Autolysis.

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Orfy

For the love of beer!
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I think it would be beneficial to have a discussion on Autolysis and possibly write a Wiki Article and post a link in the stickies. It might save a lot of debate in multiple threads.
For those who don't know it is when the enzymes in a cell, this case yeast run out of nutrients and starts working on the cell it's self thus killing it.

I personally think it is a bit like Hot Side Aeration. Much feared but little evidence of anyone experiencing it. I don't think any one on here has posted that it as affected their beers regardless of time in contact with trub.
According to books and articles I've read on wine I've seen it sated that if the Wine is left in contact with the Lees (trub) then it can have an affect on the wine after around 18 months.
I would not disagree if someone left a beer in the primary for 12 months plus and said that they could taste something different. As for how long it tacks for the actual autolysis to start is not something I've looked into.
 
Several people on here have posted that autolysis has effected their beers including at least one moderator.

I'm not sure people understand what autolysis might taste like if it created flavor compounds in excess of threshold levels. For example, nobody seems to mention that bready and meaty flavors can be produced by autolysis despite the former being one of the primary flavors in Champagne and the latter being the primary flavor of marmite. How could you ever hope to know if autolysis is flavoring your beer if you are only looking for one of several flavors it can cause?

Like HSA, it may be hard to prove that autolysis causes off flavors in beer because those same off flavors can be attributed to another cause. This means the question is unanswered, not that autolysis does not cause off flavors.

I hope it is uncontroversial to say that autolysis does occur in beer. The only question is whether or not is produceds off flavors.

Homebrewers that do not sterile filter or pasteurize leave beer on contact with the lees until it is drunk (autolysis in Champagne occurs primarily in the bottle) although fining and racking for kegged beer can reduce the amount of yeast in the product to very small levels.
 
The more points of view the better.
It's good to get truth from first hand experience rather than myths from hearsay.
I've had no experience of it but I've never left anything on yeast for over 3 months.
 
I've only experienced autolysis when gnoshing on Vegemite and Marmite, so I am quite familiar with the 'beefy' aromas often associated with autolysis in the homebrewing arena, though I have never experienced those aromas or flavors in any beer coming out of my brewery. The longest I have ever had beer on the cake (where, in my mind, the autolysis is far more likely and obvious to even an inexperienced palate and nose) is about 3 months, same as you Orfy.

I'd said many times here on the forum that yes, autolysis does happen in beer, but not nearly in the timeline that alarmists seem to suggest.
 
Well as far as bottle conditioning goes I've never had a problem with autolysis. I've had beer conditioned for two years with a good 3mm of yeast at the bottom without any problems. I've never left beer in the primary for more than one month but I have left mead for about four months (with about 2in of sediment) without issue.
My thinking is that healthy yeast can go dormant and last for a very long time while maybe unhealthy yeast can't enter its dormant phase and continues to look for food even inside itself. I think certain strains maybe more prone to autolysis than others, which maybe why specific wines where that quality is desirable have special strains to give it that flavor.
 
I've never experienced it either. I've left a cider in a primary for 4 months and tasted no off flavors.

Does it happen? I'm sure it does. The fear people have of leaving beer in a primary for a month is probably misguided. Maybe someone can have a dialogue with the people from Wyeast or White Labs on when this is a problem and when the average homebrewer needs to worry about it.
 
I've never experienced it and don't fear it. I've left beer in the primary for at least 6 weeks with no issues. I don't doubt that it does exist but do doubt that contributes much to off flavors except in extreme conditions. I'm curious as to whether ending fermentation with higher temperatures may increase the chances.
 
I've never experienced it either. I've left a cider in a primary for 4 months and tasted no off flavors.

Does it happen? I'm sure it does. The fear people have of leaving beer in a primary for a month is probably misguided. Maybe someone can have a dialogue with the people from Wyeast or White Labs on when this is a problem and when the average homebrewer needs to worry about it.

Thats a good idea. I'm sending an email to Wyeast if someone else wants to cover the others.
 
Interesting timing.....I just posted this thread, but I'm unsure if my flavor problem was a result of autolysis or something else.....

No one has ever given me a beer to sample and said "this is what autolysis tastes like", so I have to go off descriptions I've read (rubber/plastic flavor). If the beer in question from my thread is suffering from autolysis, I think it might be a result of vastly overpitching + 40 days in primary, or maybe just the overpitching combined with a very light grain bill.
 
Thats a good idea. I'm sending an email to Wyeast if someone else wants to covering the others.

