[Robert]

^^^^^
Deleted lengthy reply to above.  See here

https://r.tapatalk.com/shareLink?url=https%3A%2F%2Fwww%2Ehomebrewersassociation%2Eorg%2Fforum%2Findex%2Ephp%3Ftopic%3D33304%2E0&share_tid=33304&share_fid=40079&share_type=t

[Robert]

I just racked the second generation WLP833 batch.  Final attenuation and pH virtually identical to the first generation, just finished a bit faster as noted above.   Tastes just as clean, crisp and Pilsnery, too.  I'll be repitching the yeast again this weekend, again in an identical wort.  Well, I do keep changing the hop bill.  Gotta have some variety in life.

[MattyAHA]

I just racked the second generation WLP833 batch.  Final attenuation and pH virtually identical to the first generation, just finished a bit faster as noted above.   Tastes just as clean, crisp and Pilsnery, too.  I'll be repitching the yeast again this weekend, again in an identical wort.  Well, I do keep changing the hop bill.  Gotta have some variety in life.

frickn eh man

[ynotbrusum]

Thanks Robert.  I have some in the pipeline and I’m just sampling some that are spunded to plastic bottles.  The yeasts seem consistent from pitch to pitch so far.  Just a couple repitches so far and with later generation on a particular strain - 2206 (8th gen with only the last one under pressure - 12 psi).  All clean and tasty.  I did not track like you all of the details.  I have a Tilt and have racked with 3-4 points left....not scientific by any means but a data point, none the less.  Thanks for your more precise tracking of data!

Cheers.

[Robert]

Thanks Robert.  I have some in the pipeline and I’m just sampling some that are spunded to plastic bottles.  The yeasts seem consistent from pitch to pitch so far.  Just a couple repitches so far and with later generation on a particular strain - 2206 (8th gen with only the last one under pressure - 12 psi).  All clean and tasty.  I did not track like you all of the details.  I have a Tilt and have racked with 3-4 points left....not scientific by any means but a data point, none the less.  Thanks for your more precise tracking of data!

Cheers.

I'm tracking details as long as my attention span holds so this thread can serve as a resource.   It seems we've addressed a number of the questions (rumors?) about pressure fermentation raised in the accounts found both in textbooks and on the forums and blogs, leaving as the biggest open question: does it have long term detrimental effects on the yeast?  I'll try to gather enough batch data to put that one to rest. 

[Robert]

Third generation batch has finished up and been crashed, and I just have to find time this evening to rack it and harvest the yeast, which I hope to repitch again in a few days.

The batch again tracked nearly identically, went faster still if anything.

There has, I'll note, been a slight drop in final AA as it appears on my spreadsheet over the three batches:   80.4%, to 79.8% to 77.9%.  BUT I must also note that the actual difference between the highest and lowest is just 0.3°P, doubtless within the margin of measurement error.   If it's real at all, it could be just selection of more flocculent cells due to my harvesting methods.  I'm not able to say at this point that there has been any significant, observable difference in the performance of the yeast over the three fermentations.  pH has tracked normally, and tasting samples are showing the same excellent results.

So far, I'd have to say that there don't seem to be any harmful effects of pressure fermentation on the yeast affecting its suitability for repitching, at least with this strain under these particular conditions.   

[Robert]

Fourth generation suggests any concern I had about possible reduced attenuation over generations was unfounded, probably just noise in the data.   Fourth generation tracking close to second.  I think after I've taken this out past five generations,  I'll post comparative attenuation and pH data for all batches so others can interpret it for themselves.   By then I'll also have some tasting notes on fully conditioned beers.   On that note, I just pulled samples from the first two generations and wish I'd implemented this long ago.

[goose]

Rob:  You should write an article for Zymurgy for this!

[Robert]

Rob:  You should write an article for Zymurgy for this!

Oh, I think it's way too early to think about that!  I'm hardly an authority on the subject at this point, a bunch of reading and four or five batches in.  But think I've found a niche, or specialty, that really excites me and is giving me a sense of discovery again in my brewing,  and I'm going to keep pursuing this.   At some point when I feel I could make a contribution that goes beyond what I've been able to find written out there (admittedly that's not much,) or at least have sufficient understanding of the matter to present a practical guide, I'd certainly consider it.

[Robert]

Here's some data on the first six generations of WLP833 pressure fermented and directly, serially repitched. Make of it what you will.

There have been some variations in water treatment, hopping, etc. as I'm playing around with recipes, but for the most part I've been as consistent as possible:  the grain bills have been identical -- 100% locally produced pale malt, from the same batch -- except for #6, which contained a portion of a honey/melanoidin type, which I assume would make it marginally less fermentable; mash program also standardized (Hochkurz 30/30/10.)

