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Overbuilding yeast starters vs top cropping

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beervoid

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Hello everyone,

I was wondering what would be a better way to reuse yeast. Right now i'm overbuilding starters but I'm growing tired of making the yeast starters and DME is quiet pricey.

Just wondering if top cropping will give me similar results and which method would be giving me better quality yeast that I can re-use more often.

Cheers!
 

isomerization

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I would say overbuilding is great for long term storage (1-12 months) of yeast you want to reuse but not right away.

I believe top cropping works best on specific yeast strains (eg British) while harvesting yeast cakes post fermentation should work for any strain. Both of these techniques would be best used within 1 week, sooner the better.
 

gregkeller

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What about making some extra wort when brewing, then run it off into a pot that you can quick boil while you are brewing, toss it in the fridge to cool and then when you pitch into your finished batch, you decant a few of the mL's into your starter and grow that up. Doesn't have to be much. I'd think that if you were going to save 500 mL as a culture to grow up your next starter, you would only need a 50 mL of slurry. Adds an extra few steps, so it comes down to the time vs. money question. For me, with two little boys running around the house, time is more important to me, so I grow a 5L starter, save 500 mL in a mason jar and use that next time. Lots of DME used, but doesn't add any extra time to my process.
 
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beervoid

beervoid

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I would say overbuilding is great for long term storage (1-12 months) of yeast you want to reuse but not right away.

I believe top cropping works best on specific yeast strains (eg British) while harvesting yeast cakes post fermentation should work for any strain. Both of these techniques would be best used within 1 week, sooner the better.
Are you saying that top cropped yeast stored in the same conditions as an overbuild, namely some beer is less longer viable?
 
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beervoid

beervoid

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What about making some extra wort when brewing, then run it off into a pot that you can quick boil while you are brewing, toss it in the fridge to cool and then when you pitch into your finished batch, you decant a few of the mL's into your starter and grow that up. Doesn't have to be much. I'd think that if you were going to save 500 mL as a culture to grow up your next starter, you would only need a 50 mL of slurry. Adds an extra few steps, so it comes down to the time vs. money question. For me, with two little boys running around the house, time is more important to me, so I grow a 5L starter, save 500 mL in a mason jar and use that next time. Lots of DME used, but doesn't add any extra time to my process.
That's not such a bad idea actually, I could collect some wort but I'd have to water it down to get the right gravity. I usually make 1.070 gravity beers while a starter is preferably in the 1.040 range.
 

gregkeller

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That's not such a bad idea actually, I could collect some wort but I'd have to water it down to get the right gravity. I usually make 1.070 gravity beers while a starter is preferably in the 1.040 range.
What about just collecting something from your second runnings when the gravity is around the 1.040 range?
 

gregkeller

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I think I remember reading something (maybe in the "Yeast" book) that doing a starter, letting the yeast finish, and then drop out (cold crash) allows the yeast to sort of "top up" their reserves and go into hibernation in your fridge for a longer period of time. When you top crop you are harvesting actively fermenting yeast from an environment where they are chugging along eating sugars and then you change their surrounding before giving them a chance to get ready to go to sleep.
 

isomerization

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Are you saying that top cropped yeast stored in the same conditions as an overbuild, namely some beer is less longer viable?
No, I’m saying top cropped yeast is done (at least my understanding) to obtain actively fermenting yeast for quick reuse. If you want to save yeast for a new starter, then I’d overbuild versus top crop.
 

bierhaus15

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Top cropping provides the cleanest and healthiest yeast, given the culture can provide it. Top cropping also leaves the yeast with more glycogen and other endogenous reserves to maintain cell function while in storage. Yeast produced via propagation sees a decrease in overall glycogen, but it becomes normalized after second generation fermentation. Therefore, top cropped yeast is better for long term storage than propagated yeast, given it is stored properly (<5C for no more than 3 weeks).
 

isomerization

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Top cropping provides the cleanest and healthiest yeast, given the culture can provide it. Top cropping also leaves the yeast with more glycogen and other endogenous reserves to maintain cell function while in storage. Yeast produced via propagation sees a decrease in overall glycogen, but it becomes normalized after second generation fermentation. Therefore, top cropped yeast is better for long term storage than propagated yeast, given it is stored properly (<5C for no more than 3 weeks).
By propagation, you are referring to yeast harvested from a fermentation (ie not an overbuilt starter) correct?

