A fermentation cellar is a special room in which the fermentation process during beer production takes place in a controlled manner. For this process, the brewer brings beer wort and yeast together in a controlled manner, as the temperature, humidity and air circulation in the fermenting cellar must be precisely controlled in order to achieve the best quality. On its way to the cellar, the chilled wort is added with yeast and supplied with sterile air to ensure yeast propagation. The amount of yeast used is approx. 0.5-1.0 liters per yeast per hectoliter of cold wort – this corresponds to approx. 15 million yeast cells per milliliter of wort.
During fermentation, the fermentable sugars in the wort are converted into alcohol and carbon dioxide. Cooling the fermenter counteracts the heat generated during the process. Brewers are talking about draught beer right now. The new beer is fermented with yeast in the fermentation cellar. During this process, the maltose molecules dissolved in the beer are converted into alcohol and carbon dioxide. Some breweries also use this fermentation to harvest new yeast. The fermentation times are 8 to 12 days for bottom-fermented beers and 4 to 6 days for top-fermented beers. During the last 2 days of fermentation, the green beer is slowly cooled to around 3°C. The sugar is then almost fermented and the cooling facilitates the removal of the yeast. During fermentation, brewers distinguish between bottom-fermenting and top-fermenting yeast and beer. In general, it can be said that bottom-fermenting yeast settles at the bottom of the kettle at the end of fermentation, while top-fermenting yeast rises to the surface of the draught beer. In the classic production method, bottom-fermented beers are fermented cold (up to 10°C) and top-fermented beers are fermented warm (16°C to 25°C).