OP
OP
Bob
Well-Known Member
Thanks, guys. I just got sick of writing the same thing in a dozen different threads. Figured I'd put it in one central location. 
Cheers!
Bob
Cheers!
Bob
Why Not to Pitch On Your Yeast Cake
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I agree with this post but I do have experiment results that confuses the issue for me. Four samples pitched with dry yeast at recommended rates following both dry pitch and rehydration as well as O2 injection vs. none all ended up with FG = 1.014 and what I was expecting. The control sample pitched at 14x recommended rates ended up FG = 1.010.
The "recommend" rate was .5 grams per 1/2 gallon wort as calculated from a recommended pitch of 11grams for 5 gallons. Were the samples underpitched or does a gross overpitch really attenuate more?
How did the overpitched sample taste?
I have to find my tasting notes to be sure but I'm pretty sure it was the most "clean" one of the five samples just as you'd expect.
SpanishCastleAle
Well-Known Member
Good write-up Bob. Kaiser did some experimenting with this and made a thread about it (too lazy to look it up...not too lazy to wash my cakes and pitch a measured amount from them ). IIRC, his experiment was inconclusive but as I recall he found contradictory info on it (like Denny posted earlier itt). His research led him to believe that homebrewers and pros were on opposite ends of the spectrum (i.e. homebrewers often believe under-pitching increases esters but the pros believe over-pitching increases esters).
Another thing I don't like about over pitching onto a cake is that you had all that extra yeast that could have been saved for another batch.
Lastly, I can't remember where I read it but I thought I read that the final cell count in a batch of beer made from wort of a given gravity/composition was fairly constant regardless of pitch rate (unless way too low). IOW, the yeast only multiply to a certain count and the original pitch rate determines how much growth that needs to occur to hit that count. That might help explain why it doesn't really affect attenuation unless you way underpitch. BTW, I don't think what I just wrote is inconsistent with Berrriffic's earlier post where he said:
EDIT: Here's Kaiser's experiment from his BrauKaiser page but the thread he made here had some good discussion. HBT Search is not working for me so I can't look it up.
EDIT2: Found a thread on it here. On the first page of that thread I provided a link to some of the other threads I mentioned above.
). IIRC, his experiment was inconclusive but as I recall he found contradictory info on it (like Denny posted earlier itt). His research led him to believe that homebrewers and pros were on opposite ends of the spectrum (i.e. homebrewers often believe under-pitching increases esters but the pros believe over-pitching increases esters).Another thing I don't like about over pitching onto a cake is that you had all that extra yeast that could have been saved for another batch.
Lastly, I can't remember where I read it but I thought I read that the final cell count in a batch of beer made from wort of a given gravity/composition was fairly constant regardless of pitch rate (unless way too low). IOW, the yeast only multiply to a certain count and the original pitch rate determines how much growth that needs to occur to hit that count. That might help explain why it doesn't really affect attenuation unless you way underpitch. BTW, I don't think what I just wrote is inconsistent with Berrriffic's earlier post where he said:
Due to the bolded word.
EDIT: Here's Kaiser's experiment from his BrauKaiser page but the thread he made here had some good discussion. HBT Search is not working for me so I can't look it up.
EDIT2: Found a thread on it here. On the first page of that thread I provided a link to some of the other threads I mentioned above.
nutty_gnome
Well-Known Member
I would like some clarification to make this information applicable in practice.
I wash yeast. After I wash, I get what is essentially a cylinder of creamy tan yeast at the bottom of my jar. I can calculate the volume of a cylinder and find out how many milliliters of washed yeast cake I have.
What I want to know is: If in our 12 plato, 5 gallon example, I was supposed to pitch 228ml of slurry, can I get the same results by pitching a washed yeast cake that is 1/4 that volume (in this example 57ml of washed yeast cake). Or did I misunderstand the satement in the thread that a cake contains 4 times more yeast by volume than a slurry?
This information would help me to know what size jars to wash yeast into so I could gauge how much I'm pitching. N_G
I wash yeast. After I wash, I get what is essentially a cylinder of creamy tan yeast at the bottom of my jar. I can calculate the volume of a cylinder and find out how many milliliters of washed yeast cake I have.
What I want to know is: If in our 12 plato, 5 gallon example, I was supposed to pitch 228ml of slurry, can I get the same results by pitching a washed yeast cake that is 1/4 that volume (in this example 57ml of washed yeast cake). Or did I misunderstand the satement in the thread that a cake contains 4 times more yeast by volume than a slurry?
