The distinction between top- and bottom-fermented beers is familiar to all homebrewers, but the term “hybrid” is often met with curiosity. And while many of our styles were forged by the clash of ingredients, technology, and local and outside influences, there are a few that are defined by their own duality. California common and cream ale are two that Americans can claim as true hybrids.
The more elusive, though, are German Kölsch and altbier of the Rhine Valley. Not only are they quite different from all other German brews, but each is also distinctive enough to be the calling card of a city, and it is this provenance that sets them apart.
The two cities that they call home, Köln (Cologne) and Düsseldorf, are separated by barely 20 miles, but the cultural differences and rivalries are great. Ironically, the two beers share some essential brewing methods, and they are both something of a challenge to make well. If you’re up to the task, they can be brewed by following a few unique and rigid guidelines. Beyond that, the possibilities are actually rather broad if you want to make some interesting and very personalized hybrids, German-accented or otherwise.
Kölsch and altbier combine top fermentation (typical of ales) and cold conditioning (typical of lagers). I love the self-explanatory, seemingly oxymoronic designation obergaerige lagerbier (top-fermented lager beer) that is often used to refer to these two indigenous German brews.
The yeasts used for both are specialized, selected over centuries to accommodate the environs and critical to their brewing. Tailored to the mild climate of the Lower Rhine Valley, Kölsch and altbier yeast work most comfortably at 55 to 65 degrees F, conditions that suppress the fruity esters and spicy notes associated with the ales of Britain and the other top-fermented brews of Europe.
Lagering is done at a modest 40 degrees F for about four to six weeks, warmer than the near-freezing condition of bottom-fermented lagerbiers. The character of the yeast and the lagering method suggest that these strains have been culled from bottom fermenters but adapted to slightly higher temperatures (much like the California Lager yeast used to make California common).
Beyond that, brewing Kölsch and altbier is merely a matter of selecting a proper grain bill and hop schedule, and selecting one of the several yeasts available to craft your homebrew. The stickiest requirement is ensuring that the yeast is comfortable during fermentation, always a consideration, but more so with these.
Kölschbier is the lighter of the two, always a shade of gold. This means, of course, that it is made primarily with Continental pilsner malt, and usually that malt alone. A simple bill of pilsner malt from Germany or Belgium, mashed for high fermentability, will produce classic Kölsch. Traditional wort strength is OG 1044 to 1048. I like to mash at about 148 degrees F, leaving little residual dextrine.
Malted wheat is not a stranger to Kölschbier grist, and it will add a bit of mouthfeel and depth. A touch of Vienna malt, up to 15 percent, will also provide extra character and deeper gold color.
Should you opt for a more dextrinous brew, mash into the low 150s, or use about 5 percent dextrine malt in the grist. Caramel flavors are not part of the Kölsch profile, so stick with dextrine malt over light caramel/crystal varieties. If you use American two-row malt, light specialty or toasted malt addition is advised. Extract brewers should use the lightest malt extract available, either on its own or with a touch of wheat or Munich malt extract.
K. Florian Klemp
K. Florian Klemp is an award-winning homebrewer who thinks there is no more sublime marriage than that of art and science.