I decided to take my own advice and send one to them, since I mostly use Wyeast. I also emailed Jamil and JP on the Brew Strong account to see if they could cover autolysis on an upcoming show.

I basically asked the folks at Wyeast how much autolysis is a problem to the average homebrewer. Should we worry about it in the primary, bulk aging, in the bottle etc, or if it is just a bogeyman.
 
It is possible that people enjoy beer with autolysis derived flavors under certain conditions just as people enjoy skunked and oxidized beer under certain conditions. In fact if you say that you like 6 month old beer, as many home brewers do, what would you identify as the desire able characteristic of 6 month old beer that fresh beer lacks? It is probably oxidized compounds or perhaps even autolysis. Just because it is deemed pleasant, doesn't mean it hasn't occurred.

This goes back to the fact that people seem to not understand the range of flavors that autolysis can give.
 
This goes back to the fact that people seem to not understand the range of flavors that autolysis can give.

I find this to be a bit of a semantic quibble; for the purposes of homebrewers, I simply can't imagine autolysis to contribute positively to a taste experience.

As far as off-flavors are concerned, the sherry notes of oxidization are indeed something that I enjoy in specific beers. Nothing something I'd want in a witbier or bitter, but definitely expected and relished in an old ale or barleywine.
 
I find this to be a bit of a semantic quibble; for the purposes of homebrewers, I simply can't imagine autolysis to contribute positively to a taste experience.

Really? You don't think beer drinkers might enjoy bready or nutty flavors in beer?
 
Are you suggesting that these flavor compounds are a function of autolysis and not malt-derived?

I'm suggesting that they can be caused by autolysis. Obviously there are other sources for these flavors in beer and the introduction of bready or nutty flavors by autolysis will not be as easily detectable in beer as in mead or wine. That doesn't mean it doesn't happen though.
 
I'm suggesting that they can be caused by autolysis. Obviously there are other sources for these flavors in beer and the introduction of bready or nutty flavors by autolysis will not be as easily detectable in beer as in mead or wine. That doesn't mean it doesn't happen though.

I certainly acknowledge that autolysis does indeed happen and I suspect that the introduction of bready and nutty flavors may likely be more easily detected relative to style (and, related to this, gravity). If, for example, bready or nutty notes show up in an American Light Lager or Classic American Pilsner, I would have reason to look to autolysis as a possible contributing factor. Again, not pleasant or expected flavors relative to the style. But that raises the question of time needed for autolyzed compounds to reach detectable levels. If autolysis isn't prevalent in crisp, clean lagers that have undergone very lengthy (3-4 months) lagering in contact with large amounts of yeast, then I argue it is indeed a bogeyman in most ales.

My point through all of this is that autolysis, even at very low detectable levels, takes a considerable amount of time to develop.
 
I certainly acknowledge that autolysis does indeed happen and I suspect that the introduction of bready and nutty flavors may likely be more easily detected relative to style (and, related to this, gravity). If, for example, bready or nutty notes show up in an American Light Lager or Classic American Pilsner, I would have reason to look to autolysis as a possible contributing factor. Again, not pleasant or expected flavors relative to the style.

My point through all of this is that autolysis, even at very low detectable levels, takes a considerable amount of time to develop.

Sure, and the extreme autolysis derived flavors (rubbery, sulfury, even meaty) are probably pretty rare. I think it is fair to say that autolysis ought not to be a major concern to homebrewers if their practice are reasonable. I just disagree with communicating that it is not of primary importance by claiming that it does not occur which I think is either dishonest or misguided.
 
I think it is fair to say that autolysis ought not to be a major concern to homebrewers if their practice are reasonable.

And on this point we most certainly agree! In the wide world that is HBT and beyond, I consider autolysis rare enough an animal to be in the same category as the thylacine.
 
I do believe in autolysis.

I made a Dunkelweizen and carbonated most of the bottles at around 70C for about 10 days. That’s how long it took and I was surprised about that b/c there was still plenty of yeast in the beer when I bottled it. I also bottles a few bottles with lager yeast and kept those in the basement at 50-55C. After about a month the beer that I kept at 70C for carbonation started to deteriorate in flavor quickly 1.5 month after brewing. It can’t say exactly what taste it started to get, just that I really started to dislike it and oftentimes ended up pouring it in the sink. But the bottles carbonated with lager yeast stayed fresh for much longer. I just recently had the last one which was a little more than 3 month old at that point and it didn’t show the deteriorated flavor.

Call me paranoid, but I consider it good practice not to leave the beer longer on the yeast than necessary. Unfortunately that could easily lead to premature racking. But if you know the FG of the beer you can account for that.

