Home Brew Forums > Home Brewing Beer > Brew Science > Yeast propagation
Thread Tools
Old 07-31-2012, 11:41 PM   #1
Feedback Score: 0 reviews
Join Date: May 2010
Location: Seattle area, WA
Posts: 112
Liked 2 Times on 2 Posts

Default Yeast propagation

I am trying to gain a practical understanding of yeast propagation, as it relates to starters. I keep seeing something that I just can't make any sense of.

White Labs says that a single stage starter will create a 4-5 times increase in cell count, and Wyeast says it's more like 6 times, almost entirely regardless of the volume of the starter (ignoring the lower end, because obviously the yeast cannot continue once they have fully attenuated). This is for starters that are aerated and agitated.

This means that if you put 100 yeast cells into a 1.040 starter that is 100 gallons in volume, you will end up with between 400 and 600 yeast cells, and then they will just stop reproducing. Obviously, at such a ridiculously low cell count to volume ratio, the properties of the wort would be almost perfectly unchanged, and yet the yeast just stop reproducing. So here you have a 1.039999 wort with almost exactly as much oxygen in it as before you started, and for some reason the yeast in it won't do anything anymore. If you decant off the beer and repitch the yeast into a nearly identical but different 100 gallons of wort, they'll then reproduce up to 1600 - 3600 cells, and then again stop.

Does anyone understand what's going on here? Can you explain it it me?

CrustyBrau is offline
Reply With Quote
Old 08-01-2012, 03:25 PM   #2
Feedback Score: 0 reviews
Join Date: Feb 2012
Location: Baltimore, MD
Posts: 171
Liked 19 Times on 9 Posts


The volume of the starter has a large effect on the final cell count. I'd assume that when White Labs/Wyeast say you get 4-6 times the number of yeast, they're probably assuming you make a 'standard' 1L starter using a stir plate or something like that.

You can see some example yeast cell count versus starter volume curves here: http://www.yeastcalc.com/growthcharts.html

bdh is offline
Reply With Quote
Old 08-01-2012, 03:29 PM   #3
Look under the recliner
Feedback Score: 0 reviews
pjj2ba's Avatar
Join Date: Jul 2006
Location: State College, Pennsylvania
Posts: 3,374
Liked 200 Times on 165 Posts
Likes Given: 22


I think the problem is that the scale is not linear at the very low range of yeast numbers. I read through Chris White's yeast book, and I believe if I am remembering right, was that if you pitch a large amount of yeast into a starter, you will not get as much cell division compared to pitching 1/4 the amount of yeast. I guess sort of a terminal yeast population. A volume of wort of a given OG will give you X yeast, whether you pitch .1X yeast, or .5X yeast (the time to get there will be different though) Pitching for a starter is different than for beer production. You want lots of cell division in the starter, but much less in beer fermentation
On Tap: Ger. Pils, OKZ (std Amer. lager), CZ Pils, Maibock,
Kegged and Aging/Lagering:CAP, CAP II, Wheat lager, Imperial Pilsner, Ger. Pils, OKZ (std Amer. lager), OKZ II (for base malt comparison), light beer - yes, light beer, Belgian IPA, IPA,
Primary: Pale Ale
Brewing soon: Saison
Recently kicked : ( IPA, Bock, Saison,
Pilsner Urquell Master Homebrewer
(1st NYC 2011, 2nd NYC 2012)
P U crowns winners in its inaugural master HB competition
pjj2ba is offline
Reply With Quote
Old 08-01-2012, 03:36 PM   #4
Feedback Score: 0 reviews
Join Date: Apr 2011
Location: Croatia
Posts: 995
Liked 48 Times on 45 Posts
Likes Given: 13


I believe this article will clear most of your questions:
We are only 10,000 years into beer... there are thousands of years left to go!
Things are bound to change!!

Brewroom with HERMS build
Fermentation chamber and Keezer.. a.k.a. FermKeezer
diS is offline
Reply With Quote
Old 08-11-2012, 11:34 PM   #5
Feedback Score: 1 reviews
Join Date: Jul 2012
Posts: 134
Liked 5 Times on 5 Posts


Originally Posted by diS
I believe this article will clear most of your questions:
Thank you! ! I just happened across this thread and that article was the most easily understandable explanation of yeast handling I have read. I now know how to get more from my yeast. Thanks again and I'll have a pint in your honor. Cheers Kev

kev is online now
Reply With Quote

Thread Tools

Similar Threads
Thread Thread Starter Forum Replies Last Post
Yeast Propagation ipscman Brew Science 13 02-04-2011 05:32 PM
Yeast Metabolism: Starters to condition yeast to environment of wort Gremlyn Brew Science 8 04-28-2010 10:34 PM

Forum Jump