Excellent yeast info source raises question..

Murphy and sons are the UK's "main" brewery supplier. Their website has loads of info, this link relates to yeast management. Note they say that leaving a top fermenting yeast on the wort for too long will tend to reduce the quality of the beer due to autolysis. This goes against what seems to be accepted practice on this forum to primary ferment in carboys for 2-3 weeks without removing the head. However, if the liquid level in the carboy is close to the neck, much of the yeast will be expelled via airlock or blow off tube.

http://www.murphyandson.co.uk/BrewingArticles/YeastManagement.htm

There are going to be several differences between the large fermenters in a pro brewery and the 5 or 6 gallon fermenters in a home brewery.

The biggest difference is volume. In a large fermentation vessel, there is a considerably larger amount of pressure on the bottom of the tank from the large volume of liquid. The yeast would be under increased stress on their cell walls at these pressures. Most pro breweries will have conical tanks where they can dump the yeast as it collects on the bottom. I'm guessing the link recommends skimming for open fermenters.

I'd imagine it would be very rare to suffer the effects of autolysis in a home environment.

-chuck

I do not believe the pressure at the bottom of a 360 gallon fermenter (typical microbrewery) ih very different from my 6 gallon bucket. Measured as head of water, mine is 2 feet, there's is 8 feet, 4 times more, but in psi terms miniscule, but stand by for the scientists to add their two penny worth (10 cents worth).

Commercial breweries have tall tanks where the yeast after flocculating are under tremendous pressure in a tiny area and therefore are also up to 10 to 20 f higher in temp than the beer. It hastens the process of yeast breaking down and dying much faster than five or ten gallons of beer over the relatively large flat area the yeast in your carboy will provide. Since they are a commercial supplier my guess would be the info would be more relevant to the brewers using large multi barrel cylindroconical fermentors. Just my two pence (since we're taking UK here hehe)

Granted, it may be a small numerical difference on paper, but what difference is that on the scale of a cell wall of yeast?

Men and women can swim with no pressure diving suit 100 feet down in the sea. Their skin cells do not collapse and die....a skin cell is quite like a yeast cell. cell wall, mainly composed of water, nucleus, membrane....

Just being devil's advocate here, not a qualified micro-biologist by any means...

Following the logic of the swimmer, how long could they stay at that depth before cell walls did start to collapse? I'm guessing there are other factors at work in brewers yeast than there would be in human skin cells. Are yeast cell walls weaker post-fermentation?

This is a commonly accepted difference between home scale and production breweries. I wonder if there is research material documenting it.

PSI is pounds per square inch. It's a unit of area.

Sure, if you go by heads of water, it's just 4x or so more. 4x is quite a bit, but you're right that yeast can easily handle that delta.

The conical, since at the bottom the area is much, much smaller probably adds another large multiplier on top of that.

In the pressure ferment thread, kaiser mentions that commercial breweries can have 15+ psi of pressure on their yeast.

But then again, lots of people in that thread have created pressure ferments at 20+psi without issue, with top fermenting yeast.

I mean, we bottle condition, leaving the yeast at 30 psi (at room temp) for weeks or months letting it carb up and condition, and we don't see autolysis in those bottles. Maybe there's not enough yeast, but I'd expect to have tasted it in lighter beers if that were the case.

I've yet to see someone, anyone show autolysis and consistently reproduce it. Just because some reputable website mentions it doesn't mean that I'll throw out lots of things that I've seen with my own eyes

BOBTHEukBREWER said:

Men and women can swim with no pressure diving suit 100 feet down in the sea. Their skin cells do not collapse and die....a skin cell is quite like a yeast cell. cell wall, mainly composed of water, nucleus, membrane....

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So.....you're arguing that autolysis doesn't happen? Are you just playing both sides of this and seeing what the consensus is? Your first post seemed to be worried about it, but then you pretty much dismiss it here....

Autolysis is the breaking down of the yeast cells, which means collapse and die.

