Fermentation
The wort is pitched with yeast in large pitching tuns at 16.25 - 18.75º C then after 8-12 hours transferred to smaller fermentation tuns where the fermentation really starts.
At the start of fermentation, a black "pitch" consisting of yeast, hop resin, protein and wheat fat forms on top of the wort. This has to be carefully removed. The head isn't beautiful but consists of large bubbles and is quite loose. As fermentation progresses, a white covering of yeast develops which lasts throughout fermentation. Yeast for repitching is harvested from the centre, before the head starts to collapse.
Fermenation takes 3 to 5 days, depending on the pitching temperature, the amount of yeast pitched, cellar temperture and size of the fermentation temperature.
Usually 1 litre of yeast is pitched per 5 hl wort.
Fermenting vessels vary enormously in size - from 4 hl to over 100 hl.
The pitching tun is huge in large breweries - as much as 600 - 700 hl.
The pitching and fermenting tuns are not lacquered. The lactic acid produced in the fermentation eats away the lacquer very quickly.
Fermentation temperature varies between 17.5 and 20º C.
The higher the fermentaion temperature, the sourer the finished beer.
The fermentation is a combination of the action of the yeast and lactobacillus.
The lactobacillus is more anaerobic than aerobic. It grows faster in closed bottles than in open vessels.
I think that will do for today. Though we aren't finished with fermentation yet.
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