# The Great Yeast Underpitch, Overpitch Experiment



## pdilley (18/8/09)

Following on from the previous brewing experiment that smashed to bits the advice to get fermented beer off of the yeast as soonnas possible (experiment record was 84 days left on the yest cake with no bad effects) the next big brewing experiment will be yeast underpitching and overpitching. Will you be participating?

This experiment consists of mixing upmextract or brewing an all grain batch. Then splitting the end wort into 3 separate fermenters. In fermenter one you deliberately underpitch the amount of yeast. In fermenter two you pitch the normal ratio of yeast to wort. In fermenter three you deliberately overpitch the amount of yeast.

Brew out the beer, bottle or keg and do a taste comparison between the three.

Cheer,
Brewer Pete


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## jimi (18/8/09)

Brewer Pete said:


> Following on from the previous brewing experiment that smashed to bits the advice to get fermented beer off of the yeast as soonnas possible (experiment record was 84 days left on the yest cake with no bad effects) the next big brewing experiment will be yeast underpitching and overpitching. Will you be participating?
> 
> This experiment consists of mixing upmextract or brewing an all grain batch. Then splitting the end wort into 3 separate fermenters. In fermenter one you deliberately underpitch the amount of yeast. In fermenter two you pitch the normal ratio of yeast to wort. In fermenter three you deliberately overpitch the amount of yeast.
> 
> ...



Hi Pete
Just noticing your thread title, did BYO mag do this / spark this idea? If so what did they think (sorry if this is spoiling the 'blind')


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## Kai (18/8/09)

What's this about smashing to bits the advice of getting beer of the cake as soon as possible?


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## manticle (18/8/09)

Brewer Pete said:


> Following on from the previous brewing experiment that smashed to bits the advice to get fermented beer off of the yeast as soonnas possible (experiment record was 84 days left on the yest cake with no bad effects) the next big brewing experiment will be yeast underpitching and overpitching. Will you be participating?
> 
> This experiment consists of mixing upmextract or brewing an all grain batch. Then splitting the end wort into 3 separate fermenters. In fermenter one you deliberately underpitch the amount of yeast. In fermenter two you pitch the normal ratio of yeast to wort. In fermenter three you deliberately overpitch the amount of yeast.
> 
> ...



Sounds interesting. Would consider if I can get a hold of a couple more fermenters.


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## pdilley (18/8/09)

Kai: The upcomming article will have the full gory details, but a synopsis is tasters preferred the same beer batch left on the cake for a month or the same batch that was split and racked into a secondary fermenter to the same batch bottled right away after fermentation completed.

Jimi: Yep. The previous experemt should be released soon in an upcomming issue. This one is just starting up. I think I caught wind of it in a recent BBRadio podcast.

Manticle: I've got 20! All my large ones save one are engaged already. I do have 5 of the glass 5L demi's free. That lets me split a batch of wort into 5 and do 1. Severely underpitched 2. Underpitched 3. Normal pitch 4. Overpitched 5. Severely overpitched 

Cheers,
Brewer Pete


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## manticle (18/8/09)

Brewer Pete said:


> Kai: The upcomming article will have the full gory details, but a synopsis is tasters preferred the same beer batch left on the cake for a month or the same batch that was split and racked into a secondary fermenter to the same batch bottled right away after fermentation completed.



What that suggests is that the threat of autolysis has made everyone pack darkies and be super cautious. It also suggests that beer that's given a chance to clean up after itself is generally better (or preferred) than beer that's bottled without said chance.

That doesn't equate to beer should be left as long as possible on the yeast cake - just that yeast cleaning/longer fermentations (including proper secondary fermentation) are good things.



> Manticle: I've got 20!


I've got four. I feel like a small child.


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## pdilley (18/8/09)

Its not how many you have but how often you can keep them fermenting!


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## Scruffy (19/8/09)

So you've got a huge brick of yeast and you're breaking the three bears portions off it... or are you making a starter - and what wort are you using for the starters - see where I'm going?


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## manticle (19/8/09)

Brewer Pete said:


> Its not how many you have but how often you can keep them fermenting!



No, it's not how often you can keep them fermenting it's how slowly you can drink the results.

Everything conspires against me.


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## katzke (19/8/09)

manticle said:


> What that suggests is that the threat of autolysis has made everyone pack darkies and be super cautious. It also suggests that beer that's given a chance to clean up after itself is generally better (or preferred) than beer that's bottled without said chance.
> 
> That doesn't equate to beer should be left as long as possible on the yeast cake - just that yeast cleaning/longer fermentations (including proper secondary fermentation) are good things.



I have not read the article but from personal experience as well as others and what I have read about leaving a brew on a yeast cake, for a month or 2, is not a problem.

My suspicion is that it is a big brewery problem associated with using large conical fermentors. Such fermentors will collect a deep layer of yeast. In the case of most homebrewers we get a relatively thin layer of yeast. Just an idea anyway.

Think about it. If leaving beer on old yeast was bad then bottle conditioned beer would be awful stuff. So it must be something besides just leaving the beer on yeast.

As to pitching rates it will be interesting to see the outcome. I will continue to pitch a packet of dry yeast in my batches. I am enjoying not only brewing but also the results much more. Plus with my 2 selections of only American Ale yeast and English Ale yeast I have removed a big variable to recipe formulation.


