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brewing process
Belgium has a large variety of top-fermentation beers in the full range of density and colour,
flavour and aroma, with or without bottle conditioning: “Spéciale Belge Ale” amber beers,
Trappist beers, abbey beers, white beers, heavy blond, saisons.
Top-fermentation beers bear the signature flavour of the brewing water, selected malts,
unmalted wheat, rice or maize, hops, herbs and spices and yeast.
Brewing water
Unlike the extremely low mineral content of pilsner brewing water, brewing water for top-
fermentation beer is high in calcium, magnesium and their salts, sulphates and chlorides.
These range from pale to amber or dark brown, coloured in the kiln or torrefied in the
drum (direct flame). It is mainly the malt grain that determines the basic flavour of top-
fermentation beers.
Unmalted wheat (up to 40% max)
For white beers.
Rice or maize
These do not contain any proteins and are used to reduce the protein concentration in
the malt, which is sometimes too high.
To obtain heavy beers and a high degree of fermentation.
Bitter hopping:
for top-fermentation beers, high alpha, non-sour hop varieties added at
the start of the boiling process are mainly used to bitter the beer.
A selection of aroma hops is added at a later stage and provides the desired aroma
Late hopping:
aroma hops are added at the end of the boiling process in order to pre-
vent the hop aroma from being lost due to evaporation as the brew is boiling.
Dry hopping:
extreme hop aromas are obtained by adding aroma hops after the fer-
mentation process, so that alcohol-soluble hop oils are also released.
The use of hops became widespread in the 15th century. Before then, all beers were
flavoured with herbs and spices. However, herbs and spices still contribute to the com-
plexity of the flavour and aroma in hopped beers. A blend of herbs and spices is known
as a “gruut”. Some frequently used herbs and spices are bog myrtle, rosemary, corian-
der, juniper berry, cinnamon, anis seed, cloves, sage and bay leaf.
Fermentation process
A yeast strain selected from the top-fermenting species known as
, which is active at high temperatures (ambient temperature 15°C to 25°C), is
used to ferment the brew.
Top-fermenting yeasts can be divided into two subspecies:
• non-phenolic: top-fermenting yeasts that are
exclusively fruity
and thus do not
give off a phenolic, smoked aroma
• phenolic: top-fermenting yeasts that give off a
smoked, phenolic aroma
mented by a more or less discernible fruitiness
Thanks to its top-fermentation beer brewing tradition handed down across the genera-
tions, PALM Breweries has amassed an impressive collection of yeast strains. Every
yeast strain has its own “character”; in other words, its physical behaviour during fer-
mentation and the aroma it creates.
After the main fermentation, which takes 5 to 7 days, the brew is subjected to a warm
maturation phase (lagering) at approximately 20°C until the apple scent (acetaldehyde)
and the rancid butter odour (diacetyl) have disappeared. After this the brew is chilled to
0°C. The cool temperature helps to flocculate excess tannins and proteins (forming cold
turbid matter) and to precipitate the yeast, which further refines the flavour.
Brewer Stijn Bundervoet