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General Category => Yeast and Fermentation => Topic started by: denny on April 06, 2016, 07:21:19 PM

Title: Confessions of a Yeast Abuser
Post by: denny on April 06, 2016, 07:21:19 PM
http://www.experimentalbrew.com/blogs/denny/confessions-yeast-abuser
Title: Re: Confessions of a Yeast Abuser
Post by: HoosierBrew on April 06, 2016, 07:29:25 PM
That's very cool, Denny. Good to know I'm not the only one who's gone down that road. I agree that it's important to know the rules thoroughly before you break them. Lots of experience helps you break the rules with a good chance of success. Glad it turned out nice.
Title: Re: Confessions of a Yeast Abuser
Post by: 69franx on April 06, 2016, 07:33:11 PM
+1
Title: Re: Confessions of a Yeast Abuser
Post by: Stevie on April 06, 2016, 07:35:20 PM
I hate making starters. I see them as another chore on level with cleaning kegs, fermenters, or bottles. I prefer to make my starters 5 gallons at a time and repitch. This requires some pre-planning, but at least I get a keg full of beer out of it.
Title: Re: Confessions of a Yeast Abuser
Post by: tommymorris on April 06, 2016, 07:36:05 PM
Glad to read that. I think I under pitched my current lager.  It too was 2.5 gallons. I did a 1.5L starter for 12 hours planning to pitch at high krausen. I tried to cold crash a few hours  and decant. It didn't work I poured out about half the liquid and I think a lot of yeast decanting. It took 48 hours to show a small krausen. I'm hoping for good beer.
Title: Re: Confessions of a Yeast Abuser
Post by: narvin on April 06, 2016, 07:38:03 PM
You need help  :)
Title: Re: Confessions of a Yeast Abuser
Post by: denny on April 06, 2016, 07:39:14 PM
You need help  :)

Indeed...on many levels!
Title: Re: Confessions of a Yeast Abuser
Post by: dls5492 on April 06, 2016, 08:13:56 PM
enjoyed it very much. Thanks for sharing. I have a confession, I have abused yeast also. I am glad I am not alone any more.  ;)
Title: Re: Confessions of a Yeast Abuser
Post by: zwiller on April 06, 2016, 08:31:20 PM
+1 Nope; you're not alone and my beers do not suffer. 

Denny, I guess I was wrong to assume you would always have a constant supply of fresh yeast since it is named after you...  Don't you have some sort QC thing to do regularly to make sure it's up to snuff?  ;D
Title: Re: Confessions of a Yeast Abuser
Post by: denny on April 06, 2016, 09:11:01 PM
+1 Nope; you're not alone and my beers do not suffer. 

Denny, I guess I was wrong to assume you would always have a constant supply of fresh yeast since it is named after you...  Don't you have some sort QC thing to do regularly to make sure it's up to snuff?  ;D

Yeah, I brew beer!  I only get yeast once or twice a year...almost everything I use is out of date.  But since I almost always make a starter, it doesn't matter much.  This was kind of a "how far can I push it?" thing.
Title: Re: Confessions of a Yeast Abuser
Post by: Iliff Ave on April 06, 2016, 09:35:28 PM
I abust yeast regularly and love my results. It's the only thing that I pretty much ignore advice on for the types of beers I brew. Very surprised that my lager yeast abuse has created such fine beers IMHO...
Title: Re: Confessions of a Yeast Abuser
Post by: RPIScotty on April 06, 2016, 10:37:07 PM
+1 Nope; you're not alone and my beers do not suffer. 

Denny, I guess I was wrong to assume you would always have a constant supply of fresh yeast since it is named after you...  Don't you have some sort QC thing to do regularly to make sure it's up to snuff?  ;D

Yeah, I brew beer!  I only get yeast once or twice a year...almost everything I use is out of date.  But since I almost always make a starter, it doesn't matter much.  This was kind of a "how far can I push it?" thing.

Are you buying in bulk or repitching?
Title: Re: Confessions of a Yeast Abuser
Post by: klickitat jim on April 06, 2016, 11:29:35 PM
I abust yeast regularly and love my results. It's the only thing that I pretty much ignore advice on for the types of beers I brew. Very surprised that my lager yeast abuse has created such fine beers IMHO...
I fear I qualify as a yeast abuser do to abandoned stirplates, and pitching entire 1L starters, even to "It" beers.
Title: Re: Confessions of a Yeast Abuser
Post by: Hooper on April 07, 2016, 02:09:24 AM
I think dumping a 66F starter into 45F wort is yeast abuse...but like throwing our kids in that cold water...after the shock they will probably thrive anyway...
Title: Re: Confessions of a Yeast Abuser
Post by: Pricelessbrewing on April 07, 2016, 04:43:06 AM
+1 Nope; you're not alone and my beers do not suffer. 

