Author Topic: slurry repitch calculator  (Read 1346 times)

Offline brewinhard

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slurry repitch calculator
« on: March 19, 2016, 01:24:39 PM »
Now that Mr. Malty is down (which I frequently use to estimate yeast pitches), does anyone have another trusted yeast pitching rate calculator out there that I can check out?

I am looking for one that can incorporate age of the harvested slurry when estimating repitches.  I currently have 150 mL of dense, compact slurry of WY Thames Valley II that was harvested 3/4 and I want to repitch it on 3/23 into a 1.054, 5.5 gallon batch.

Thanks...

Offline Bob357

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Offline Pricelessbrewing

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Re: slurry repitch calculator
« Reply #2 on: March 19, 2016, 04:49:04 PM »
Bob that does not support slurry...

For harvesting from post fermentation (primary/conical etc). I would use this https://www.wyeastlab.com/com-yeast-harvest.cfm as a baseline.

For starter harvesting, the % of slurry that is yeast is much higher so I would use a 3.33x the density based on my own personal experience.

For me, I can get about 40B cells into a 40-45mL slurry after decanting the starter. Roughly 33% slurry, gives a density around 2.89B per mL. 

From there you can calculate the total amount of cells you had when harvesting, apply the viability loss of

% remaining = 0.8^n where n is the number of months since harvesting.

Then you have the approximate number of cells remaining to date. Enter that into the yeast starter calculator of your choice.

Online tommymorris

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Re: slurry repitch calculator
« Reply #3 on: March 19, 2016, 10:16:54 PM »
I bought the mr malty app a few years ago. It is still working fine.

Offline brewinhard

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Re: slurry repitch calculator
« Reply #4 on: March 19, 2016, 10:23:24 PM »
I never got around to buying it.  Stupid me. Is there any way to get a hold of it now? 

Was thinking of making a starter with my saved slurry as it appears that the slurry I have saved would be potentially underpitching by at least 75-85 billion cells. That is fully estimated of course. I would usually have no problem just pitching the slurry and having a longer than normal lag time, but I am attempting to run a cooler than average ferment which would put my cell count even more out of whack and I also want to repitch this same strain into a big RIS after this next batch.  I just want to be sure the yeast are healthy and providing me with enough fresh vital cells for the big RIS. 

Anyone have any idea how much of my harvested slurry to add to "X" amount of wort to tackle a 5.5 gallon batch of 1.054 OG? Most calcs I have looked at are requiring about 208 billion cells to finish the job.

Any thoughts?

Offline Stevie

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Re: slurry repitch calculator
« Reply #5 on: March 19, 2016, 10:46:52 PM »
App is still available on iOS

Offline brewinhard

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Re: slurry repitch calculator
« Reply #6 on: March 19, 2016, 11:16:40 PM »
thanks.  I am looking at it right now.

Offline Stevie

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Re: slurry repitch calculator
« Reply #7 on: March 21, 2016, 08:22:48 PM »
Site is back up. I just used it to find a whitelabs equivalent.

Offline brewinhard

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Re: slurry repitch calculator
« Reply #8 on: March 21, 2016, 08:31:31 PM »
Site is back up. I just used it to find a whitelabs equivalent.

Yay!  He must have been waiting for me to finally purchase the app.  ;)

Offline Adamg8504

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Re: slurry repitch calculator
« Reply #9 on: March 30, 2016, 11:21:27 AM »
I have incorporated Homebrewdads Excel based pitching calculator into my spreadsheet, just for reasons like this.  I would prefer to not have to rely on websites and apps that may be down from time to time.

http://www.brewunited.com/downloadable_yeast_calculator.php

It's nice that it has an option to over harvest so you can keep ~100B ish cells for the next starter.
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