Can you over ferment?

How long is too long to leave beer in carboy, before transferring to Corny kegs?

Is there such a thing as too long and affecting the beers flavor?

Not as long as you dont leave in there for like 6 months with a regular beer. Ive fermented some beers for as long as 2 months in the primary, they turned out just fine, probably even better than if I had let them only ferment for 2 weeks like I usually do.

you're fine.

I just asked this same question 2 days ago, my bock extract beer has been sitting in primary over 2 months and it's doing fine.

I left a beer in primary for almost ten years. We moved and the bucket ended up under a pile of stuff. When I finally discovered it, the wort smelled fine. I dumped it because I didn't know better. If I had it today, I would add some yeast and bottle. Beer is incredibly resilient. Just keep on, keeping on and you will be pleasantly surprised.

Unless it's been on the yeast for over 6 months, I wouldn't worry at all. If it's been on the yeast for over 6 months, then I would just taste it and see where it's at... If the temps were stable, and within the range for the yeast, or cooler, than you would be (95% chance) fine with the long storage time.

I've gone 6 weeks on the yeast so far, for my longest primary. I'm planning a barley wine that will be 4-8 weeks (or longer) on the yeast before aging for another 4+ weeks on oak... I'm also thinking of brewing my old ale again, with similar time lines. Basically, I'll start tasting the brew after about 4-6 weeks to see where it's at. If it needs more time, then I'll let it ride longer. If not, then I'll start it aging on oak.

I just bottled up my honey cream ale last night. It went 5 weeks on the yeast... Very clean flavors in the hydrometer sample I tasted... Looking forward to trying it once carbonated.

Brewham, what was the batch that you dumped (due to not knowing any better)? It does go to show how a batch can go for even longer than we might think without ill effects... I suspect that you didn't have an airlock in that primary, right?

Well the current thought is that longer is better. How long? 3 weeks? 1 month? 6 months? The truth is, we don't know. If someone is saying 'don't leave it in there for x number of months', they are guessing. People are successfully pushing that envelope all the time.

What we do know is that the quality of ingredients and more importantly, the quality of yeast is MUCH better. Many are foregoing the secondary and leaving the beer in the primary on the yeast with great results.

With people willing to leave it longer on the yeast, we are getting an idea of how long we can go, but I haven't heard any recent stories about how long is too long.

I'm starting to think (as many are I'm sure) that there's almost no real limit to how long you can leave something on the yeast, at least at our scale. In the huge primaries that big breweries use, sure. But we're not talking about that much wort sitting on top of the yeast cake here. The pressure on our yeast is such a tiny fraction compared with that, it's almost funny. Maybe if you had a full barrel sized conical, and you had it full with wort, and you left it like that for months on end, you might have an issue. Then again, you might just have the best batch you ever made (to date)...

IF you have any doubt, a simple taste test will reveal all. If it tastes just nasty, after an extended period on the cake, then it probably went too long... Although, you could just cover it back up and see how it is in X more weeks/months. :rockin:

It really depends on the beer. I leave anything higher than 7.5 percent abv alone for at least 5 months before even thinking of transferring, but most beers lower than that I will get bottled within 2 or 3 months.

I've gone almost 5 months in primary and the beer was fantastic.

Brewham said:

I left a beer in primary for almost ten years.

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Holy S*** 10 years? There must be some award for that!

God once left a beer on the yeast for eternity, and it was good.

TTB-J said:

God once left a beer on the yeast for eternity, and it was good.

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Revvy did THAT?!?

How long is eternity ?

How long is eternity ?

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According to the guys at my LHBS, a week. Ugh.

A lot of folks here will tell you that it's better to leave fermenting in primary for prolonged periods of time without a secondary.

It's the possible myth that yeasts clean up after themselves and improve the quality of the beer with prolonged primaries.

I call it a possible myth because, despite of the massive support, including from book authors, so it seems, I have yet to find a single scientific study that proves the theory.

I think it's just anecdotal observations. From a microbiology point of view, it does not make any sense to me, but I am currently making a short experiment to try to confirm or deny this possible myth.