Denny, I guess I was wrong to assume you would always have a constant supply of fresh yeast since it is named after you...  Don't you have some sort QC thing to do regularly to make sure it's up to snuff?  ;D

Yeah, I brew beer!  I only get yeast once or twice a year...almost everything I use is out of date.  But since I almost always make a starter, it doesn't matter much.  This was kind of a "how far can I push it?" thing.

The longest I've gone on old yeast successfully was about 10 months. I recently attempted a 27 month old vial I "found" in my fridge. It was propped up in a small starter @ 1.020 and pitched into a half gallon of cider. The cider had major THP. Definitely got some brett in there.
Title: Re: Confessions of a Yeast Abuser
Post by: brulosopher on April 07, 2016, 05:09:33 AM
I like when the yeast abuses me
Title: Re: Confessions of a Yeast Abuser
Post by: brewinhard on April 07, 2016, 01:19:55 PM
I like when the yeast abuses me

Atta boy!  Now your thinking you dirty old man.
Title: Re: Confessions of a Yeast Abuser
Post by: zwiller on April 07, 2016, 03:12:30 PM
It's probably the old punk rocker in me, but I really am put off by the anal mathematical website cell count calculator I need a microscope and a stir plate let me get my lab coat to brew beer approach to yeast starters and that is the primary reason I rebel against it. 
Title: Re: Confessions of a Yeast Abuser
Post by: denny on April 07, 2016, 03:19:34 PM
+1 Nope; you're not alone and my beers do not suffer. 

Denny, I guess I was wrong to assume you would always have a constant supply of fresh yeast since it is named after you...  Don't you have some sort QC thing to do regularly to make sure it's up to snuff?  ;D

Yeah, I brew beer!  I only get yeast once or twice a year...almost everything I use is out of date.  But since I almost always make a starter, it doesn't matter much.  This was kind of a "how far can I push it?" thing.

Are you buying in bulk or repitching?

I get shipments from Wyeast once or twice a year.  But I do a lot of repitching in between shipments.
Title: Re: Confessions of a Yeast Abuser
Post by: denny on April 07, 2016, 03:20:52 PM
+1 Nope; you're not alone and my beers do not suffer. 

Denny, I guess I was wrong to assume you would always have a constant supply of fresh yeast since it is named after you...  Don't you have some sort QC thing to do regularly to make sure it's up to snuff?  ;D

Yeah, I brew beer!  I only get yeast once or twice a year...almost everything I use is out of date.  But since I almost always make a starter, it doesn't matter much.  This was kind of a "how far can I push it?" thing.

The longest I've gone on old yeast successfully was about 10 months. I recently attempted a 27 month old vial I "found" in my fridge. It was propped up in a small starter @ 1.020 and pitched into a half gallon of cider. The cider had major THP. Definitely got some brett in there.

I've been able to resurrect a 3 1/2 year old pack of WY3522.  Why I did that, I don't know.
Title: Re: Confessions of a Yeast Abuser
Post by: denny on April 07, 2016, 03:21:20 PM
I like when the yeast abuses me

Atta boy!  Now your thinking you dirty old young man.
Title: Re: Confessions of a Yeast Abuser
Post by: blair.streit on April 07, 2016, 03:25:56 PM
I'm curious if you guys feel that you "compensate" in any way when you've abused your yeast? For example, if the yeast is old do you aerate more than you would otherwise or maybe throw in a little extra yeast nutrient?

I'm asking because I've struggled with vitality on repitching in a couple of previous batches (yeast pooped out early on the second batch). I've been attributing this to inadequate aeration in the first batch or possibly waiting too long to collect the yeast.

That said, pitching lager yeast in the mid 40's and fermenting at 50 may be too tough an environment to get away with yeast abuse. Thoughts?
Title: Re: Confessions of a Yeast Abuser
Post by: denny on April 07, 2016, 03:31:21 PM
I'm curious if you guys feel that you "compensate" in any way when you've abused your yeast? For example, if the yeast is old do you aerate more than you would otherwise or maybe throw in a little extra yeast nutrient?