This information would help me to know what size jars to wash yeast into so I could gauge how much I'm pitching. N_G
conpewter
Well-Known Member
Might be useful to weight the carboy before making your "Starter beer" of a normal gravity, then when you rack off that and are ready to put your big beer on it, you can weigh it again and determine how much yeast slurry is there and if you need to pour any of it off.
BioBeing
Well-Known Member
I had an issue with this, based on what I know about coenzyme A from studying lipid synthesis in other systems. Acetyl-CoA levels in most systems do not vary much in different growth states. This apparently holds true for yeast too [Yoshioka and Hashimoto (1984) Agric. Biol. Chem. 48; 207-209].
In delving a bit deeper, acetyl-CoA, acyl-CoAs and fusel alcohols are required to make the flavor active acetate esters. The enzymes that put these together are called ester synthases, the major one being ATF1. The transcription of the gene encoding ATF1 appears to be key step in the process, and is regulated in a complex manner: it is inhibited by oxygen and unsaturated fatty acids; and activated by fermentable sugars and nitrogen. Anything that affects the activity of these synthases will affect the ester formation.
Here is a review I am plodding through... Flavor-active esters: adding fruitiness to beer. Let me know if you cannot get the pdf They are talking about this mainly in the context of high gravity lagers, that get diluted prior to packaging, which is apparently how most lagers are commercially made! High gravity worts lead to increased ester production, although addition of maltose instead of glucose can diminish this effect. All very complicated!
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.
I agree with you. In that case, since you're not aerating the beer to encourage yeast growth, you need to use as much yeast as you can.
BioBeing
Well-Known Member
Bit more reading... Acetate esters mentioned above are only one form of volatile ester that contribute to flavour. The next class are the ethyl esters.
Acetate esters: (in which the acid group is acetate and the alcohol group is ethanol or a complex alcohol derived from amino acid metabolism)
Ethyl esters (in which the alcohol group is ethanol and the acid group is a medium-chain fatty acid [MCFA])
Ethyl ester production appears to be a bit less studied, but seems primarily depended on the amount of medium chain fatty acids present. Ethyl esters tend to follow the same pattern as acetate esters, except they do not change with the sugar content of the wort and adding unsaturated fatty acids leads to a decrease in ethyl ester production. Increasing the temp of the fermentation increases the amount of acetate esters more than ethyl esters. In fact, ethyl hexanoate levels hardly change between 20 and 26*C.
Acetate esters: (in which the acid group is acetate and the alcohol group is ethanol or a complex alcohol derived from amino acid metabolism)
- ethyl acetate (solvent like aroma),
- isoamyl acetate (banana aroma),
- phenyl ethyl acetate (roses, honey).
Ethyl esters (in which the alcohol group is ethanol and the acid group is a medium-chain fatty acid [MCFA])
- ethyl hexanoate (anise seed, applelike aroma),
- ethyl octanoate (sour apple aroma)
- ethyl decanoate (floral odor).
Ethyl ester production appears to be a bit less studied, but seems primarily depended on the amount of medium chain fatty acids present. Ethyl esters tend to follow the same pattern as acetate esters, except they do not change with the sugar content of the wort and adding unsaturated fatty acids leads to a decrease in ethyl ester production. Increasing the temp of the fermentation increases the amount of acetate esters more than ethyl esters. In fact, ethyl hexanoate levels hardly change between 20 and 26*C.
Paddle_Head
Well-Known Member
I have similar questions.
I guess I'm struggling with the concept of slurry concentration.
For example, I wash my yeast using the technique from the sticky at the top of this page. I start with an initial volume of ~64 oz of water to mix up my yeast cake, and end up after all the settling & transfers with 8oz sample jars of very clean looking yeast. Now if I diluted with 40 oz of water initially, that slurry would be much more concentrated in the final 8oz jar. Or if I made my slurry with the same amount of water, but a washed yeast from a sample with a much higher OG, there would be much more yeast suspended in that initial 64oz of slurry.
I understand the concept of counting cells with a microscope, as well as various other plating/microscopic techniques for quantifying bacterial load. All of which seem a bit more of an investment in time/$'s than I'd care to make.
I do think the idea of quantifying a washed and compressed amount of yeast seems pretty robust. Maybe using a graduated cylinder at some point in the starter process?
Also no idea if prolonged refrigerated storage would dilute viability over time either of yeast.