Another problem with being on the yeast for too long is deteriorating head retention due to the yeast releasing head retention negative compounds including an enzyme (proteinase A) that works on the head retention positive proteins.

This being said I don’t do secondaries for my ales b/c they are bottled/kegged anyway after 3 weeks and the added work and O2 uptake is not worth the benefit they would get from being taken off the yeast.

While many brewers have seen improvements in beer quality by leaving the beer longer on the yeast b/c their beers may have been racked too early before, we should make sure that we don’t overcompensate to the other extreme and leave the beer on the yeast for too long thinking that it wouldn’t harm it.

As always, there is a tradeoff between the gained benefit and the added amount of work or time constrains. We are not full time brewers and can’t attend the beer as soon as it needs attention.

Kai
 
I completely agree. You gain a lot by leaving beer on the yeast longer than the standard "5-7 days" that kits say. I haven't had time to experiment. I'd be willing to bet there is a specific time where you are doing more harm by leaving it on the yeast.
 
Thanks for your thoughts, Kai. Indeed, we should all be aware that there will always exist a point of diminishing returns regarding time spent on the yeast; the difficulty is identifying that point related to the potential for autolysis.

What is your hypothesis regarding the cause of autolysis in your Dunkelweizen? If anyone can speak with authority about such matters from HBT membership, I should say it is you!

Jason
 
I have been keeping my brews in the primary for a month, are there any benefits to leaving your beer in primary for a month+...
 
hopsalot, the way I understand this whole issue is that after primary fermentation there are beneficial results to leaving the beer on the trub/yeast cake. The yeast will clean up some byproducts of the primary fermentation and obviously leaving it for a shorter time will not. This is the secondary FERMENTATION phase. I have left my beers on the yeast for up to 5 weeks (time constraint) and not yet noticed any flavors from autolysis. But then again, after reading that article its hard to say if one could even pick them out unless it was an extreme case.

Either way, I think I am going to start doing a 3 week in primary then bottle routine vs. a longer stint in the primary.
 
What is your hypothesis regarding the cause of autolysis in your Dunkelweizen? If anyone can speak with authority about such matters from HBT membership, I should say it is you!


I appreciate the confidence in my assessment but at the end I’m just one data point and other brewers may have different experiences.

If the deteriorated flavor indeed came from autolysis (If I find another bottle that was carbonated cold I should compare the pH of the warm and cold carbonated beers as autolysis is known to raise the beer pH. This is actually how you could tell that autolysis is going on: the beer pH goes up again) I blame it on the weissbier yeast being held warm for too long. These yeasts are known to be very active which also means that they loose vitality more quickly than other yeasts. This is one reason why some German brewers bottle their Weissbiers with lager yeast. But I have been told that this practice has largely been abandoned due to the added complexity (second yeast) and sometimes strong flocculation of the lager yeast. The latter leads to unsightly clumps in the beer. I had one of these beers in Germany and there was also a diacetyl note to the beer which is not uncommon when Kraeusen is used for bottling.

The next time I brew this beer I’ll add some lager yeast to all the bottles. This also works better for me b/c I don’t have to haul the beer into a warm room in the house.

But I have bottled other beers that way (e.g. pale Ales) and they seemed much more flavor stable. In this case the yeast was WY1056.

Kai
 
I may have a completely unscientific comparison I can provide. I brewed 10 gallons of an Irish Red nearly 4 months ago. I fermented in 2 separate fermentors. 5 gallons was kegged about 30 days +/- after pitching and gravity readings had stabilized. The other 5 gallons just happens to still be sitting in the fermentor. At the time I kegged the 5 gallons, I only had 1 available keg. I had planned on bottling the other 5 gallons, but the holiday season hit, parties, family visiting, etc. and quite honestly I just didnt get to it. I knew it was there, but I didn't feel like I needed to panic. I did move it to a 45 degree room after about 6 weeks and it has been sitting in there ever since.

I now have an open keg and will keg it this week.

I made a note to report back here in 2 weeks when I do a side by side comparison. Not that there aren't multiple variables at play here, but I definitely have a brew that has been sitting on yeast for 4+ months and if there are any distinguishable flavors from autolysis, I should taste them.
 
For me, I find the longer a beer sits in primary, the more yeast flavors I detect in the final product, not autolysis flavors, just yeast flavors, that to my taste buds are out of place in most styles of beer. I don't want my pales ales to taste yeasty. The beers are crystal clear so it is not suspended yeast.
 