I'm asking because I've struggled with vitality on repitching in a couple of previous batches (yeast pooped out early on the second batch). I've been attributing this to inadequate aeration in the first batch or possibly waiting too long to collect the yeast.

That said, pitching lager yeast in the mid 40's and fermenting at 50 may be too tough an environment to get away with yeast abuse. Thoughts?

Nope, no compensation here...at least not in any consistent way.  And I abuse lager yeast just as you mention.

Let me say right here that this obviously isn't the best way to do things, and I don't recommend yeast abuse as a regular practice.  You have to be prepared for the fact that you may lose a batch of beer.  But I've found I can get away with it more often than not.
Title: Re: Confessions of a Yeast Abuser
Post by: blair.streit on April 07, 2016, 04:08:44 PM
Yeah the "punishment" I took was finishing at 1.024 instead of 1.019. Not the worst thing in the world. I just blended it with another batch and left plenty of yeast in suspension to lager for a bit longer. Not tragic.... 
Title: Re: Confessions of a Yeast Abuser
Post by: zwiller on April 07, 2016, 04:27:28 PM
Back when I was fighting dry beers it was suggested to me that due to the longer growth phase, the yeast kick into overdrive and over-attenuate when underpitched...  I bought into it, did some starters, and no change.  I still think this hobby is way more forgiving than we make it seem.  Anyone ever have a mash that didn't convert?  Remember worrying about it?   ;D
Title: Re: Confessions of a Yeast Abuser
Post by: 69franx on April 08, 2016, 05:31:12 PM
Back when I was fighting dry beers it was suggested to me that due to the longer growth phase, the yeast kick into overdrive and over-attenuate when underpitched...  I bought into it, did some starters, and no change.  I still think this hobby is way more forgiving than we make it seem.  Anyone ever have a mash that didn't convert?  Remember worrying about it?   ;D

Nice  8)
Title: Re: Confessions of a Yeast Abuser
Post by: euge on April 11, 2016, 09:33:49 PM
I just repitched some lager-yeast but did it according to mrmalty. Pitching on a whole cake has not produced spectacular results for me.
Title: Re: Confessions of a Yeast Abuser
Post by: charles1968 on April 12, 2016, 12:23:43 PM
I don't buy the theory that pitching rate significantly affects flavour. The whole topic is full of pseudoscientific explanations, such as that underpitching causes stress (actually the opposite is true).

Anyway here's a 2008 paper suggesting that pitching rate makes very little difference to flavour, except for diacetyl level rising with high pitching rates (http://www.ncbi.nlm.nih.gov/pubmed/19018524).

Low pitching rate is completely fine in my experience. The only problem besides waiting a day or so longer is that there's higher risk of infection before the wort is colonized by yeast.

Abstract (my emphasis):
Quote
The volumetric productivity of the beer fermentation process can be increased by using a higher pitching rate (i.e. higher inoculum size). However, the impact of the pitching rate on crucial fermentation and beer quality parameters has never been assessed systematically. In this study, five pitching rates were applied to lab-scale fermentations to investigate its impact on the yeast physiology and beer quality. The fermentation rate increased significantly and the net yeast growth was lowered with increasing pitching rate, without affecting significantly the viability and the vitality of the yeast population. The build-up of unsaturated fatty acids in the initial phase of the fermentation was repressed when higher yeast concentrations were pitched. The expression levels of the genes HSP104 and HSP12 and the concentration of trehalose were higher with increased pitching rates, suggesting a moderate exposure to stress in case of higher cell concentrations. The influence of pitching rate on aroma compound production was rather limited, with the exception of total diacetyl levels, which strongly increased with the pitching rate. These results demonstrate that most aspects of the yeast physiology and flavour balance are not significantly or negatively affected when the pitching rate is changed. However, further research is needed to fully optimise the conditions for brewing beer with high cell density populations.


A more recent paper (http://onlinelibrary.wiley.com/doi/10.1002/jib.242/abstract)
Quote
With increasing numbers of cells introduced into the wort, the content of the esters and fusel alcohols increased, while the acetaldehyde concentration decreased. These changes affected the final quality of the beer.

Which contradicts the popular homebrewers' notion that underpitching makes yeast express esters more strongly because they're "stressed".

