least the more advanced brewers view on the subject. Thanks.

Who said you are doing anything wrong? How are you measuring your pitch rates?

Top cropping is relatively common and used by some commercial breweries as well. I do it often with some yeasts - the yeast is super healthy. I often reserve it in a sanitised container with some boiled cooled water and refrigerate it. I use it to make starters.

Rather than wack it straight in I would be inclined to make a starter so you can better calculate your pitching rates but other than that, it's a great way of reculturing healthy yeast.

No idea about how many generations you can do this for but I guess Mr acetylaldehyde will let you know if you push it too far.

Science wise you're just using healthy active yeast to make beer. No more complicated than that.

xbattlex said:

Anyway, I've been doing this for 6 batches now, kind of as an experiment, and it's been working fine.

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I would say that your experiment has been a success!

Most excellent.

Thanks for the answers folks. They are greatly appreciated. And killian, I actually was just kinda winging it on the pitching rate. But, now I have found a much better way of measuring my cell counts. If anyone is interested the webpage was pretty helpful about this subject. Anyway, I either didn't know, or just couldn't think of the term "top cropping," so seeing that was a huge help. And, just so y'all know, all my babies are bubbling happily here by my side. Thanks again.


Ike

Ok-so the url messed up-sorry. But, you get the picture, I hope.

Me and a bunch of other biologists went on a tour of our local microbrewery (Picaroons) a few weeks ago. They had four large open fermentors and said that once the beer reaches high krausen they scoop it all off in a big bucket and set it aside to let all the yeast fall out of suspension. Once they have a new batch ready they simply pour off the liquid and pitch the sedimented yeast into the next batch. I was also surprised to find out they used the same yeast strain (ringwood) for all of their beers, from SOB, ESB, winter warmer, IPA to stouts. They have been brewing this way for 15 years and not had any problems.
Well once the tour was over and the group got back to the local bar and we had a few beers, this became the topic of discussion. 15 years of constant repitching from rapidly dividing yeast should introduce thousands of new mutations, but thats part of the evolution of a brewery's own yeast strain. Just like how california lager yeast acclimated and evolved to the warmer climate of california, the picaroons yeast would have acclimated to the local environment.
After that the conversation sloppily moved on to the evolution of human society due to the reduced nomadic lifestyle by growing grain for beer (beer = human evolution!). Anyway, I dont know if this helps, but Picaroons has been doing the same thing for 15 years and the beer still tasted great.

correct me if i'm wrong here guys, and i probably am. but isn't the yeast in the krausen some of the least flocculating of the yeast in the batch? if you keep selecting these yeast aren't you sifting the DNA of the culture toward the low flocculation end of things?

if i'm wrong pleas tell me why. i would love to learn something new here.

TipsyDragon said:

correct me if i'm wrong here guys, and i probably am. but isn't the yeast in the krausen some of the least flocculating of the yeast in the batch? if you keep selecting these yeast aren't you sifting the DNA of the culture toward the low flocculation end of things?

if i'm wrong pleas tell me why. i would love to learn something new here.

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ale yeast are all "top fermenting" so the active process takes place in the krausen - and the yeast that are active, are healthy and good for pitching.

Flocculation refers to the resting of the yeast at the bottom of the fermenter, post-fermentation, and does not come into play when we are talking about the krausen during peak fermentation.