Concerns about over pitching

[harebearva]

I'm brewing this weekend and plan to use a 25ml slurry in a starter. (I do 2.25 gal batches so I often do not get much yeast slurry) My target is 1.056 in 2.25 gallons with a slurry (week old WLP001) viability of about 82% and about 1.7 billions cells/ml.
I need about 88 billion cells for my brew and have about 43 in my slurry. using yeastcalc, and mr malty, a 1 liter starter puts me at about 130 billion cells. Mr Malty says a starter under 1 liter is a bad idea. Am I safe over pitching by 40 billion cells? I figure a faster fermenting, cleaner brew would result. Or can I do a 700ml starter which is more like over pitching by 20 billion cells. Of course there is a lot of guess work in slurries!

Thanks.

 

[FarmerTed]

Read this, and then don't lose any sleep over it.

 

[LLBeanJ]

I assume you're using Jamil's stir plate formula on Yeastcalc to come up with the 130B cell count (that's the only way I could get to the 130B cells you cited). From what I understand, Jamil's formula is rather conservative and Kai's formula is closer to reality, which is what I use, and that would put you at ~175B using the same variables as before. Since it's almost double what you need, I'd either a) cut the starter down to .5L or b) go ahead with a 1L starter and pitch only half. You can save the other half in a sanitized container in the fridge until you are ready to brew with that strain again. It will keep for 6 months or longer with no problem.

 

[harebearva]

I assume you're using Jamil's stir plate formula on Yeastcalc to come up with the 130B cell count (that's the only way I could get to the 130B cells you cited). From what I understand, Jamil's formula is rather conservative and Kai's formula is closer to reality, which is what I use, and that would put you at ~175B using the same variables as before. Since it's almost double what you need, I'd either a) cut the starter down to .5L or b) go ahead with a 1L starter and pitch only half. You can save the other half in a sanitized container in the fridge until you are ready to brew with that strain again. It will keep for 6 months or longer with no problem.

Tanks for the info. Your info on Kai led me to the thread below. I like your idea. 1 liter starter, and pitch as close to 88 billion as I can and bank the rest. Thanks for the heads up.
Good thread here!
https://www.homebrewtalk.com/f163/yeastcalc-com-now-two-stir-plate-options-396992/

 

[kanzimonson]

If given the choice, I'd rather overpitch by a little bit rather than risk underpitching. 50% extra might be a little high, but I wouldn't worry about 10-25% more.