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Why Not to Pitch On Your Yeast Cake

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Bob

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Knocking out onto a yeast cake is never a good idea. It is - outside of a very, very few specific instances listed below - always over-pitching.

Many amateur brewers report acceptable results by this practice. That's fine, and I applaud their success. Their success does not excuse that this is bad brewing practice.
[Author's note: I categorically refuse to argue with anyone about this. If you practice this and have success, I wish you all the success and enjoyment in the world. Better and more knowledgeable brewers and brewing scientists than you or I could ever be support what follows. If you can bring to bear some significant data from the field of brewing science which indicates otherwise, please send it to me; I like the taste of crow when I deserve it. Otherwise, please don't cloud the issue.]

Over-pitching is always detrimental to the beer. This does not say the beer will taste awful. Rest assured, however, that were one to place samples of the exact same beer - one fermented by overpitching and one by properly inoculating the wort - the properly pitched example will taste better. Blind taste tests prove it.

The two most obvious effects of over-pitching are off-flavors. First, yeast material in excess quickly leads to autolysis, which has flavor by-products with very low flavor thresholds. In properly-pitched beers, this effect can take months to show itself. In beers with an excess of yeast solids, it can manifest in a matter of weeks - in fact, the time spent in a home-brewer's primary.

Second, tasters have observed thin beer, beer lacking in body and mouthfeel. To be perfectly honest, the exact cause of this effect is unknown, but it is strongly correlated with over-pitched yeast, so a connection is highly likely.

Third - and most important for the home-brewer - is suppression of esters. Yeast rely on the growth phase to reproduce enough cells to fully colonize the wort. In that phase, they use malt-based nutrients and the oxygen you provide during aeration to synthesize the components needed to build new cell walls during reproduction. While they're reproducing they're producing esters. All yeast produce esters, even lager yeast, and all beers benefit from ester production (yes, even lagers). Just because you can't taste as much ester from WLP840 as you can from Ringwood doesn't mean that WLP840 doesn't throw esters! Esters are absolutely necessary to beer, theory about "clean yeast" be damned.

When you over-pitch the colony doesn't need to reproduce. Thus measurably fewer esters are produced. This, while always detrimental to beer flavor, is noticeable in American and English strains and very pronounced with certain more flavorful strains, like Belgians.

The brewery where I served my apprenticeship was a Ringwood brewery. If you know yeast, you know Ringwood is very flavorful; most would say too flavorful. We fermented
more than a dozen styles with Ringwood, including such "clean" (meaning non-estery) styles as American Pale Ale and Wee Heavy. In order to brew those styles, we deliberately pitched more yeast than the following technique said we needed. This relative over-pitching, combined with temperature manipulation, deliberately suppressed ester formation. By manipulating the cell counts at inoculation we could produce the same flavor effect as switching strains entirely. Importantly, we did not simply dump in more yeast; instead, we pitched at a carefully-determined higher rate than normal.

Okay, Bob, what's the d*mn rate? You've had your rant, now get to the Straight Dope. ;)

The standard, according to Fix, Daniels, Bamforth et al., is one million active cells per milliliter of wort per degree Plato. Or:

1,000,000*1ml*1°P

Constants:


  • There are 3785 ml per US gallon, or 18,925 ml in 5 US gallons. Round this up to 19,000 (19L) for ease of calculation if you do predominantly 5 gallon batches.
  • One °P is roughly equivalent to 4 points of gravity. For an approximation, 1.048 is thus 12°P. This goes askew above around 1.060; in fact, you may find it simpler to consult a chart like this: http://plato.montanahomebrewers.org/ - or use the formula:
{Plato/(258.6-([Plato/258.2]*227.1)}+1 = Specific gravity

Thus, for 5 gallons of wort at 12°P, we need

1,000,000 * 1 ml * 12°P, or 12,000,000 cells per ml.

12,000,000 * 19,000 = 228,000,000,000 - that's 228 billion cells.

You can expect around 1 billion active cells in a ml of harvested slurry, depending on how much trub and break material makes it into the fermenter. My counts ranged from 0.5 billion to 2 billion, depending on style brewed and brewery practice. 1 billion is a solid average across a dozen different breweries, professional and amateur.

Thus, 228 ml of freshly-harvested slurry is the correct pitch for 5 gallons of 1.048 wort. Conveniently, that's only a few ml less than that found in one cup (8 fluid ounces).