Please find them...I would be really interested in the aeration vs none results too.
cheezydemon3
Well-Known Member
I have been dumping out 1/2 to 2/3 of my yeast cake for about a year now and pitching on that.
I guess I make better beer, but I have improved other techniques.
Did we need a whole thread for.... POUR OUT SOME OF THAT HUGE CAKE DUDE!!!
Not too scientific, but I shoot for half of a typical cake.
I guess I make better beer, but I have improved other techniques.
Did we need a whole thread for.... POUR OUT SOME OF THAT HUGE CAKE DUDE!!!
Not too scientific, but I shoot for half of a typical cake.
mdwmonster
Well-Known Member
As I read this, I'm begining to think that washing yeast might be something worth trying. Any idea how long the yeast will last? Seems like every batch of beer I brew calls for a different yeast, but if possible, I'd like to start keeping some on hand (if for no other reason than to give me something else beer related to mess with).
Also, I assume when you are talking about the volume of the yeast, you are refering to just the yeast settlement at the bottom, and not the full volume of the starter/washed yeast jar.....right?
Also, I assume when you are talking about the volume of the yeast, you are refering to just the yeast settlement at the bottom, and not the full volume of the starter/washed yeast jar.....right?
slowbie
Well-Known Member
According to the stickied thread on yeast washing, Bernie Brewer has used yeast as old as a year. The specific post is here.
Don't cloud the issue? On this newsgroup? AHHHHHHhaha
hahahahahahahahahahahahaaaaaaaaaaaaaaaaa!!!
Well, if there are more yeast working on the wort, then even
if that yeast is not particularly efficient at breaking down
some particular sugar, if there are enough of them, you
will still get more attenuation. Aren't the yeasts that give
you less attenuation also quick flocculators?
I wouldn't pitch onto a yeast cake because of the trub, but
if someone wants to, as another poster said, just dump out
some of it.
Ray
Paddle_Head
Well-Known Member
Yep. There is a thread somewhere on making a "yeast bank" if you'd like to store yeast for >1 year.
Edit: Here it is-
https://www.homebrewtalk.com/f13/guide-making-frozen-yeast-bank-35891/
bad practice?
Isn't that entirely subjective?
In Belgium there's a Trappist or Abby brewery that sends buckets of it's spent yeast cake to the local pubs where people will mix it in their beer or take a shot straight.
!!~ YECH ~!! But it's all subjective.
I won't be mixing spent yeast with beer 'cause I don't like it. But bad practice? What if they like it ?
Isn't that entirely subjective?
In Belgium there's a Trappist or Abby brewery that sends buckets of it's spent yeast cake to the local pubs where people will mix it in their beer or take a shot straight.
!!~ YECH ~!! But it's all subjective.
I won't be mixing spent yeast with beer 'cause I don't like it. But bad practice? What if they like it ?
gtpro
Well-Known Member
The only problem is I got a pretty busy schedule and I just dont think I have time to count to a billion.
Honestly, I would only consider washing specialty liquid yeast that costs $8-9 per dose, with Safale or notty, the dollar or two well worth pitching fresh.
Honestly, I would only consider washing specialty liquid yeast that costs $8-9 per dose, with Safale or notty, the dollar or two well worth pitching fresh.
OP
OP
Bob
Well-Known Member
BioBeing - Thanks for the enzyme studies! That's, like, Wow!
Theoretically, as the slurry in the starter flask has a much higher concentration of yeast solids, this would be true. According to Fix - and other researchers have borne this out - only 25% of the average mixed-material slurry is yeast solids. A starter slurry will have non-yeast solids too, but you'd need to do a series of cell counts to determine a baseline for your setup.
What's important is the cell count.
That's why it's a Rule of Thumb, not something hard and fast.
Your technique may make a runny slurry, it may make a thick slurry. Different yeasts will also present different physical characteristics. For example, Wyeast 3787 is runny, like pancake batter, while 1187 is rather thicker, sort of like pancake batter after several seconds on the griddle. (That's a lame metaphor, but it's the best I can think of off the top of my head!)
If you want to seriously quantify cell counts the only real way to do it is with a hemocytometer and a microscope.
According to the sources and my experience, viability of harvested, unwashed slurry drops off precipitously over time. In the OP I noted 25% per each seven days stored. What that works out to be for washed yeast, I really can't say; I have no data from which to draw conclusions.
Regardless of calculated storage, some degradation is bound to occur over time, whether it's washed or simply harvested. The wise brewer will build up a starter from his stored yeast and pitch the slurry from that.
