Re: Open fermentation?
- I used to work in a brewery (UK) that had large open fermenters. The
reason is as Harry & others have said- CO2 is heavy, so it collects.
However, thats not all. The fermenter must only be filled about 3/4
full, this allows for a good head of CO2 to sit ontop of the brew. In
the UK, top fermenting English Ale yeast has the property of creating
a thick, foaming head during the early vigourous ferementation, then
an almost leathery crust in the latter half of the fermentation.
The CO2 sits ontop of the crust.
We used to barral the beer via a tap at the base of the tank, and the
crust would drop with the beer, staying totally intact. I often
remeber seeing dead flies and wasps lying ontop of the crust, but the
beer was as never effected. The flies were dead becuase the
fermentation created an anoxic environment.
So why cant you do it at home? Well, there's two reasons: we dont
have fermentations large enough to make HUGE amounts of CO2- a
healthy breeze would blow away the CO2 from the top of an open 5
gallon polythene bin, and secondly, we dont culture our own yeasts,
so we're stating from scratch every time, with a yeast which is a
good all-rounder, but not perfect for YOUR recipe, with YOUR water
qualitym and YOUR fermentation temperatures. This is why comercial
breweries maintain there own yeasts, and its a very importance