Jamil
Zainasheff recommends a modified pitch rate, advocating 0.75 million cells per ml per °P for ale ferments and 1.5 million for lagers. My experience tells me the standard rule of thumb - 1 million - is quite sufficient for both ales and lagers. If it makes you lager brewers feel better, pitch at the higher rate. It won't harm anything.

The professional small-brewery practice is to harvest yeast from the cone of a conical fermenter and re-pitch a measured amount into the next batch (usually by weight: 1 pound of slurry per barrel of wort). This practice can, without washing or other more-advanced care of the yeast, be extended to ten or more generations. In professional practice I can get between ten and fifteen generations, depending on strain.

Harvesting yeast is shockingly easy! It takes about five minutes after racking.

Here's how:

Equipment Needed:

1 scoop - stainless steel or glass
2-6 glass containers w/lids
Sanitizer

Procedure

  1. Thoroughly clean and sanitize all equipment.
  2. Carefully - you don't want to scratch or ding your plastic fermenter - scoop slurry from the fermenter to the jars.
  3. Close jars tightly and immediately refrigerate.

That's it! Honest!

Always harvest more than you've calculated is necessary. For one thing, you might have goofed a calculation; I do that all the time. For another, harvested slurry - unwashed yeast - loses viability rapidly. Tests have shown that approximately 25% viability is lost per every seven days spent in cold storage. If you must store the slurry longer than seven days, wash the yeast.

The same can be done with starters. Rather than pitching a large starter - with all the attendant diluent - have the foresight to chill the starter container for several days before you pitch to precipitate the yeast. Then decant the spent starter wort and pitch the starter slurry. NOTE: This slurry has approximately four times the yeast solids as harvested slurry, so accommodate this factor in what you learned above!

To be fair, let me list a few of the exceptional circumstances in which knocking out onto a yeast cake might make sense from a pitch-rate standpoint. If you're planning to ferment a very big ale - Imperial Stout, Barley Wine, Quadruppel - starting a smaller beer - Dry Irish Stout, Nut Brown Ale, Belgian Blonde - and knocking out onto the dregs of that beer might actually be feasible, cell-wise. Same with a bigger lager, like Bock. Still, it's better to know how much yeast you're pitching than just dump freshly-brewed wort into the old fermenter. The only way to really know is to harvest the slurry and measure it.

Harvesting is easy, and is smarter than just knocking out onto a "yeast cake".

It allows you to pitch your yeast out to many more generations (10 to 15) than simply dumping fresh wort into your fermenter (which works maybe thrice).
It's excellent, professionally-endorsed brewing practice.
It removes an unknown from your brewing process, i.e., how much yeast is being pitched.*

If a thing is worth doing, it's worth doing properly. It's worth doing to the best of your ability, effort, and means. Knocking out onto a yeast cake not only doesn't really save you anything at all, it also is guaranteed to brew mediocre beer in the vast majority of circumstances. You've learned how to harvest yeast quickly and painlessly.

Now go clean your fermenter. ;)

Cheers!

Bob

* It will never cease to amaze me that brewers who will obsess over how many grams of Saazer are added at flameout, or the differences between US and Canadian 2-row malts, will just put any ol' amount of yeast in their fermenter.


SOURCES

Bamforth, Charles. Standards of Brewing. Boulder, CO: Brewers Publications, 2002.

Daniels, Ray.
Designing Great Beers: The Ultimate Guide to Brewing Classic Beer Styles. Boulder, CO: Brewers Publications, 1996.

Fix, George. An Analysis of Brewing Techniques. Boulder, CO: Brewers Publications, 1996.

Noonan, Greg. New Brewing Lager Beer. Boulder, CO: Brewers Publications, 2003.