Correct.
Good question! Apparently, and in the absence of contrary data, the answer would be "Yes." The samples were not underpitched.
Presumably the gross overpitch simply sent the colony into overdrive, metabolizing everything they possibly could. That's the only thing I can imagine.
That's not a brewing practice. That's a thing drinkers do. Has nothing to do with brewing practice.
What equates with good or bad brewing practice is not subjective. There are standards. Ask Dr Bamforth.
Cheers, folks! Great discussion!
Bob
Theoretically, as the slurry in the starter flask has a much higher concentration of yeast solids, this would be true. According to Fix - and other researchers have borne this out - only 25% of the average mixed-material slurry is yeast solids. A starter slurry will have non-yeast solids too, but you'd need to do a series of cell counts to determine a baseline for your setup.
What's important is the cell count.
That's why it's a Rule of Thumb, not something hard and fast.
Your technique may make a runny slurry, it may make a thick slurry. Different yeasts will also present different physical characteristics. For example, Wyeast 3787 is runny, like pancake batter, while 1187 is rather thicker, sort of like pancake batter after several seconds on the griddle. (That's a lame metaphor, but it's the best I can think of off the top of my head!)
If you want to seriously quantify cell counts the only real way to do it is with a hemocytometer and a microscope.
According to the sources and my experience, viability of harvested, unwashed slurry drops off precipitously over time. In the OP I noted 25% per each seven days stored. What that works out to be for washed yeast, I really can't say; I have no data from which to draw conclusions.
Regardless of calculated storage, some degradation is bound to occur over time, whether it's washed or simply harvested. The wise brewer will build up a starter from his stored yeast and pitch the slurry from that.
Correct.
Good question! Apparently, and in the absence of contrary data, the answer would be "Yes." The samples were not underpitched.
Presumably the gross overpitch simply sent the colony into overdrive, metabolizing everything they possibly could. That's the only thing I can imagine.
That's not a brewing practice. That's a thing drinkers do. Has nothing to do with brewing practice.
What equates with good or bad brewing practice is not subjective. There are standards. Ask Dr Bamforth.
Cheers, folks! Great discussion!
Bob
After reading all of this, I racked from primary to secondary after 12 days, and dumped half the yeast cake, then pitched a new batch of the same recipe onto the cake. I'll do some taste testing. But I will note that I have active airlock activity after just 3 hours.
First time I've pitched on a cake, I'm interested in how it works out. For some it's a science, for some it's a rigid process, for others, it's just fun.
First time I've pitched on a cake, I'm interested in how it works out. For some it's a science, for some it's a rigid process, for others, it's just fun.
COLObrewer
Well-Known Member
Does anyone have insights on pitching to the cake after a secondary? Is there a higher or lower percentage of viable yeast in a secondary cake as opposed to a primary cake?
It's certainly alot cleaner than primary trub, I've started going back to using secondary (at times) for the purpose of collecting a cleaner batch of re-useable yeast.
Keep on brewing my friends
It's certainly alot cleaner than primary trub, I've started going back to using secondary (at times) for the purpose of collecting a cleaner batch of re-useable yeast.
Keep on brewing my friends
nutty_gnome
Well-Known Member
While the yeast is cleaner, many posts on these boards suggest that harvesting from secondary will yield you the least flocculent and slowest performing fraction of the beasties. So, after a few washings, you have something that isn't at all like the intial 'charge' of yeast. Thats my understanding.
OP
OP
Bob
Well-Known Member
Nutty Gnome is Nutty, but he's not wrong.
Yeast from the clearing tank may be more free of trub, but the yeast is not of good-enough quality for use. Better to harvest yeast from the primary and pitch as-is slurry or wash the trub away.
Bob
Yeast from the clearing tank may be more free of trub, but the yeast is not of good-enough quality for use. Better to harvest yeast from the primary and pitch as-is slurry or wash the trub away.
Bob
COLObrewer
Well-Known Member
That makes perfect sense, Thanx!
cheezydemon3
Well-Known Member
Again, Bob, I admire your initiation of the discussion, and to start trouble, but the evil's of TRUB are, in my opinion, exaggerated, and in question, especially if there is short exposure to said trub.
slowbie
Well-Known Member
I don't recall anyone here talking about trub being such a terrible thing. The only reference I remember is when Bob said that the slurry at the bottom of your primary is only about 25% yeast whereas the bottom of a starter is nearly 100% yeast and that pitching rates should be adjusted accordingly. Did I miss something?
cheezydemon3
Well-Known Member
sorry, not just Bob, but he definitely cites trub as one reason not to pitch on a cake.
