Splitting yeast slurry into 6 fermentations

[oceanic_brew]

I'm doing a series of tests to try and learn the flavor contributions of every hop and malt that my LHBS sells. I'm splitting a number of 5.5 gallon batches into 6 brew pots for boil and then into 6 1 gallon fermentors.

I'm trying to figure out the best way to calculate the yeast additions, although I'm using 1968 I will only be testing the difference between 6 different hops on this go.

Each batch will be approximately .91 G of wort at a OG of 1.061

I just harvested the slurry from a 5.5 g batch of 1.040 mild that I pitched 222 billion sells in and I'm using the Mr.Malty calculator to step it up and see how much a 5.5 G batch would increase the yeast count. After adding the values it's showing me that the yeast count of the slurry should total 942 billion.

Is it accurate to use this calculator for such a large step?

I've harvested the batch into one full 500 ml mason jar and filled 6 250 ml mason jars 1/3 the way up with slurry which gives me 1L of slurry.

I'm figuring this gives me:

471 billion cells for the 500 ml and
78.5 billion for each 1/3 full 250ml jar.

Mr Malty calculates that I need only 38 billion cells however I'm over twice that.


Does this all seem to add up to anyone?

I'm not concerned about losing some of the highlights of the 1968 from a little over pitch (if that even happens) but of course do not want to hamper my ability to truly taste the hops do to off flavors from an over pitch. Is it even over pitching at this rate?

Would love to hear your thoughts, been meaning to do this "elements" for quite some time and getting pretty excited about it.

 

[rhys333]

Just doing a quick estimate, I figure you need about 40B cells/gallon batch. Off a 5.5 gallon batch I usually get 4 pint sized mason jars full of slurry that equals about 400ml each after setting, and just one of this should be enough for what you need. Estimating at 1.5B cells/ml you need a measly 30ml (2 tablespoons worth) per gallon batch. This assumes fresh slurry.

 

[BeardedBrews]

I've made the same Oktoberfest recipe with a single dry pack of 34/70 as well as a nearly full quart jar of slurry from a previous batch. I have not been able to pick up any effects of over-pitching, but I'm also not a BJCP judge.

My opinion is that in the application you're talking about, an over-pitch is a non issue. More important to treat all batches the same so you can pick up the changes in the hops.

 

[oceanic_brew]

Yeah, after some thought I have to agree.

A slight over pitch with 1968 in a batch that's solely intended for learning my hops isn't gonna matter.

Thanks!

 

[rhys333]

I find those yeast calculators are overly conservative re cell counts. Fresh slurry is about 1.5B/ml (on the safe side) so your count is probably way higher than your 942B estimate. You're safe to just stick a good tablespoons worth in each gallon batch and call it a day.