The beers all are tasting very clean and perfectly lager like, no fermentation related faults I can detect.  I'd say better than beers made using a modified Narziß fermentation program.  No detriment to foam qualities or any other parameter I've noticed, except for a possibly less-than-expected hop aroma.  I hesitate to say that, really not sure.  More tasting notes may follow.

What follows is, for each batch, four numbers:  Apparent Attenuation, room temperature mash pH, chilled wort pH (adjusted at 10 min. in kettle with acid,) and beer pH.   PLEASE NOTE that the actual range of variation in the actual Apparent Extract/FG is <0.5°P/1.002 for worts with OE's all very near the average of 12.65°P, and the stated accuracy of the digital refractometer is +/-0.2°P, and further error may be introduced in correcting for alcohol.  Again, make of this what you will.

#1  80.4%, 5.55, 5.02, 4.33
#2  79.8%, 5.53, 5.08, 4.31
#3  77.9%, 5.53, 5.06, 4.31
#4  78.5%, 5.59, 5.12, 4.30
#5  76.6%, 5.47, 5.09, 4.36
#6  77.2%, 5.57, 5.02, 4.27

[denny]

Rob, what, if any, benefits have you found to pressure fermentarion?

[Robert]

Rob, what, if any, benefits have you found to pressure fermentarion?

Off the top of my head:  as I mentioned, I think these taste better than my typical Narziß or other "fast" lagers.  (And this is super fast. I could be turning these around faster than my "pipeline" usually dictates.)  So there MAY be an actual advantage in terms of beer quality. 

But from a purely practical standpoint, I don't have to get the wort down to a traditional lager pitching temperature,  which can be really dificult a lot of the year.  (Although there's been a recent discussion here about whether that's always necessary.)  And drawing a sanitary sample is dead easy, pop on a picnic tap and it's already pressurized.  It just occurred to me that you can also just ignore it, not actually having to take samples, because you aren't looking to raise the temperature any more at a given point like with most fast lager methods, and you can trust fermentation is pretty much complete in 2-3 days.  If I weren't taking lots of measurements for the sake of this thread, I'd probanly just leave it for a week and cold crash, knowing it was surely ready, just like an ale.

At any rate, I haven't found a DISadvantage yet.  It's easy enough, and gives such results,  that I think it's my new SOP for lagers.  Puts them on exactly the same schedule as ales, too, from kettle to fermenter to keg to tap.  I'll let you know if my opinion ever changes.

The only question I still have, is just how many generations the yeast will go.  I'm not statistically savvy enough to tell if that data I posted means anything really, but I'd guess this wouldn't get the 25 or so generations that some of us have stretched to.   But that doesn't matter much.  I just wanted to be sure you could in fact repitch.  You can.  (Note that I've been slowly depressurizing the fermenter during cold crash so the yeasties don't get the bends when I open up to harvest them.  Don't know if this makes any difference, but it fits my process since I don't spund.)

[ynotbrusum]

There is a recent discussion on the MBAA podcast featuring Dr. Maitreya Dunham, a biologist at University of Washington, whose lab tracked Dr. Tom Schmidlin's yeast (Postdoc Brewing) over several re-pitchings (they were careful to note that re-pitching is not a generation, rather multiple generations would occur in a single re-pitching point to a re-harvest point).

http://masterbrewerspodcast.com/130-yeast-genome-changes-during-serial-repitching

What I took away is that the likelihood of some genetic drift that is detectable increases after 10 re-pitches.  However, whether the taste is affected is a different matter, as Dr. Tom re-pitched many more times than that, with no noticeable effect and when he noticed an effect, he quit that batch of yeast further.  It is an interesting listen, while somewhat technical in nature.

[Robert]

There is a recent discussion on the MBAA podcast featuring Dr. Maitreya Dunham, a biologist at University of Washington, whose lab tracked Dr. Tom Schmidlin's yeast (Postdoc Brewing) over several re-pitchings (they were careful to note that re-pitching is not a generation, rather multiple generations would occur in a single re-pitching point to a re-harvest point).

http://masterbrewerspodcast.com/130-yeast-genome-changes-during-serial-repitching

What I took away is that the likelihood of some genetic drift that is detectable increases after 10 re-pitches.  However, whether the taste is affected is a different matter, as Dr. Tom re-pitched many more times than that, with no noticeable effect and when he noticed an effect, he quit that batch of yeast further.  It is an interesting listen, while somewhat technical in nature.

Thanks, I'm way behind on those podcasts.  I'll have to get caught up, especially that one.  And I'll try to reform my terminology.  I always thought of "doublings" during a fermentation and "generations" as batches of beer fermented.  Maybe that's no longer standard.

[BrewBama]

That’s the podcast I mentioned in another thread concerning yeast behavior after recycling yeast. Pretty interesting how quickly they morph.


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