What conditions cause autolysis - yeast death and rupture?

[MagicSmoker]

Right. I know there are ways to pressurize beer. I was trying to figure out a way to pressurize without allowing extra gas to be absorbed into the liquid (like the conditions at the bottom of a very large fermenter where the pressure comes from the depth of the liquid, not the pressurized headspace).

But that is interesting information.

The pressure at the bottom of a cylindrical tank will be the same regardless of diameter, so...
If you want to simulate a tall fermenter without requiring a huge volume of liquid for your test, then make it out of 3/4" SCH 40 PVC pipe.

 

[Dynachrome]

I like that I have an envelope house.

I could do one about twenty feet tall in the sunroom.

 

[freisste]

The pressure at the bottom of a cylindrical tank will be the same regardless of diameter, so...
If you want to simulate a tall fermenter without requiring a huge volume of liquid for your test, then make it out of 3/4" SCH 40 PVC pipe.

I actually imagined that, but assumed it was impractical. If it is practical, I think it is a good way to simulate the big boys. As you say, diameter is irrelevant to pressure.

 

[Leadgolem]

Hmm. The long tube is a good idea.

I hate to bring this up, but yeast cannibalization is a different process then autolysis. Inducing it through denial of nutrients, or excessive yeast stress, isn't going to produce any useful data. Autolysis occurs as a result of the enzymes present in the yeast cell after death. I rather doubt the chemicals, and therefore flavors, are the same.

 

[Dynachrome]

Hmm. The long tube is a good idea.

I hate to bring this up, buy yeast cannibalization is a different process then autolysis. Inducing it through denial of nutrients, or excessive yeast stress, isn't going to produce any useful data. Autolysis occurs as a result of the enzymes present in the yeast cell after death. I rather doubt the chemicals, and therefore flavors, are the same.

I read this earlier, it didn't filter through though.

Are you saying that my growler experiment is too small?

 

[freisste]

My thought was the following:

People always say autolysis is a homebrew myth that the big boys deal with because their fermenters are so large. The size leads to higher pressure. This is a simple way to simulate the pressure the big boys get.

If you don't use a long tube (or similar) you can likely still achieve a condition which causes autolysis. Similarly, if you DO use it, you may NOT achieve the situation. It was just a thought that I thought might help.

 

[Dynachrome]

Ha, This reminds me of an older discussion:

marcelo's build idea

....Now, what 'bout "food safe PVC"?

If I'm going to do it, I might as well be able to use it for regular fermenting.

 

[Leadgolem]

I read this earlier, it didn't filter through though.

Are you saying that my growler experiment is too small?

Not exactly. Your growler experiment is a reasonable first experiment. I just don't think it will be definitive by it's self. There are still a fair number of factors that haven't been accounted for with that experiment.

Mostly, I was trying to point out that beating up on live yeast wasn't a useful thing to do when you are trying to study autolysis. It isn't any trick at all to induce yeast cannibalization, which we already know produces off aromas and negatively effects flavor.

My thought was the following:

People always say autolysis is a homebrew myth that the big boys deal with because their fermenters are so large. The size leads to higher pressure. This is a simple way to simulate the pressure the big boys get.

If you don't use a long tube (or similar) you can likely still achieve a condition which causes autolysis. Similarly, if you DO use it, you may NOT achieve the situation. It was just a thought that I thought might help.

Pressure is one of the factors that the growler experiment does not account for. However, I'm not sure it's necessary to account for it. If you are running the experiment for primary scientific reasons, then yes. A long tube or some other method to simulate the pressure of a larger fermentor would be useful. If you are only interested in autolysis as it effects, or doesn't, homebrew then it isn't necessary. Homebrewers don't typically have fermentors that are deep enough to produce the pressure you are talking about.

Another factor that had occured to me is the chemical composition of the brew it's self. PH, mineral and/or salt content. I seem to remember salt being used to encourage autolysis in soy sauce production. I'll see if I can dig up the reference. Temperature also springs to mind. After all, why is it that so many sources recommend aging at cellar temps?