ChshreCat said:

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Perhaps instead of facepalming, you could show us some article published by the brew scientists where they compare the beer quality from beer fermented for long vs. short periods of time on primaries, if your post was in response to my previous one, that is.

That would be far wiser. Just a thought.

It's the possible myth that yeasts clean up after themselves and improve the quality of the beer with prolonged primaries.

I call it a possible myth because, despite of the massive support, including from book authors, so it seems, I have yet to find a single scientific study that proves the theory.

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http://www.landesbioscience.com/journals/cc/MadeoCC8-4.pdf

TTB-J said:

http://www.landesbioscience.com/journals/cc/MadeoCC8-4.pdf

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That would be far wiser

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And it looks like that won't happen...

Indyking said:

A lot of folks here will tell you that it's better to leave fermenting in primary for prolonged periods of time without a secondary.

It's the possible myth that yeasts clean up after themselves and improve the quality of the beer with prolonged primaries.

I call it a possible myth because, despite of the massive support, including from book authors, so it seems, I have yet to find a single scientific study that proves the theory.

I think it's just anecdotal observations. From a microbiology point of view, it does not make any sense to me, but I am currently making a short experiment to try to confirm or deny this possible myth.

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So what's a diacetyl rest doing? I'm pretty sure that would be the yeast cleaning up after itself...

IffyG said:

So what's a diacetyl rest doing? I'm pretty sure that would be the yeast cleaning up after itself...

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A diacetyl rest is done when fermentation is not completed, hence the increased temperatures to activate the an otherwise almost dormant yeast but there must be sugar available to ferment!

After 1 week of fermentation, most Ales will have little or zero subtract (sugar) for the yeast to use as energy source to work! So, they supposedly clean up after themselves, but what source of energy they use to do so in a fully fermented solution? I never bought that idea; I think it’s possibly wrong. It’s just one of those things that get perpetuated and become perceived facts.

IMHO, Ales benefit from prolonged fermentations because it allows the sediment to settle down better improving the appearance and possibly the flavor by reducing the amount of yeast carried over to the keg/bottle. Modern yeasts don’t autolyse like they used to do in the past, so the prolonged fermentations won't hurt. I do it myself!

Thanks guys!

Now I know I don't have to force it in to my wknd schedule if I don't have time to transfer it.

Indyking said:

A diacetyl rest is done when fermentation is not completed, hence the increased temperatures to activate the an otherwise almost dormant yeast but there must be sugar available to ferment!

After 1 week of fermentation, most Ales will have little or zero subtract (sugar) for the yeast to use as energy source to work! So, they supposedly clean up after themselves, but what source of energy they use to do so in a fully fermented solution? I never bought that idea; I think it’s possibly wrong. It’s just one of those things that get perpetuated and become perceived facts.

IMHO, Ales benefit from prolonged fermentations because it allows the sediment to settle down better improving the appearance and possibly the flavor by reducing the amount of yeast carried over to the keg/bottle. Modern yeasts don’t autolyse like they used to do in the past, so the prolonged fermentations won't hurt. I do it myself!

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Yeast cells use enzymes to catabolize other forms of energy in the absence of simple sugars. They actually use enzymes to convert other simple sugars to glucose as well (take a look at the metabolic pathways for energy uses in any textbook). But in the absence of simple sugars, they catabolize alcohols (as in fusel alcohols) and starches. I don't know this last part for sure but I'd imagine they also catabolize esters in a similar situation.

No, I don't have a scientific paper to defend this. And if you like the taste of your beers after putting them into the bottle the second primary fermentation is complete, then go for it. But just because you don't buy it doesn't mean it isn't true.

ayoungrad said:

Yeast cells use enzymes to catabolize other forms of energy in the absence of simple sugars. They actually use enzymes to convert other simple sugars to glucose as well (take a look at the metabolic pathways for energy uses in any textbook). But in the absence of simple sugars, they catabolize alcohols (as in fusel alcohols) and starches. I don't know this last part for sure but I'd imagine they also catabolize esters in a similar situation.