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## Pollux (19/8/09)

The leaving it on the yeast cake experiment was done in conjunction with BBR.....

http://www.basicbrewing.com/index.php?page=radio

Go down to the show from the 28th of May 2009 for the results.


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## QldKev (19/8/09)

katzke said:


> I have not read the article but from personal experience as well as others and what I have read about leaving a brew on a yeast cake, for a month or 2, is not a problem.
> 
> My suspicion is that it is a big brewery problem associated with using large conical fermentors. Such fermentors will collect a deep layer of yeast. In the case of most homebrewers we get a relatively thin layer of yeast. Just an idea anyway.
> 
> ...



I though depending on yeast strain and temperatures all influence the level of autolysis that occurs; and also that the Vegemite taste was from the weaker / dead cells. You have noticed you can pitch 2 side by side brews and get varying results from the yeast activity, same with the issue of autolysis. Autolysis will occur in brews, but as long as it is undetectable by the consumer it is acceptable. In bottled beer the yeast layer is normally from healthy yeast as the dead yeast has dropped out and is at a ratio it does not impart detectable autolysis flavors. Even in worse cases of autolysis depending on beer style it may not be picked up, eg in a porter or stout you would not notice it and in a clear lager you could detect it easier. 

Look forward to reading your research. It is research that can break the status quo.

QldKev


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## mckenry (19/8/09)

Brewer Pete said:


> the next big brewing experiment will be yeast underpitching and overpitching. Will you be participating?
> 
> Cheer,
> Brewer Pete



Hey Brewer Pete,
FWIW, I underpitched once and picked up my only AG infection. May or may not be linked, but no, I will not be participating in that one... Happy for others to try, then report.
mckenry.


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## muckey (19/8/09)

mckenry said:


> FWIW, I underpitched once and picked up my only AG infection.




actually this makes sense to me. one of the things about pitching rate is having enough cell count to outcompete anything else that happens to get in there so getting an infection when underpitching is entirely possible.

unfortunately I wont be able to participate but I expect that the difference in the samples should be quite noticeable. will be interested to see the results


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## AndrewQLD (19/8/09)

> Following on from the previous brewing experiment that smashed to bits the advice to get fermented beer off of the yeast as soonnas possible (experiment record was 84 days left on the yest cake with no bad effects) the next big brewing experiment will be yeast underpitching and overpitching. Will you be participating?




That is an awfully big call to make.
I would have thought that unless the experiment (and I haven't heard the program) was done using a variety of yeast strains on a variety of different beer styles then the results are inconclusive. Higher gravity/alcohol beers would have a totally different effect on a yeast cake than would a light beer, also the amount of yeast cake would make a difference as well.
As far as underpitching/overpitching, who knows? But why would you do either?

Andrew


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## muckey (19/8/09)

not sure about overpitching but I beleive underpitching is done deliberately in certain styles to stress the yeast and increase production of esters.

I do agree that different beer styles will have an effect on the trub but I would have thought that yeast health would be a bigger factor - just my 2c


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## Pennywise (19/8/09)

I'll have a fermenter spare in a day or so. If a couple of us in Melb could chuck one in each and have a designated brewery to leave the fermenters in I'd be up for it. I'd be very interested in the results as I think many others would be.

Just a thought


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## Screwtop (19/8/09)

Brewer Pete said:


> Will you be participating?




Sorry Pete but no again, different yeast strains react in different ways to varying treatments.

Cheers,

Screwy


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## mikem108 (19/8/09)

Depending on the yeast strain, underpitching can give pretty disgusting or desirable results, same with over pitching I have found from personal experience, also how would you be controlling the amount of aeration given to each pitch to make sure they were equal unless you used pure O2.
I think the yeast cake debate was settled a long time ago. Jamil's been bangin on about no secondary for quite some time now


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## hazard (19/8/09)

AndrewQLD said:


> That is an awfully big call to make.
> I would have thought that unless the experiment (and I haven't heard the program) was done using a variety of yeast strains on a variety of different beer styles then the results are inconclusive. Higher gravity/alcohol beers would have a totally different effect on a yeast cake than would a light beer, also the amount of yeast cake would make a difference as well.
> As far as underpitching/overpitching, who knows? But why would you do either?
> 
> Andrew


Get the latest copy of BYO if you can - 12 different brewers participated with whatever style of beer they were brewing. It is not a comprehensive scientific experiment, but provides plenty of evidenece that leaving beer on yeast cake, in a home brew environment, doesn't have a bad effect on beer.

If you want to know more about pitching rate experiement, follow this link
http://www.byo.com/blogs/pitching-rate-experiment.html


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## AndrewQLD (19/8/09)

hazard said:


> Get the latest copy of BYO if you can - 12 different brewers participated with whatever style of beer they were brewing. It is not a comprehensive scientific experiment, but provides plenty of evidenece that leaving beer on yeast cake, in a home brew environment, doesn't have a bad effect on beer.
> 
> If you want to know more about pitching rate experiement, follow this link
> http://www.byo.com/blogs/pitching-rate-experiment.html



Thanks hazard, I have the issue. I wouldn't consider 1-2 weeks an extended time on a yeast cake ( I thought we were talking weeks not days) and while there were no off flavours evident the jury is still out on which beer was preferred, the one immediately racked or the extended one. Your beer will be ok on the yeast cake, but you might or might not like the flavor differences. Not a very conclusive experiment really. I should say this is my interpretation of the article and others may read it differently.