BOBTHEukBREWER said:

Men and women can swim with no pressure diving suit 100 feet down in the sea. Their skin cells do not collapse and die....a skin cell is quite like a yeast cell. cell wall, mainly composed of water, nucleus, membrane....

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Our cells do not have cell walls.

Autolysis is a very obvious and offensive flavor - you'll know when you run into that problem right away. The fact is that homebrewers who do extended primaries rarely run into it. Back when I played with continuous fermentation of applewine, it took about four months for autolysis to occur.

https://www.homebrewtalk.com/f163/secondary-not-john-palmer-jamil-zainasheff-weigh-176837/

I can agree that top fermenting yeast might be less susceptible to surviving the extra pressure and heat than other types of yeast, so that makes sense. The big issue is still the difference between commercial and homebrew fermenters and techniques.

Relevant quote from Jamil:

Jamil: And if you are using healthy yeast and the appropriate amount and the thing is... homebrew style fermentors..if you are using a carboy or plastic bucket which have that broad base when the yeast flocculate out they lay in a nice thin layer. When you're dealing with large, tall...one of the things you know people go "Well the commercial brewers they remove the yeast because it is gonna break down, die, and make the beer bad. We should be doing the same thing." That's where alot of this comes from. But the commerical brewers are working with 100 bbl fermenters that are very tall and put a lot of pressure on the yeast. The yeast are jammed into this little cone in the bottom and they are stacked very deep and there is a lot of heat buildup. The core of that yeast mass can be several degrees C higher than the rest of that yeast mass and it can actually cook the yeast and cause them to die faster and cause those problems with flavor and within a couple of days the viability of that yeast which the commercial brewers are going to reuse is going to drop 25%, 50% over a couple of days so they need to get that yeast out of there. You don't have that restriction as a homebrewer. You've got these broad fermenter bases that allow the yeast to be distributed evently. It's an advantage for cleaning up the beer. You have the advantage that the yeast don't break down as fast. You don't have as high a head pressure. There are a lot of advantages.

BOBTHEukBREWER said:

Men and women can swim with no pressure diving suit 100 feet down in the sea. Their skin cells do not collapse and die....a skin cell is quite like a yeast cell. cell wall, mainly composed of water, nucleus, membrane....

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Whoa. You should see a doctor IMMEDIATELY.

zepolmot said:

Our cells do not have cell walls.

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I'm pretty sure they do mate; I'm actually pretty sure all cells have cell walls....

Cell membrane - plants and animals have cell membranes, only plants have cell walls!

Edit:

Plants, animals and fungi have cell membranes, only plants and fungi have cell walls (on the whole)!

DannPM said:

I'm pretty sure they do mate; I'm actually pretty sure all cells have cell walls....

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Actually, human skin cells have a plasma cell membrane. Yeast cells have a cell wall. They are physically different structures.

Kaiser - PSI is pounds per square inch. It's a unit of area. Sorry mate, it is a unit of pressure. Zepolmot, our cells presumably have boundaries or edges, I am not worried about terminology. Kaiser - So.....you're arguing that autolysis doesn't happen? Who is this addressed at, it followed your own post.

I am guessing here, but maybe a little autolysis is a good thing, and is subtle. Maybe above a certain yeast concentration, it is a bad thing. The Company referred to in my original post are very reputable, and indeed offer laboratory services such as water analysis, yeast maintenance, trouble shooting. I doubt they would have mentioned it if it wasn't an issue.

My original assessment was that perhaps we aren't their target audience and professional scale breweries are.

twigboy2000 said:

Actually, human skin cells have a plasma cell membrane. Yeast cells have a cell wall. They are physically different structures.

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Plasma Cell Membrane, Cell Wall, both sound like the same thing to me :cross: I took Astronomy and Geology for my science credits in college...I guess this is where that shows?

BOBTHEukBREWER said:

Kaiser - PSI is pounds per square inch. It's a unit of area. Sorry mate, it is a unit of pressure. Zepolmot, our cells presumably have boundaries or edges, I am not worried about terminology. Kaiser - So.....you're arguing that autolysis doesn't happen? Who is this addressed at, it followed your own post.

