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trevorc13 12-31-2010 02:29 PM

Mr. Malty Question
 
So I cleaned my yeast on 12/4 and I'm getting ready to use it. I went to www.mrmalty.com to see how much yeast to use for my starter. It says that pitching from a slurry, I need 223 ml of yeast! That's about 7.5 oz! Is this right or is this calculating it without using a starter. If that's the case, how much would I use with a starter? I hear that yeast won't multiply by more than four times, so should I use a quarter of 7.5 oz for my starter? I guess I'm just confused on this. :drunk:

trevorc13 12-31-2010 02:40 PM

...also, in the top section I input my information for the beer I got the yeast from. It says the viability is about 50%, if that makes any difference. That's also the reason I feel I should make a starter.

Teaman 12-31-2010 02:50 PM

If I wash my yeast and have a nice white solid layer in the bottom of my mason jar then I look at it just as a store purchased vial. As in 1oz is about 100bill cells. So I take that and use the proper size starter, or starters, to achieve my pitching rate. With a normal 1.050 - 1.060 I usually use about 1oz of yeast cake from the fridge with a 1qt starter and it's going in a few hours. This works for me.
I used Mr. Malty in conjunction with a chart in "How To Brew" book and figured it out from there.
By the way, 1oz of yeast in the bottom of a small mason jar is about 1/2 inch thick.

melchermatt 12-31-2010 03:20 PM

7.5oz without a starter is about right. A shade under a cup - it's not that much. Mr Malty is giving you the amount without a starter. You can make a starter as teaman suggests if you wish, or just pour in the slurrey.

Calder 12-31-2010 03:36 PM

If your beer was good and you used good sanitization practices to capture the slurry, just pitch the slurry as recommended. Mr malty is saying you have sufficient yeast cells in the slurry to start the batch.

There is no limit to the amount of reproductions from a yeast; it multiplies, then you have new yeast that can multiply providing the conditions are right.

kanzimonson 12-31-2010 05:42 PM

Here's a method I use when I have an insufficient amount of slurry to figure out what size starter I need to make (reposted from elsewhere):

Let's say I'm making a 1.060 ale, pitching 5.5 gallons. I have a jar of reharvested slurry that is exactly four weeks old from today, and the yeast is very compacted into a 50mL puck. I go to Mr Malty, set the parameters of my beer, set the age of the yeast, go to the "Reharvesting" tab, set the Yeast Concentration to 4.0, set the Non Yeast Percentage to 15.

Mr Malty says that I need 229billion healthy yeast cells, which would be 134mL of my yeast in its current state. I have 50mL, or 37% of what I need (50/134). If you multiply 37% by 229billion cells, you find that I have about 84billion healthy cells.

Here's where things get fuzzy. As I understand it, the Mr. Malty calculator works such that a vial of yeast with 100% viability has 100billion cells. So if I have 84 billion cells, this is the equivalent of having one vial of yeast at 84% viability, right? So then I flip to the Liquid Yeast tab, manually set my viability to 84%, set the Growth Factor so that it says I need 1 vial. Doing this, it says I need to make a 1.23L starter with a stir plate.

Teaman 12-31-2010 07:39 PM

Quote:

Originally Posted by kanzimonson (Post 2514012)
Here's where things get fuzzy. As I understand it, the Mr. Malty calculator works such that a vial of yeast with 100% viability has 100billion cells. So if I have 84 billion cells, this is the equivalent of having one vial of yeast at 84% viability, right? So then I flip to the Liquid Yeast tab, manually set my viability to 84%, set the Growth Factor so that it says I need 1 vial. Doing this, it says I need to make a 1.23L starter with a stir plate.

I agree. It gets a bit fuzzy. I don't know how you can accurately figure out how many yeast cells you have. I guess you can get kinda close and that's good enough.

kanzimonson 01-01-2011 03:55 PM

Yeah, I definitely agree that I'm making a lot of assumptions here, but I figure if I under or over pitch by even as much as 10% that's not terrible. So long as you can avoid the equivalent of dumping one old vial in a huge beer, or (satan forbid) dumping wort onto an entire yeast cake, you're probably doing a good job.


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