Episode #4 now up at http://www.brewingtv.com
We talk with Jeremy King, a yeast guru about the mystery of open fermentation. Turns out, not so mysterious after all and totally doable for homebrewers. BTV’s own Mike Dawson gives it a whirl and takes his top off.
all for brew, brew for all!
Good show, I just watched it.
That fish gutter thing is really neat and would make a great cool ship as well. Have you guys ever compared the beers made in an open bucket fermentation vs. the fish gutter?
The 3068 fermentation was surprisingly tame based on my experiences. I currently have one at 17 C and it is pushing out of the bucket which is covered with a pot lid.
Kai
I just watched it too, and I’m skeptical that there is a big difference between a bucket with a lid and airlokc and one open for three days. Especially if you peek each day. Of course I have correlated an increased inceidence of acetobacter infection, with my peeking activity.
The fish gutter thing, I could see that making somewhat more of a difference as far as oxygen.
It was definitely and interesting watch. There was one thing mentioned that I saw a problem with. There was a statement that the CO2 holds a cloud about the wort not allowing anything to get into it. Well, what about the first 4-6 hours when there is not activity? It’s not as if you pitch and magically CO2 starts. Is there something (like a cheese cloth) placed on top during this time period?
Here’s a British Pale Ale recipe that a local homebrew club did. Steve Jones, the brewer at Oliver’s (a local British brewpub… if you’ve been to The Wharf Rat / Pratt Street Ale House by Camden Yards, he’s been the brewer there for 13 years), was kind enough to give his complete recipe. He uses Ringwood exclusively, on a Peter Austin open fermentation system. One thing to note is not just the open fermentation, but the mixing/rousing that happens repeatedly during the first half of fermentation. I would assume that this contributes a decent amount of O2, in addition to driving off CO2.
http://www.crabsbrew.org/index.php?option=com_content&view=article&id=63&Itemid=65
That is definitely a problem in a homebrew setting. In a brewery where they are repitching active yeast, fermentation begins much more quickly than at home.
I’d say a cheesecloth is a good practical way to prevent contamination during the entire process, while staying true to the notion of open fermentation. Its traditional too.
Most homebrewers who use open fermentation recommend keeping the fermenter covered until active fermentation is under way.
That’s been my practice. I think I get less foaming / blowoff that way. When the krausen starts falling I clamp it shut. Plus I like peeking and the occasional top cropping and when the lid isn’t clamped on it’s easier.
Last year I didn’t get the ester profile that I wanted in my Belgians with the lid loose which may have been from over O2-ing but I think I’m going to keep things tight this year just to make sure.
Thats opposite of what is supposed to happen with open fermentation, it is supposed to result in more esters. I guess the question is, more than what?
Maybe I won’t change that then. One variable at a time. Last year I used O2 to aerate. This year I will be using my wine whip.
I tried open fermentation on a couple batches about 8-10 years back. I really couldn’t detect any difference in the beers I used it for, so I stopped doing it.
II wonder what aspect of open fermentation is the causing those esters. I have a hard time believing it is the lower pressure by not having an airlock. Maybe it is the O2 that gets to the yeast? But that O2 only gets to the top of the Kraeusen and not beyond that.
In commercial brewing the depth of fermenters used for open fermentation vs. the depth of the conicals used for closed fermentation can easily make a difference. But in home brewing there is not much change.
W/o seeing, or better yet tasting, a good side-by-side experiment done on that subject I’m leery to jump to conclusions here.
This does not mean interested brewers should not give this technique a try.
Kai
I think this is where I got the idea in my head:
“If pressure is applied above 1 bar a formation of higher esters is visible. This
can also happen in tall fermentation vessels due to pressure. On the
contrary, open or shallow vessels will give lower ester levels.”
That’s from a paper posted in this thread:
http://www.homebrewersassociation.org/forum/index.php?topic=185.0
There seemed to be some evidence to the contrary though later on in the thread.
Also, I wonder what the pressure increase is inside a closed fermenting bucket / carboy.
To my knowledge it is the other way around. Increased pressure reduces esters and fusel alcohols. Pressure fermentation can therefore be conducted at higher fermentation temperatures w/o the usual side effects of increased esters or higher alcohols.
The pressure in a bucket or carboy is ambient pressure (1 bar) on top and ~1.05 on the bottom if I assume the beer stands about 50 cm (1.5 ft) high.
In a 30ft conical the pressure in the cone is about 2 bar. For every 10 m (30ft) of water or beer depth there is a pressure increase of about 1 bar.
Kai
Very interesting. This method has been practiced for a very long time. I’ve seen photos of open fermenters in large breweries where they were skimming off the yeast for reuse. I wonder what if any kind of contamination occurs during this process.
Will there be any pressure due to an airlock or blowoff tube (possibly a tiny amount)? I imagine there is some resistence there, maybe more so in the case of the blowoff tube. Maybe it’s insignificant.
That’s how I formed my opinion, and I totally agree with you, Kai.
Yes, it is about the same pressure difference as placing the carboy a few floors higher. I calculated this once and the pressure caused by ~2 cm worth of water column in the air lock is really small.
My conclusion was that if this pressure difference makes a difference in beer taste those of us living on the coast would be making much more estery beers than those who live high up in the mountains.
Kai