How much yeast do I have?

[Dan Pratt]

I made a 1.8L starter on the digital stir plate with WLP001 to 1040 gravity last week and I decanted 2 x 500mls into these jars, the remaining 0.8L went into the session ale. I washed them with distilled water last night and was wondering how much yeast I would have in each.

From my numbers on BS2.0 my 1.8Lt starter was 316 billion and the amount I pitched into the beer was ~ 140billion....that would tell me I have somewhere in the area of 60-100billion cells.... :huh:

 

[Yob]

only looks to be about 20ml Pratty, if that.

Its helpful to mark 10ml increments up the side so you can get an accurate gauge, then you can plug that into Mr Malty to get a rough count (Particularly with compacted slurry)

 

[MaltyHops]

You can use the method outlined in the post below but you will need to transfer the yeast into a smaller container as it's a bit hard to estimate the volume of the yeast solids as a percentage of the roughly 480mL of liquid in your picture.

I would pour off as much of the clear liquid as possible without stirring up the yeast too much (save some the excess liquid in a sanitised container if you don't have any boiled/cooled water).

Then swirl the bottle to stir up the yeast and pour into a 100mL sanitised jar - use a bit of boiled/cooled water rinse out any remain yeast in the big bottle.

When the yeast in the 100mL settles, the yeast solids will probably look like 25% of the 100mL total volume, which according to the table you'd have maybe 6.0 E8, which means 6 x 10^8 = 0.6 billion cells per mL.

Finally multiply 0.6 billion/mL by 100mL and you arrive at 6 billion cells in your sample.

Also came across a Wyeast page Yeast Harvesting / Re-Pitching
containing a way of estimating how many yeast cells might be
present in a sample as follows:



T

 

[mosto]

From research I've done, a clean, washed sample of yeast will contain approx 4 billion cells per ml. As Yob said, I'd estimate around 20 ml of yeast there which would make around 80 billion cells, which lines up with you're estimate.

 

[Dan Pratt]

thanks for the info, a few good ways to figure out the amounts.