No, I don't have a scientific paper to defend this. And if you like the taste of your beers after putting them into the bottle the second primary fermentation is complete, then go for it. But just because you don't buy it doesn't mean it isn't true.

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There is a lot more scientific information about yeast metabolism in the food industry than in the brewing industry. This website has some interesting info.

Yeasts needs sugar, vitamins and minerals as source of energy. I don't think they can use enzymes, even if they do, that would be likely less than 1% of their major energy source.

When brewing yeasts reach their attenuation capacity, they stop any significant metabolism, unless you add more sugar to the solution. The idea that yeasts keep working after their major source for energy, sugar, is depleted, does not make any sense.

I'm not arguing the fact that prolonged primary fermentations has some benefits as I believe it does like I pointed out in my previous post, but ain't because the yeasts are cleaning up your beer, so I highly suspect.

Your link isn't really very helpful - its a layman's explanation and therefore an oversimplification.

I will admit that me saying "startch" is definitely an overstatement. It is more accurate that yeast do catabolize slightly more complex sugars in the absence of glucose. Some, but not all - at least according to Briggs.

ayoungrad said:

Your link isn't really very helpful - its a layman's explanation and therefore an oversimplification.

I will admit that me saying "startch" is definitely an overstatement. It is more accurate that yeast do catabolize slightly more complex sugars in the absence of glucose. Some, but not all - at least according to Briggs.

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How about this one? Note that table 3-1 refers to the very yeast species that we use for Ales. Enzymes are not substrates for yeasts. Sugars are. Enzymes are necessary for metabolism but without sugars, they mean nothing. The other non-sugar sources they have in the substrate columns refer not as source of energy per se but source of nitrogen. They do mention that yeast can use non-conventional carbon sources different from sugar, but that is not utilized to generate energy, just for metabolism during sugar consumption.

Even wikipedia, which is likely less scientific, talks about the same thing.

It seems a no-brainer. If you want that yeast to work and “clean-up” after fermentation is complete, you've got to add more sugar, otherwise, the yeast will just sediment and rest.

Indyking said:

Yeasts needs sugar, vitamins and minerals as source of energy. I don't think they can use enzymes, even if they do, that would be likely less than 1% of their major energy source.

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Yeast is chock full of enzymes and they are used in most cellular functions.

Here's an article from '93 Brewing Techniques by George Fix. It is specific to diacetyls, but you can get the idea.

If you look at the references, you will see why it's difficult to find specific studies on this. A lot of the ground work for what is being discussed was laid more than fifty years ago.

If you are interested in understanding more, get Fix's Principles of Brewing Science, good stuff in there.

Indyking said:

A diacetyl rest is done when fermentation is not completed, hence the increased temperatures to activate the an otherwise almost dormant yeast but there must be sugar available to ferment!

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Actually, you're not quite correct. A diacetyl rest IS commonly done near the end of active fermentation, but that's not because the yeast won't digest diacetyl later. They actually don't digest the diacetyl until fermentable sugars (preferred food) are gone. Sort of like a big buffet. The deviled eggs (diacetyl) may not be scarfed up until the prime rib (fermentable sugars) are gone.

Yeast can digest diacetyl after the FG is stable, and will. It's just that to encourage them, we raise the temperature a bit and do that at the end of fermentation. You don't have to. The key is to give the beer 1-3 days after active fermentation is finished to clean up the diacetyl, sometimes longer in cool temperatures. Racking before that may mean that any remaining diacetyl may not be digested.

beerkrump said:

Here's an article from '93 Brewing Techniques by George Fix. It is specific to diacetyls, but you can get the idea.

If you look at the references, you will see why it's difficult to find specific studies on this. A lot of the ground work for what is being discussed was laid more than fifty years ago.

If you are interested in understanding more, get Fix's Principles of Brewing Science, good stuff in there.

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Yes, consumption of diacetyl is a perfect example of yeast cleaning its own byproducts during fermentation, I'm not arguing that! For the D-rest to occur properly though, there must still be substrate (sugar) for the yeast to use as source of energy. That's why John Palmer recommends the D-rest in the last stage of fermentation but NOT after fermentation is complete!

