Estimating cell count in yeast cake

[brownni5]

A couple weeks ago, I brewed a pale Belgian Ale with Wyeast 3739 (I've read surprisingly little about this yeast, but the starter smelled nice), in part to have a low ABV Belgian on tap, but also to have a good yeast cake to pitch a 1.095 Belgian Dark Strong onto.

I wouldn't be with probably any other yeast type, but I'm now afraid of over pitching. Is there any way to be sure how much yeast I'm pitching on the BDS without removing the yeast/trub from the fermenter? And now that I'm typing it, that doesn't sound like the worst idea. Just trying to minimize exposure I suppose.

 

[CascadesBrewer]

Good question! I have seen estimates about a yeast cake for a low gravity beer having in the 600B range to estimates that are 3 or 4 times that. I am curious for myself to help calculate the cell count of a jar of slurry. If the entire cake has 600B cells, and I get 4 jars out of the cake, then I each jar should have around 150B cells.

 

[ba-brewer]

Somewhere in this video Chris white says there are 4 or 5 time as much yeast in the cake as what you originally pitched.


I use the MrMalty slurry calculator and it seems to give good result. When the cake is fresh it does not take too to make a pitch.

I ferment trub free wort and only get maybe a half of pint of compacted slurry when it is finished from a fresh starter.

 

[Tyler B]

For anyone who might be interested in the video but doesn't want to invest almost 2 hours...

Around the 46 minute mark, Chris mentions that there are about 1-3 billion cells per mL in both liquid yeast and "yeast collected from the bottom of the beer after fermentation". He refers to both of these as slurry.

Shortly after the 57 minute mark, he states that the finished beer has 4-5 times more yeast than what you started with.

I haven't invested too much time and thought into this, but the two seem to agree. For example, I just pitched 1.5 packets of dry yeast (about 100 billion cells) into an IPA and got a 1 L cake that will probably compact/settle into a 500mL cake. So... apparently I should end up with around 500-600 billion cells.

I'm trying to decide how much of this to pitch into the RIS I'm brewing in a couple of days. I'm leaning towards half of the cake.

Edit: typo