Yeast & Fermentation

In Kelheim, two worlds ferment side by side. The monastery beer from Weltenburg is bottom-fermented, while the wheat beer from the Bräuhaus in the old town is top-fermented. The difference lies in the yeast: bottom-fermenting yeast works at cooler temperatures and sinks to the bottom when finished, while top-fermenting yeast works warmer and rises to the surface.

A Dunkel like the Barock Dunkel ferments at low temperatures of around 8 to 10°C. Fermentation proceeds slowly, the yeast produces almost no fruity esters, and the beer tastes cleanly of malt. It's then cold-conditioned for weeks afterward so the flavor rounds out and suspended particles settle.

Wheat yeast is a different animal. It ferments at around 18 to 24°C, almost room temperature, and in doing so produces aromatic compounds: esters that smell of banana and phenols reminiscent of clove. These aromas are the signature of wheat beer, and they come from the yeast, not from any added spices.

Because wheat yeast isn't fully separated out after fermentation, Hefeweizen stays cloudy — and that's by design. Kristallweizen, by contrast, is a filtered wheat beer without the yeast haze.

A Weizenbock like Schneider's Aventinus needs more time, because the yeast has to work harder against the higher sugar content, and a strong beer needs to mature carefully. The yeast remains top-fermenting; only the sugar content of the wort increases.

Kloster Weltenburg and the Weißes Bräuhaus thus demonstrate, within just a few miles of each other, how differently beer can taste even though both are made from nothing more than water, malt, hops, and yeast. Exactly how long the beers age in Kelheim and Weltenburg depends on the brewery and isn't specified here.