I'm with Screwtop on the overpitch/underpitch experiment, too many variables from one yeast strain to the next for any meaningful results, and too many variables with individual brewing practices as well. As Muckey pointed out some yeast and some beer styles could benefit from under pitching, but most won't which would make the results unreliable overall.

Andrew

Andrew


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## Renegade (19/8/09)

Sounds Good - I'll be up for conducting this experiement, starting late-September. Can I use all the Coopers Yeasts that have been living in my fridge? Why not give something common a good run ! Will combine all together and measure out from the mix, to ensure consistent yeast quality. 

Aiming for 3 x 8 litre fermentations, how does this sounds for a dry yeast allocation?

Batch 1: 1 gram
Batch 2: 4 grams
Batch 3: 10 grams

No starters on any of them, straight into the wort. 

Perhaps I'll do a partial (25% pilsener grain, 50% pale liquid malt, 25% LDME) in a style with no spec. grains, and use some hersbrucker, and aim for 25IBU - I suspect that a subtle grain & hop flavour will accent slight variations due to pitching variances. 

Already have the perfect containers, have been collecting 10kg whey protein buckets with very tight sealable lids from the gym. All I need is to set up some sort of CO2 release system. Three airlocks singing a symphony sounds exciting! But I would probably just use blow-off tubes (because I only have one airlock, and see no point in buying more). 

Just on 'spare fermenters', isn't there an issue with headspace if people are using their full-seized barrels for small batches ?

We should nominate a couple of judges for this too. Obviously Butters could be one, if he is keen. 

Any non-participants might like to contribute to postage costs if they want to be involved.


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## Renegade (19/8/09)

I should add that I personally *don't* think there will be any discernable difference, but this is a good way to determine it either way.


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## Scruffy (19/8/09)

It's a great idea. And I'm most certainly not trying to deride your efforts Pete...

But only splitting into three demijohns?

I would have thought 2 or 3 _identical sets_ of three; 

...then, would the 5 litre batch experiment predict larger volume outcomes?

There's been beardy men in white coats telling us stuff for a while now...

Over-pitching can be a bad thing.

Chris White of White Labs says:



> If the beer is over-pitched, yeast do not grow though a complete growth cycle. This results in few new yeast cells, which makes for unhealthy yeast and low viability by the end of fermentation.


Thus, if you intend to harvest and re-pitch, or if the yeast run out of steam and crap out before the intended attenuation is reached, you may be in for problems. The flavour/aroma profile of the yeast may be adversely affected. The reproductive cycle of the yeast is when the esters, phenols, and other flavour precursors are produced.

In my case, I reckon I under-pitch. The risks from under-pitching are much greater I fink than the risks from over-pitching; extended lag times, weak reproduction, insufficient fermentation power, and possibly too much ester production.

Here's a bit from beeradvocate.com:



> From what I understand, the issue with over-pitching has to do with the same biological survival mechanism that brings us attenuation. When yeast reach a point where there is no longer enough food to sustain their numbers they go dormant and wait for more food to be introduced. Now, over-pitching becomes an issue if the ratio of cells to food is too low. This will cause incomplete or stalled fermentation as the yeast will drop out of solution and wait for more food. Additionally, they seem to stop reproducing once they reach a point where they can no longer sustain. So say your first beer had a starting gravity of 1.050. If you took a cup of that slurry and re-pitched it into another wort of equal gravity they will reproduce to roughly the same number of cells as was the final number of cells in the original beer.



Initial cell count will have its greatest effects in terms of chemical by-products of reproduction, not fermentation itself, such as phenols and esters. This is why many recommend under-pitching on Hefeweizens for example; forcing the yeast to reproduce to environmental capacity from a small cell count maximizes the production of such by-products.

Best practice is to pitch the appropriate amount of yeast, which is easily learnt by clicking on Mr Malty Pitching Rate Calculator and entering your specific information.

But Pete, you might find something we've overlooked... (you have form!) - good luck!


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## Nick JD (19/8/09)

I underpitch lambics. :blink:


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## Online Brewing Supplies (19/8/09)

Kai said:


> What's this about smashing to bits the advice of getting beer of the cake as soon as possible?


Yeah this interested me to? To be objective and scientific I hope you have taken pH readings of the wort/finished beer as things progressed.This will tell you a lot about what the yeast is doing.
GB


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## Thirsty Boy (19/8/09)

Kai said:


> What's this about smashing to bits the advice of getting beer of the cake as soon as possible?



I hope its smashed to bits at any rate -- lousy advice in my book if anyone has been giving it.

Getting the beer off the main cake reasonably soon after the yeast has finished doing all the stuff it is supposed to ... now there might be an argument for that


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## manticle (19/8/09)

katzke said:


> I have not read the article but from personal experience as well as others and what I have read about leaving a brew on a yeast cake, for a month or 2, is not a problem.
> 
> My suspicion is that it is a big brewery problem associated with using large conical fermentors. Such fermentors will collect a deep layer of yeast. In the case of most homebrewers we get a relatively thin layer of yeast. Just an idea anyway.
> 
> ...



