[Kaiser]

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."
 

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

[bluesman]

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.

[ndcube]

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.

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.

[denny]

This does not mean interested brewers should not give this technique a try.

That's how I formed my opinion, and I totally agree with you, Kai.

[Kaiser]

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.

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.

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

[hopfenundmalz]

The yeast is one of the variables here.  True top croppers will perform better, from what I have read.  The Peter Austin Ringwood and WLP Essex strains come to mind.

The German Wheat beer strains are said to like open fermenters.  If you are ever at Sierra Nevada's Taproom in Chico, there is a small window at the left end of the bar.  Go look in, and you might see the Kellerweiss fermenting in the open fermenters.  They put these in for that beer, from what I understand.  Most everything else in in big to huge conicals for the Chico Strain.

[jkeeler]

hey guys, glad to see we sparked a healthy discussion of the technique as it applies to homebrewing.

The more technical aspects aside, the fermentation went off without a hitch!  No contamination and certainly fa more esters produced (at least on the nose).

Mike is kegging the beer this weekend and we will be doing some tasting notes early in the week.  We'll compare the batch to a closed fermented hefe, another wheat beer (from episode #1 actually) and some commercial examples.  We'll film this and put it on next week's episode, 6/11...so look for that for the report!

The recipe Mike used for this open fermentation is his house Hefe recipe, so he's been making it a long time with very consistent results.  I'm guessing he will be able to detect the differences.  He's also a BJCP certified judge, so he'll give the beer hell with his critique.

happy brewing!

[dean]

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?

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.

Okay Denny, gotta ask.  Since you're Mr. Cheap'n EZ, why did you start sealing it and using an airlock then?   

[denny]

Okay Denny, gotta ask.  Since you're Mr. Cheap'n EZ, why did you start sealing it and using an airlock then?   

Because I already had the stuff to seal it...it wasn't like I had to go buy it.  I guess I could have just kept going with open fermentation, but if you saw the condition of the room I ferment in, you'd understand why I was nervous about that.  It was an experiment and when I didn't see any benefit, I went back to the old way.  Maybe more experimentation using different yeasts would have given me different results, but I wasn't interested.