What exactly do you mean "slurry"

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brewzombie

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I'm used to the word slurry meaning a thick mixture where something is in suspension. I get that "slurry" in the context of brewing means a yeast suspension, but how thick is that slurry? If I rack off my primary, leaving minimal beer behind, is it a slurry if I scoop a cup (of cake?) from the bottom? Do I have to add liquid and resuspend the yeast to get a slurry? If so, how much liquid? I've looked at the Mr. Malty pitch calculator, but I find the settings confusing (how thick? how viable? how much non-yeast?)

The beer has been in the primary for a month (it's a hefeweizen and I'm not racking to a secondary as I've heard there's little benefit). I'm familiar with starters but not reusing yeast. The next beer will be a weizenbock (so definitely bigger). I've heard a cup of yeast cake/slurry for a regular beer. Is this a good rule of thumb. Should I use 2 cups for a big beer? Should I freshen up the month old yeast with a starter (1 cup in 2 L)? So many questions.
 
If you put the cursor on the bottom tab on Mr. Malty under the yeast slurry category it will give you an idea about how it is calculating slurry. I rack out as much beer as I can and then use the last little bit to suspend the yeast. I would use the Mr. Malty calculator to get an idea about how much you want to pitch as the closer you can get to what your beer needs the better. +/- 20% would be ideal...obviously harder to do this from a slurry than a starter though.
 
If you put the cursor on the bottom tab on Mr. Malty under the yeast slurry category it will give you an idea about how it is calculating slurry. I rack out as much beer as I can and then use the last little bit to suspend the yeast. I would use the Mr. Malty calculator to get an idea about how much you want to pitch as the closer you can get to what your beer needs the better. +/- 20% would be ideal...obviously harder to do this from a slurry than a starter though.

Thanks for your reply:

What you describe here is what I was thinking, so this would be "thick yeast" or 4.5 billion/mL on Mr. Malty? That sensible enough.

If harvesting from the primary, there would be significant trub content...so would you pick 25% non-yeast content?

What date should I pick for yeast viability? The day of harvesting seems a little too late for a long fermentation like mine...should I pick the day I estimate primary fermentation is finished (about 1-2 weeks into fermentation)?
 
Using these settings, it looks like I need < 1/2 cup thick slurry for for a 1.050 beer and < 1 cup for my weizenbock (1.081). Does that seem right?
 
What you describe here is what I was thinking, so this would be "thick yeast" or 4.5 billion/mL on Mr. Malty? That sensible enough.

Not even close. You get ~4.5 billion cells per ml of pure yeast solids. Slurry is nowhere close to pure yeast solids. On average, slurry is 25% yeast solids. The slider on the calculator lets you scale sightly around that number, IIRC.

What date should I pick for yeast viability? The day of harvesting seems a little too late for a long fermentation like mine...should I pick the day I estimate primary fermentation is finished (about 1-2 weeks into fermentation)?

Date of harvesting.

Cheers!

Bob
 
Using these settings, it looks like I need < 1/2 cup thick slurry for for a 1.050 beer and < 1 cup for my weizenbock (1.081). Does that seem right?

Work in milliliters. It's easier. Here's a conversion calculator.

1 US cup (8 fl. oz.) = 237ml

According to the calculator, 1.050 requires 86ml for ale and 171ml for a lager. For 1.081, 135 and 271. Those numbers are dependent on fresh yeast harvested and pitched same day.

I always use the Hybrid selection instead of Ale or Lager on the calculator, because I was taught 1 million cells per ml of wort per degree Plato. It works regardless of style (though it IS a bit underpitching a lager).

Cheers,

Bob
 
I'm used to the word slurry meaning a thick mixture where something is in suspension. I get that "slurry" in the context of brewing means a yeast suspension, but how thick is that slurry?

Bad 1995 picture showing yeast slurry on the left for re-pitching, very little liquid.
800 mL/100L was the pitching norm for lagers.

1e6ec6c5.jpg



Cheers,
ClaudiusB
 
OK. So the slurry in the picture is roughly the default thickness on Mr. Malty (about 2.4 billion per mL). Sounds like you're saying leave the defaults alone in your slurry looks like the above. Is that right?

As for yeast viability. Won't the yeast be less viable if I keep my beer in the primary for a month instead of transferring to a secondary? I would have thought to use the date of the end of primary fermentation.
 
The thickness of the slurry is mainly dependent on two factors: The strain of yeast and the amount of trub in the fermenter. Some yeasts are thin and runny, others are thick and "cake". Trub - like hops particles and break material - thickens the slurry.

Thus, if you're harvesting Wyeast 3787 (Trappist High Gravity) from a Belgian Blonde, it'll be the consistency of runny pancake batter. If you're harvesting Ringwood from a hoppy Pale Ale, it'll be much more thick.

Yeast will lose little if any viability if harvested from a fermenter that's had beer in it for a month. The best place to store slurry is under beer. ;)

Commercial brewers harvest at racking time. Racking time for commercial brewers is faster than we need as homebrewers, because full tanks aren't making money.

Cheers,

Bob
 
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