EDIT: This wasn't the original reference, but it works I think.
http://en.wikipedia.org/wiki/Yeast_extract

 

[Dynachrome]

Yeah, I'm trying to roughly duplicate regular home brew conditions.

The tall tube fermentor is probably fairly well off track.

No basement heaters.
No sunlight warming it up.
Small, but not un-imaginal size fermentor.

My thesis: What happens when you let your beer sit on a yeast cake for "an extended" period of time.

 

[Dynachrome]

Yesterday.

 

[Leadgolem]

Sort of a side note. I had been leaving a batch of concord wine in my bottling bucket, because it was really to sweet for my tastes. It had been sitting in there, and slowly fermenting more, for about 6 weeks. This was after two weeks in primary. Sometime in the last week it developed a soy sauce like flavor to it. Not the tang you get from acetic acid, this was different. It isn't so bad that I can't drink it, but I bottled and pasteurized today. I took the lees, and mixed then with salt until I had a saturated salt solution. The resulting liquid tasted like a fruity version of soy sauce to me. I've got 2 750ml bottles of that stuff in my store room, I'll check on them in a couple months.

I know, not scientific. Not really conclusive of anything, interesting though. If it comes out well, I might start making my own homebrew soy sauce.

 

[Facinerous]

Kind of joking, but kind of serious. 2 liter soda bottles can withstand quite a bit of pressure without rupturing. If you wanted to replicate pressure from hundreds of gallons of brew, why not do it with psi.

Just brew a small batch, maybe one liter, put in bottle, cap and let ferment. I'm pretty sure the yeast would crap out and die from the pressure before the bottle burst, but precaution is a good idea either way. That otta kill off the little yeasties and get a quick taste for ya.

(This part is an edit cause I wanted to do the math for some fun)

You can quote me if I'm wrong, cause I'm not an engineer but heres some math for replicating brewery pressures just for funzies.

Pulled up numbers from quick google searches

One gallon of water weighs 8.34 pounds. One gallon of water is 231 cubic inches, or 0.133681 cubic feet. So 8.34/231 equates to one cubic inch of water weighing .0361 pounds. I think >_<

That being said one cubic foot of water would exert 0.4332 PSI, or roughly a half a pound. All I did this for is to figure out how much water weighs if it stands one foot high. (A quick google search semi confirms this, they wiki.answers.com says 0.44)

Now, I've only been a home brewer for a short period of time, and I haven't really paid attention to how tall the average breweries fermenter would stand, but having looked at the things I would assume somewhere between 30 to 50ft. For my math I'll just say 40 ft for now. (Quote me if I'm wrong) A 40 foot fermenter containing liquid would exert about 17.328 PSI at the bottom. Thats actually not nearly as much as I had thought it would be. One more thing about this part is the calculations is strictly for pure water, not wart. So the numbers may be slightly skewed, but still within 5-10% I'm thinking.

Going back to Google which lead me to once again wiki.answers.com. One atmosphere is roughly 14.5 PSI. Once again... Not nearly as much as I thought it would have been. If I were to assume that the average carbonating pressure is 2-2.2 Atmospheres then that would only come out to about 14.5 PSI (Eleminating 1 atmosphere because its already there from the air pressure we all exist in). Didn't even use the old calculator for that one >_<

Going full circle. The average plastic bottle can hold 80 PSI safely with 100 PSI absolutely being the limit... Thanks Google... So if you were to try my 2 liter bottle theory and actually get the yeast up to 80 PSI you would be replicating about a 100 foot fermenting chamber. I don't think you would need to goto that extreme, but hey... It would be your call.

With all the math being done I've realized a few things having never really thought about all this before. One is that the giant fermenters that breweries use don't exert nearly as much pressure on the yeast cake as many (especially me) would think. Also, I don't know what kind of pressure it would take to kill off yeast, because obviously the brewing practice has proven that yeast can survive beyond 2 atmosphere with no problems.

