Hops

Does hops actually grow in Cologne? No, cultivation plays no meaningful role in the city or its surroundings. Cologne's brewers buy their hops from German growing regions, above all from the Hallertau in Bavaria, whose hops have held PGI status since 2010. Which specific varieties go into which brand is treated by most breweries as a trade secret.

The Convention calls for a beer that is 'hop-forward.' What's meant is a clearly noticeable yet gentle bitterness that doesn't scratch on the palate. According to the BJCP guidelines, Kölsch sits at 18 to 30 IBU (International Bitterness Units, a measure of bitterness). A German Pils, by comparison, reaches 22 to 40, and an Altbier 25 to 50.

When it comes to hopping, brewers distinguish between bittering hops and aroma hops. Adding hops early in the kettle boil extracts bitterness, since the hop acids only dissolve properly with longer boiling. Adding them late in the boil instead yields more aroma, because the volatile oils would otherwise simply boil off as steam. Kölsch favors restraint: a touch of floral and herbal character, nothing overstated.

You can really taste the result by trying a Kölsch and a Pils side by side. The Pils bites back a bit harder in the finish, while the Kölsch ends softer and drier. A high degree of fermentation helps with this, since less residual sugar means less to soften the bitterness. The hops remain a supporting player, not the star, and that's exactly part of the style. You can't see it in the glass, but you can taste it right away whether Reissdorf, Päffgen, or another house has leaned more toward aroma or more toward bitterness.