Why you shouldn't use cornies for fermentation

[Octavius]

First off, I've been using cornies for fermentation for years with no problems. Many, many advantages.

However, I was down at my local home brew store store chatting to one of the guys (they are very knowledgeable about brewing). He says that the geometry of a corny is all wrong - it is too high (say, compared to a brewing bucket). The extra height of liquid (extra pressure) stresses the yeast.

This isn't going to stop me but I'm thinking you guys must have an comment or two about this.

I'm thinking about commercial breweries where the fermenter is way taller than a corny and all the yeast concentrated into a small area of the conical.

Cheers!

 

[Hammy71]

That's funny. Guess they've never been to a brewery. Crimey, the fermentation towers at places like Sierra Nevada (and most commercial breweries) are stories high and relatively narrow. That is TONS of pressure.....

 

[thadius856]

The extra height of liquid (extra pressure) stresses the yeast.

This guy's losing his mind.

Yeast will happily fart CO2 all day long until they explode a glass bottle.

If what he said were true, the whole concept of fermenting in a close system under pressure would fail. There'd be no such thing as a spunding valve. You'd be unable to carb bottles using sugars. Etc etc...

(Edit: without "stressing" the yeast and mucking up flavors, that is)

 

[dyqik]

Geometry has no relevance at all to 5 gallons of wort in corny or bucket - the pressure at the bottom of a corny is determined entirely by the height from top to bottom, so it's pretty much the same as at the bottom of 14 gal conical, or a commercial scale yorkshire square, or if you want numbers, 0.58 psi above atmospheric pressure (24" depth). If that's a problem, we should probably be careful using yeast and recipes from breweries in Denver, which is typically 3 psi below sea level...

 

[LordUlrich]

He is correct, IN THEORY In practice it is not a significant diffidence. The shape of the fermenter does impact the pressure, as to get the same volume of liquid into a a skinny tank will result in a taller column.
The big breweries do face this as an issue, and that is part of why the cone of conicals have separate jackets reducing the stress on the yeast by dropping the temperature.

 

[Thedutchtouch]

warning... science nerd posting...

assuming for argument sake that wort = water (we all know the SG is a bit different but not enough to really matter in this case), the amount of water needed to equal 1 atmosphere of pressure at sea level is 15 feet. your yeast is therefore under 1.2 atmospheres of pressure when under 3 feet of wort. there are studies in the scientific literature that reference yeast function perfectly fine under up to 50 megapascals (~500 atmospheres) of pressure. figure out how to build a fermentation chamber that can stand that type of pressure (it's about 7200 PSI) and then we can start worrying about the effects of pressure on yeast.

more technical info available here and elsewhere... http://www.scielo.br/scielo.php?pid=S0100-879X2005000800012&script=sci_arttext#Abstract

 

[logdrum]

Well... You're somewhat right. 1 atmosphere=14.7 psi; 1 psi=2.31 ft of head, so: 14.7x2.31=33.9 ft of head-your 24" cornie gets you just under 1psi at the bottom where the yeast live

 

[Thedutchtouch]

Well... You're somewhat right. 1 atmosphere=14.7 psi; 1 psi=2.31 ft of head, so: 14.7x2.31=33.9 ft of head-your 24" cornie gets you just under 1psi at the bottom where the yeast live

even in a closed system you still need to add in the 1 atm from the actual atmosphere, no?

 

[WileECoyote]

Octavius, Can you ask the guys at the home brew store what they were smoking when they told you that?

And is their another home brew store you can get your supplies from?

Cheers

 

[Facinerous]

Here is a cool little thing that I found a while back that I think is of relevance. May help you figure out wether or not to use cornies.

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.

 

[BreezyBrew]

I think this is a perfect example of someone who is trying to sound informed but really doesn't have any evidence to back it up. Kind of like when people thought maggots came from meat.

 

[vNmd]

First off, I've been using cornies for fermentation for years with no problems. Many, many advantages.

Kind of a neat idea. Slimmer, easy to clean, non scratchable while cleaning, I like it. What do you do for airlock?

