measuring yeast count after starter

[Redtab78]

This may be a dumb question.....BUT how exactly is the yeast measured when in a slurry? In other words if I need 2L of yeast, does that mean a 2L volume of yeast with the starter wort all together after the fermentation?

When I make a starter, I make 1.5-2L of starter wort and then pitch the smack pack or whatever Im using into that, set it on the stir plate, and when its all done (initial fermentation is obvious) then is my total amount of yeast 2L?

OR

Is the total volume of yeast only what is at the bottom after crashing? In which case MOST of my yeast starters after stirring and crashing is only MAYBE 250ML sitting at the bottom, so my volume of yeast is only 250ml.


I am just trying to understand....when a yeast calculator says I need 1 gal of yeast....that I don't actually need 1 gallon of the visable yeast sitting on the bottom...I know it sounds stupid, as that would be ridiculously over pitching...but then again, I could be entirely way wrong!

 

[Begin2Brew]

I think you are getting yeast volume confused with starter volume.

The started volume is the amount of wort the yeast needs to replicate to a specified cell volume.

If you use a starter calculator it will tell you, based on your viable cells, how must wort you need to produce the proper pitch count. You can cold crash the starter and just pitch the yeast slurry.

 

[fourfarthing]

My view has always been that the volume is the amount of slurry. I always decant and dump most of the starter wort as well.

 

[Redtab78]

I have been watching videos all morning on using a haemocytometer for counting for large batch brewing, and found myself pondering how the commercial guys make starters for say a 5 or 7bbl batch.

Using brewers friend calculator, suppose I was making 95 gallons of 1.065 wort, the calculator says I need 4,289 Bil cells. Which means I would need 4.29L of slurry....

So, based off that, if I was to make 4.29 worth of starter wort, and then pitched a smack pack into that, and put it on a stir plate, does that simplicity mean I will have the needed 4,289 Bil cells after the starter wort was done? Or is there were recounting cells after the starter becomes important?

 

[fourfarthing]

You would need to do it in stages if starting with a smack pack.

 

[Begin2Brew]

I have been watching videos all morning on using a haemocytometer for counting for large batch brewing, and found myself pondering how the commercial guys make starters for say a 5 or 7bbl batch.

Using brewers friend calculator, suppose I was making 95 gallons of 1.065 wort, the calculator says I need 4,289 Bil cells. Which means I would need 4.29L of slurry....

So, based off that, if I was to make 4.29 worth of starter wort, and then pitched a smack pack into that, and put it on a stir plate, does that simplicity mean I will have the needed 4,289 Bil cells after the starter wort was done? Or is there were recounting cells after the starter becomes important?

You will not get 4,289B cells in a 4.29l starter. A slurry is a think concentration of cells. A starter will have no where need that concentration of cells. The most you will get is around 700B cells.

With counting cells you need to take into consideration the concentration or dilution of the media the cells are in.

 

[Redtab78]

So how would a brewery archive a 4,289 bill cell starter?

 

[LLBeanJ]

So how would a brewery archive a 4,289 bill cell starter?

Just like we do, but on a larger scale. They would start with a small starter and build up the cell count gradually using a succession of incrementally larger starters until they achieve their pitch volume.

They might also buy a ready-to-pitch qty from one of the major yeast suppliers and use it for an initial batch, then collect slurry from that batch to inoculate the next batch. They would repeat this for several batches until they determine that they need to get new yeast. Most breweries have a set limit on how many generations they will go before starting over with fresh yeast. When they collect the slurry, their lab will take a sample and estimate the cell density and use the count to determine how much slurry is needed.

 

[Redtab78]

So when the calculator says that I would have enough yeast with a 2L starter for a 5 gallon batch, should I make a 1L starter, and then a few days later (without decanting) add another 1L? Is this how the commercial breweries would build up a starter?

After reading what I did about the microscope and counting, this got me to wondering if my process is all messedmup, and I am under pitching....when I use the calculator online, it tells me I need a 300 bill starter...so 1 pack of wyeast into a 1L on a stir plate... I know for us at 5 gallons that is fine, but that's why I asked about commercial breweries....

I watch videos, and see these guys pitching what appears to me as a 2L flask of yeast, but I'm wondering if those flask are almost all yeast cells with only a little wort so liquefy it, or is that just a slurry that could be cold crashed and would only have a few inches at the bottom of yeast...

 

[LLBeanJ]

So when the calculator says that I would have enough yeast with a 2L starter for a 5 gallon batch, should I make a 1L starter, and then a few days later (without decanting) add another 1L? Is this how the commercial breweries would build up a starter?

Ideally, you would want to approximately double your starter size (give or take) when stepping up and with the exception of very small steps (say, <.5L or so), you would want to crash & decant before moving to the next step. The size of the steps depends on the quantity and viability of the yeast you are starting with. If you had a fresh pack of 100B cells (high quantity and viability), you could probably just go with a 2L starter right off the bat and call it good. If, on the other hand, you have some clean yeast you harvested from a starter 9 months back (low quantity and viability), you would want to start with a small initial step, say maybe .25L, then .5L for step 2, and then 1.25L for step 3. In that example, I would not bother crashing and decanting between steps 1 & 2, but I would before step 3.

Here's the calculator I use: http://www.yeastcalculator.com/

I use that calc for all brews to determine cell count needed and for determining step size when making starters. Also, I normally only use clean yeast when I make starters. If direct-pitching fermenter slurry, I assume 1.0-1.5B cells per ML slurry and use a measuring cup to pitch what I need. Starters from clean yeast (freshly bought or harvested from previous starters) and direct-pitching fermenter slurry are what I use exclusively. I don't wash yeast and I don't pitch new vials/packs without first making a starter. Only on very rare occasions do I use dry yeast, but when I do, if I decide I want to save some for later, I'll let the yeast ferment the batch and then collect a small amount (a couple tablespoons) of slurry from the fermenter and make up a starter and harvest from there. This would be the only exception to what I describe above about only using clean yeast for starters.

To use the calculator, select the beer type and enter batch size to find the cell count needed. Then enter your starting yeast quantity and viability date. Finally, start playing around starter volumes for the steps. Ideally, for optimal yeast health you want to keep the inoculation rate between 50 and 100 (again, give or take) for each step. If using a stir plate, use the Kai Troester option, as it seems to be more accurate than the Jamil Z option.

I watch videos, and see these guys pitching what appears to me as a 2L flask of yeast, but I'm wondering if those flask are almost all yeast cells with only a little wort so liquefy it, or is that just a slurry that could be cold crashed and would only have a few inches at the bottom of yeast...

It could be either. If it's a commercial brewery, they're likely pitching slurry with minimal starter beer, so multiple steps and decanting between each. Some homebrewers decant and pitch mostly slurry, while others pitch the whole starter. I usually decant first, but I've pitched the whole starter on occasion and didn't notice any ill effects.