I wouldn't have thought a month was a problem. I have had the same curiosity about bottle conditioning. It's been suggested to me that the amount of dead yeast within will be minimial enough not to effect flavour. I've no idea how much science that's based on.

Personally I find my brews improve with time on yeast (still not months though).

an open question about autolysis: I read somehwere that autolysis releases sulphur but I've also read that it causes vegemite flavours. Does it cause both or only one and if so which one? Had a shall remain nameless Vic micro on tap last night that tasted like a pint of vegemite. Emailed the brewery who suggested my palate was keen but confused and what I was actually tasting was roasted malts. I wondered if the beer had autolysised but didn't put that in the email because I didn't want to look like a knowitall prat.


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## haysie (19/8/09)

manticle said:


> an open question about autolysis: I read somehwere that autolysis releases sulphur but I've also read that it causes vegemite flavours. Does it cause both or only one and if so which one? Had a shall remain nameless Vic micro on tap last night that tasted like a pint of vegemite. Emailed the brewery who suggested my palate was keen but confused and what I was actually tasting was roasted malts. I wondered if the beer had autolysised but didn't put that in the email because I didn't want to look like a knowitall prat.



for my palate,aroma judging of autolysis, i had to taste it. i stored a few very small slurrys whitelabs oo2 oo5 wyeast 3522 1084 us05 for quite a few months (8), Vegemite was the overiding aroma in every sample albeit the 3522 still had a heap of funk and not so much meatiness as some call it. Yet never ever tasted that same flavours in a bottle of beer, I would expect the brewery guru`s to tell us all about stability because they have the measuring devices at their disposal. For mine, autolysis exists and would carry the afterttaste post fermentation.


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## pdilley (19/8/09)

The original experiment is a same wort, three way split, same yeast but different volume pitch.

I don't have the fermenters to spare in the size range as all are in use.

My own experiment will use same wort, 5 separate 5L sized demijohns, same yeast 5 different volume pitch rates.

I don't participate in BYO but follow along. The purpose of all these experiments is to actually empower the brewer against not the receiving of, but simply the not accepting of bad advice from professed experts and even books on home brewing. Someone who does something first hand and knows the results will listen politely when someone tries to tell them something counter to what their first hand experience has shown them but will have a hard time not discounting that person for the advice they are giving and unfortunately/fortunately for all future advice in other areas. So it behooves us all to try out these experiments that test the "status quo" of published presumed fact.

For example, I brew high ABV Meads, up to 18%, they sit on the yeast for an extremely long time, even racked they will still sluff lees and we are talking up to a year or more. There is no where for off flavours to hide, and a lot of money riding on a batch per volume than with beers. I have never had a Vegemite tasting Mead yet to date. The sakes can push 22%.

Yet already we have professed truths that long time on the yeast might not affect light beers but higher gravity beers you won't get away with it. We also have the same argument against BIAB beers winning competitions in reverse, the dark beers yeah they can win but they will never win a light beer category in competition.

Its in my character to question as I do it all the time in the government. In the majority of cases I find no one can back up a process or reason things are done beyond thats what we always have done or a no you can not do something else.

I develop a lot of respect for proposed truths that I first hand find out are true. But there has not been that many of them yet.


Cheers,
Brewer Pete

EDIT: The last I heard on the radio regarding the BYO yeast cake experiment, the longest brew was almost 3 months on the cake with no discernible problems in the flavour. I'll listen to that brewer that did a first hand test before anyone on here who has not left a beer on the cake for nearly 3 months and find out themselves first hand.


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## buttersd70 (19/8/09)

Balls.

That's all I really have to say.

edit: in the context of bollocks, as opposed to tennis.

3 months on a yeast cake?.....if that was an English Mild or Bitter 3 months is too old, yeastcake or not.....american-centric much?


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## AndrewQLD (19/8/09)

Brewer Pete said:


> I develop a lot of respect for proposed truths that I first hand find out are true. But there has not been that many of them yet.
> 
> 
> Cheers,
> ...



And when that same experiment has been run 20 times using different yeasts, recipes, brewing techniques,fermentation temps, storage temps and has not shown any signs of off flavors then I'll listen to that advice as well. One successful experiment does not necessarily make a truth. There is just not enough proof that it will work repeatably.

Andrew

Andrew


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## Renegade (19/8/09)

AndrewQLD said:


> One successful experiment does not necessarily make a truth. There is just not enough proof that it will work repeatably.



Andrew, I agree with your stated viewpoint - repeatability is the benchmark of scientific _theory_. But it should be recalled that Brewer Pete proposed this project, and then stated this: 



Brewer Pete said:


> Will you be participating?



.. of which could be read as an invitation to simultaneously do this brew experiment with Pete. Rigourous process-driven samples from several hobby-brewers.The more people that do it, the closer we come to a suitable answer. Perhaps debunk a few myths, perhaps not..

I have been considering this thread all day today, and have decided that, what the heck, my next brew will be a 3-way split. The consideration in such an experiment is that the final product is shipped to a handful of 'tasters' within the AHB community. I am not equipped of articulating the flavour rainbow as well as others. 