Yankeehillbrewer
Well-Known Member
But don't you think it is in the best interest of your fresh wort to have a freshly cleaned & sanitized Fermentor?
I'm not sure what you mean by short exposure? your new wort will be sitting on all that old trub for at least 3 weeks, and by the time it's done the original yeast could up 2 months old or more. By that time Autolysis could become an issue, even though many claim it to be a myth of sorts. Isn't it best to just eliminate the possibility by cleaning your primary and pitching a proper amount of yeast slurry?
scottlindner
Well-Known Member
If you don't trust the sanitization of your first batch, how can you trust it in the second?
I have done as many as five beers in a series onto the same active yeast cake (I pull out at least 50% between batches). Just last night I drank one that was the third in a series that was in a keg for 1.5 years at room temp. No infection, tastes awesome. Being sanitary isn't a problem for me, but if it's your problem.. then don't repitch.
As for the affects of overpitching (the purpose of this thread), I couldn't say. I haven't done enough testing to determine any appreciable difference between batches that went onto too much yeast, from those that went onto a more appropriate or even lesser amount of active yeast.
Cheers,
Scott
Yankeehillbrewer
Well-Known Member
Didn't say I had a Sanitation problem, I'm very serious about sanitation, it's the first step in making good beer. It just doesn't make sense, to me, to not clean out the old trub and the Krausen ring. It's not so much about Sanitation, but about not having all that extra crap in your fresh wort.
h4rdluck
Well-Known Member
its all just preference i guess.... I don't see it as crap...i just see it as more of the same as what i am adding. The krauzen ring? Theres just going to be another. The trub? Its just going to settle to the bottom. The autolysis? Never been a problem for me.
Again. There are plenty of theories and paper research. But what I care about it what you can actuality get away with an personally its a lot more than what a lot of people here suggest.
Again. There are plenty of theories and paper research. But what I care about it what you can actuality get away with an personally its a lot more than what a lot of people here suggest.
scottlindner
Well-Known Member
If sanitization isn't the problem, then it's trub and autolysis you're concerned about. Both are very debatable if they'll affect your beer in any appreciable way.
When i first started repitching onto active yeast cakes I kept a rag submerged in my iodophor solution during the brew to ensure it was sanitary and used it to clean the kraussen gunk out of my fermenter. I still use a plastic pail so that's easy for me to do. I stopped doing that when I realized I couldn't tell the difference. Could judges at the NHC? Possibly, maybe even likely, but I can't tell so why bother? I haven't submitted a single beer to a competition and I don't have any intent to, so why bother, it's good enough for me. So what I think you should do is leave a beer in your primary for a month, bottle or keg, and drink. If you can tell it tastes like crap, don't repitch. If you can't, maybe you should give it a whirl.
I recently had a brew in primary sitting on dead yeast, trub, and bathing in krausen gunk for four months. I tasted the gravity sample while racking into a corny. One of the most fantastic beers I've ever made. Maybe it was just a good brew sesson, or fresher grain, or the slight amount of extra crush I added on my Barleycrusher, or maybe the trub and autolysis boggyman didn't visit my fermenter that day? i dunno which, but my first impressions with those two fears are that they don't exist.. maybe my taste buds suck?
Scott
Yankeehillbrewer
Well-Known Member
well we'll just have to agree to disagree
scottlindner
Well-Known Member
What's your purpose? Do you disagree that my taste buds might suck, or that NHC judges really can't taste very much?
One strategy has a higher risk of infection, but hedges against Autolysis. It may or may not exist in homebrewing, but until someone proves it doesn't, neither way is the "right" way.
Though, to be fair, I would reuse a fermenter before washing a cake. Seems safer to me.
Yankeehillbrewer
Well-Known Member
To convert this entire forum to doing things my way, which is the right way and only way. Why? Because I said so.
scottlindner
Well-Known Member
We agree..
chriswilkes33
Well-Known Member
Why would me not making a starter irritate you?
scottlindner
Well-Known Member
I completely agree. There's no one way, and if you look at some of great styles we enjoy today, their history of those styles evolved using very different methods.
It's my opinion that as Americans (assuming we all are), we tend to focus on the science, rather than the art, in most things. I see this thread as a good example of that. It's great to know the science, but I can show you a great beer using terrible science, and a terrible beer using great science.
Scott
