top cropping recover

[cicquetto]

recovering all the yeast through top cropping in a pre batch of 5gal, will I have enough yeast to ferment a 20gal batch?

 

[Weezy]

Different yeast strains yield differing amounts of top yeast. But even the best I'd think wouldn't give you enough for 20 gallons ime.

 

[user 246304]

It also goes to when in the ferment you collect, your slurry density, is it immediately repitched or stored, etc. Lot of variables at play but more than anything else you do what you can to be consistent each and every time, with each and every process. Then you can know if you like/dislike your finished beer, you can tweak with better confidence.

 

[cicquetto]

wyeast 3944 witbier immediately repitched

 

[user 246304]

Ciquetto, what I'm saying is that depending on where you are in your fermentation, you will have a greater or lesser krausen to draw from. And there is also the issue that if you pick too early or too late, you might be selecting for early flocc'ers or over-attenuative yeast. It's not an easy answer, at least none that I can say. Without an accurate way of knowing how many you have - without a hemocytometer - you won't know the density of your slurry and hence how much is in, say, a quart of skimmed yeast slurry.

All this is said, under a presumption you want an "ideal" pitch, which we know never or rarely happens in the real world. I know there are approximations, just can't remember where I've seen them, sorry. Try Chris White, I'd suggest. And I'll do some digging myself.

 

[Smellyglove]

From my experience you need about 75ml of bottom cropped yeast for a 6.6gallon fermentation at about 1.055-1.065 OG. This "calculation" has worked for several years for me. You need to see what is acceptable yeast to pitch, and what is trub, to discard the trub. I'm speaking of "acceptable" to "acceptable just a tad minus" when I mean 75 ml. But dense slurry. Typical at least five days in the fridge.

So for a 20g I'd say about 180-225ml of dense slurry if the OG isn't to high. Harvest what you can from the top. Let it sit and compact in the fridge, and if you see you're low, add from a bottom-crop.

 

[cicquetto]

Ciquetto, what I'm saying is that depending on where you are in your fermentation, you will have a greater or lesser krausen to draw from. And there is also the issue that if you pick too early or too late, you might be selecting for early flocc'ers or over-attenuative yeast.

the first crop (12-24h) in the most attenuative?

 

[user 246304]

the first crop (12-24h) in the most attenuative?

No, the yeast that hangs out and continues to party - you know the type, they never leave - those are typically the most attenuative.

 

[cicquetto]

No, the yeast that hangs out and continues to party - you know the type, they never leave - those are typically the most attenuative.

ok, if I want to select the most attenuating yeast I must first discard the first crop.

 

[user 246304]

ok, if I want to select the most attenuating yeast I must first discard the first crop.

If that's what you want, yep. If you truly want the most attenuative, I'd do basically what smellyglove is suggesting, harvest from the bottom. Draw the top (of the tank bottom) layer off. The bottom yeast layer, mixed in with trub, will be the early quitters; the middle layer will be balanced; and the most attenuative will be on top. In a CCV, that's why they dump the first portion of yeast, turn the racking arm to harvest from the sweet spot (or just use a sight glass and draw from the bottom of the tank - now cleaned of the early flocculators), and discard the top layer. They want consistent performance, and that's the best practice to help with that.

If you're top cropping, generally, you'd skim the first part laced with brown trub, discard, skim the second part as your harvest.

Just a thought, but I'd caution against taking a strain not known for being attenuative, and seeking the most attenuative of that strain. What you're basically doing is selecting the weirdos, the mutants, possibly, and over time you're likely going to start getting off fermentations. If you want more attenuation, I'd just suggest getting a more attenuative yeast.

 

[cicquetto]

ok thanks, I could use the most attenuating yeast to ferment a belgian imperial stout based on brewdog recipe of AB:05 that in the last brew has remained little attenuated.