For me, I find the longer a beer sits in primary, the more yeast flavors I detect in the final product, not autolysis flavors, just yeast flavors, that to my taste buds are out of place in most styles of beer. I don't want my pales ales to taste yeasty. The beers are crystal clear so it is not suspended yeast.

Why do you think they aren't autolysis related? What does autolysis taste like?

Like you say, the longer you let it sit the less yeast in suspension so you aren't actually tasty yeast per se. If you can't identify the source of the flavor, why rule out autolysis?
 
I actually haven't ruled out autolysis. I guess I put myself in the camp that believes that autolysis does exist. That was a interesting link posted by RedIroc. In reading that, it makes me wonder about true autolysis flavors, versus what people are lead to think they are. It seems to me that many of the particulary nasty smells would require either the presence of O2, or a contaminating anerobic bacteria. Swamp gas is produced by anaerobic bacteria. Nasty flavors produced by these is more than simply yeast autolysis. I guess I would think that if there is no contamination, and no O2, then as the yeast cells break open, I don't think that in itself so much would lead to the off flavors typically ascribed to yeast autolysis - but may be the yeasty flavor I'm tasting.

Actually having some experience working with yeast in the lab, I'd actually be surprised that autolysis is not occuring. The question then is, to what degree and how much does it take before it becomes a noticible off flavor.
 
I think what we have here is a failure to communicate beginning with our sense of smell and taste and then relating that to English. I've noticed this quite a bit lately in the forums.

Someone will post a astringent off flavor and everyone is off to the races and pretty soon something chlorophenolic gets diagnosed. I am convinced that many times the OP has no idea what astringent tastes like (It tastes like grape skins or a tea bag) or what chlorophenolic is.

So to that end, here is what some expers say that autolysis tastes like:

How to Brew - By John Palmer - Autolysis
Emphasis mine.
[FONT=Verdana, Arial, Helvetica, sans-serif]When a yeast cell dies, it ruptures - releasing several off-flavors into the beer. When you have a large yeast mass on the bottom of the fermentor, you have a large potential for off-flavors due to autolysis. If this ever happens to you, you will know it. The smell is one you will never forget.
...
My knees buckled. My wife turned green and ran to the door coughing and choking. The stench was appalling! It was heinous! The noxious aftermath of a late night of cheap beer and pickled eggs would be refreshing compared to the absolute stench of autolysis. I hope I never have to smell it again.
[/FONT]
[FONT=Verdana, Arial, Helvetica, sans-serif]Luckily, the propensity of yeast to autolyze is decreased by a decrease in activity and a decrease in total yeast mass. What this means to a brewer is that racking to a secondary fermenter to get the beer off the dead yeast and lowering the temperature for the long cold storage allows the beer to condition without much risk of autolysis. At a minimum, a beer that has experienced autolysis will have a burnt rubber taste and smell and will probably be undrinkable. At worst it will be unapproachable. [/FONT]
[FONT=Verdana, Arial, Helvetica, sans-serif]As a final note on this subject, I should mention that by brewing with healthy yeast in a well-prepared wort, many experienced brewers, myself included, have been able to leave a beer in the primary fermenter for several months without any evidence of autolysis. Autolysis is not inevitable, but it is lurking.[/FONT]
Brew Your Own: The How-To Homebrew Beer Magazine - Recipes - Beat Yeast Bite
Nico Freccia
21st Amendment
Note Graf on Autolysis. Emphasis mine.
This process releases all kinds of nasty compounds into the beer, including fatty acids and sulfur- and nitrogen-containing compounds that cause the aromas and flavors described above as meaty, rubbery, and sour.
BJCP Exam Study Guide
Sulfury/Yeasty These flavors, not to be confused with DMS, have the aroma and taste of rotten eggs, shrimp or rubber. The compounds responsible for these flavors originate from sulfur-containing amino acids such as cysteine and methionine. Possible sources include yeast autolysis, bacterial spoilage and water contamination. These flavors can be quite putrid and are not desirable in any style. In the same family are sulfitic flavors, which recall the aroma of a struck match. They are usually due to the overuse of antioxidants, and while rare in beer, are quite common in wine and cider.
I think we need to encourage people to identify precisely what they taste and smell and begin to use a common reference. Thankfully one exists.

flavorwheel.gif


More info here:
http://www.alabev.com/taste.htm
 
I made a note to report back here in 2 weeks when I do a side by side comparison. Not that there aren't multiple variables at play here, but I definitely have a brew that has been sitting on yeast for 4+ months and if there are any distinguishable flavors from autolysis, I should taste them.

