Mr. Malty calculator question

[ryan_howard]

Ok, I hope this doesn't sound stupid, but here goes.

I'm messing around with the Mr. Malty calculator and trying to get familiar with yeast math and science. I'm going to try to harvest and store some yeast from the batch I have going right now (first time, never tried before). But, I want to understand this better before experimenting.

I have Mr. Malty set for a 5 gallon batch and am using the "Repitching from Slurry" tab. I'm leaving the two sliders set in the middle (since this is a hypothetical batch). At the settings I have, it says I will need 177 billion cells.

By messing with the calendar, I get the following mL of slurry needed:

• use immediately: 83 mL
• one month old: 177 mL
• 2-11 months old: 744 mL
• 12+ months 7,435 mL

Now, my plan is to collect two 150 mL baby-jars of yeast, and I'm hypothesizing they'll fit the criteria in the sliders (average concentration, average non-yeast material)

So here is how I interpret this:

• If I were to reuse this yeast within a month, I could just measure out the 177 mL and be right on, possibly without even a starter.
• Longer than a month, and I would need to make a starter, but hopefully just use one of the two baby jars.
• Longer than a year, according to the calculator, the yeast really isn't viable at this point.

Ok, how did I do? Where are my mistakes?

Thanks!

 

[HopOnHops]

I haven't been yeast harvesting for long, but I feel that if you make an appropriate sized starter with whatever yeast, they will reach an equilibrium.

Are you using a stir plate?

 

[ryan_howard]

No, I don't have a stir plate.

So, how much of the harvested yeast do you use to make your starter. Any amount?

 

[HopOnHops]

I do everything using 16oz mason jars. I'll pour a few liters of sanitized water onto the yeast cake, pour that into a glass jar, let that sit for a bit and pour whatever I can of the middle layer into sanitized mason jars. I don't worry about cell count because I feel the stir plate setup will give you the most yeast possible because of the continuous O2 absorption. I built mine for ~25 bucks. The money I've saved has definitely paid for that, a 2L flask, and then some

 

[HopOnHops]

Also unless it's a similar style I prefer to harvest yeast from the starter. I'll make a 2L starter and make 2-3 jars of yeast (none if it's a huge beer). It's like unlimited yeast and all I need is DME