[Al Hounos]

It's surprisingly hard to find detailed top cropping information on the internet or in homebrew literature. Even the "Yeast" book barely has a few paragraphs.

I've just started experimenting with this method, specifically with Wyeast 1318, and I have some questions.

1. Why is the first (brown) head discarded?
Apparently to remove hop compounds and trub, but are there other, nastier things such as bacteria or wild yeast in the first head? I ask because I've always had good results pitching bottom-harvested slurry with trub and hop debris.

2. How much can be harvested from each skim, and how many times can one skim from a single batch? In other words, does removing the entire yeast head affect the donor beer's fermentation?

3. Since top-cropped yeast is extremely vital and active, it would seem that directly pitching from one actively fermenting batch to another would be ideal. In this case, how should pitching rates be estimated? I'd imagine one would need surprisingly little, given our resident yeast expert S. cerevisiae's posts on smaller, more active starters.

Thanks!

[S. cerevisiae]

1. Why is the first (brown) head discarded?
Apparently to remove hop compounds and trub, but are there other, nastier things such as bacteria or wild yeast in the first head? I ask because I've always had good results pitching bottom-harvested slurry with trub and hop debris.

Discarding the brown head is a practice that seeks to make the final product smoother by removing polyphenols and other compounds that have been scrubbed from the wort.  One of the strengths that top-cropping brings to the table is that wild yeast and bacteria do not floc to the top.

2. How much can be harvested from each skim, and how many times can one skim from a single batch? In other words, does removing the entire yeast head affect the donor beer's fermentation?

Many brewers skim their crop when the wort hits 50% apparent attenuation.  I recently discovered that this practice is not optimal with true Yorkshire strains.  The mid-head has to be "beaten" back into the wort, or one will end up with a diacetyl bomb.  I am now waiting until the end of fermentation to take my crop when using Yorkshire strains.

3. Since top-cropped yeast is extremely vital and active, it would seem that directly pitching from one actively fermenting batch to another would be ideal. In this case, how should pitching rates be estimated?

I am estimating that clean compacted cropped yeast should contain between 2.5 and 3.0 billion viable cells per milliliter depending on cell size.  Sixty milliliters of compacted top-cropped slurry should easily handle 19 liters of normal gravity wort.   If the yeast is taken at mid-ferment, one should be able to go down to as low as 30 milliliters of compacted top-cropped slurry.

One of my New Year's resolution is to start counting again.  Counting yeast cells is one of my least favorite brewing-related activities because there is very little payoff in a home brewery. Counting is nowhere near as rewarding as streaking a plate.  It is akin to watching paint peel.

[Al Hounos]

Thanks for the answers!

I pulled the brown head at 48 hours and did another full skim at about 72 hours on a recent batch. It felt like I was removing an awful lot of great-looking yeast from a beer that was still fermenting. If I get diacetyl or poor attenuation from the donor batch, next time I'll leave a good portion of the second head behind and probably mix it back in. Now that I know how little is actually needed to pitch a new beer, I won't feel the need to take the whole head anyway.
Thanks again.

For any other beginners like me reading this, if you can plan your brews accordingly, top cropping is not only the easiest pitching method (versus rehydrating dry yeast or making liquid starters), but it should also yield an extremely clean, viable pitch. For example, I recently made a 1.045 batch, a 1.055, and a 1.065 batch in succession, each about 4 days apart. I pitched the wyeast 1318 top crop from each batch into the next, and it allowed me to pitch a large amount of healthy yeast into three batches after making only one small starter for the first beer. Less starters, less work, less chance for contamination.

Of course, the catch is that you have to like top cropping (usally English??) strains. Thankfully I do.

[hopshead]

2. How much can be harvested from each skim, and how many times can one skim from a single batch? In other words, does removing the entire yeast head affect the donor beer's fermentation?

Many brewers skim their crop when the wort hits 50% apparent attenuation.  I recently discovered that this practice is not optimal with true Yorkshire strains.  The mid-head has to be "beaten" back into the wort, or one will end up with a diacetyl bomb.  I am now waiting until the end of fermentation to take my crop when using Yorkshire strains.

I just used for the first time White Labs Burton Ale (WLP023) I wonder if it is a "Yorkshire" type?

I cropped this at 48 hours.  I checked on it at 24 hours after pitch as that is the ballpark 50% attenuation time per White labs ( http://www.whitelabs.com/yeast/wlp023-burton-ale-yeast ).  But, at 24 hours the yeast on top was very foamy and didn't look dense enough to harvest.

