Fermentor shape

[Spurtrax]

I have heard JZ mention the shape of the fermentor will effect beer flavor. Has anyone done any experiments with this? Is a short fat fermentor better than a tall skinny one for ales or lagers? Is any style turn out best with a specific shape of vessel?

[ajdelange]

You can bet that the manufacturers and large brewers did many experiments before arriving at the accepted 'optimum' shape in which modern cylindroconicals are built. I'm sure individual styles would benefit from different height to diameter and cone pitch ratios but as the majority of beers brewed in these are light lagers I'm guessing that the current geometry is optimized for those. I have seen arguments that certain styles (ales, wheat beers...) should not be brewed in cylindroconicals but of course they are.

[11amas]

and then there is the cool ship thingy, very shallow, that defies the current conical shape and dimensions.

[JohnF]

I would say the design aim of cylindroconical fermenters is primarily to produce a tall narrow fermenter and less to optomize beer quality per se. I don't think anyone ever thought shallow fermenters were making bad beer but they wanted to fit more tanks in a given space without decreasing beer quality (at least not much).

Anecdotes:

Fix wrote that once height/width got beyond I think 1.2:1 that the tank was prone to producing localize heterogeneous fermentations rather than a single homogeneous fermentation. There are easy solutions to this though, like pumping the beer out of and back into the tank to mix.

I think it was Orval that was quoted in Brew Like a Monk as having purchased modern tanks but only filled them half full because they thought lower height/width was superior.

So I guess in general more shallow is better for the beer and less shallow is better for production capacity per square foot. Tanks at 1:2:1 or so balance both concerns.

[11amas]

Well, once you start getting really tall and narrow you will supress ester formation so there is an aspect to the height:width ratio but I don't think homebrewers have to worry about that; I saw someone do some math comparing cornies to carboys saying that the ratio in that example was a minute pressure difference.

[ajdelange]

I would say the design aim of cylindroconical fermenters is primarily to produce a tall narrow fermenter and less to optomize beer quality per se. I don't think anyone ever thought shallow fermenters were making bad beer but they wanted to fit more tanks in a given space without decreasing beer quality (at least not much).

I think it's fairly obvious that trying to do lagers in vessels that are traditionally used for top cropping yeasts isn't going to work very well. In a cylindroconical bottom flocculating yeast are easily managed and it is for these that these things were optimized. Chill bands are easier to manage than attemperating coils in the beer (impossible to CIP, total disaster if a pipe springs a leak - of course it's a total disaster if a chill band springs a leak too) and can be used to set up circulations that keep the yeast in suspension (you don't have to pump the beer - it pumps itself). The cone sides provide area onto which the yeast can settle (remember these are called "unitanks" because you can not only ferment in them but lager and condition as well).

So I guess in general more shallow is better for the beer and less shallow is better for production capacity per square foot. Tanks at 1:2:1 or so balance both concerns.

Don't buy that. Lagers were fermented in tall vessels well before cylindroconicals came along. Not as tall as some of the modern cylindroconicals of course but still pretty tall.

[ipaisay2.0]

My two cents (maybe three):
1) try to carry or at the very least stabilize 5 gallons in a flat shallow pan vs a tall container. The taller container would be easier to move and stabilize from moving on a homebrew level.

2) Just the shear space you save with a taller vessel is key compared to a short squatter one.

3) It is not as much about the shape of the fermentor but rather the pressure that is on the yeast during fermentation. In a cylindroconicals, you'll get more pressure from weight (gravity) of the beer on the yeast and therefore you will get less ester and phenolic expression of the yeast. Now on a homebrew level, our 5, 10, 15 gall fermentors are probably not getting as much of the pressure suppression that commercial breweries get with larger BBL fermentors have. This is also why I think commercial breweries can afford to ferment a little warmer than homebrewers b/c they can suppress some of the esters/phenolics with the pressure of the beer and why many homebrewers tend to have more ester and phenolic issues across the board of beer styles. A typical 5 or 10 gallon fermentation in a bucket/carboy/conical doesn't get the same pressure but still more than a low flat (square/rectangle) fermentor.

as a side note, check out the brewing TV episode that shows the "Top Off" approach to fermentation. They briefly talk about this topic, but more at "open fermentation".

[JohnF]

I would say the design aim of cylindroconical fermenters is primarily to produce a tall narrow fermenter and less to optomize beer quality per se. I don't think anyone ever thought shallow fermenters were making bad beer but they wanted to fit more tanks in a given space without decreasing beer quality (at least not much).

I think it's fairly obvious that trying to do lagers in vessels that are traditionally used for top cropping yeasts isn't going to work very well. In a cylindroconical bottom flocculating yeast are easily managed and it is for these that these things were optimized. Chill bands are easier to manage than attemperating coils in the beer (impossible to CIP, total disaster if a pipe springs a leak - of course it's a total disaster if a chill band springs a leak too) and can be used to set up circulations that keep the yeast in suspension (you don't have to pump the beer - it pumps itself). The cone sides provide area onto which the yeast can settle (remember these are called "unitanks" because you can not only ferment in them but lager and condition as well).

So I guess in general more shallow is better for the beer and less shallow is better for production capacity per square foot. Tanks at 1:2:1 or so balance both concerns.

Don't buy that. Lagers were fermented in tall vessels well before cylindroconicals came along. Not as tall as some of the modern cylindroconicals of course but still pretty tall.

I don't doubt that a 50 barrel ale brewery and lager brewery would use differently shaped tanks, but as you get to 300-500 barrel tanks I think the reason that breweries go more up than up and out is economic. Even in a single brewery with different sized tanks the bigger ones have a larger height:width ratio. I think this is an entirely economic decision and not a judgement that for 200 barrel ferments of Sierra Nevada Pale Ale (or whatever) you need different tank geometry than for a 600 barrel ferment.