Zainasheff, Jamil. "Proper Yeast Pitching Rates." Mr. Malty. 24 May 2007. 03 March 2010. < http://www.mrmalty.com/pitching.php >
 

Denny

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OK, no argument, but some discussion, OK? You say "When you over-pitch the colony doesn't need to reproduce. Thus measurably fewer esters are produced." Dr. Clayton Cone of Lallemand says pretty much the opposite...."ester production is related to yeast growth but not in the way you might think. The key element to yeast growth and ester production is acyl Co-A. It is necessary for both yeast growth and ester production. When it is busy with yeast growth, during the early part of the fermentation, it is not available for ester production. Ester production is directly related to biomass production. Everything that increases biomass production (intensive aeration, sufficient amount of unsaturated fatty acids, stirring) decreases ester production. The more biomass that is produced the more Co-enzyme A is used and therefore not available for ester production. Anything that inhibits or slows down yeast growth usually causes an increase in ester production: low nutrient, low O2." The full article is at http://www.danstaryeast.com/library/yeast-growth. Care to comment?
 

COLObrewer

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You are correct sir! . . . . . . . .
. . . . . . . I just wanted to use that smilie is all.
 
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Bob

Bob

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Denny,

No worries. The "please don't argue with me" comes from constant bickering with people who want to argue with established brewing science with "it works for me". You're not doing that. You've made a good point, for which I thank you!

I wonder, however, how to mesh that data with the other source material and observed phenomena. If what he says is true, under-pitching will lead to suppressed ester production, and widely-reported observation proves that false - all manner of flavor-impacting byproducts become noticeable when the variable is significant under-pitching. Moreover, widely-reported observation proves that over-pitching leads to significantly suppressed ester production; the corollary is that little or no reproduction taking place is the culprit of that phenomenon.

I'm not calling into question his (or your) scholarship, not by any means. It's just the first I've come across such an assertion, so it's incumbent on me to be skeptical, especially as it apparently flies in the fact of well-recorded (professional and amateur) known phenomena.

I have seen this:

It has been noted that a drop in available O2 from 8 ppm down to 3 ppm can cause a four fold increase in esters.
observed in other media, but never the discussion of Co-enzyme A.

Interesting.

You've made me think. I'll be careful of you in the future. ;) And I'll dig further into this Co-enzyme A business.

Regards,

Bob
 

permo

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So the moral of the story is that overpitching will lead to less stressed out yeast and thus less yeast character. What about it's effects on attenuation?

For a beer like a double IPA, where i want neutral yeast profile and high attenuation, I would assume a yeast cake and cool fermentation that is slowly increased in temperature until it finishes would be perfect.....
 
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Bob

Bob

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So the moral of the story is that overpitching will lead to less stressed out yeast and thus less yeast character. What about it's effects on attenuation?

For a beer like a double IPA, where i want neutral yeast profile and high attenuation, I would assume a yeast cake and cool fermentation that is slowly increased in temperature until it finishes would be perfect.....
Attenuation is, to the best of my knowledge, not affected by over-pitching. In other words, pitching more than the required amount of yeast will not increase attenuation. There are many factors at work in attenuation, more than simply a surplus of yeast will accommodate.

The ability of the particular strain to metabolize different sugars, and the presence of sugars in the wort (accessible to yeast) are more important than how many cells are present. In other words, if you have a surplus of sugars which your yeast cannot metabolize, no increase in colony size will attenuate those sugars. For example, you could put five pounds of slurry in a 5-gallon batch of beer rich with lactose and no real difference in attenuation would be seen.

Attenuation can be adversely affected by underpitching; the literature is clear on that issue.

Make sense?

Bob
 
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Bob

Bob

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Hmm... I just pitched a APA onto a yeast cake last night. It is US05, neutral yeast and also fermenting at 61F liquid temp.

We'll see how it turns out :confused:
I'm sure it'll turn out fine. I'm just as sure it'd be better if you took the time to pitch an appropriate quantity of yeast. ;)

Cheers! :mug:

Bob
 

SkiSoloII

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Just one quick question on harvesting technique. Have you got a scoop that will fit down the neck of my carboy? I've been trying to figure that out- I've "yeast washed" before, but I'd just like to scoop. A bit lazy, I guess. ;)

Dave
 

conpewter

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Just one quick question on harvesting technique. Have you got a scoop that will fit down the neck of my carboy? I've been trying to figure that out- I've "yeast washed" before, but I'd just like to scoop. A bit lazy, I guess. ;)

Dave
I'd just rack off the beer, then pour it into your container, no need for the measuring cup (as long as the container is marked, or you go by weight)
 

BendBrewer

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Boy, counting those little cells is a real pain in the butt. j/k

You have provided a lot of information that is over the heads of most homebrewers, but I want to walk away making sure that I learned properly.