Obviously I've cherry picked these quotes to support my argument, but the best anyone can really say about pitching rate & perceptible flavour is that there's no clear scientific evidence of a relationship.
Title: Re: Confessions of a Yeast Abuser
Post by: zwiller on April 12, 2016, 02:52:59 PM
8)
Title: Re: Confessions of a Yeast Abuser
Post by: narvin on April 12, 2016, 04:01:50 PM
I don't buy the theory that pitching rate significantly affects flavour. The whole topic is full of pseudoscientific explanations, such as that underpitching causes stress (actually the opposite is true).

Anyway here's a 2008 paper suggesting that pitching rate makes very little difference to flavour, except for diacetyl level rising with high pitching rates (http://www.ncbi.nlm.nih.gov/pubmed/19018524).

Low pitching rate is completely fine in my experience. The only problem besides waiting a day or so longer is that there's higher risk of infection before the wort is colonized by yeast.

Abstract (my emphasis):
Quote
The volumetric productivity of the beer fermentation process can be increased by using a higher pitching rate (i.e. higher inoculum size). However, the impact of the pitching rate on crucial fermentation and beer quality parameters has never been assessed systematically. In this study, five pitching rates were applied to lab-scale fermentations to investigate its impact on the yeast physiology and beer quality. The fermentation rate increased significantly and the net yeast growth was lowered with increasing pitching rate, without affecting significantly the viability and the vitality of the yeast population. The build-up of unsaturated fatty acids in the initial phase of the fermentation was repressed when higher yeast concentrations were pitched. The expression levels of the genes HSP104 and HSP12 and the concentration of trehalose were higher with increased pitching rates, suggesting a moderate exposure to stress in case of higher cell concentrations. The influence of pitching rate on aroma compound production was rather limited, with the exception of total diacetyl levels, which strongly increased with the pitching rate. These results demonstrate that most aspects of the yeast physiology and flavour balance are not significantly or negatively affected when the pitching rate is changed. However, further research is needed to fully optimise the conditions for brewing beer with high cell density populations.


A more recent paper (http://onlinelibrary.wiley.com/doi/10.1002/jib.242/abstract)
Quote
With increasing numbers of cells introduced into the wort, the content of the esters and fusel alcohols increased, while the acetaldehyde concentration decreased. These changes affected the final quality of the beer.

Which contradicts the popular homebrewers' notion that underpitching makes yeast express esters more strongly because they're "stressed".

Obviously I've cherry picked these quotes to support my argument, but the best anyone can really say about pitching rate & perceptible flavour is that there's no clear scientific evidence of a relationship.

One thing to remember is that a lot of these experiments are done with lager yeasts, because that's where the industry money is.  There are also differences I've noticed even across ale yeasts, so what's applicable to a pale ale might not be to a Belgian Saison.
Title: Re: Confessions of a Yeast Abuser
Post by: narcout on April 12, 2016, 04:51:59 PM
Anyway here's a 2008 paper suggesting that pitching rate makes very little difference to flavour, except for diacetyl level rising with high pitching rates (http://www.ncbi.nlm.nih.gov/pubmed/19018524).

This one came to opposite conclusion regarding diacetyl, though it was studying high gravity fermentation with lager yeast. 

I think this stuff is interesting and fun to read, but I don't know if it is all that relevant to what I'm doing. 

"As expected, increasing the pitching rates led to faster fermentation rates and higher yeast cell counts. Formation of 2-methyl-1-propanol increased with increasing pitching rate, but the formation of 2- and 3-methyl-1-butanol decreased.  The pitching rate did not alter ester formation in these experiments, with the exception of isoamyl acetate, where the level declined with an increased pitching rate.  Lower pitching rates led to higher levels of diacetyl and 2,3-pentanedione. The effect of pitching rate on flavour compounds clearly merits further investigation."

http://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.2007.tb00259.x/pdf
Title: Re: Confessions of a Yeast Abuser
Post by: charles1968 on April 12, 2016, 06:39:34 PM
Anyway here's a 2008 paper suggesting that pitching rate makes very little difference to flavour, except for diacetyl level rising with high pitching rates (http://www.ncbi.nlm.nih.gov/pubmed/19018524).

This one came to opposite conclusion regarding diacetyl, though it was studying high gravity fermentation with lager yeast. 

I think this stuff is interesting and fun to read, but I don't know if it is all that relevant to what I'm doing. 