Also what do you mean by second generation fermentation? Transition from lab adapted to homebrew fermenting?
 

bierhaus15

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By propagation, you are referring to yeast harvested from a fermentation (ie not an overbuilt starter) correct?

Also what do you mean by second generation fermentation? Transition from lab adapted to homebrew fermenting?
A propagation (fermentation) is essentially the same as a home brew starter (overbuilt or otherwise).

The second generation refers to the first actual large scale fermentation where the propagated yeast is used for beer production and not yeast growth.
 

isomerization

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A propagation (fermentation) is essentially the same as a home brew starter (overbuilt or otherwise).

The second generation refers to the first actual large scale fermentation where the propagated yeast is used for beer production and not yeast growth.
I don’t think I’d agree with the first statement, especially in conjunction with the second statement, which seems to imply that going through a fermentation will change the phenotype of the yeast culture. Maybe I’m confused though lol.
 

bierhaus15

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Not sure what is so confusing. A propagation and home brew starter achieve the same thing: yeast growth via aerobic fermentation, resulting in increased yeast mass for pitching. Fermentation with said yeast could be better described as "First Generation Beer."

Either way, top cropped yeast is healthier yeast for storage than yeast saved from a propagation/starter.
 

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What about making some extra wort when brewing, then run it off into a pot that you can quick boil while you are brewing, toss it in the fridge to cool and then when you pitch into your finished batch, you decant a few of the mL's into your starter and grow that up. Doesn't have to be much. I'd think that if you were going to save 500 mL as a culture to grow up your next starter, you would only need a 50 mL of slurry. Adds an extra few steps, so it comes down to the time vs. money question. For me, with two little boys running around the house, time is more important to me, so I grow a 5L starter, save 500 mL in a mason jar and use that next time. Lots of DME used, but doesn't add any extra time to my process.
I never use DME for building starters. I use harvested wort from a prior brewing session (I add a couple of quarts to my sparge volume). I boil and cool it before inocculating the batch. I do use DME to prime my beer on bottling day. I also overbuild my starter by 500ml to harvest for future use. Been succeeding with this protocol for 5+ years now
 

isomerization

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Not sure what is so confusing. A propagation and home brew starter achieve the same thing: yeast growth via aerobic fermentation, resulting in increased yeast mass for pitching. Fermentation with said yeast could be better described as "First Generation Beer."

Either way, top cropped yeast is healthier yeast for storage than yeast saved from a propagation/starter.
It’s fairly well accepted that higher gravity fermentations have a negative affect on yeast health/viability.

So while they might achieve the same thing (increased yeast mass), I don’t agree that a starter and a bulk fermentation can be considered the same.
 

bierhaus15

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It’s fairly well accepted that higher gravity fermentations have a negative affect on yeast health/viability.

So while they might achieve the same thing (increased yeast mass), I don’t agree that a starter and a bulk fermentation can be considered the same.
Who said anything about higher gravity? None the less, most yeast strains actually see an increase in viability and fermentation performance after the first generation, so unless you are only fermenting barleywines, re-pitching from an active fermentation at 12-14P is not an issue. If it was, the thousands of breweries that harvest and re-pitch yeast from their fermenting beers would have a serious issue. Even industrial breweries making high gravity-adjunct lagers repitch multiple generations. What brewery over 1 million barrels yr has the capacity to propagate enough yeast for a 5,000 bbl fermentation each and every time? They don't and they are fermenting wort at 17P.
 