Let's say a wort is split into 3 x 7litre fermenters, and each is dosed with a yeast volume (under/suggsted/over). All are fermented under identical conditions, primary fermenter only, no finings, and bottled with precisly the same primer quantity. Each of the three bottles would have a different coloured cap, lets say red, green, gold. 

These three colour samples would be sent to the agreed 'tasters', who would have no knowledge of which colour equated to which pitching rule. 

They would need to appreciate that they aren't judging the 'style' of the beer, or the complexities of the hop/malt/yeast, but rather the perceived negative traits of under/over pitching. 

One brewer could ship a 3 x 3-Pack (red, green, gold) to three agreed 'tasters', and they would ideally have organised for another local 'taster' to be there for the test. So that's up to six points of feedback from one brewer's experiment. 

If Pete does it, I do it, and AndrewQLD does it, that's up to 18 points of feedback. Enough to compile a bit of analysis. Sure it's a target demographic, but what better a bunch of people to conduct & test the notion? 

Will you be participating, Andrew?


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## Kai (19/8/09)

It looks like we've diverged into two different discussions based on these BYO collaborations. Back to the first one, leaving beer too long on the yeast cake definitely is a negative. However, it can also definitely be said that sometimes there is too much emphasis on getting the beer off the yeast as early as possible. But for anyone who things the idea of leaving beer on the cake too long is smashed, I have an american brown ale in primary that's been sitting on my back verandah for a couple months that I welcome you to try....


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## Renegade (19/8/09)

The thread was about pitching rates?


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## Kai (20/8/09)

Oh yeah, pitching rates... 

#1: pitch enough yeast to generate a ferment that produces a beer that attenuates well and promptly. 

#2: refine your pitching rate (and perhaps your wort aeration) to produce a flavour profile you want from your yeast.

#3: if #2 buggers up #1, or #1 buggers up #1, refer to #1.

There is no way you can apply hard-and-fast rules to pitching rates at home. Don't worry about 'em unless you've got a microscope to count them, a pH meter to monitor your ferment and a dissolved oxygen meter to measure your aeration. Propagating a healthy starter culture is the number one tool any brewer has and all that takes is a little attention to detail and a sniff here & there...


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## katzke (20/8/09)

AndrewQLD said:


> And when that same experiment has been run 20 times using different yeasts, recipes, brewing techniques,fermentation temps, storage temps and has not shown any signs of off flavors then I'll listen to that advice as well. One successful experiment does not necessarily make a truth. There is just not enough proof that it will work repeatably.
> 
> Andrew



You are way to simple in saying there is no proof. Every beer style is different. That said there is more evidence that removing a brew too soon is worse then leaving it longer.

I think the reason for the article is someone wrote that autolysis is a problem and somehow it became you need to remove the brew as fast as possible from the yeast.

I am not a wagering person but I bet that more beer is sub par because it is not left long enough on the yeast then is ruined because it is left too long. I know my beer has improved once I realized it takes time to make beer.

I have read way too many times advice saying to ferment for a week and rack for a second week then bottle. Our award winning craft brewer turns beer over much slower then that. I can not remember the exact number of days but I recall 27 days as the figure I was given. This is from a brewer who is the 12th largest brewer in the USA. They have a full lab staffed by scientists at their disposal to control every controllable aspect of the brewing process.

It is also interesting that no one commented on the problem being related to breweries using large conical fermenters. They concentrate the yeast in a small space as opposed to a flat bottomed fermenter.

I say autolysis is not a problem for home brewers. Do I have any evidence? No, just experiential evidence. Good enough for me. Also as home brewers we have much more to be concerned about then this. I have tasted a few beers and never had one that was tasted like it was left too long on the yeast cake. I have tasted good beer and bad beer but the ones that stuck out were the ones that were weaned way to early.


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## AndrewQLD (20/8/09)

Renegade said:


> > And when that same experiment has been run 20 times using different yeasts, recipes, brewing techniques,fermentation temps, storage temps and has not shown any signs of off flavors then I'll listen to that advice as well. One successful experiment does not necessarily make a truth. There is just not enough proof that it will work repeatably.
> >
> > Andrew
> 
> ...



I was actually referring to the "leaving the beer on the yeast cake experiment" that the OP reffered to in first thread, not the pitching rate experiment. And no I won't be participating, too many variables in my opinion to form any kind of meaningful results.




katzke said:


> You are way to simple in saying there is no proof. Every beer style is different. That said there is more evidence that removing a brew too soon is worse then leaving it longer.
> 
> I think the reason for the article is someone wrote that 'autolysis is a problem' and somehow it became 'you need to remove the brew as fast as possible from the yeast'.
> 
> ...



I didn't really think my response was "simple", just the opposite actually.
Thanks for admitting that you don't have any real evidence regarding autolysis effects, and I would agree that perhaps it doesn't have a negative effect over a short time. My original comments regarding this were based on the OP' comment 
"Following on from the previous brewing experiment that smashed to bits the advice to get fermented beer off of the yeast as soonnas possible"

Nothing could be further from the truth and that's what concerned me.