"As expected, increasing the pitching rates led to faster fermentation rates and higher yeast cell counts. Formation of 2-methyl-1-propanol increased with increasing pitching rate, but the formation of 2- and 3-methyl-1-butanol decreased.  The pitching rate did not alter ester formation in these experiments, with the exception of isoamyl acetate, where the level declined with an increased pitching rate.  Lower pitching rates led to higher levels of diacetyl and 2,3-pentanedione. The effect of pitching rate on flavour compounds clearly merits further investigation."

http://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.2007.tb00259.x/pdf

If you dig around for the few published scientific studies, you'll find conflicting results but next to no evidence for a consistent effect on flavour. I think the take-home message is that advice on pitching rate is likely to be another brewing myth waiting to be properly debunked.

You're right that it might be specific to particular strains. Until better evidence comes in, however, I'm going to continue disregarding all advice on pitch rates and pitching rate calculators. I've always thought estimated cell counts are wildly inaccurate anyway. And if you pitch a starter into the main wort, all the supposed flavour benefits of high pitch rate go out of the window anyway.
Title: Re: Confessions of a Yeast Abuser
Post by: narvin on April 12, 2016, 07:22:41 PM
The benefit I see from using some kind of calculator is consistency and repeatability.  You may not know how many cells you're truly pitching until you do a cell count, but your process is the same each time.  Of course, pitching a single smack pack is repeatable as well, but I find I get better results with a starter.  YMMV.
Title: Re: Confessions of a Yeast Abuser
Post by: charles1968 on April 12, 2016, 08:22:53 PM
There's certainly no harm in trying to be consistent. I do wonder if it matters as much as people claim though. Yeast multiply until they've consumed all the sugar and then drop out. It happens every time, however many you start with. I haven't seen any compelling evidence that the starting number affects flavour, but I accept that it's possible.
Title: Re: Confessions of a Yeast Abuser
Post by: klickitat jim on April 12, 2016, 08:31:26 PM
Since we're on the subject. Is cold crashing considered yeast abuse? Guilty!

Some time ago I caught a Brew Strong episode where Jamil said that he read a study while working on his yeast calculator that chilling rapidly causes yeast to express 30% more esters. He didn't reference the study. I vaguely remember us talking it up here on the forum with many folks agreeing and some disagreeing. I was in the disagree side but admit that it could be my lack of detection skills.

Just recently I heard him reference this study again on a Jamil Show episode. He still didn't reference the study, but he did provide some additional info about it. Someone asked him how fast is too fast and he said that the study claimed you can chill 2F per hour without getting any negative effect.

So, when I cold crash, there are two 6 gallon batches in my temp controlled chest freezer and I simply change the setting to 30F. It takes at least 24 hrs for the steadily running chest freezer to drop from 72F (ale final temp) to 30. 42 degrees in 24 hrs is less than 2F per minute. With lagers, 68F D rest to 30 is only 38F in 24 hrs. Apparently I'm not detecting extra esters because even when I let er buck I'm not chilling fast enough to get greater than 2F per hour.

Proof that sometimes a little info = worrying about nothing.
Title: Re: Confessions of a Yeast Abuser
Post by: denny on April 12, 2016, 08:32:58 PM
There's certainly no harm in trying to be consistent. I do wonder if it matters as much as people claim though. Yeast multiply until they've consumed all the sugar and then drop out. It happens every time, however many you start with. I haven't seen any compelling evidence that the starting number affects flavour, but I accept that it's possible.

Ya know, Charles, I was about to say I agreed with you until the bolded part.  I can't agree with that.  If it was true, you'd only need to pitch a single yeast cell.  I think consistency of results is a good thing and it's what I aim for.  But I've also found that you have a lot of leeway in the constituent parts that make up the result you want.
Title: Re: Confessions of a Yeast Abuser
Post by: charles1968 on April 12, 2016, 08:47:15 PM
Proof that sometimes a little info = worrying about nothing.

Yes I think I tend to overthink everything and I suspect other brewers do too, but maybe overthinking is part of the fun.
Title: Re: Confessions of a Yeast Abuser
Post by: RPIScotty on April 12, 2016, 08:49:23 PM
Proof that sometimes a little info = worrying about nothing.

Yes I think I tend to overthink everything and I suspect other brewers do too, but maybe overthinking is part of the fun.

