Author Topic: Yeast Pitch Rate - Pt. 2: Viable Cell Count vs. Vitality | exBEERiment Results!  (Read 1774 times)

Offline brulosopher

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Over the last few years, homebrewers have been made very aware of the importance of proper yeast pitch rates, which many ensure by making a starter a few days prior to brewing. While this certainly increases cell counts, it has little impact on the vitality of the yeast, a factor purported to be just as, if not more, important than viable cell count. In this xBmt, Ray Found compares a conventional yeast starter to a method designed to improve yeast vitality, results are in!

http://brulosophy.com/2015/06/29/yeast-pitch-rate-pt-2-viable-cell-count-vs-vitality-exbeeriment-results/

Offline beersk

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Interesting. Very interesting! Wonder how much difference it makes having the stir plate versus intermittent shaking a starter...
die Schönheit der bier...

Jesse

Offline brulosopher

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Interesting. Very interesting! Wonder how much difference it makes having the stir plate versus intermittent shaking a starter...
I wondered the same thing. Colin was pretty clear to recommend spinning it on a plate for 4 hours, hence our decision to do so. On our scale, though, I'd guess shaking every 20-30 min would probably work fine.

Online brewday

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Love it.  Just to clarify, was either batch hit with O2 prior to pitching the starters?
Jon Weaver

Offline brulosopher

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Love it.  Just to clarify, was either batch hit with O2 prior to pitching the starters?
Nope!

Online brewday

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Love it.  Just to clarify, was either batch hit with O2 prior to pitching the starters?
Nope!

Reading back through the comments it looks like Ray did indeed shake both carboys to aerate.  Oh well, looks like a good opportunity to continue the experiment!

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Do not aerate the batch. This maximizes “vitality.”

Fascinating.  Any further explanation on this?
Jon Weaver

Offline brulosopher

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Do not aerate the batch. This maximizes “vitality.”

Fascinating.  Any further explanation on this?
Not that I can provide, I'll try to get more from Colin.

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There's a serious error in the interpretation of the Coor's England experiment. 

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Coors England developed an amazing method that is perfect for homebrewers to steal. Take a stir plate and make a starter. Add yeast and 10˚P [1.040 SG]. Aerate for 4 hours. At the end of 4 hours pitch into the wort. Do not aerate the batch. This maximizes “vitality.” Vitality is the most difficult to measure and important parameter in yeast. A standard starter is fermented out and then re-pitched. This [a vitality starter] uses continuous air and only allows the starter to spin for 4 hours. No alcohol is produced. The yeast respires but does not enter fermentation until after it’s pitched into the wort.

A batch grown starter never respires in the truest sense unless the glucose level is held below the Crabtree threshold of 0.3% glucose weight by volume.  This phenomenon is due to something known as carbon catabolite repression (some researchers believe that is it due to respirative metabolic pathway saturation).  Whether or not there was an appreciable amount of ethanol produced during the 4 hours that the culture was spinning is up for debate.  However, all reproduction is fermentative in wort that has a glucose level that is above the Crabtree threshold. What happens is that O2 and a small amount of carbon are shunted to the respirative metabolic pathway for the production of ergosterol and unsaturated fatty acids (UFAs).


With that said, I have preached yeast vitality (i.e., health) over cell count for a while now.  That's why I preach pitching at high krausen over allowing a starter to ferment out.  High krausen occurs when the cell count reaches maximum density for the medium into which it was pitched.   Allowing a culture to proceed beyond this point results in reduced vigor upon pitching unless dissolved O2 is increased due to lower ergosterol and UFA reserves.  Pitching at high krausen is a part of the perceived magic in my method.  It reaps the rewards of batch propagation while only paying a partial price with respect to vigor.  Initial O2 demands are lower because the ergosterol and UFA reserves are not as depleted as they would be if the fermentation was allowed to proceed to quiescence. 

Offline Stevie

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High jack - popular mechanics has an interview with Marshall that just posted today. Go read it.

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Jon Weaver

Offline brulosopher

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High jack - popular mechanics has an interview with Marshall that just posted today. Go read it.
A link for the lazy...

http://www.popularmechanics.com/home/food-drink/interviews/a16233/marshall-schott-brulosophy-beer-experiments/

What a cool experience!

Offline HoosierBrew

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High jack - popular mechanics has an interview with Marshall that just posted today. Go read it.
A link for the lazy...

http://www.popularmechanics.com/home/food-drink/interviews/a16233/marshall-schott-brulosophy-beer-experiments/

What a cool experience!

Yeah, very cool Marshall. Nice work !
Jon H.

Offline brulosopher

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High jack - popular mechanics has an interview with Marshall that just posted today. Go read it.
A link for the lazy...

http://www.popularmechanics.com/home/food-drink/interviews/a16233/marshall-schott-brulosophy-beer-experiments/

What a cool experience!

Yeah, very cool Marshall. Nice work !
Thank you!

Offline brewinhard

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Wow!  What a testament to all your hard work...

Congratulations on the article and thanks for sharing your results!  I love it!  Once you reach 100 exBEERiments, you should compile them all for a "tell-all" book.  Seriously, I would buy it!  I was telling my buddy the other day about your site and how they are the ideas in brewing that we all wonder about but never had the balls to test them out ourselves. 

Well done and wicked cool!

Offline denny

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As much as I commend Marshall for doing these experiments, don't let it discourage you from doing your own!  Don't blindly believe him, me, or anyone else.  Try things for yourself and discover your own reality!
Life begins at 60.....1.060, that is!

www.dennybrew.com

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