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 Home Brew Forums > Need help with pitch rate / starter sizes
05-13-2011, 04:58 AM   #1
SenorWanderer
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 Need help with pitch rate / starter sizes

I'm about to make a starter of WY2487 HELLA BOCK for a maibock I'm brewing next week. Here's what I know:

wort volume: 6 gallons
OG: 1.070 (17.5 plato)
yeast "born on date": 01/25/11

Mr. Malty Pitch Rate Calculator says that I need 579 billion cells. Another way to look at it is I need 26.5 million cells per ml of wort. In order to get there I need to put 5 packs of yeast in to an almost 12qt starter (Intermittent shaking). I have only 1 pack of yeast, that, according to Mr. Malty is only 22% viable.

Obviously I plan to step up a starter, but I'm not sure where to start. Well, actually I know exactly where I'm going to start, just don't know what that's going to get me.

I'm going to pitch the 22% viable yeast pack into a 1 gallon starter. How do I figure out how many cells that yeast cake has, and then what size the next starter should be? Wyeast has a pretty nifty pitch rate calculator, but it doesn't take viability into account, and it presumes that i'll be adding fresh wort to the starters, instead of decanting the beer.

I really wish Mr. Malty had a "reverse calculator" of sorts, that would tell you how many cells you get from pitching 'x' amount of cells into 'y' volume of 'z' gravity wort. Is there a formula for this that I'm just not finding?

One thing that I've tried is setting up the calculator for 1 gallon of 1.040 wort with my yeast. Under these conditions I'll achieve the 28 billion cells needed for an ale with a 1.06qt starter. Is it safe to presume then, that using a 4qt starter will get me somewhere in the neighborhood of 100 billion cells? It just so happens that 100 billion cells is the stated amount of cells in a fresh Wyeast smack pack. Could I then consider my fresh yeast slurry to be the same as 1 new smack pack at 100% viability and pitch that into the appropriate size starter? According to the calculator I'd need to pitch 13.48qt, or just over 3 gallons.

What do you think of my logic, because that's ALL I can come up with!?!

As usual, TIA!

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05-13-2011, 06:06 AM   #2
rockfish42
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I just did some fiddling you can hit ~100 billion cells with a 1.78 liter starter. From there I'd just treat it like you were starting from a new 100% viable pack, which sadly seems like you'd need at least 2 packs to hit the right pitch rate for the next step.

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05-13-2011, 08:25 AM   #3
SenorWanderer
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thanks for the reply rockfish. Can you tell me how you got those numbers? do you have a formula?

thanks!

edit: yeah, now i see what you did. put in the date and OG of the starter, then change the volume until it calls for 100 billion cells. well done, sir. well done! Thank you for illuminating a new way to use the pitch rate calculator!!

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05-13-2011, 01:17 PM   #4
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Here's what I do, I'll use your exact example:
First you select 'liquid yeast', 'intermittent shaking', 6 gal batch size, check the 'calculate viability from date' box, and enter the mfr date in the box (1/25/11). Slide the 'growth factor' all the way to the right.

Then start adjusting the 'OG' box until you see a '1' in the '# of vials or packs needed with starter'. Adjust it as high as you can go until that 1 changes to a 2, then back it down to where it says 1 again. The size starter it tells you is the biggest starter you 'should' make with such a small amount of yeast. Doing this I got 1.014 in the 'OG' box and .71 gal for the starter size and; (the whole point of this step) 121 billion cells in the '# of yeast cells needed (in billions)' box.

So you're going to make a .71 gal starter (intermittently shaken) from your old vial and get 121 billion cells.

Now enter 1.070 in the 'OG' box, uncheck the 'calculate viability from date' box and enter 121 in the 'Viability %' box. It will then tell you how big your second step starter needs to be (but make sure it still says 1 in the '# of vials or packs needed with starter' box). Unfortunately for you, it's still a 2.62 gallon starter.

Hopefully that all made sense. All we're doing here is calculating how much yeast we get from our first step, then entering that amount of yeast as our 'vial or pack' and calculating how big of a second starter we need. The reason it works like this is because 100% viable vials/packs of yeast conveniently have 100 billion cells. So 90% viable packs have 90 billion cells, and 121% viable packs have 121 billion cells.

Bottom line is that for big lagers it is often easier to just make two batches. The first batch is a low gravity lager that you can reasonably make a starter for (even for a 1.048 beer you'd still have to step it up). Then use the cake for the big beer. It just so happens that Wednesday night I made a lager starter (1.8L stirplate) from yeast made in January and will be stepping it up tonight (another 1.8L stirplate) just to make a 1.050 beer. Lagers need LOTS of yeast.

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05-13-2011, 06:11 PM   #5
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Thanks for the reply! Your method makes total sense. I really like the way we're all manipulating the calc to suit our needs, just wish 'he-who-shall-not-be-named' would add some features to make this all a little easier.

I think it all might be a moot point right now, as I went ahead and made the 1g starter last night and show no activity at all this morning (no, i didn't smack it, just poured it in, it was getting late). The yeast is old, but I'd typically expect something after 12 hours. I'm going to hit it with O2 again and give it another 12h but might just end up getting the WLP833 when I go to the LHBS for ingredients tomorrow. The reason the yeast is so old to begin with is the WY2487 is one of Wyeast's spring seasonal strains, and I kinda flaked my Maibock this year.

The first thing on the agenda when my living situation is more permanent is slants for the 4-5 strains I use regularly!!

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05-13-2011, 06:16 PM   #6
bottlebomber
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You might just consider making a smaller beer with a 2 liter starter and then pitching onto the yeast cake after its done. Guaranteed to have enough then

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05-13-2011, 06:29 PM   #7
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FWIW, that Hella Bock yeast is not the Ayinger strain but WLP833 allegedly is. I've confirmed 2487 is not Ayinger through Wyeast. They wouldn't come right out and tell me the source but from the hints they gave me, 2487 should be Schloss Eggenberg (Samiclaus).

I always smack the packs but I do it just seconds before I rip it open and pour it in. When I do lager starters I chill the flask/starter wort all the way down to ~40* F, then I aerate it well. Then I take the ~40* F smackpack, smack it and immediately pour it in. Then onto the stirplate and let it naturally warm up to room temp and ferment. I chill it like that so I can get maximum O2 in the wort.

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