I'm an engineer. I can't get anything done unless I've invested at least 4 hours into overthinking it.
Title: Re: Confessions of a Yeast Abuser
Post by: denny on April 12, 2016, 08:58:00 PM
Proof that sometimes a little info = worrying about nothing.

Yes I think I tend to overthink everything and I suspect other brewers do too, but maybe overthinking is part of the fun.

I used to overthink things, than with experience I found that there are so many things that just don't matter, or matter only in a general sense.  Pragmatism became my rule and it's served me well.  But this is a hobby and if you enjoy the overthinking part, be my guest.  Personally, I have other things to expend my brain on!
Title: Re: Confessions of a Yeast Abuser
Post by: charles1968 on April 12, 2016, 08:59:05 PM
Ya know, Charles, I was about to say I agreed with you until the bolded part.  I can't agree with that.  If it was true, you'd only need to pitch a single yeast cell.

That's where you start needing laboratory techniques - isolate a single cell on a plate and step up, keeping everything completely sterile. Possible but not a standard homebrewing technique and not very quick.

If you think of wort as a battleground in which all sorts of unseen microbes compete, then pitching a healthy population that gives yeast a headstart over bacteria or wild yeast makes perfect sense. A lag of a week or so is too long - you want yeast to poison the wort with alcohol and acid quickly so bacteria don't get a toehold. But as long as you pitch enough for that, I don't think adding more makes any difference.

I can't think of a time underpitching has given me any problems. Even with lager. Actually, pitching rate is probably least important with lager (unless you're a commercial brewery) as the low temp stops bacteria and nonlager yeast growing.
Title: Re: Confessions of a Yeast Abuser
Post by: charles1968 on April 12, 2016, 09:13:01 PM
I'm an engineer. I can't get anything done unless I've invested at least 4 hours into overthinking it.

It's a great trait in some walks of life. The same can be said for anxiety - a great characteristic for people who manage risk.

As long as you don't resort to spreadsheets when deciding what pair of jeans to buy...
Title: Re: Confessions of a Yeast Abuser
Post by: klickitat jim on April 12, 2016, 09:13:38 PM
I feel a challenge coming!

1 gallon batches- something that doesnt require much work or hops, like an extract blonde.
One gallon fermented with Mr Malty calculated slurry amount
One gallon autoclaved and aseptic transfer pitched with a single colony. (Unless you have a scope to grab a single cell, but I think a tiny single colony ought to prove the point)
Blind Triangle test

The trick would be to also autoclave your oxygenation wand...
Title: Re: Confessions of a Yeast Abuser
Post by: Joe Sr. on April 12, 2016, 11:33:45 PM

There's certainly no harm in trying to be consistent. I do wonder if it matters as much as people claim though. Yeast multiply until they've consumed all the sugar and then drop out. It happens every time, however many you start with. I haven't seen any compelling evidence that the starting number affects flavour, but I accept that it's possible.

Ya know, Charles, I was about to say I agreed with you until the bolded part.  I can't agree with that.  If it was true, you'd only need to pitch a single yeast cell.  I think consistency of results is a good thing and it's what I aim for.  But I've also found that you have a lot of leeway in the constituent parts that make up the result you want.

IME under pitching a high gravity beer will lead to under attenuation.

So I agree with Denny that the yeast don't necessarily consume all the sugar before they drop out.

But I also think you need proper aeration and consistent fermentation temp ( ie no temp swings).

More importantly I think thy you need to know how your yeast performs. I use the same four or five strains regularly and repitch until performance changes. Sometimes it's flocculation. Sometimes it's attenuation. No infections yet from this practice.


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Title: Re: Confessions of a Yeast Abuser
Post by: charles1968 on April 13, 2016, 07:07:00 AM


IME under pitching a high gravity beer will lead to under attenuation.

So I agree with Denny that the yeast don't necessarily consume all the sugar before they drop out.

But I also think you need proper aeration and consistent fermentation temp ( ie no temp swings).

If you ferment under an airlock, don't aerate, but also underpitch, a stuck ferment is very likely with British yeast strains. But the real problem in that case is ergosterol running out. Most British homebrewers use buckets with loose fitting lids, which reduces the need to aerate, but we still get stalls sometimes. I think the same issue explains the DuPont stall, rather than the much blamed back pressure.

Likewise some ale yeasts shut down after a sudden temp drop. That can happen whatever the pitch rate.