Are you saying that an appropriate amount of yeast for a "standard" beer, 1.044-1.050 is a cup of harvested yeast?

How do you measure the increments of additional yeast to add when brewing bigger beers. (I think I get how to determine how much I should use based on the gravity, but are you weighing the yeast, measuring the volume, eye-balling it?)

Thanks for your post. I am looking to make great beer not just something that is drinkable and this info is helpful
 

mojotele

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I never much liked the idea of pitching on to a yeast cake. It just seemed sloppy and lazy, two things that never make for good beer.
 

hoppymonkey

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This is why I love brewing.So so much learn thanks to you beer geeks. I hope to be a beer geek sometime in the future and then quit my job and brew all the time.( money allowing of course)
 

meddin

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Awesome write up Bob! I do, however, have a question regarding harvesting:

I assume you should only harvest from the primary in order to get the most viable cells, correct? What about any spent hops or hot break that might be there as well? I tend to have more than I think would be good for this. Even after straining my wort after chilling still, it seems like I have a lot of hops left in the fermentor. Especially if I'm using pellets.

Thoughts?
 

2bluewagons

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Wondering if the practice of using yeast cake in the event of stuck fermentation has a place here?

See thread: https://www.homebrewtalk.com/f13/psa-foolproof-stuck-ferment-fixer-72072/

As Evan! says in this thread, despite best practices in proper yeast pitching, sometimes the FG isn't as low as one would like. When pitching a beer that is 80-90% fermented onto a cake, I would think that disadvantages discussed when using the cake as a primary fermentation method would be minimized?

Hope this qualifies as discussion, not disagreement. :D
 

jds

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Thanks for the reads, Bob and Denny.

Bob, I'm curious: How do you go about estimating the break content of a harvested yeast on the homebrewer scale? For those of us without conical-bottom fermenters, it can be hard to guess at the quantity of cake needed, since some of it is break material.

Graduated cylinder and time to settle, maybe?
 
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Bob

Bob

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Just one quick question on harvesting technique. Have you got a scoop that will fit down the neck of my carboy? I've been trying to figure that out- I've "yeast washed" before, but I'd just like to scoop. A bit lazy, I guess. ;)
As conpewter wrote, it's still not hard. A technique that's worked for me is to gently swirl the carboy until the slurry is of a fairly uniform consistency, then pour it into the storage jars.

Boy, counting those little cells is a real pain in the butt. j/k
Not if you know how to use a microscope!

http://www.brewingtechniques.com/library/backissues/issue2.4/allen.html

Are you saying that an appropriate amount of yeast for a "standard" beer, 1.044-1.050 is a cup of harvested yeast?
As near as makes no practical difference, and in absence of proper cell counts, yes. It's a rule of thumb which works well.

How do you measure the increments of additional yeast to add when brewing bigger beers. (I think I get how to determine how much I should use based on the gravity, but are you weighing the yeast, measuring the volume, eye-balling it?)
Take another look at the article. You're measuring slurry in milliliters based on the estimated quantity of yeast in the slurry and what you need to inoculate the wort according to the rule of thumb.

I know, it can be confusing. Took me forever to get the hang of it. ;)

Thanks for your post. I am looking to make great beer not just something that is drinkable and this info is helpful
No problem! Glad to help!

I assume you should only harvest from the primary in order to get the most viable cells, correct? What about any spent hops or hot break that might be there as well? I tend to have more than I think would be good for this. Even after straining my wort after chilling still, it seems like I have a lot of hops left in the fermentor. Especially if I'm using pellets.
You're going to have a high proportion of glop to yeast. That's why you get exponentially more yeast in a starter slurry - there's less trub. According to Mr Malty:

"There are about 4.5 billion yeast cells in 1 milliliter of yeast solids (solids with no excess liquid). According to Fix, in a slurry, only about 25% of the mass is yeast solids."

When I've done counts, I've found approximately 1 billion cells in a sample of slurry. That coincides fairly accurately with what JZ and Fix report. If you brew a high proportion of heavily-hopped beers - or have a lot of break and hops material ending up in your primary - you may have less. That's a tough thing to judge without resorting to the hemocytometer and microscope.

As Evan! says in this thread, despite best practices in proper yeast pitching, sometimes the FG isn't as low as one would like. When pitching a beer that is 80-90% fermented onto a cake, I would think that disadvantages discussed when using the cake as a primary fermentation method would be minimized?

