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You are here: Home --> Forum Home --> Brewing Forum --> Brewing Discussion --> Brett pitch rate

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ingoogni
nl
314 Posts


| How does cell density max out. Is there a population sensing mechanism that's different for each species. spp., and/or strain?

Yes. ec.asm.org/content/10/4/466.full.pdf+...



Posted 34 days ago.
Edited 34 days ago by ingoogni

ercousin
Charter Member
Toronto, Canada
77 Posts


Dan. When you say 200 M/mL, what kind of slurry is that?

Is that supposed to mean that the 15 mL of sedimented yeast (out of the 35mL vial volume) in a WLP001 vial is 200M/mL?

That doesn't seem to really follow math-wise. Say you estimate that a vial has 100B cells in it. At 200M/mL, you would need 500mL to contain 100B cells.
2




Posted 34 days ago.

rayfound
Charter Member
Riverside, CA
313 Posts


It seems a good point in the discussion for me to mention my philosophy on the matter. 

I have a hypothesis that the cell count in a vial of yeast is wildly variable from strain to strain, and it doesn't matter. 

Not to say that number of cells doesn't matter, but if 15ML of sediment = 100B in one strain and 200B in another strain, I still suspect they perform about the same - # of cells doesn't strike me as an important measure when comparing different cultures - biomass might be better. A fewer number of larger cells, one might deduce, would perform similarly to a larger count of smaller, less capable ones. 

I could be totally wrong, but let's call it an untested hypothesis. It would also comport with what DanABA was saying, about max cell density for some strains being MUCH higher, but the calculators continue to work and give good results. It makes sense to me that the calculators built around cell count... we're using cell count as a sort of proxy for  a metric that is more likely to really be "Yeast-metabolism" (think yeast version of "man-hours" for labor). Cell count makes sense for comparing similar strains, but might not be relevant beyond that. 


I dunno, I am spitballing a bit, admittedly. 
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Posted 34 days ago.

testingapril
Charter Member
Atlanta, GA
595 Posts


Eric, I believe Dan was referring to max cell density during growth, so basically max cell density in a starter.




Posted 34 days ago.

ingoogni
nl
314 Posts


After Boulton introduced the aerated starters breweries observed that they generated the same amount of biomass with their starters and more (Sacch.) cells compared to the traditional non aerated starters. The cells are smaller and these smaller cells performed as good as the bigger ones, both inoculated at the same cell count. Pitching at the same biomass rates the smaller cells performed better, faster fermentation and produced a cleaner product. (the latter may well have been because of the much fitter cells, can't look it up as I can't find the reference any more on the web)




Posted 34 days ago.
Edited 34 days ago by ingoogni

rayfound
Charter Member
Riverside, CA
313 Posts


Sounds like my hypthesis might be wrong. That's interesting. 
2




Posted 34 days ago.

chino_brews
Charter Member
Eden Prairie, MN
301 Posts


Is this in the Boulton and Quain book? 
2




Posted 34 days ago.

mchrispen
Bastrop, TX
485 Posts


Bamforth has also documented the pressure and CO2 issues at our favorite macro… similar, but lesser effects occurred even at 3 barrels. I don’t have the book in front of me, but if I recall, he said that at homebrew scales, we are usually fermenting at atmospheric or under 1.1 bars with buckets and carboys – with airlocks, and that 5-15 gallon conicals could mimic the effect at something like 8 psi, after 3/4 sugar break. My brain is dead from a long drive weekend again – so I may be completely off.

I need to look this up – I have the Boulton book as well. I can check tomorrow.

2




Posted 34 days ago.

ingoogni
nl
314 Posts


 Bamforth; Brewing : New Technologies page 177
www.yumpu.com/en/document/view/393039...

Looks like I have not remembered it entirely correct




Posted 34 days ago.

chino_brews
Charter Member
Eden Prairie, MN
301 Posts


So cell mass of anaerobically propagated cells is larger, but the ratio of cell wall to cell mass is better (or at least higher) with the smaller aerobically propagated cells?
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Posted 34 days ago.

DanABA
Las Vegas
25 Posts


Eric - Yeah, what Dan said.  When we are talking about "maximum cell density" here, we are talking about the maximum number of cells that will be reproduced in a starter, not how much is packed into a slurry.    



Posted 34 days ago.

homebrewdad
Charter Member
Birmingham, AL
2480 Posts


That would definitely be the usable math... at least, for me.
2




Posted 34 days ago.

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