Dear Mr. Wizard,
I moved away from the use of the glass carboys and moved to a conical fermenter. I have brewed good beer with glass, but now with the conical fermenter, I’m not sure exactly what to do. For instance, I would normally rack my beer to the second fermenter and begin to lager the beer. Now with the conical fermenter, I do the same thing but instead of racking the beer into a secondary carboy I dump the yeast and keep it in the same conical fermenter. In the past when I used the glass carboys, I would transfer my beer into a keg and have great beer. Now when I transfer my beer from the conical fermenter to a keg, there is a lot of sediment at the bottom of the conical fermenter (that I did not have with the glass carboys). Will this remaining yeast and trub at the bottom of the fermenter have a significant effect on the flavor and clarity on my beer, or do I have to do a second dump of this remaining yeast mid way through the lagering of my beer? Or . . . is this stuff at the bottom of the fermenter important in order to condition my beer?
Diamond Bar, California
Mr. Wizard replies:
Most small cylindroconical tanks have two ports on the bottom; one on the side of the cone and one on the bottom. The upper port is used to rack beer out of the tank above the sediment layer. Some racking ports have a curved arm that can be rotated to change the location of the arm inside of the tank making it flexible for batches with more or less yeast and trub in the bottom of the tank. I am assuming that your fermenter does not have this second fitting, otherwise you would not be asking this question.
The reason for getting rid of yeast and trub after primary is two fold. Too much yeast carried into aging can cause flavor problems if aging lasts more than a couple of weeks. This is especially important if the beer is aged warm and the yeast begins to autolyze or decay. This can lend some unpleasant yeasty, meaty, broth-like flavors to beer. Trub is good to get rid of because it too can contribute unpleasant flavors. The other benefit of removing yeast and trub is that it improves beer clarity, especially if you put the beer in a keg. There is nothing more aggravating than getting a pint full of yeast from a keg!
If you bottle your beer you want to make sure you have enough yeast for conditioning and it is possible to produce very clear beer with very little yeast given enough time. This is true of aging in general and you may want to add a very small dose of yeast at the time of bottling if you fear there may be insufficient yeast in your beer.
Most larger commercial conical fermenters do not have racking ports because they are hard to clean if not removed from the tank. This works well for smaller breweries, but when cellars are hard-piped and hooked into automated cleaning systems, such devices are difficult to deal with. These breweries have a single port on the bottom of the tank and wort, yeast and beer all flow in and out of this common port.
Brewers with this style of fermenter will remove most of the yeast from the bottom of the tank before pumping the beer out. Some of this yeast is discarded because it contains trub and much of the yeast will be saved for future use. Some brewers periodically “blow the cone” after yeast has been cropped for re-use and the beer is aging. The idea behind this practice is that the yeast that falls to the tank during aging may autolyze and this will release lots of yummy food for bacteria to feed on if there are any present. It also helps to eliminate autolyzed yeast flavors.
Again, this is done after most of the yeast intended for re-use has been cropped and the cone is blown every day or so. I know of one commercial brewer who has practiced this for years and they now do this automatically and limit the cone blows to a certain volume to minimize beer loss. If you do this you will have very little sediment when it comes time to rack the beer.
Another possibility if cone blowing is not appealing is to build a little probe of sorts that attaches to the bottom of the tank and extends straight up into the cone. This will allow sediment to fall below the tank outlet and will allow you to rack clear beer. In order to clean the tank out you will need to remove this probe, and when you do, it will be kind of messy. A fancier version of this is to have a fitting that connects to the bottom of the tank with two connections. One connection serves as the low point outlet and the second connection as a probe extending upwards. This can be a little tricky to make, but it can be done and they work well. Just like a racking arm this device should be removed from the tank for cleaning.
Conical fermenters are a bit different than using a separate primary and secondary fermenter, but once you get your technique dialed in they are much easier to use. I like that only one tank is required for fermentation and aging because that means less cleaning and also reduces the risk of contamination during transfers because there are fewer required.