isomerization

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Who said anything about higher gravity? None the less, most yeast strains actually see an increase in viability and fermentation performance after the first generation, so unless you are only fermenting barleywines, re-pitching from an active fermentation at 12-14P is not an issue. If it was, the thousands of breweries that harvest and re-pitch yeast from their fermenting beers would have a serious issue. Even industrial breweries making high gravity-adjunct lagers repitch multiple generations. What brewery over 1 million barrels yr has the capacity to propagate enough yeast for a 5,000 bbl fermentation each and every time? They don't and they are fermenting wort at 17P.
Of course professional breweries do that, but we’re talking about homebrewers here.

When saving yeast for use in a new starter (not direct pitching like a pro brewery), you’re at much higher risk to capture post-fermentation rather than pre.
 

bierhaus15

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Of course professional breweries do that, but we’re talking about homebrewers here.

When saving yeast for use in a new starter (not direct pitching like a pro brewery), you’re at much higher risk to capture post-fermentation rather than pre.
Not really different when it comes to yeast. Every brewery, home or professional, starts with 1 loop of yeast and grows it up from there. The principles are the same.

Also, the intention of yeast starters is not to make healthy yeast, its purpose is to grow yeast for pitching. The residual liquid from a starter is not an ideal environment for yeast storage; containing very low ABV, little to no isomerized alpha (anti-bacterial), and full of residual yeast byproducts like acetylaldehyde and diacetyl. The whole benefit of top cropping is that you are harvesting the yeast at the peak of their reproductive cycle. Done properly there is very little risk of bacterial contamination (unlike bottom harvested yeast) and the yeast glyogen reserves are at their highest and stay high when stored cold. The residual sugar collected with the yeast ferments out leaving an environment free of oxygen and hostile to other wild yeast/contaminates.

What else can we argue about? :)
 
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beervoid

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Not really different when it comes to yeast. Every brewery, home or professional, starts with 1 loop of yeast and grows it up from there. The principles are the same.

Also, the intention of yeast starters is not to make healthy yeast, its purpose is to grow yeast for pitching. The residual liquid from a starter is not an ideal environment for yeast storage; containing very low ABV, little to no isomerized alpha (anti-bacterial), and full of residual yeast byproducts like acetylaldehyde and diacetyl. The whole benefit of top cropping is that you are harvesting the yeast at the peak of their reproductive cycle. Done properly there is very little risk of bacterial contamination (unlike bottom harvested yeast) and the yeast glyogen reserves are at their highest and stay high when stored cold. The residual sugar collected with the yeast ferments out leaving an environment free of oxygen and hostile to other wild yeast/contaminates.

What else can we argue about? :)
You've convinced me to try some top cropping but I make about 7.5% alcohol beers. I read on the White Labs website one should not harvest yeast from beer higher then 6.5%

Do you still recommend I go this route?
 

Vale71

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The beer will reach 7.5% only at the end of fermentation. The idea with top cropping is that you harvest very early in the fermentation and do not wait until the end as the yeast that's floating on the surface is no longer involved in active fermentation anyway. In a commercial setting ideally you would transfer the appropriate amount of harvested yeast directly to another fermentor where a new batch has just become ready for pitching. Failing that you just store the yeast in your fridge until it's needed.
 
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The beer will reach 7.5% only at the end of fermentation. The idea with top cropping is that you harvest very early in the fermentation and do not wait until the end as the yeast that's floating on the surface is no longer involved in active fermentation anyway. In a commercial setting ideally you would transfer the appropriate amount of harvested yeast directly to another fermentor where a new batch has just become ready for pitching. Failing that you just store the yeast in your fridge until it's needed.
Cheers for that, my beer is 24h in so I will harvest some today and see how it goes.
 

Gadjobrinus

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The whole benefit of top cropping is that you are harvesting the yeast at the peak of their reproductive cycle. Done properly there is very little risk of bacterial contamination (unlike bottom harvested yeast) and the yeast glyogen reserves are at their highest and stay high when stored cold. The residual sugar collected with the yeast ferments out leaving an environment free of oxygen and hostile to other wild yeast/contaminates.