Regards
Andrew


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## Online Brewing Supplies (20/8/09)

Kai said:


> There is no way you can apply hard-and-fast rules to pitching rates at home. Don't worry about 'em unless you've got a microscope to count them, a pH meter to monitor your ferment and a dissolved oxygen meter to measure your aeration.


Kai ,Yes that's the truth, unless you can do the above forget your experiments.They are just going to be subjective results.Still it will be interesting to see what results that it comes up with and how they are interpreted .
GB


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## katzke (20/8/09)

AndrewQLD said:


> Andrew, I agree with your stated viewpoint - repeatability is the benchmark of scientific _theory_. But it should be recalled that Brewer Pete proposed this project, and then stated this:
> 
> 
> 
> ...



So translate from Aussie for me for I am confused.

Do you think people should leave the beer on the cake?

Do you think that people should pull it off as soon as possible?

What proof do you have to back up your answer?


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## AndrewQLD (20/8/09)

katzke said:


> So translate from Aussie for me for I am confused.
> 
> Do you think people should leave the beer on the cake?
> 
> ...



1. No

2. yes, as soon as possible after fermentation is _complete

_3. Probably about as much as you, my own experience of countless brews, reports of other brewers ect. And the same as you, I have no definite proof that it works best this way or that, the difference being I am not telling people that it does.

That's about as good a translation as I can make it.
Sorry if we disagree, but that's the nature of brewing, no one way is best.

Andrew


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## katzke (20/8/09)

AndrewQLD said:


> 1. No
> 
> 2. yes, as soon as possible after fermentation is _complete
> 
> ...



Thanks. I really was confused. 

Disagreement is part of the fun of brewing. As long as we can agree to disagree.

Almost got on the bad list in our club because I wrote bad things about that Canadian Belgian style beer some of you are upset about loosing access to. La Fin De whatnots. Tastes like bubble gum Soda to me. Good thing all beer does not taste like that or I would have to force myself to drink wine. And that is an awful thought.


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## pdilley (20/8/09)

Hey guys, as back in the original posts, I get this from BBRadio podcasts, not BYO directly as I do not subscribe to magazines.

If you want to listen to the radio show that started me questioning things:
May 28, 2009 - BBR-BYO Experiment Results
James Spencer, Steve Wilkes, and Chris Colby, editor of Brew Your Own magazine, taste James' experiment beer and read the results from brewers around the world.
iTunes link
Streaming MP3 link

After this show I read even my books with a critical eye now. I had particular discord with Designing Great Beers, Ray Daniels book. Look at the yeast chapter. And others I noticed a pattern in this book. One source says A, but another source says B... lets call A the homebrewer <fill in the blank> and lets call B the professional <fill in the blank>. Missing is "This is what I've done and found out." instead B agrees with many sources. Reference number. Reference lookup. A single book from 1948.

Daniels on yeast pitching rates. Homebrewers are severely underpitching. Then he goes on to say this makes perfectly fine beer. Then he goes on that this is bad and you should be pitching high rates. Again without first hand experience or logical reasoning as to why.

This is not a beginner book. I see this style of loose reasoning all over the brewing literature. There is a lot of skip over to what you should agree is the right way.

Skip to AHB posts and Mr. Malty calculator and high pitching rates are thrown about in posts as the way to do it.

I know from the references I looked up in the back of Daniel's book that underpitching rates as low as a gram dry yeast per 20 litres will produce acceptable results if you are to believe Daniel's referenced sources. Email correspondence with an individual, email contents not disclosed, take his word for it! But also take his word that this is wrong and you really need to pitch high rates as one can find on Mr. Malty. -- confused yet?

Thats not the point, the whole point and original intent again for those who have already lost the plot: "Get people to judge advice with a critical eye and not take it at face value, no matter who it comes from." Try the advice, try the counter. Judge the results for yourself. Learn. Move on.


Now onto the actual thread.

This is where I found out about it:

July 30, 2009 - Yeast Biology and History
Chris Colby, editor of Brew Your Own magazine, sheds some light on the scientific workings and background of our favorite fungus. We also talk about the next phase of the collaborative experiments.
iTunes link
Streaming mp3 link

If you want a proper test you need a double blind test. The taste tester should not receive colour coded or marked bottles that in any way can identify which beer pitch rate it is nor the brewer (the later will be difficult if a package arrives in the mail). A BJCP judge would be preferred if you can organise one. I have a club full of BJCPs if not.

The BJCP receives the beer. Any affixed label should be random alpha-numeric codes, one half identifies the brewer, the other half identifies the brewers personal choice of what to assign to each of the three pitch rate beer samples. This way it no order rhyme or reason can be determined by the BJCP, he is working blind with only taste to guide him.

019A = Bob

019A0FD = A label Bob can assign to any of the beers he wants
0191A93 = A label Bob can assign to any of the beers he wants
019AE17 = A label Bob can assign to any of the beers he wants

The brewer sends the BJCP the beer and then sends a separate person a list of which label number belongs to which pitch rate.

The BJCP posts the taste results along with each label number. The separate person posts the list of what number each brewer assigned to each pitch rate. The reader can match the two together knowing their is no influence on the BJCPs subjective taste results.


Cheers,
Brewer Pete


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## haysie (20/8/09)

PP perhaps.

