Cell Count in Yeast Cake

Yeast & Fermentation
1

Hi all, first time poster!

TLDR: I have no idea how much top-cropped (or yeastcake-harvested) yeast to pitch into a ~1.055 OG Octoberfest (5.5 gallons)

I am planning on making an Octoberfest (late I know) on August 18th. Instead of making a boring old starter, I decided to spring for some ingredients and use up the Northern Brewer hops in my freezer and make a steam, which I will do on August 10th. While different from San Fransisco Lager Yeast, Wyeast’s bavarian lager has very similar characteristics (and is likely distantly related) to the SF lager yeast typically used in steams.

Anyway, I’m planning on making a 1.5L starter + yeast nutrient with the BL yeast (smack pack), pitching in the low 60s for the steam. Then I am planning on top-cropping as much as I can at high krausen (24-36 hours?) off the steam, harvesting into a sanitized mason jar, and pitching that into my Octoberfest Lager at around 50 degrees.

this being my first lager, I am obviously worried about stressing the yeast, excessive sulphur production, etc., however the proprietor of my LHBS told me that it was not advisable to pitch onto an existing yeast cake. I had heard this wasn’t a good idea (but not a horrible idea), as there is a lot of other material in this (dead cells, trub, etc.), but he mainly cited the fact that if you overpitch, the cells won’t have an adequate growth phase.

I am left with a few alternatives:

1.) top crop and grow a 1.5-2 L starter for the Oktoberfest 2.) top crop and pitch as-is (maybe a cup?) 3.) rack the steam off the cake, harvest a cup or two (increased as I know the bottom contains dead yeast, trub, hop matter, etc.) the night before, and cold pitch into the o-fest lager

EDIT: someone on another site just commented that I won’t be able to top crop since this is a lager yeast. aka. a BOTTOM fermenting yeast. Even if there is a krausen, it doesn’t sound like it will have huge amounts of yeast cells in it. Maybe I’ll just reserve some of my steam starter and do a second starter…making this entire exercise circuitous and pointless. Gotta love homebrewing!

2

I’d just use the repitch from slurry numbers on Mr Malty and use the cake. If the trub and other non-yeast material didn’t hurt your first batch, why should they be such a concern for your second? If trub is excessive, try letting it settle next time and trasfer off of it before pitching, this way you get a cleaner yeast cake…

Another thought: if you ferment in a bucket you can try to skim off the upper layers (yeast) and leave the bottom layer (trub) behind…

3

Maybe this is a dumb question, but I have fermented my lagers in buckets and could not see the process, but:

With bottom fermenting yeast and cooler fermentation temps, is there any top crop to be harvested?

4

I think you’re better off waiting until your steam is completely fermented and then using half of the yeast cake for the Oktoberfest. After transferring the steam off the cake, fill the carboy with a half gallon of water, swirl it up real good, then let it settle for about twenty minutes. Pour off just the liquid leaving the trub behind. Pitch half of that into your lager. Save the other half (in a sanitized container) for a future batch.

5

Have you done it this way? Did it work pretty well? I assume the theory is that the trub settles faster than the yeast…

6

[quote=“560sdl”]Maybe this is a dumb question, but I have fermented my lagers in buckets and could not see the process, but:

With bottom fermenting yeast and cooler fermentation temps, is there any top crop to be harvested?[/quote]

not a dumb question. A GREAT question that I didn’t consider. Some say a krausen does form with the bottom-fermenting strains, but I’ve also read that they do not contain high cell counts. Whuda thunk I couldn’t TOP crop yeast from a BOTTOM fermenting strain.

Brilliant of me.

7

I have siphoned a liter off the bottom of a fermenting lager and pitched it into another batch. It worked out fine. I have no idea how many cells it was but they were healthy. Quality is more important then the quantity with yeast.

I like to let it ferment out. It shouldn’t take much more than a week anyway. The cake will have between 700-900 billion cells depending mostly on pitch rate and oxygen levels. Since I have a good guess of how many cells there are I can figure pitch rates from slurry reasonably well.

8

[quote=“Conroe”]I have siphoned a liter off the bottom of a fermenting lager and pitched it into another batch. It worked out fine. I have no idea how many cells it was but they were healthy. Quality is more important then the quantity with yeast.

I like to let it ferment out. It shouldn’t take much more than a week anyway. The cake will have between 700-900 billion cells depending mostly on pitch rate and oxygen levels. Since I have a good guess of how many cells there are I can figure pitch rates from slurry reasonably well.[/quote]

so you took an autosiphon, started it in an (actively fermenting?) ale pail of lager and just made sure the liquid moving through it was cloudy, kind of moving it around the bottom of the fermenter?

Did you decant/chill afterwards?

9

I just siphoned it and pitched it. I think I moved it around a little (it was years ago.) As I recall I had active CO2 production within 24 hours.

10

Since prior to pitching, I racked the beer off the settled trub, I siphoned into a clean sanitized ale pail, then into two mason jars in the fridge. decanted, and I think the slurry at the bottom is pretty much pure yeast. Hopefully doesn’t need a starter, as I’m brewing the Octoberfest on Sunday…