At 48 hours the crop was much better (I didn't discard 1st skim but this is a practice I need to start doing).  This morning, 60 hours after pitch, the yeast was blowing off through blow off tube (SS brewbucket).  I am now thinking that the stuff blowing off is really what I wanted to harvest. 

I hope I like this strain, it appears to be a true top cropper, and easy to spot when "it's ready" to harvest.

[dilluh98]

I just brewed a pale ale with WY1318 - the first true top cropping strain I've ever used. Holy cow is there a lot of head! I skimmed the brown head at ~20 hours and then at 48 hours there was almost a full foot of thick, gooey off white head in the bucket. I'm glad I opted for a 4 gallon batch in the 7 gallon bucket. I skimmed about 150 mL  at 60 hours (not sure what that'll compact down to in the fridge) and left the rest.

Mark - you mentioned that the yeast might have to be "beaten back" at the risk of having a diacetyl bomb. How does one do this in practice?

I have to say - if you haven't brewed with a true top cropper, you should definitely try it just for the fun of it. I've never seen so much head in the fermentor ever, it's a much different texture/consistency than any other strain I've used and cropping for a re-pitch was incredibly easy.

[troybinso]

Many brewers skim their crop when the wort hits 50% apparent attenuation.  I recently discovered that this practice is not optimal with true Yorkshire strains.  The mid-head has to be "beaten" back into the wort, or one will end up with a diacetyl bomb.  I am now waiting until the end of fermentation to take my crop when using Yorkshire strains.

Can you elaborate on this? What causes the diacetyl to form if you don't beat the mid-head back?

[Slowbrew]

Many brewers skim their crop when the wort hits 50% apparent attenuation.  I recently discovered that this practice is not optimal with true Yorkshire strains.  The mid-head has to be "beaten" back into the wort, or one will end up with a diacetyl bomb.  I am now waiting until the end of fermentation to take my crop when using Yorkshire strains.

Can you elaborate on this? What causes the diacetyl to form if you don't beat the mid-head back?

My guess on this:  The diacetyl formed during the mash and fermentation which is normal.  Removing too much yeast may lead to incomplete cleanup by the yeast after fermentation is complete. 

My understanding is the after the sugars are gone, the yeast clean up their leftovers for us.  If we remove too many they can't clean it all up.

Paul

[dilluh98]

Many brewers skim their crop when the wort hits 50% apparent attenuation.  I recently discovered that this practice is not optimal with true Yorkshire strains.  The mid-head has to be "beaten" back into the wort, or one will end up with a diacetyl bomb.  I am now waiting until the end of fermentation to take my crop when using Yorkshire strains.

Can you elaborate on this? What causes the diacetyl to form if you don't beat the mid-head back?

This is my confusion as well. What approximate percentage of the yeast is in the head vs the liquid wort during the most active phase of fermentation for a top cropping yeast? I can't imagine that no yeast exists in the liquid wort but I suppose it is possible that if you skim ALL the active head (which is a lot of yeast!) the wort might not have enough at the end to clean up its own mess. There must be diffusion/transfer from the head down into the liquid wort.

I'm mostly wondering about this "beating back" idea. If one doesn't beat back the head into the beer mid-fermentation are you assured a diacetyl bomb?

[beersk]

I always give my beers a gentle but firm stir after top cropping to keep the yeast roused. I believe this is what he meant by "beating back" the yeast.

I usually skim the brown crud when I see it forming, usually about 24 hours, then again at maybe 36 hours, and then maybe one more time before I start seeing a creamy texture to the krausen. That's when I top crop yeast to use. Anywhere between 48 and 72 hours typically. I don't get diacetyl, so it hasn't been an issue. I'm thinking that as long as the yeast looks thick and creamy, it's ready to top crop. And give it another gentle but firm stir.

[Phil_M]

I always give my beers a gentle but firm stir after top cropping to keep the yeast roused. I believe this is what he meant by "beating back" the yeast.

I usually skim the brown crud when I see it forming, usually about 24 hours, then again at maybe 36 hours, and then maybe one more time before I start seeing a creamy texture to the krausen. That's when I top crop yeast to use. Anywhere between 48 and 72 hours typically. I don't get diacetyl, so it hasn't been an issue. I'm thinking that as long as the yeast looks thick and creamy, it's ready to top crop. And give it another gentle but firm stir.