I love this idea. Let us know how it turns out. I would imagine the two beers would taste different, but I wonder how different.

As for me, I think autolysis is mostly a boogey man. Does it exist? Sure. Does it happen in beer? Absolutely. Will it show up for the average homebrewer who leaves his beer in primary for 1-3 month? Probably not. Sure, it may happen on a microbial level, but I dont think anything is going to happen to effect the flavor and/or aroma. I have left beers on the primary cake for up to two months and have never noticed anything in the flavor or aroma that would suggest rubber; and certainly nothing like Palmer's experience.
 
Well approx 3 years ago when my neighbor was starting to homebrew, my neighbor brewer a batch of beer with a very meaty flavor and aroma. I have never tasted or smelled anything similar. Was it autolysis? I don't know, but from the descriptions given I would think so. I believe that if you brew with good techneiques and healthy yeast (which my neighbor was not) you will probably never taste any yeast autolysis in your beer.
 
dammit, now you guys have me going through my homebrew library searching for nutty and meaty notes.

thanks a lot! ;)
 
I read that section in Palmer's book, but he wasn't talking about a smell that came a fermenting beer, it came from a pot of rice that had been boiled (for his wife's hobby) and something came up and it was forgotten about until several days later. He said some wild yeast must have gotten in and it made a terrible funk. I think this isn't the best anology as this most likely was contaiminated, and certainly exposed to the air, not in a container with an airlock. So the smells he's talking about I think are due to more than just autolysis of yeast, probably a bacterial contaminant and would most certainly be a worst case scenario. I think this situation would in fact be very rare and I believe many of the other sources are also referring to particularly bad case examples. I am still suspicious that autolysis is occuring.

Ok, I just did a little more reading. Unfortunately, many of the brewing journals aren't available on-line. Here's some info. that I found on wine though, and I think it is pertinent. The only caveat being that the fermentation of wine occurs at higher temperatures so everything would be accelerated in time.

The set up is they grew yeast in synthetic grape juice until no sugars remained and fermentation was complete. The yeast are now considered lees. They then transfered the yeast to a synthetic wine (12%ABV) that had been oxygenated or not and then began to measure various compounds. According to their results, they see markers of yeast autolysis almost immediately after begining the aging on the lees (like beer left on the yeast cake)
Impact of Oxygen Consumption by Yeast Lees on the Autolysis Phenomenon during Simulation of Wine Aging on Lees
J. Agric. Food Chem., 2003, 51 (9), pp 2584–2590

"The amount of released nitrogen was followed for 2 weeks and the total nitrogen released was measured after 3 weeks of aging. Released nitrogen was previously described as the main measurable factor of yeast autolysis in wine (27). Indeed, we noticed that nitrogenous compounds (Figure 2) were released during simulation of wine aging: protein release ranged from 67.5 to 85.5 mg L-1"

jf0259819f00002.gif

Figure 2. Protein release by lees in the medium during storage at 28 °C of S. cerevisiae lees in a synthetic model wine (lees concentration ) 2 x 10(8 cells mL-1): (solid symbols) stirred lees + oxygen (KLa ) 2 h-1); (open symbols) stirred lees + argon

This is in line with the comments by remilard and the link posted by RedIroc about wine production. I actually really like wines that are "sur lee" and I can easily say that I have never tasted any of the flavors typically listed for those of yeast autolysis in beer in these wines - except yeasty/bready. Certainly not rancid or meaty.

I think that it is not the yeast autolysis that is the bogeyman, it is the supposed off flavors that is the bogeyman. Yeast autolysis always occurs (I'm being a bit of a technical scientist here), but this typically does not lead to strong off flavors. I think you have to do something really wrong to get the real nasty flavors.

In perusing the abstracts of papers dealing with yeast autolysis in beer (these I can obtain, but not the whole paper), much of the concern is about long term stability of the beer, not real strong off flavors - flavors that could occur is the beer is mishandled
 
Great write up, and I think you hit the nail on the head. It probably most likely does happen, but the average homebrewer is not overly likely to get strong off flavors keeping their beer on the primary cake for 1-3 months.
 
I agree with pjj2ba's asessment and his comments on Palmer, however, I think Palmer was giving an example of what autolysis smells and tastes like amped up and in an environment apart from beer (ie in its rawest state). He later softens it up a bit with this:

(Requoted)
[FONT=Verdana, Arial, Helvetica, sans-serif]At a minimum, a beer that has experienced autolysis will have a burnt rubber taste and smell and will probably be undrinkable. At worst it will be unapproachable. [/FONT]
 
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