What else can we argue about? :)
Sorry, this is related to top-cropping, but tangentially so.

Bierhaus, you probably said it here or on another site so sorry for the redundant question if so. I am committed to open fermentation and top cropping, but it's difficult as I brew in roughly 11.5 g cast brewlengths. You know the rousing thing I've toyed with for quite some time but ignoring that, an open vessel suitable for this amount of pitched wort is on mind. Can't remember what brewlength you do. If in my neighborhood, what do you use?

Secondly, and I know you've covered this somewhere, just can't find it, sorry. When to skim/top-crop. If one were following, say, the Black Sheep or TT regime, my guess is they skim the "dirty krausen" (can't recall the German, if indeed it's a German name), and go into the rousing regime immediately after discarding this first, "dirty" krausen (none of the protocol descriptions describe when they actually begin the rousing, so far as I can recall).

They do this rousing for 3 days, or what I imagine is an attenuation marker? They then top crop.

The main ferment free rises to 20-21 C, held here up to 3 days. Slow cool to 10C (no less than 36 hours), held there for 48 hours. "Excess yeast" removed, goes to a closed conditioning tank for 24-48 (preferably, 48) hours, finally racked into cask.

Does this seem right, in terms of at least what the northern breweries do with respect top-cropping?
 
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beervoid

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Another questions for the top croppers.

I've got a floating diptube. So what I've done now is just put pressure on my keg and I poured about 200ML from the top.
Wondering how much cells I have now approximately?
 

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Another questions for the top croppers.

I've got a floating diptube. So what I've done now is just put pressure on my keg and I poured about 200ML from the top.
Wondering how much cells I have now approximately?
I could be casting absolutely unintended aspersions, but I can tell you I've seen things along the lines of "2 x 5 gallon buckets." And the ales were always extraordinary.
 

bierhaus15

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Can't remember what brewlength you do. If in my neighborhood, what do you use?

Secondly, and I know you've covered this somewhere, just can't find it, sorry. When to skim/top-crop. If one were following, say, the Black Sheep or TT regime, my guess is they skim the "dirty krausen" (can't recall the German, if indeed it's a German name), and go into the rousing regime immediately after discarding this first, "dirty" krausen (none of the protocol descriptions describe when they actually begin the rousing, so far as I can recall).
I can brew up to 15 gallons, but typically make 12 gallons and split the wort into two plastic buckets and pitch different yeasts. I've pretty much tried fermenting UK yeasts in everything; carboys, buckets, 10 gallon fish tank (poor man yorkshire square - would not recommend), plastic conical, and an anvil fermentor. For ease of top cropping, a 6.5 gallon bucket and a fermentation chest can't be beat IMO. Having also brewed with UK yeasts in horizontal and conical FV's, I am a firm believer that horizontal/rectangular is much better for ester development and obviously top cropping. Same for lagers.

For top cropping, I used to take gravity readings but now just crop the larger second krausen after the first krausen and "dirt" - hop oils, ect has been removed or pushed to the side. This is typically around 48 hrs or 55% attenuation. Viability on this yeast has been very high, typically 96-98%.

Simple answer: For Yorkshire rousing systems, a typical process is to start rousing around 18 hrs into fermentation, and continue for 10 minutes every 4 hrs. Rouse up to 48 hours. I know breweries do it differently and for different reasons (flavor development v. yeast health and flocculation) but typically you want to rouse earlier in the process and stop before the yeast go anerobic. Or do it later if you like a butterscotch-y, diacetyl flavor in your ales. More recent science says you can largely ignore the rousing process for yeast health and attenuation by oxygenating to around 15ppm. Different yeasts have different 02 requirements, so that needs to be considered as well.
 