Really, what a load of waffle. Its a forum not a "YOUR BLOG"


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## Darren (20/8/09)

Would the effect of leaving the beer on the yeast for longer in the low-pitched beer, than the high-pitched beer, create a perceptional change in the resultant beer?

cheers

Darren


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## Online Brewing Supplies (20/8/09)

Darren said:


> Would the effect of leaving the beer on the yeast for longer in the low-pitched beer, than the high-pitched beer, create a perceptional change in the resultant beer?
> 
> cheers
> 
> Darren


Now that adds some complexity to the equation.Still pH readings will answer that. Do you have a answer ?
GB


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## Darren (20/8/09)

Without the same pH meter being used for each beer, I would suggest using a nominal time post-predicted final gravity (two weeks say),

Still not sure how pH meter would help though. Blinded, triangle taste testing would probably be the only confirmatory test IMHO.

cheers

Darren


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## kirem (20/8/09)

what about the gravitional effect from moon cycles on a low/high pitched beer?


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## buttersd70 (20/8/09)

FFS, when I start to see the logic in the question that Darren is puts forth....then something is wrong.....

And as for BJCP judging of the result....

pfffft.  

If you want _reliable _sources....discard the homebrewers, discard the homebrewers that have _become _writers, discard the "imho brigade", and go with the professionals....have a read of the chapters 11 through 15 (yes, 5 whole chapters) dedicated to 'yeast biology', 'metabolism of wort by yeast', 'yeast growth', 'fermentation technologies', and 'beer maturation and treatments' in "Brewing Science and Practice", by Dennis E. Briggs, Chris A. Boulton, Peter A. Brookes and Roger Stevens.

Authors credentials: 
Dennis Briggs was formerly Senior Lecturer in the British School of Malting and Brewing in the University of Birmingham. With Jim (J.S.) Hough and Roger Stevens, he wrote Malting and brewing science (1971; and a second edition with Tom (T.W.) Young in 1980/1981). Other publications include Barley (1978) and Malts and malting (1998). 

Chris Boulton is currently at the Coors Brewers Technical Centre at Burton-on-Trent. He is the co-author, with David Quain, of Brewing yeast and fermentation (2001). 

Peter Brooke spent over 30 years with Allied Breweries and Carlsberg Tetley, including 6 years as Director of Tetley's Leeds Brewery. He was also President of the Institute of Brewing from 1997 to 1999. 

Roger Steven was formerly Senior Lecturer in Pharmaceutical Chemistry at Sunderland Polytechnic. As well as being a co-author of Malting and brewing science, he has edited the Institute of Brewing's monograph on Hops and the Flavour and fragrance journal. 

I will leave any arguments in the capable hands of the aforementioned gentlemen......


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## Online Brewing Supplies (20/8/09)

So I will ask the question, why does pH drop during fermentation ?If you can answer this you are half way there.I am not trying to be smart but it's where you need to start.
GB


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## Darren (20/8/09)

GB,

High pitched wort will ferment fast and probably ferment to a lower gravity in a very short time.

Low pitched wort will be subject to wild-yeast and acetobacter species contamination at a greater proprtion when compared to brewing yeast (yes it depends on how-low).

CO2 in wort will decrease pH. Lactic acid by-products of stressed yeast and acetobacter contamination will both cause a drop in pH.

Flavour will be different.


cheers

Darren


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## pdilley (20/8/09)

You're going to make his eyeballs glaze over Gryph if you get him into having to learn about proton excretion of H+ ions, FAN consumption and organic acid release during yeast growth cycles. Darren wouldn't have the ability to go buy a book and read up on it in short enough time to post.

Darren, FAN is your acid buffer, its also stimulates your yeast growth. Low FAN, low growth, high FAN high growth. But with higher growth you still have enough FAN to buffer your acid output of the yeast growth cycle. Lets add in that the yeast are releasing organic acids into the wort during this cycle. The acidification of your fermenting wort will help the process of any acetolactate in suspension convert to diacetyl and acidification can sometimes result in lower dimethyl sulfide production. 

Another question to ask, is will you be having the influence capability or desire to control the levels during fermentation in your home made beer and get the needed equipment or do you want to go on if you do wish to use your own taste preference as the test.


Cheers,
Brewer Pete


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## Online Brewing Supplies (20/8/09)

What happens during fermentation is yeast unloads organic acids which reduces pH.The problem is that , if the wort pH drops to rapidly ,the yeast , which has a genetic structure that relies on pH indicators (nitrogen) floc's out early. The result is the off flavour characteristic's (aldehyde's etc) and under attenuations.So starting with the correct mash pH is so important.This is just a small part of brewing science. So every time I stress watching pH levels it's for a reason.To understand pH is to get a better beer.
GB


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## Darren (20/8/09)

Yes Pete,

Free amino nitrogen? My eyes are not glazing over.

Buffering ability of any aqueos solution will be controlled by the amount of dissolved CO2. This will actually control the pH.

Acetobacter contamination (low pitch rates and time) will drive the pH to autolysis of brewers YEAST resulting in stalled fermentation and acid.

cheers

darren

EDIT: I am a microbiologist with a PhD

EDIT again: Was that quick enough for you?

