Other beers brewed with the usual hops are either piney or citric. On the other hand, Kolsch beer is a balance of both. Brewing beer Kolsch style requires a special kind of top-fermenting yeast called the White Labs WLP029 German ale Kölsch yeast. It’s a German ale yeast developed and perfected over the years. But that’s not all…
German noble hops are the hops or choice with a good Kölsch. Hallertau, Tettnang, Spalt. Some brewers like Willamette, Liberty, and Fuggles. Stay away from the American citrusy hops. Transcript: Enter Martin Keen – The Homebrew Challenge to brew 99 beers styles in 99 weeks.
Kölsch (thanks to the groundwater chemistry in Cologne) tends to have a slightly mineral character in the finished beer. Unlike in an English bitter (when you should absolutely not try to mimic the so-hard-it-might-break-your-glass water quality of Burton-on-Trent), you actually do want to get a touch of that Cologne-water feel in your beer.
In 1985 as many breweries were trying to mimic these Kölsch beers, The Kölsch Konvention formed. Twenty-two brewers signed contracts stating only brewers in and around the city of Cologne could define their beers as a true Kölsch. This is why whenever American brewers have a Kölsch on tap, it is labeled as a Kölsch “style” beer.