Hope this qualifies as discussion, not disagreement. :D
Sure! I think the important thing to note here is that Evan is not advocating starting on the cake, but "pitching a beer that is 80-90% fermented onto a cake" to polish off those last few points of gravity.

Bob, I'm curious: How do you go about estimating the break content of a harvested yeast on the homebrewer scale? For those of us without conical-bottom fermenters, it can be hard to guess at the quantity of cake needed, since some of it is break material.

Graduated cylinder and time to settle, maybe?
Without actually performing cell counts - which is fun and about as expensive as a stir-plate starter setup - it's hard to estimate. I work from experience. When you harvest from a conical, you can draw off and discard the first "dregs" you see; when you start seeing nice, tan yeast, you're there. It's a matter of knowing what good yeast looks like.

Perhaps a good method is to brew up a nice, big starter and refrigerate it. The slurry you'll see in there is exactly what good, pure yeast looks like.

I stick with Fix and JZ's estimate of 25% of the slurry being yeast solids.

Good discussion, guys! I'm going to have a look at the OP over the next few days and see if I can't make it, er, less inflammatory. :D

Cheers! :mug:
 

meddin

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I'm going to have a look at the OP over the next few days and see if I can't make it, er, less inflammatory. :D
Funny :). I didn't think it was inflammatory at all actually. A very informative read!
 
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Bob

Bob

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Funny :). I didn't think it was inflammatory at all actually. A very informative read!
Well, one really shouldn't say things like "always" and "never". I was trying to make a point.

And inflammatory does tend to start interesting conversations, doesn't it? :p

Bob
 

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Since you said in extreme circumstances it would be appropriate, about what Plato or OG would you need to have a 5gal 1.040 beer's cake be a proper pitch rate?

I tried to figure this out from your write up, but no where did I see how many ml there are in a standard cake.

Also, one other question...it seems to be general rhetoric around here that commercial breweries "just pitch a ton of yeast." I wouldn't say 1M cells as a pitch rate is much more than what we follow, I know that you only have experience from one Ringwood brewery, but is it possible that some NON-ester requiring breweries do "over"-pitch according to your write-up?
 

Beerrific

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Since you said in extreme circumstances it would be appropriate, about what Plato or OG would you need to have a 5gal 1.040 beer's cake be a proper pitch rate?
Yeast tend to replicate 3-5 times from the correct pitching number to the final number in the beer. So, at the high end, 1.120 from a 1.040.

Also, one other question...it seems to be general rhetoric around here that commercial breweries "just pitch a ton of yeast."
I think they have very general guidelines....maybe something like "use 5 gallons of fresh slurry" or "10lbs of slurry." I am sure it is not exact but gets them in the ballpark and assuming that yeast packs equally tight in the cone, they are at a minimum pitching the same amount everytime.
 

KayaBrew

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I never much liked the idea of pitching on to a yeast cake. It just seemed sloppy and lazy, two things that never make for good beer.
Well put. It is extremely lazy and unsanitary. Bob talked me out of pouring wort onto a cake over a year ago, with many of the same arguments he made in his OP (albeit they were dumbed down for me!)

The practice of knocking out onto a cake irritates me as much as homebrewers who refuse to make yeast starters for their White Labs vials and Wyeast smack packs. Again, if something is worth doing, it's worth doing right.
 

DKershner

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Yeast tend to replicate 3-5 times from the correct pitching number to the final number in the beer. So, at the high end, 1.120 from a 1.040.
So if I were making a beer that is about 1.17 OG in the end, but adding sugar frequently to get there, I would want to use an entire cake, right?

I know this is not a typical use case, but this is the only beer I was going to pitch onto a cake, normally I grow starters from slants...
 

Beerrific

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So if I were making a beer that is about 1.17 OG in the end, but adding sugar frequently to get there, I would want to use an entire cake, right?

I know this is not a typical use case, but this is the only beer I was going to pitch onto a cake, normally I grow starters from slants...
I am actually not sure if you should include the later sugar additions when calculating yeast. Maybe Bob has an opinion....

You would also be good to use an entire cake from 5 gallons of a 1.040 beer into 10 gallons of a 1.060 beer.
 