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I can brew up to 15 gallons, but typically make 12 gallons and split the wort into two plastic buckets and pitch different yeasts. I've pretty much tried fermenting UK yeasts in everything; carboys, buckets, 10 gallon fish tank (poor man yorkshire square - would not recommend), plastic conical, and an anvil fermentor. For ease of top cropping, a 6.5 gallon bucket and a fermentation chest can't be beat IMO. Having also brewed with UK yeasts in horizontal and conical FV's, I am a firm believer that horizontal/rectangular is much better for ester development and obviously top cropping. Same for lagers.

For top cropping, I used to take gravity readings but now just crop the larger second krausen after the first krausen and "dirt" - hop oils, ect has been removed or pushed to the side. This is typically around 48 hrs or 55% attenuation. Viability on this yeast has been very high, typically 96-98%.

Simple answer: For Yorkshire rousing systems, a typical process is to start rousing around 18 hrs into fermentation, and continue for 10 minutes every 4 hrs. Rouse up to 48 hours. I know breweries do it differently and for different reasons (flavor development v. yeast health and flocculation) but typically you want to rouse earlier in the process and stop before the yeast go anerobic. Or do it later if you like a butterscotch-y, diacetyl flavor in your ales. More recent science says you can largely ignore the rousing process for yeast health and attenuation by oxygenating to around 15ppm. Different yeasts have different 02 requirements, so that needs to be considered as well.
Awesome. Many thanks, bierhaus, this gives a lot to work from and experiment on going forward. I have many slants from BL (thank you for your insight), and recently slanted up WLP006, which I hope to be the basis for a strong bitter and several single-hop best bitters.
 
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I could be casting absolutely unintended aspersions, but I can tell you I've seen things along the lines of "2 x 5 gallon buckets." And the ales were always extraordinary.
Thanks for replying.
Im not quiet sure what you mean by this statement.
Are you saying with the 200ml I can ferment 2 5 gallon batches?
 

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Generally speaking, a thin top crop (1:4 yeast to beer) typically needs around 250 ml of slurry for 5.5 gallons at 12P, pitching at 0.75 m/c/ml/P. For the thickest top crop, 100 ml of yeast solids are usually enough for 5.5 gallons at the same gravity/pitch rate.
 

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At work (a North Yorkshire brewery) we skim (top crop) when we’re about to put the beer on chill to drop the yeast out and stop fermentation (approx day 4-5). The beer then gets transferred to CT before being racked to casks.
 

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Thanks for replying.
Im not quiet sure what you mean by this statement.
Are you saying with the 200ml I can ferment 2 5 gallon batches?
I'm sorry, I was probably not very helpful. I was just saying that when I visited Stoke-On-Trent, there was no counting or even a tight amount of starter, slurry, etc., that they used. They literally filled two 5-gallon buckets and dumped it into an open fermentor. I loved their beer.
 

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I'm sorry, I was probably not very helpful. I was just saying that when I visited Stoke-On-Trent, there was no counting or even a tight amount of starter, slurry, etc., that they used. They literally filled two 5-gallon buckets and dumped it into an open fermentor. I loved their beer.
Sounds familiar
 

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At work (a North Yorkshire brewery) we skim (top crop) when we’re about to put the beer on chill to drop the yeast out and stop fermentation (approx day 4-5). The beer then gets transferred to CT before being racked to casks.
Thank you, HTH, very helpful. I would like to ask some questions below, and hope I'm not abusing your generosity. Getting some information from a practicing Northern England brewer basically geeks me out.

One thing I'm trying to figure out is Black Sheep's very gradual drop from fermentation temp of 20-21C down to 10C, over no less than 36 hours. They then hold here 2 days, and the brewer indicated, if I'm not mistaken, this is their diacetyl rest (puzzled by a drop in temp as a diacetyl rest, that's all). Excess yeast is removed, and it goes to a CT for 24-48 hours. They then rack to cask. They do mention yeast counts, both in the CT and when racked to cask. I don't know if these are counted in lab each time, or by sheer practice they can be confident of their counts at these stages?