I don't know how much pressure it takes to gernade the average glass bottle, but that does happen. I give it up to those little yeasties. They impress me with their tenacity.

 

[JuanMoore]

Kind of joking, but kind of serious. 2 liter soda bottles can withstand quite a bit of pressure without rupturing. If you wanted to replicate pressure from hundreds of gallons of brew, why not do it with psi.

I already suggested an accurate way to accomplish this earlier in the thread (using a spunding valve). This would allow the pressure to be set to mimic the hydrostatic pressure in a large unitank exactly. The OP didn't like this idea because they thought the increased dissolved CO2 could have an additional effect on the yeast, and wouldn't be comparable to the effects of the hydrostatic pressure alone.

A 40 foot fermenter containing liquid would exert about 17.328 PSI at the bottom.

Wort and beer are both slightly denser than water, so it would be slightly higher, but your math is correct. With the exception of macro breweries, the unitanks typically aren't that tall though. Most microbrewery fermenters are in the 10'-25' tall range (or at least the fluid containing portion), and the hydrostatic pressure at the bottom of the tank is typically 6-12 psi.

If I were to assume that the average carbonating pressure is 2-2.2 Atmospheres then that would only come out to about 14.5 PSI (Eleminating 1 atmosphere because its already there from the air pressure we all exist in).

You're mixing up two very different concepts. Carbonation is measured in volumes, not atmospheres (pressure). A beer carbonated to 2 vol means that every liter of beer has 2 liters of CO2 at STP dissolved in it. A beer with moderate carbonation like 2.5 vol will have a headspace pressure between 8 psi at freezing and 34 psi at room temp. Those are both gauge pressure too, so the absolute pressures would be 1atm higher.

Also, I don't know what kind of pressure it would take to kill off yeast, because obviously the brewing practice has proven that yeast can survive beyond 2 atmosphere with no problems.

Yeast can survive very high pressures, and don't even show changes in morphology below 500atm (7,000+ psi). The types and ratios of flavor compounds they produce changes quite a bit with just small pressure being applied though. Most commercial fermenters don't have airlocks like we homebrewers use, but rather spunding valves to let the pressure escape. Many breweries set the spunding valve pressure to 10-15 psi, which adds to the hydrostatic pressure of 6-12 psi at the bottom of the tank. This typically reduces the formation of esters, fusel alcohols, acetyl, and foaming, but can also increase diacetyl and acetaldehyde. Those are generalizations though, and the actual results are very dependent on the yeast strain. It's one method that some commercial breweries use to speed fermentation, as it allows warmer fermentation temps without the fusels and esters that normally come with that.

 

[Facinerous]

Thanks for quoting me, and for the extra info

 

[freisste]

Now, I've only been a home brewer for a short period of time, and I haven't really paid attention to how tall the average breweries fermenter would stand, but having looked at the things I would assume somewhere between 30 to 50ft. For my math I'll just say 40 ft for now. (Quote me if I'm wrong) A 40 foot fermenter containing liquid would exert about 17.328 PSI at the bottom. Thats actually not nearly as much as I had thought it would be. One more thing about this part is the calculations is strictly for pure water, not wart. So the numbers may be slightly skewed, but still within 5-10% I'm thinking.

Incorrect. You have to add the pressure exerted by each foot plus the pressure from above it. This ends up being an infinite sum (integral) as layers get thinner, so a depth of 40ft probably has pressure around 30 or 35 psi, not 17. Either way, the rest of your math seems to hold.

 

[JuanMoore]

Incorrect. You have to add the pressure exerted by each foot plus the pressure from above it. This ends up being an infinite sum (integral) as layers get thinner, so a depth of 40ft probably has pressure around 30 or 35 psi, not 17. Either way, the rest of your math seems to hold.