Guys don't fight me on this. When your ale stops fermenting, the yeast goes dormant due to the lack of substrate! There is no cleaning up by the yeast! The cleaning up is simply dormant yeast slowly settling down in the bottom of the fermentation vessel. Since modern genetically modified yeasts don’t go into autolysis in the absence of substrate, you can allow the fully fermented beer to rest for prolonged periods of time resulting in a better sediment formation.

Trust me.

Indyking said:

Trust me.

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Over all those authors and their "anecdotal" work? Nah.

It's obvious that you have it stuck in your head that yeast requires sugar to do anything. Just be aware that there are processes that move compounds in and out of the yeast cell with little or no loss of energy. Some of these are slow to finish.

Much of this "clean up" is done in a transitional period between the fermentation phase and the stationary phase. None of this is like a light switch, one second yeast is munching sugars and the next, boom, dormancy.

Also, from the article I referenced...

Table I
Diacetyl formation in three yeast strains.
Day_________Diacetyl Level (mg/L)
_____W-206____W-34/70____W-308
1_____.18_______.15________.18
3_____.25_______.20________ .48
5_____.23 _______.18________ .92
7_____.18 _______.14 ________.75
9_____.14 _______.09 ________.65

As we can see, the diacetyl level is dropping from day 7 to day 9. This is occurring after active fermentation has stopped.

You asked for documentation from a brewing scientist. I found you some, but you refuse to accept it.

Just because you don't understand it, that doesn't make it not true.

So the taste of green beer is simply because of yeast still in suspension????

Seems kinda hard to believe, as green beer doesn't taste very yeasty

Indyking, the problem I had with your original post is that you said:

It's the possible myth that yeasts clean up after themselves and improve the quality of the beer with prolonged primaries.

I think you either stated yourself incorrectly or misunderstand what people have previously said.

A good number of people on here suggest not transferring to secondary and instead just leaving the beer in the primary fermenter. No one has suggested that a "prolonged primary" exists. I don't even know what a prolonged primary is. Some people have simply suggested to leave the beer in the primary fermentation chamber for longer and forgo transferring it into a secondary fermenter.

The same clean-up will occur in either chamber. Yeast will help metabolize diacetyls, sulfur compounds and volatile fatty acids. They need sugar but there is always some small amount left even after primary fermentation is "complete". This happens if the beer is left in the primary fermentation chamber or if it goes into a secondary fementation chamber. Most of the yeast go dormant when concentrations fall to very low levels but not 100% of them. Some people just feel that the risks of oxidation (or infection) involved in transferring to a secondary fermentation vessel are greater than any theoretical gain in clarity.

Again, I don't know if the issue here has been a misunderstanding or misinterpretation but there is no such thing as "prolonged primary fermentation" and I have not seen such a concept suggested on this site.

Sorry but one other thought here.

Using bold letters for something that clearly flies in the face of popular opinion (be it correct or incorrect opinion) is always going to result in people responding from all directions.

And saying "don't fight me on this" or "trust me" is only more of the same.

I don't know Indyking's background. But I do know that even if it involves a PhD in biochemistry, it is certainly not the only PhD in biochemistry in the world and likely not the only one on this site either. There are scientists, engineers and doctors all over this site.

If you bring up an new thought or idea, why not phrase it as such and have a discussion. Even you admit to feeling a "fight" response from the board on this thread. And it is because how your thought was stated.

Is it everyone else with the issue or is it you?

ayoungrad said:

Sorry but one other thought here.

Using bold letters for something that clearly flies in the face of popular opinion (be it correct or incorrect opinion) is always going to result in people responding from all directions.

And saying "don't fight me on this" or "trust me" is only more of the same.

I don't know Indyking's background. But I do know that even if it involves a PhD in biochemistry, it is certainly not the only PhD in biochemistry in the world and likely not the only one on this site either. There are scientists, engineers and doctors all over this site.