I am guessing here, but maybe a little autolysis is a good thing, and is subtle. Maybe above a certain yeast concentration, it is a bad thing. The Company referred to in my original post are very reputable, and indeed offer laboratory services such as water analysis, yeast maintenance, trouble shooting. I doubt they would have mentioned it if it wasn't an issue.

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Obviously psi is a unit of pressure, but it's in relation to a unit area. Obviously I could have framed the sentence better. But, obviously, you can't just say "the fermenter's only twice as tall!!! Not that much more pressue!" when you're not taking into account the unit of area that pressure is exerted over. Your explanation didn't take into account the area aspect of pressure, so I mentioned it. No need to insist full rigor in a simple aside, unless you're getting defensive.

Obviously autolysis happens. The link I posted talked about it. And about how you pretty much have to be a professional brewer to experience it.

Like I said, all evidence presented to us shows that it's pretty hard to create and even harder to reproduce on a homebrew scale. On a commercial scale, it's probably not so hard. Those guys work on a commercial scale.

Therefore, when someone whom supplies professional breweries talks about autolysis, I think "ok, cool". But I don't think that it affects me in the least. No one, out of all the batches brewed on this forum, and out of all of the inquiring minds has managed to produce autolysis in a consistent way. So, yea, at the homebrew scale, with wide bottomed fermenters and relatively small conicals, I would say that you don't have to worry about it.

The fact that you can bottle condition for years with no autolysis should be enough for pretty much anyone to realize that we don't have a lot to be worried about.

It's not that some autolysis is good, but rather that it's not really happening at our scale. Don't just assume it's happening, and say "well, some of it must be good then". Because if it is happening, even a little, those whom brew at the extremes, aka leave in primary for 7 months, bottle condition for years, etc, etc would see more of it than the rest. But no one's seeing any of it consistently, much less more of it under certain conditions. So, the evidence that we have available to us is that it's not happening on our scale. With the counter evidence being some text on a website from someone in a different industry with different equipment and circumstances than homebrew.

BOBTHEukBREWER said:

Kaiser - PSI is pounds per square inch. It's a unit of area. Sorry mate, it is a unit of pressure. Zepolmot, our cells presumably have boundaries or edges, I am not worried about terminology.

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You can't dismiss "terminology" when it means you're talking about two physically different things. Terminology is quite important then.

I ate a apple the other day, tasted like an orange. It was orange and had a thinck peeling than all the other apples, but I'm not going to get mixed up with terminology

Cell walls and cell membranes can be seen in an egg.

The hard outer shell of an egg is the cell wall, there is a thin skin underneath the wall which is the membrane.

If you managed to stay underwater for two weeks or so, straight, it actually would be quite dangerous and very potentially lethal. Using divers as an example is very flawed, not just because the whole cell-wall issue is NOT one of terminology but of physical reality (you're trying to make an assumption of one structure based on a completely different one... nonsense), but because even the time scales are vastly different.

Autolysis CAN be an issue in homebrewing, but it takes a very long time on top of a lot of yeast. Unless you keep the beer in a primary fermenter without removing yeast for an excessively long time (even a few months would probably not create any noticeable issue), you should be fine.

Very subtle autolysis is actually a desirable feature in some big, darker, aged beers (though not to the point of meaty), just like a bit of oxidation can be. Autolysis can be an enormously powerful flavor, but to say that it's always strong is just as ridiculous as saying it's NEVER an issue - it's a matter of degree (ie how many cells are autolyzed). It's NOT a yes/no, true/false, present/not present thing. In fact, there is probably a very small proportion of autolyzed cells in almost every batch of beer we make, just that it rarely crosses the threshold of being noticeable. On the flip side of the coin, if you want to taste autolyzed brewer's yeast in pretty much the purest form possible, eat a spoonful of Vegemite, because that's precisely what it is.