Calculating the number of yeast cells in a conical yeast draw

I recently set up a 15 gallon conical placed into a temp controlled refrigerator as a fermentation chamber.

I am testing it out with a 10 gallon beer I have brewed many times.  It is an IPA with a S.G. of 1.064.

Using Beersmith 2 I recalculate the batch size to 15 gallons.  I am then told I will need 667.4 Billion yeast cells to create this beer.  Or, I need 4 packs of Safale 05.  It is my understanding that a 11.5g package of dry yeast yields 200 billion yeast cells.

I will be harvesting yeast from the conical using a 1.5" sightglass that will yield 44.4ml of yeast.  My question is, how do I figure out how many billions of yeast cells comes out of a sigthtglass of raw yeast?

Thanks

Cool question. Short answer is "do cell counts."

The amount in that sight glass seems low. If it is 1.5" i.d., I wouldn't be surprised if it actually holds more.

What you harvest is going to vary batch to batch. Trub, OG, temperature, pH and nutrient levels are going to be factors in determining the quality of the yeast. Accept it, embrace it, it's ok.

What you want to do is drop trub right after the most vigorous part of fermentation is over. Be gentle. Just crack the valve open until it starts to flow. It often will stop and just a slight opening of the valve will get it moving again. You want the valve open just enough for movement, no more, or else you'll draw down the center plug and leave the yeast on the conical sidewall. Stop once it becomes creamy and flows easily.

The next 3/4 of a gallon will be yeast of variable quality. You want the smoothest, cream colored portion (the center third). So, if it is thick "peanut butter;" that is viable, but very tired. Draw this off for a day or two, and you'll see the creamy portion that you want to harvest. The top of the yeast cake is often powdery by comparison and you don't want that, either.

My estimate is about a liter of slurry for 15 gallons is a good place to start. Another half liter is good if you want to reduce esters. Two liters for a for a lager. In these conditions, vigorous fermentation should be done in 4 to 5 days. The yeast may take another 5 days to attenuate the last 10 points plus eliminate diacetyl and acetaldehyde.

Thanks brewfun.. A very good explanation. 

So it will take me some time to draw out the yeast I seek.  I will sanitize a large jar and save the yeast to it.

Now, when repitching, do I treat it as a slurry when I use the yeast tool in Beersmith to calculate the volume I need?


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The answer to my question above is yes, I treat my harvested yeast as a slurry.  Beersmith will tell me how much slurry I need based on a number of factors.  A good explanation is offered here as well:  http://www.mrmalty.com/calc/repitch.html

Here is some additional information regarding yeast harvesting procedures:  http://www.wyeastlab.com/com-yeast-harvest.cfm

Since with a conical you can drop the tired and powdery unwanted cells, and take only the best cells, do you just re-pitch the slurry? 

Or do you do a fresh starter using those strong cells? 

While the conical certainly sounds better at harvesting the quality cells than a carboy/bucket, it seems like the yeast is still 100% "used" and may benefit from a restart under ideal conditions.  Does that depend on what you first fermented?

MaltLicker said:

Since with a conical you can drop the tired and powdery unwanted cells, and take only the best cells, do you just re-pitch the slurry? 

Or do you do a fresh starter using those strong cells? 

While the conical certainly sounds better at harvesting the quality cells than a carboy/bucket, it seems like the yeast is still 100% "used" and may benefit from a restart under ideal conditions.  Does that depend on what you first fermented?

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Great questions Maltlicker.

I am new to life with a conical so do await answers from more experienced brewers.  But I will tell you my ideas and plans of operation and maybe somebody will offer comments on both of our questions.

Beersmith, in the Tools > Yeast Starter will let me know the quantity of slurry I need based on my batch size and the gravity of my planned beer.  In addition, I would be giving BS the Production/Harvest Date of my saved yeast.

This allows me to assume that BS's calculations takes everything into account and produces an accurate cell count for me.  Now, if my handling, storage and sanitation are what it needs to be I should be ok to simply pitch the slurry.  Common sense would dictate that I may desire a starter if storage has been a long time or I have used a number of generations of the yeast.

My hope has been to eliminate the building of a starter every time I want to brew.  But I will, as I do now, always have dry yeast as a backup.

And yes, Malt, the conical is easier to use.  I actually went to this because I wanted to eliminate hauling carboys, tipping them and cleaning.  The yeast handling is secondary but I am very excited about it.

I do not have the experience to comment on whether pitching to a particular wort is dependent on what style of beer the yeast had made earlier.

MaltLicker said:

Since with a conical you can drop the tired and powdery unwanted cells, and take only the best cells, do you just re-pitch the slurry? 

Or do you do a fresh starter using those strong cells? 

While the conical certainly sounds better at harvesting the quality cells than a carboy/bucket, it seems like the yeast is still 100% "used" and may benefit from a restart under ideal conditions.  Does that depend on what you first fermented?

Click to expand...

Essentially, the beer is a starter. Ideally, the cells harvested have budded from the original generation. The main benefit of conical harvesting is the ability to drop heavier trub from the slurry and harvest the healthiest portion of yeast. A bucket or carboy only lets you swirl and spit whatever got in when you filled it.

If you're going to store the yeast for a couple of weeks, then yes, feeding it a little wort will wake it up.

For the most part, the previous beer is not consequential to repitching. I can take the harvest from a Stout and repitch it into a light colored wort without darkening it or effecting the flavor, if I have the creamiest portion. This is mainly due to the slurry being less than 3% of the total batch volume. In the example I gave Rep, the amount is about 2.5%.

I won't harvest from a beer that is about 8% or over because the yeast tends to be tired and have longer lag times or take longer to finish.

If you're going to go more than about 3 generations, then feeding the yeast with nutrient really helps the longevity. I feed with Fermaid K and get 12-16 generations before I have to reorder.

brewfun said:

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If you're going to go more than about 3 generations, then feeding the yeast with nutrient really helps the longevity. I feed with Fermaid K and get 12-16 generations before I have to reorder.

Click to expand...

Do you add the nutrient during storage?  Or, into the wort when pitching?

Rep said:

Do you add the nutrient during storage?  Or, into the wort when pitching?

Click to expand...

Very end of the boil. I hydrate mine into a paste with wort early in the boil. Then thin it out with boiling wort right before I add it. It just seems to blend and dissolve better.

brewfun said:

Rep said:

Do you add the nutrient during storage?  Or, into the wort when pitching?

Click to expand...

Very end of the boil. I hydrate mine into a paste with wort early in the boil. Then thin it out with boiling wort right before I add it. It just seems to blend and dissolve better.

Click to expand...

Thanks

I have some of this hanging around and will try it again.