A primer on yeast strains and Belgians

The story of yeast management and Belgian beers is a fascinating one, as the practices differ significantly when compared to more common styles. The following article provides some observations about the Belgian phenomenon.

Much of the material comes from a talk given by White Labs president Chris White at The Spirit of Belgium 2001, held January 13 and 14 in Arlington, Virg. The accompanying graphic gives details about the differences between Belgian yeast strains offered by White Labs.

We’ll begin the story in 1881, when Emil Christian Hansen developed pure culture techniques. Before this time, Belgian style beers were, well, simply beer. But by isolating a particular strain of yeast, Hansen’s discovery showed that one could make what one encyclopedia calls "dependable beers."

Lager onslaught

The discovery made widespread lager brewing possible. Ale and Belgian styles began to fade, and lagers took over the world, a trend that was only somewhat slowed by the renaissance of craft brewing in the past two decades. More recently, brewers are discovering that Belgians are to craft brewing what paint is to a painter. While a few years ago Belgians were hard to find at American microbreweries, today about one in ten have a Belgian or two on tap. And the number is increasing rapidly.

But we get ahead of ourselves. While the world became enchanted with clean-tasting beers, the Belgians stuck to their traditional styles and wild yeast. (This of course changed over time. Lagers are now the most popular beers in Belgian, too, but the traditional styles still flourish in small and medium size breweries around the country).

The diversity of Belgian beers almost defies classification, but most fall into the following styles: Belgian Ale; Belgian Strong Ale; Biere de Garde; Flanders Brown and Red Ale; Grand Cru; Lambics — Gueze, Kriek, Saison; Trappist ales — Dubbel and Tripel; Witbier; and Pilsner.

Belgian beers are characterized by significant yeast character — aromatic, fruity, phenolic, strong, dry. What yeast compounds contribute to the flavor of Belgian beers? Esters — ethyl acetate (solvent); isoamyl acetate (banana); alcohols — isoamyl alcohol, 2,3-butanediol; acetaldehyde (green apple); diacetyl; sulfur compounds (H2S, DMS); and phenolics.

Characteristics of Belgian fermentation include increased phenol production. These are hydroxylated aromatic rings, aromatic alcohols. It is the same kind of compounds used in antiseptics and is less volatile than aliphatic fusel alcohols.

Attenuation and flocculation is also much different than in normal brewers yeast. Some old Saison strains only attenuate 50 percent. They have to have very low initial gravities — in the mid-1020s. And the cells are usually smaller than other brewing yeast and are less-clustered. What does this low attenuation mean to brewers? Well, this is one of the main reasons that the strains are mixed, to increase the attenuation.

Things have changed at Belgian breweries ove the past century. Many have adopted modern brewing techniques. Father Theodore isolated Chimay yeast in 1948, by the use of pure culture techniques. Chimay beers have been brewed with pure strains ever since.

To Belgian brewers, yeast is everything, it is sacred. The rest of the brewing process and ingredients are not as heavily guarded. Indeed, some of the larger Belgian breweries and even small ones have some of the most sophisticated lab equipment and procedures in the industry. And their quality control is second to none.