+1

My last batch of bitter was split between 1318 and 1968. Both carboys were well swirled 3 days after pitching. I didn't notice any diacetyl in the final beers, and I know I've gotten it from 1968 when I haven't swirled. Fermentation temps never exceeded 70^o.

I'm starting to think that diacetyl is an indicator of a need to change your process, and perhaps that doesn't mean a diacetyl rest. I've heard that German breweries don't do rests, that they are able to control fermentation temps/yeast health to the point that the yeast will happily remove diacetyl while still at cold temps. I recently purchased CAMRA's "Brew Real Ale at Home" book, and the author mentioned rousing/beating the yeast back into suspension being a mechanism for reducing diacetyl. As homebrewers, we may always need to do diacetyl rests with lagers, but ales? I think we can nail those if we try. British brewing techniques seem to transfer to homebrew scales much more readily.

I'm considering going all open fermentation on my British beers.

[beersk]

I always give my beers a gentle but firm stir after top cropping to keep the yeast roused. I believe this is what he meant by "beating back" the yeast.

I usually skim the brown crud when I see it forming, usually about 24 hours, then again at maybe 36 hours, and then maybe one more time before I start seeing a creamy texture to the krausen. That's when I top crop yeast to use. Anywhere between 48 and 72 hours typically. I don't get diacetyl, so it hasn't been an issue. I'm thinking that as long as the yeast looks thick and creamy, it's ready to top crop. And give it another gentle but firm stir.

+1

My last batch of bitter was split between 1318 and 1968. Both carboys were well swirled 3 days after pitching. I didn't notice any diacetyl in the final beers, and I know I've gotten it from 1968 when I haven't swirled. Fermentation temps never exceeded 70^o.

I'm starting to think that diacetyl is an indicator of a need to change your process, and perhaps that doesn't mean a diacetyl rest. I've heard that German breweries don't do rests, that they are able to control fermentation temps/yeast health to the point that the yeast will happily remove diacetyl while still at cold temps. I recently purchased CAMRA's "Brew Real Ale at Home" book, and the author mentioned rousing/beating the yeast back into suspension being a mechanism for reducing diacetyl. As homebrewers, we may always need to do diacetyl rests with lagers, but ales? I think we can nail those if we try. British brewing techniques seem to transfer to homebrew scales much more readily.

I'm considering going all open fermentation on my British beers.

I've been wanting to do nothing but top cropped beers. I don't do full open fermentations, but just leave the lid sit on top of the bucket. I snap it down after about 3 days after harvesting.
Right now I'm doing some "lager" styles with wy1007. It's just too fun to top crop and so easy to keep yeast strains going for a long time with clean healthy yeast. I even use yeast from dark beers for lighter styles because the krausen, after all the crud is skimmed, is nice and clean. It's darker, but I don't think it's a problem.

[dilluh98]

Great info shared. Thanks!

I'm throwing caution to the wind and open fermenting this kitchen sink (trying to use up the sack of MO I have on hand so I can try a different source), bastardized pale ale:

1.052/150F mash
85% MO
15% Flaked Oats

All 50 IBUs from Magnum @ 60 min
Citra, Centenial, Simcoe @ 0 min
Citra, Centenial, Simcoe, 30 min whirlpool @ 150F

WY1318 @ 68F (probably let it ride for 2 weeks) open fermented.

I'm guessing the hop aroma is going to be poor due to the open ferment but I may chuck a few ounces of citra dry hop for a few days before packaging.

[beersk]

I suggest leaving the bucket lid on top for the beginning until you see a krausen forming, then leave the lid off if you're wanting to go fully open.

[dilluh98]

Yup. Lid was loose until krausen showed up and then I took it off.

[Phil_M]

I've been wanting to do nothing but top cropped beers. I don't do full open fermentations, but just leave the lid sit on top of the bucket. I snap it down after about 3 days after harvesting.
Right now I'm doing some "lager" styles with wy1007. It's just too fun to top crop and so easy to keep yeast strains going for a long time with clean healthy yeast. I even use yeast from dark beers for lighter styles because the krausen, after all the crud is skimmed, is nice and clean. It's darker, but I don't think it's a problem.

My reason for wanting to do open fermentations is that some of the yeast I'm "heading toward" using are going to want more oxygen. Ever seen the think rocky barm on top of a Yorkshire Square? Supposedly that can be attained in the home, given an open fermentation (oxygen) and happy, healthy yeast.