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Bob

Bob

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Since you said in extreme circumstances it would be appropriate, about what Plato or OG would you need to have a 5gal 1.040 beer's cake be a proper pitch rate?

I tried to figure this out from your write up, but no where did I see how many ml there are in a standard cake.
That's because there's not really a "standard yeast cake". You take the slurry, and you measure it.

Also, one other question...it seems to be general rhetoric around here that commercial breweries "just pitch a ton of yeast." I wouldn't say 1M cells as a pitch rate is much more than what we follow, I know that you only have experience from one Ringwood brewery, but is it possible that some NON-ester requiring breweries do "over"-pitch according to your write-up?
Well, I've got more experience than that. ;)

It is possible, yes. Note, though, that the procedures are essentially the same. As I wrote in the OP:

"The professional small-brewery practice is to harvest yeast from the cone of a conical fermenter and re-pitch a measured amount into the next batch (usually by weight: 1 pound of slurry per barrel of wort)."

According to Daniels, by weight this works out to half an ounce per gallon, which equates to 1 fluid ounce per gallon. Admittedly, this is about 2/3 the amount the math tells us we need, but this must be tempered with the fact that a brewer harvesting from a conical can eliminate much of the trub which homebrewers have mixed into their slurry. This must also be tempered with the type of yeast; different strains have different density in slurry form.

So if I were making a beer that is about 1.17 OG in the end, but adding sugar frequently to get there, I would want to use an entire cake, right?

I know this is not a typical use case, but this is the only beer I was going to pitch onto a cake, normally I grow starters from slants...
As I said, it depends on how much slurry is in the fermenter.

Regards,

Bob

Edited to add: Regarding later sugar additions, I have no first-hand experience. However, theoretically I can say that I'd pitch according to the first wort, without the sugar additions, presuming the later sugar additions occur after the ferment is in full swing. I'd also ensure that, like we always should, the first wort is aerated properly.
 

carp

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Bob thanks for the post(s). I have pitched on the cake several times (making IPAs) with what I would say is decent success, and I love the lazy factor of it. But I'm very interested in going the extra distance to make better beer, and the info you provided is quite interesting and convincing.
 

h4rdluck

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Good article. I don't think anyone would argue that its not "best practice" to use clean yeast, and not over pitch. But honestly a lot of things sound great on paper and research that don't hold up in reality.

But theres more than enough evidence on this board not to mention my own experience to say that there is absolutely nothing wrong with pitching onto a yeast cake, especially as long as you go are going for subsequently darker flavor profiles.

I have beer that's been racked off a 4th re-used yeast cake. No washing invovled. This beer as been in the closet for 4 months now. Every bottle is fresh and clean. Everyone loves it. In fact i've never had any complaints about any beer.

I won't disagree that re-using yeast cake is not optimal.

I will disagree that its bad practice or somehow makes subpar beer, or beer that won't last as long.
 

Six_O_Turbo

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LOL, Obviously we interpret some of your sources differently.

Since you "categorically refuse to argue with anyone about this." I'm not starting an argument, but do recommend that new brewers carefully and fully read your sources before making up their minds. Just a couple quick comments, then I'm done...

From Designing Great Beers (1996,2000 - Ray Daniels):

"As a general rule, homebrewers pitch far less yeast than they should. Evidence of this comes form the standard packages of yeast sold for homebrewing use. They Generally contiain only a small percentage of the total yeast population needed to achieve recommended pitching rates."

"On a commercial scale, good brewing practice calls for pitching no less than 10 million yeast cells per millimeter of wort. That's approximately 200 billion yeast cells in a 5 gallon batch. This minimum (emphasis mine) amount is intended for "normal" gravity worts, and those with a higher OG will need even more yeast."

Mr. Daniels references Yeast Management (C. Boulton p. 25-29)

Jamil has talked favorably about pitching onto a yeast cake in at least one podcast that I recall.

Jamil and John talk favorably of high pitching rates in Brewing Classic Styles as well on pages 24-25.

This isn't intended as a "your wrong" post, because you obviously are experienced in the subject, But stating "Over-pitching is always detrimental to the beer." is just inaccurate.

