Harvested yeast questions

[Vallka]

Ok so I have been harvesting my yeast now for the last 6-8 batches, washing it and collecting it into "Ozark's centrifuge tubes" and storing in the fridge.
I've been reading about pitch rates, cell counts and so on. Had a look at the pitch rate calculator.
Now how do I determine how many cells are in my vials of yeast? I have a stir plate and have done 5-6 starters already but have just winged it so far (beer has been real good)

 

[Ozarks Mountain Brewery]

without a good microscope there's really no way to tell on yeast cell count, it could be different for every tube so when I save yeast I just add one vile to a 1700mL starter and build it, usually at least 1/2 " of yeast settles to the bottom and I know its good then

 

[Mark D Pirate]

Cell counts per ml will also vary on strain , without a lab its all guesstimate but if the ferment runs smoothly and produced a desired result then you're doing well

 

[Nosybear]

Ok so I have been harvesting my yeast now for the last 6-8 batches, washing it and collecting it into "Ozark's centrifuge tubes" and storing in the fridge.
I've been reading about pitch rates, cell counts and so on. Had a look at the pitch rate calculator.
Now how do I determine how many cells are in my vials of yeast? I have a stir plate and have done 5-6 starters already but have just winged it so far (beer has been real good)

Funny, my question on just that was published in BYO this month.... Short answer, without a microscope and a hemocytometer, you'll always just be winging it, which is what I do most of the time because, well, turns out even though I have the equipment, I'm too lazy to do it properly. Winging it got me the medal to the left and that's good enough for me. But if you want to do it, there are plenty of references out there to tell you how to count yeast cells. But I'm ordering a 3000 ml Erlenmeyer so I can build a big enough starter for my lagers. Mostly it's just guesswork. And harvesting, you have no idea as to the viability of the yeast, if it's contaminated so if you're really interested on how much yeast is in your harvested slurry, you'll have to do cell counting.

 

[HighVoltageMan!]

You can estimate your yeast counts from a slurry.

One way is to build a small starter, 1/2 liter or so and you pitch roughly a tablespoon in the starter. You will hit the yeast population saturation point, usually @100-120 billion cells. From there you have starting point by which you can build more if you like. You could put roughly 1-1/2 to 2 tablespoons of yeast slurry into a 1 liter starter and your saturation point would be roughly 200-250 billion cells.

The other way is to measure the yeast slurry volume and estimate yeast count that way. If you use trub free wort to make the starter and let it spin up and grow for 24 hours, then crash cool it for 24 hours, a pure yeast slurry will be at the bottom of your flask. Make a line at the yeast, pitch it and fill the flask to the line with water and measure the volume with a measuring cup. Yeast cells vary in size strain to strain, but a 1/4 cup of pure slurry is roughly 250 billion cells, perfect for mid gravity ales. Lagers should have roughly 500 billlion per 5 gallons, or 1/2 cup, etc. If you use DME instead of trub free wort, @25% of the slurry will be trub.

Contrary to popular belief, trub is not necessary as a yeast nutrient. The wort has enough nutrients by itself.

The counts are not lab grade, but if you consistently the same method, your pitches will be close each time. The key is measure the same way each time. Consistent pitch rates are necessary for consistent beers batch to batch.

Sorry to ramble, I hope this make sense.

 

[HighVoltageMan!]

I forgot to post this link, it’s a presentation I gave to my home brew club. It explains yeast counts a little better, I hope.

https://docs.google.com/file/d/0B-6...khrZWhr/edit?usp=docslist_api&filetype=msword

 

[vthokiedsp]

Mr malty has a slurry tab in their calculator. Check out their site and step by step explanation. Pitching slurry isnt an exact science. Based on an assumed density and viability, itll tell you how many mL you will need. Works great.