After boiling, the mash becomes completely sterile. To bring new life to the beer and to ensure that the yeast, which will shortly be added, can do its work, a temperature suitable for fermentative action is necessary.

In our top fermentation process the temperature is taken to 22° C. Apart from this ideal temperature, oxygen must be also present to make the mash suitable for the action of the yeast. The mash is therefore oxygenated during the cooling, before being passed to the fermenting vat.