If you bring up an new thought or idea, why not phrase it as such and have a discussion. Even you admit to feeling a "fight" response from the board on this thread. And it is because how your thought was stated.

Is it everyone else with the issue or is it you?

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:rockin:

Every once in a while I see minor pieces of information here that I think it may be wrong, but I don't bother to argue because I'm either not sure or it's just not worth it. But the yeast-cleaning-up-after-fermentation-is-complete thing has gone too far unquestioned I think.

I have strong reasons to believe brewing yeast cells stop any significant metabolism after their main source of energy, sugar, is depleted. I have showed evidence, some less but other purely scientific to prove my point. I'm not a microbiologist but I do have a cell biology background and my PhD was done in a microbiology lab sharing knowledge with a majority of microbiologists, though all of them were bacteriologists.

The idea supported by many here is to not use a secondary fermentation and ferment your beer beyond that period where final SG has been reached, so the yeast can clean-up after themselves and result in a better final product. That just doesn't happen IMHO. I never actually secondary any Ale as a matter of fact and I also keep my primary way beyond after fermentation is complete because I simply believe that stretching that time allow solids, including inactive yeast, to sediment better maximizing the appearance and possibly flavor of the beer. It has nothing to do with yeasts cleaning-up anything. They can't do it without energy and after fermentation is complete, their source of energy is gone and they become dormant.

In the case of D-rest, like I said before, John Palmer himself in the latest edition of his book How to Brew states that it is important to do it in the right time before lagering, which is before fermentation is totally complete, so the yeast will have substrate available to clean up the diacetyl. A lot of people will tell that they actually do a successful D-rest after fermentation is finished. I believe that is wrong too.
Fermentation in lagers is very slow. It may have long passed the peak of fermentation where airlock activity is typically noticed, but there is still some residual fermentable sugars available for the D-rest, only it's very scarce, hence the need to increase the temperature to activate the almost dormant yeast.

Look. I'm sorry for the bold letters, OK, sometimes I just can't help it. You can believe whatever you want too. I'm not asking you to believe in what I'm saying about this, but perhaps you all will think about it whenever that perception comes across again.

Finally, I brewed an English Brown Ale about 3 weeks ago, which I have bottled half of the 5 gal batch right after fermentation was completed and will bottle the other half after resting the remaining in the primary vessel for a month. After all have been carbed, I will taste them in a blind fashion to see if I can tell them apart. Because I don't likely have the most accurate palate in the world, barely that, I'm looking for BJCP-certified folk here who is willing to degust them as well in the same fashion. I highly suspect there will be a noticeable difference between them, not because of the famous, or infamous, yeast clean-up paradigm, but for the reasons aforementioned in this post.

Cheers!

Indyking said:

Finally, I brewed an English Brown Ale about 3 weeks ago, which I have bottled half of the 5 gal batch right after fermentation was completed and will bottle the other half after resting the remaining in the primary vessel for a month. After all have been carbed, I will taste them in a blind fashion to see if I can tell them apart. Because I don't likely have the most accurate palate in the world, barely that, I'm looking for BJCP-certified folk here who is willing to degust them as well in the same fashion. I highly suspect there will be a noticeable difference between them, not because of the famous, or infamous, yeast clean-up paradigm, but for the reasons aforementioned in this post.

Cheers!

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This is not an experiment which in any way proves your theory, so I'm not sure why its relevant. All you prove is that there is a difference between a shorter primary and a longer primary, NOTHING about WHY that happens.

discnjh said:

This is not an experiment which in any way proves your theory, so I'm not sure why its relevant. All you prove is that there is a difference between a shorter primary and a longer primary, NOTHING about WHY that happens.

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I never said I'm doing this experiment to prove my theory. My theory is out there for whoever is interested in a second opinion. My experiment is to prove my other hypothesis that beer benefit from long resting after fermentation is complete for other reasons that has nothing to do with yeast cells cleaning up, as already mentioned.

My beer tastes much better if it sits in the primary longer, even if I do a secondary, longer in the primary is better.

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