The comment "excess yeast is removed" - would this be the harvest?

I was curious about this gradual drop, and to 10C at that. It doesn't seem they do any chill to encourage drop out. Do I understand it correctly? Any thoughts on this?

I imagine their CT is also at 10C. I know many breweries, like yours, if have it correctly, begin a secondary fermentation in the CT as they are closed. Not much, but some. Any issues with racking to cask, or are they filled on counterpressure?

I don't have a microscope and cannot count yeast. I'd like to rack without priming, just depend, as the Black Sheep brewer said, "we have plenty of residual sugar and yeast." Am I inviting broad inconsistency, or is their a protocol that might allow for this?

Finally, this involves more at the "pub" (my living room) than earlier at the "brewery" (my back yard - where today it's -6C now, -15C by tomorrow). Many suggestions to finish cask conditioning before fining. I imagine that means you remove the shive, fine, replace with a new shive, and roll the cask a bit. Is this correct? Is this waiting in order to ensure you have enough yeast in solution to do their conditioning job?

Thanks HTH, as usual. Hope I haven't drowned with questions.
 
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One thing I'm trying to figure out is Black Sheep's very gradual drop from fermentation temp of 20-21C down to 10C, over no less than 36 hours. They then hold here 2 days, and the brewer indicated, if I'm not mistaken, this is their diacetyl rest (puzzled by a drop in temp as a diacetyl rest, that's all).
This is an interesting piece of info which if I understand correct indicates that their yeast cleans up diacetyl even at lower (10c) temperatures?
I would be curious to know if this is yeast dependent and which yeast they use.
 

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Thank you, HTH, very helpful. I would like to ask some questions below, and hope I'm not abusing your generosity. Getting some information from a practicing Northern England brewer basically geeks me out.

One thing I'm trying to figure out is Black Sheep's very gradual drop from fermentation temp of 20-21C down to 10C, over no less than 36 hours. They then hold here 2 days, and the brewer indicated, if I'm not mistaken, this is their diacetyl rest (puzzled by a drop in temp as a diacetyl rest, that's all). Excess yeast is removed, and it goes to a CT for 24-48 hours. They then rack to cask. They do mention yeast counts, both in the CT and when racked to cask. I don't know if these are counted in lab each time, or by sheer practice they can be confident of their counts at these stages?

The comment "excess yeast is removed" - would this be the harvest?

I was curious about this gradual drop, and to 10C at that. It doesn't seem they do any chill to encourage drop out. Do I understand it correctly? Any thoughts on this?

I imagine their CT is also at 10C. I know many breweries, like yours, if have it correctly, begin a secondary fermentation in the CT as they are closed. Not much, but some. Any issues with racking to cask, or are they filled on counterpressure?

I don't have a microscope and cannot count yeast. I'd like to rack without priming, just depend, as the Black Sheep brewer said, "we have plenty of residual sugar and yeast." Am I inviting broad inconsistency, or is their a protocol that might allow for this?

Finally, this involves more at the "pub" (my living room) than earlier at the "brewery" (my back yard - where today it's -6C now, -15C by tomorrow). Many suggestions to finish cask conditioning before fining. I imagine that means you remove the shive, fine, replace with a new shive, and roll the cask a bit. Is this correct? Is this waiting in order to ensure you have enough yeast in solution to do their conditioning job?

Thanks HTH, as usual. Hope I haven't drowned with questions.
The drop to 10C is done when SG is around 2 points from FG. This is to encourage the yeast to drop and thus stop fermentation.

There is no specific diacetyl rest where we raise the temperature. The yeast cleans up any ‘green’ flavours during the conditioning period.

I’d be surprised if they specifically do yeast counts in the CT before racking to cask. Maybe a few times a year as a QC measure, but I’d imagine they’re confident in their process.

