There are three main fermentation techniques:
- Bottom fermentation is carried out at temperatures of between 4°C and 12°C, and produces light and crisp beers with dominant hop aromas (pils, lagers…)
- Spontaneous fermentation in open tanks, where wild yeast in the brewery ferment the wort. These yeasts are endemic to certain parts of Belgium. This produces acidic beers that are often aged in oak barrels (limbic, faro, gueuze).
- Top fermentation is carried out at temperatures of between 15°C and 24°C, and produces beers with denser and more complex flavor profiles (pale ale, stout, bière d’abbaye ou bière de garde).
La Parisienne is a top fermenting beer. The first fermentation last about 5 days and takes place at about 20°C, followed by a second “cold” fermentation at about 4°c for 15 to 21 days. The yeast’ work is slowed down and then stopped by the cooler temperature, causing the yeast to fall to the bottom of the vat, thus naturally clarifying and decanting the beer.
Third bottle fermentation
Once the second « cold » fermentation is over, the beer is bottled without any filtration or pasteurization. Liquor made out of beer and sugar is added during bottling in order to create sufficient carbonation, as the added sugar is transformed by the remaining yeasts whose action is re ignited by the storage in a cellar at 22°C for two to three weeks.
The young beer is then cellared for a minimum of one month at the brewery in order to develop sufficient organoleptic complexity. It is also during this phase that the beer is clarified in a totally natural way, as the inactive yeasts converge to the bottom of the bottle.
This third bottle fermentation is a totally natural process that produces a dense lather with a delicate and persistent bubble, and can be compared to a méthode champenoise. The presence of lees in the bottle brings added structure and complexity. This maturation process continues over time, allowing the beer to develop a wide range of secondary aromas, of those usually associated with champagne.