He went about it in a bit of an odd way, but the answer was correct. This is very basic chapter one fluid mechanics type stuff. The difference in pressures in a fluid from hydrostatic forces is the specific weight of the fluid times the difference in height. If you consider the surface of the liquid to have a pressure of zero, then the hydrostatic pressure at the bottom of a 40' tall tank of water equals 62.4 lb/ft^3 (the specific weight of water) times 40ft = 2496lb/ft^2. Then divide by 144in^2/ft^2 to convert to lb/in^2 = 17.33 psi. The specific weight of a fluid is it's density times the gravitational acceleration, and the density is the specific gravity times the density of water, so for an unfermented wort with an SG of 1.065, the pressure would be (1.065*1.94slugs/ft^3*32.2ft/s^2*40ft)/(144in^2/ft^2)=18.48 psi.

 

[TANSTAAFB]

However, the point is to discover the conditions that cause yeast autolysis in a typical homebrewing situation. Just sayin!

 

[freisste]

the pressure would be (1.065*1.94slugs/ft^3*32.2ft/s^2*40ft)/(144in^2/ft^2)=18.48 psi.

I included atmospheric pressure as well. (Pressure at the surface is 14ish, so total is about 32...apparently we are saying the same thing.

But as OP said, its irrelevant at the homebrew level.

 

[Facinerous]

Well fellas, maybe I stirred the pot a bit with my initial post on this thread. All my intention was to provide Dynachrome an option to potentially speed up yeast autolysis faster with an extremely cheap method.

One two liter soda bottle, about 1 1/2 Liters of wart, and of course the yeast.

You could easily brew a 6 gal brew, and sacrifice a half a gallon if you actually wanted to do the experiment. If it were to speed up the effect and produce the desired off taste that Dynachrome is looking for it may be worth it. Its up to him.

Either way good luck with your experiment if your still doing it.

BTW I found this little blurb a little earlier from probrewer.com Healthy Yeast

Carbon dioxide can build up quickly in yeast slurry, and if kept under pressure will cross the cell walls and kill yeast cells. Pressures over 35 psi can be toxic to yeast, and soda kegs are rated over 100 psi. So if you use these kegs, shake and vent pressure regularly, at least once per day.

 

[Dynachrome]

Thanks Facinerous


and ...


...you eyeballin' me boy?!

 

[Facinerous]

Yep... wit my good eye.

 

[Dynachrome]

..checked the burp valve today. Added a 'tidge more vodka.

It's still too murky to see through.

 

[Leadgolem]

In case anyone is interested. The soy sauce experiment is going well. The solids have pretty much separated from the liquid, and now the liquid really tastes like soy sauce. It isn't nearly so fruity now, and it is much more meaty.

 

[dantheman13]

Any updates from Dynachrome?

 

[Dynachrome]

....four months and holding. I'm not sure how long I should go. I was thinking about six months.

I'm open to suggestions though.

 

[Leadgolem]

I would think you are probably already there. I've gotten off flavors making wine in 7 weeks...

Oh, the soy sauce is a nice fruity sauce now. It's actually nice, but not for every dish you would use soy sauce in.

 

[Dynachrome]

Success.

The boogie man is alive and well.

Today was the day. I needed my burp valve back.

My first impression was under-cooked unsalted smoked ham. kind of some funky wine smell. It looked like murky prune juice.

My friend at the Local Home Brew Store is working on his BJCP. He said I hit it dead on.

The best description we could get of the smell was opening a fresh can of latex paint.

He said I should read the ingredients on yeast nutrient the first one is dehydrated autolized yeast.

It seemed like my tolerance was higher than his.

 

[Leadgolem]

Thank you for checking back in. I'll put this in the "not myth" category then.

 

[Dynachrome]

Thank you for checking back in. I'll put this in the "not myth" category then.

It surprised me. I thought it would fail.

 

[Dynachrome]

We opened it up at a home brew club meeting.

No one else had the fortitude to try tasting it.