Thanks for your time on the OP.
 

jmo88

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Surprisingly this discussion has been about overly high pitching rates rather than about all the aspects of pitching on a yeast cake. While pitching too much yeast, or too little for that matter, will certainly alter the impression of the beer – so will the dead yeast cells, break, and hop material left behind during the initial fermentation. Can someone shed some light on the effects of dead yeast, break, and hop matter leftover from the initial fermentation on the subsequent beer?
 

maskednegator

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Over-pitching is always detrimental to the beer.
we deliberately pitched more yeast than the following technique said we needed. This relative over-pitching, combined with temperature manipulation, deliberately suppressed ester formation. By manipulating the cell counts at inoculation we could produce the same flavor effect as switching strains entirely.
You're contradicting yourself here. You can't say that it's always bad but sometimes it's ok if you're deliberately trying to supress esters. "Always" and "sometimes" are mutually exclusive.
 
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Bob

Bob

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LOL, Obviously we interpret some of your sources differently.
On the contrary, we interpret them exactly the same.

From Designing Great Beers (1996,2000 - Ray Daniels):

"As a general rule, homebrewers pitch far less yeast than they should. Evidence of this comes form the standard packages of yeast sold for homebrewing use. They Generally contiain only a small percentage of the total yeast population needed to achieve recommended pitching rates."

"On a commercial scale, good brewing practice calls for pitching no less than 10 million yeast cells per millimeter of wort. That's approximately 200 billion yeast cells in a 5 gallon batch. This minimum (emphasis mine) amount is intended for "normal" gravity worts, and those with a higher OG will need even more yeast."
Which is precisely in line, if a little below, what the math tells us in my original post for a "normal" gravity wort (1.048). That's why he says "minimum". :) In the very next sentence, Daniels gives you the same rule of thumb as I gave you.

So thanks for proving my point by quoting my source back at me. If that wasn't your intent, you're going to have to be a little more clear. :confused:

Jamil has talked favorably about pitching onto a yeast cake in at least one podcast that I recall.
While I don't know for sure, I can only assume the context of the podcast was for inoculating a "big" beer. Regardless, on Mr Malty, in BYO, and many other places, JZ advocates for pitching at a proper rate. One podcast, possibly taken out of context, does not overthrow all the rest of his writing.

Jamil and John talk favorably of high pitching rates in Brewing Classic Styles as well on pages 24-25.
I've spoken of relatively high pitching rates, too. I agree there's a time and place for it. What's your point?

This isn't intended as a "your wrong" post, because you obviously are experienced in the subject, But stating "Over-pitching is always detrimental to the beer." is just inaccurate.
You are entitled to your opinion. Brewers and brewing scientists far more experienced than either you or I disagree. Guess who I'm going to agree with? ;)

You're contradicting yourself here. You can't say that it's always bad but sometimes it's ok if you're deliberately trying to supress esters. "Always" and "sometimes" are mutually exclusive.
There's no contradiction at all. Calculated over-pitching, where you target a specific pitch in order to achieve a desirable effect without the ill effects of over-pitching, is perfectly acceptable. In fact, one could argue that it's really not "over-pitching" in the purest sense of the term, because you're not pitching over what you've determined to be an acceptable amount, but that teeters on the pedantic. Uncalculated over-pitching, where you have no control over the pitch rate - like knocking out onto a yeast cake - is not acceptable, because, not knowing the pitch rate, it is impossible to predict or even estimate the impact on the beer.

There's a fine line you can walk if you know what you're doing. If you're just dumping wort into a container with heaven knows how much yeast in it, you don't know what you're doing - because you have no control over one of your ingredients.

It's a fine distinction, but it nevertheless exists.

Regards,

Bob
 

permo

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I will also say that this has been a fantastic thread and I appreciate the information.

the only time I pitch on a yeast cake is when my OG is 1.090 or greater and I want a neutral flavor profile. Strong Scotch Ale, Barley Wine, IIPA...etc..etc..

Does intentional overpitching encourage extreme attenuation? I am thinking that it does...
 

mojotele

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Does intentional overpitching encourage extreme attenuation? I am thinking that it does...
From one of Bob's previous posts:

Attenuation is, to the best of my knowledge, not affected by over-pitching. In other words, pitching more than the required amount of yeast will not increase attenuation.
I can see how it would possibly increase the rate of fermentation, but I can also understand how it wouldn't increase attenuation.
 

slowbie

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Bob, you are quickly becoming one of my favorite posters on this forum. Thanks for presenting good, well researched information in a non-inflammatory way.
 
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