The only way I’ve ever seen any brewery rack to cask is to add finings then dump the beer on top. The yeast will (slowly) finish the final two gravity points in the cask, but there will be some CO2 dissolved anyway (the beer engine and sparkler blast life into the beer when serving a pint).

Casks are stored at 10-12C, this is typical cellar/serving temperature. If the casks are stored in ambient temperatures, the beer gets much too lively and you end up with foamy beer at the pump.

With a minimum 24 hours stillage, storage at cellar temperature and the finings, this gives a clear pint with the right body and carbonation.

Hope that answers your questions
 

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The drop to 10C is done when SG is around 2 points from FG. This is to encourage the yeast to drop and thus stop fermentation.

There is no specific diacetyl rest where we raise the temperature. The yeast cleans up any ‘green’ flavours during the conditioning period.

I’d be surprised if they specifically do yeast counts in the CT before racking to cask. Maybe a few times a year as a QC measure, but I’d imagine they’re confident in their process.

The only way I’ve ever seen any brewery rack to cask is to add finings then dump the beer on top. The yeast will (slowly) finish the final two gravity points in the cask, but there will be some CO2 dissolved anyway (the beer engine and sparkler blast life into the beer when serving a pint).

Casks are stored at 10-12C, this is typical cellar/serving temperature. If the casks are stored in ambient temperatures, the beer gets much too lively and you end up with foamy beer at the pump.

With a minimum 24 hours stillage, storage at cellar temperature and the finings, this gives a clear pint with the right body and carbonation.

Hope that answers your questions
That's great. Many thanks, HTH. Just finding a solution for my home "bar," simple affair temp controlled, enough room for two pins. Very excited to hone in on your tradition, best as I'm able.
 

HTH1975

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That's great. Many thanks, HTH. Just finding a solution for my home "bar," simple affair temp controlled, enough room for two pins. Very excited to hone in on your tradition, best as I'm able.
No problem, you’re very welcome.
 

isomerization

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Not really different when it comes to yeast. Every brewery, home or professional, starts with 1 loop of yeast and grows it up from there. The principles are the same.

Also, the intention of yeast starters is not to make healthy yeast, its purpose is to grow yeast for pitching. The residual liquid from a starter is not an ideal environment for yeast storage; containing very low ABV, little to no isomerized alpha (anti-bacterial), and full of residual yeast byproducts like acetylaldehyde and diacetyl. The whole benefit of top cropping is that you are harvesting the yeast at the peak of their reproductive cycle. Done properly there is very little risk of bacterial contamination (unlike bottom harvested yeast) and the yeast glyogen reserves are at their highest and stay high when stored cold. The residual sugar collected with the yeast ferments out leaving an environment free of oxygen and hostile to other wild yeast/contaminates.

What else can we argue about? :)
Since this thread went in a more productive direction, I will just reinforce that I was not talking about top cropping. I was comparing harvesting yeast for long term storage (over a month), specifically overbuilt yeast starter versus fully fermented beer.

I will defer to your experience with top cropping for yeast storage, but unless you have plans to use the yeast as is (so no new starter), harvesting post fermentation introduces unnecessary risk.
 
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beervoid

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Tested out top cropping on day 2.

Gravity dropped from 1.075 to 1.052 when I cropped but airlock activity seems pretty slow atm. Took a sample on day 5 so 2 days after cropping and slowing of fermentation it went down to 1.042.
Can top cropping result in slowing down fermentation?
Did I top crop too early?
Can one top crop too much?
 

isomerization

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Tested out top cropping on day 2.

Gravity dropped from 1.075 to 1.052 when I cropped but airlock activity seems pretty slow atm. Took a sample on day 5 so 2 days after cropping and slowing of fermentation it went down to 1.042.
Can top cropping result in slowing down fermentation?
Did I top crop too early?
Can one top crop too much?
Did you say how much you took, initial volume and then what percent was yeast after settling? I can’t really provide input, but I’d guess this will be essential info to answer your question.
 
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