And Again: Brewer Pete does Wiki CO2 buffering and acetobacter contamination


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## Count Vorlauf (20/8/09)

kirem said:


> what about the gravitional effect from moon cycles on a low/high pitched beer?



I'm more concerned with sunspot activity, quite frankly.


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## Darren (20/8/09)

I have an ancecdotal story to tell about pH in beer.

At a brewclub meeting several (perhaps 11) people tried one of the brewers beers.

It was extremely good and flavoursome. 

I did agree that it tasted very good but to me there was something about it that reminded me of something.

I took another sip of the beer and thought....... ........................................then it came to me.

It reminded me of the time (in my first week in a biochemistry department) I accidently sucked up 0.1% HCl through a pipette. My mouth teeth and tongue fizzzzzzzzed.

I then asked the brewer whether they added acid to their beer, to which they replied YES (probably unaware that reduction of pH is a log10 scale which basically means you need to add 10x as much acid to reduce the pH by 1 pH point).

He commented that I had a very good mouth (I hope it wasn't for the wrong reasons 8)).

cheers

Darren


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## pdilley (20/8/09)

Oh in that case get involved 

free amino nitrogen (FAN), yes

Fermentation performance has shown negative affectation in worts containing 14.4 mg/100 ml FAN or less. Assimilable nitrogen was found to be the critical nutrient since amino acid supplementation reversed the effects of fermentation performance while supplementation with minerals and lipids has only minor effects. Wort FAN concentration also affect diacetyl production as already mentioned above which declines as wort FAN concentrations decreased down to 14.4 mg/100 ml; below this concentration, diacetyl production increases coincidentaly with valine depletion.

I'm not a microbiologist. Worked with higher order fungi in mycology and now that im brewing read up on the lower order which I previously ignored as it wasn't part of my work.


Cheers,
Brewer Pete


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## Online Brewing Supplies (20/8/09)

Gryphon Brewing said:


> What happens during fermentation is yeast unloads organic acids which reduces pH.The problem is that , if the wort pH drops to rapidly ,the yeast , which has a genetic structure that relies on pH indicators (nitrogen) floc's out early. The result is the off flavour characteristic's (aldehyde's etc) and under attenuations.So starting with the correct mash pH is so important.This is just a small part of brewing science. So every time I stress watching pH levels it's for a reason.To understand pH is to get a better beer.
> GB


I think the idea is to keep it as simple a possible.I dont have degrees' in micro and such but even the explanation I gave is possibly more than the average brewer can comprehend.I just hope that brewers pick up on what importance pH plays in the production of beer. Darren I agree that on a micro scale, pH is a good indicator of possible infections.BP your coverage is very good if not a little too complex ,with out me going back to my book's.  
GB


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## Darren (20/8/09)

Pete,

You are missing the issue of contamination of acid producing bacteria that will be present at low-yeast pitch levels not normally "observed" following HB preparation and consumption durations. Contaminating Acetobacter sp. dont give a damn about "brewing yeast " kinetics. They actually use pH drop kinetics to their advantage.


My bet is that the low-pitched batches will be more acidic and funky than those pitched at normal or above normal rates. Above normal will exhibit phenolic flavours (and probably be clearer) whilst those pitched at normal rates will be "yeasty" but better.

cheers

Darren


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## Online Brewing Supplies (20/8/09)

I think we need to start our own wanky yeast/fermentation thread.Those compounds can be produced by oxidisation/wort composition/infection etc .
Alcohols to aldyhydes
Amino's to fusel alco's
the list goes on!
What do you rekon?
GB


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## DJR (20/8/09)

Gryphon Brewing said:


> I think we need to start our own wanky yeast/fermentation thread.Those compounds can be produced by oxidisation/wort composition/infection etc .
> Alcohols to aldyhydes
> Amino's to fusel alco's
> the list goes on!
> ...



Why ask, just do! I found a bit about ADH enzymes the other day you can chuck in again for good measure


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## Online Brewing Supplies (20/8/09)

DJR said:


> Why ask, just do! I found a bit about ADH enzymes the other day you can chuck in again for good measure


I cant start the thread as I dont know what to call it ? Suggestions: the wanky yeast thread.Opening line ; Fu.k I need a whole forum for this !
GB


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## acoulson (21/8/09)

Gryphon Brewing said:


> So I will ask the question, why does pH drop during fermentation ?If you can answer this you are half way there.I am not trying to be smart but it's where you need to start.
> GB


  Man..... sometimes you just get a reality check and it blows you away....I've been studying brewing for more than 10 years now and you know what....never even thought about it...know the answer but never stopped to make the connection and think..... WHY. 

Sometimes we really need to ask the obvious questions.

Thank you GB


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## Pete2501 (21/8/09)

Darren said:


> Pete,
> 
> You are missing the issue of contamination of acid producing bacteria that will be present at low-yeast pitch levels not normally "observed" following HB preparation and consumption durations. Contaminating Acetobacter sp. dont give a damn about "brewing yeast " kinetics. They actually use pH drop kinetics to their advantage.
> 
> ...



I read that as _higher pitching rates help flavour_ but after reading the other posts above believe higher pitching rates can cause the yeast to konk out if the PH lvls shit themselves. 

I'm onto my 4th kit brew so I'm really just expressing my interest in the discussion going on.


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