 

[AlCophile]

Yes, once you get an idea what the ferm'n looks like in a transparent vessel, you have a good idea what's occurring in the keg. Also faster to warm or cool a metal keg, if needed. Virtually indestructible. Only caveat: the reduced square area in the corny relative to a carboy will cause the kraeusen to be much deeper, and if you vent it under pressure, you'll get a faceful of foam.

 

[Thedutchtouch]

Kind of a neat idea. Slimmer, easy to clean, non scratchable while cleaning, I like it. What do you do for airlock?

lots of people will just drill a hole in an extra lid for airlock/ blowoff tube. you could also remove the poppet from the gas in (shorter tube), and put a blowoff tube over the post.

 

[billl]

Not sure why people are being so dismissive of this. There really is no doubt that fermenter geometry plays a significant role in yeast flavors in commercial brewing. Moving to conical fermenters caused quite the stir at the major belgian breweries. It's fine to say yeast CAN ferment over a range of pressures, temps etc but it is quite another to claim their are no performance differences over that acceptable range.

Granted, when you are talking cornie vs bucket, it's like to be a pretty small difference, but you probably aren't getting the exact same beer as you would.

 

[dyqik]

Not sure why people are being so dismissive of this. There really is no doubt that fermenter geometry plays a significant role in yeast flavors in commercial brewing. Moving to conical fermenters caused quite the stir at the major belgian breweries. It's fine to say yeast CAN ferment over a range of pressures, temps etc but it is quite another to claim their are no performance differences over that acceptable range.

Granted, when you are talking cornie vs bucket, it's like to be a pretty small difference, but you probably aren't getting the exact same beer as you would.

Well, yes, but there's a bigger difference in pressure from the weather than from the geometry of the fermentation vessel (do you pitch during a high or a low? - I reckon the difference between an ale pail and a corny is about 20 mBar). It's not worth worrying about pressure due to the geometry of a 5 gal fermenter until after you've installed the pressure controlled fermentation chamber.

No one's being dismissive that there is an effect, just that it's smaller than the other uncontrolled variables.

 

[brew_ny]

Octavius, Can you ask the guys at the home brew store what they were smoking when they told you that?

and if they would like to share

S_M

 

[pickles]

And to think, I intentionally ferment at pressures up to 15psi. Well I guess I better throw away my spunding valve...

 

[diS]

Did you asked him how many is that extra pressure, I don't think it is that huge considering amount of beer in keg (5 gal)...

 

[Braufessor]

Kind of a neat idea. Slimmer, easy to clean, non scratchable while cleaning, I like it. What do you do for airlock?

I use cornies to ferment smaller batches for some 3 gallon kegs I have. I just put a blowoff tube on the CO2 threads into a milk jug of starsan. Then, when fermentation is done, I put the CO2 post on, and transfer from the 5 gallon keg to the 3 gallon keg from liquid tube to liquid tube.

I do bend the dip tube in the 5 gallon fermenter so that it sits maybe 2 inches off the bottom to avoid transferring any trub. I put about 3.5-3.75 gallons in the fermenter, planning to leave behind a half gallon or so and have 3 gallons finished product to go into the 3 gallon keg. I actually have not had any blowoff at all with that volume of beer in the fermenter.

And, +1, in regard to the "geometry" stressing the yeast. Homebrewing is not commercial brewing. There are a number of issues that simply do not translate in any meaningful way at the homebrew level. This is one of them. Cornies make great fermenters - especially for smaller batches.

You can see kind of how I set mine up - the blow off tube has been pulled off, as I was in the process of transferring the finished beer.

 

[Beernik]

He might be confused with stilling vessels. A pot still will produce a different flavor than a reflux still tower.

A 50 barrel tank is 172" x 80 diameter. Ratio = 2.15.

A corny keg is 23" x 9". Ratio = 2.56.

The ratios are different, but not that different. Just make sure it vents properly.

Btw, a 5 gallon bucket is about 18" x 12". That's a ratio of 1.5. That's a bigger difference from a tank.