Kolsch and altbier yeast strains
Cologne and Dusseldorf sit about 40 km apart on the Rhine. Each city kept brewing top-fermented ale while the rest of Germany moved to lager, then learned to make that ale taste almost as clean. The yeast strains behind them are worth knowing.
Two cities kept ale yeast alive
Kölsch comes from Cologne. It is a pale, delicate beer, usually around 4.8% ABV, with a soft malt character and a faint fruitiness. Under an agreement among the city's brewers, known as the Kölsch Konvention, the name is reserved for beer brewed in and around Cologne. It is also protected as a geographical indication in the European Union.
Altbier comes from Düsseldorf. Alt means old, a reference to the older top-fermenting method. It is copper to brown, malt-forward and firmly bitter. Our altbier guide covers the style itself.
Both are ales. Both are fermented cooler than most ales and then stored cold for weeks, much like a lager.
Kolsch strains ferment cool and drop slowly
The common liquid Kölsch strains are White Labs WLP029 German Ale/Kölsch and Wyeast 2565 Kölsch. Both are typically fermented at around 13 to 16 °C, well below a normal ale. At those temperatures they make very few esters. What they do make is a light white wine or pear note that suits the style.
They are powdery yeasts with low flocculation. A Kölsch can stay hazy for weeks. Cold storage at close to 0 °C for three to four weeks, or a fining agent, brings it bright. Do not judge the beer in the first week.
Altbier strains handle a wider range
For altbier, White Labs WLP036 Düsseldorf Alt and Wyeast 1007 German Ale are the usual liquid choices. They ferment cleanly at similar cool temperatures (around 13 to 18 °C) and attenuate well, which keeps a malty beer from tasting heavy. Wyeast 1007 in particular is known for tolerating the low end of that range.
These strains are less fussy about clarity than the Kölsch yeasts but still benefit from a few weeks of cold conditioning. An altbier that goes straight from fermenter to glass can taste a little rough around the edges.
A dry option exists for warm kitchens
Liquid yeast is hard to keep alive on a summer delivery in most Indian cities. Fermentis SafAle K-97, sold as a German ale yeast, is the dry strain most often used for Kölsch-style and altbier homebrews. It ferments cleanly in the mid to high teens and forms a thick head of foam during fermentation, so leave room in the fermenter.
It will not taste exactly like a Cologne beer. It will taste clean and bright, which is most of the battle.
Temperature control decides the result
The clean profile depends on staying cool. At 22 or 24 °C, the temperature of many Indian kitchens for much of the year, these strains produce more fruit and some fusel alcohol. The beer becomes a pleasant pale ale rather than a Kölsch.
Without a fermentation fridge, ferment in the coolest room of the house and use a water bath with frozen bottles swapped twice a day. Holding 16 to 18 °C this way is realistic. Our guide to brewing a Kölsch-style ale without a lager fridge walks through the method.
The grist and hops keep out of the yeast's way
Because these yeasts are so clean, the malt and hops show through clearly. A Kölsch is usually built almost entirely on pilsner malt, sometimes with up to about 10% wheat malt. It is bittered to around 18 to 30 IBU with German noble-type hops. Anything heavier hides the delicate fruit the yeast gives.
An altbier uses more colour and more bitterness. Pilsner and Munich malt make up most of the grist, with a little dark caramel or a few percent of roasted malt for colour. Bitterness is firm, often 35 to 50 IBU, yet the beer should finish dry rather than harsh. Soft water helps both styles. If your tap or borewell water is very hard, cut it with filtered or RO water before brewing.
Cold conditioning is part of the recipe
After fermentation the beer needs time near freezing. Both styles traditionally spend weeks in cold storage, which drops yeast, smooths the flavour and lets sulphur notes fade. Three to four weeks at 0 to 2 °C in a fridge is a reasonable home version.
Bottle conditioning works too, but keep the bottles cool once carbonated. A Kölsch that sits in a warm cupboard for a month loses the crisp edge that makes it worth brewing.
Start with one strain and one recipe
Choose either style and brew a simple recipe: mostly pilsner malt for a Kölsch, pilsner and Munich malt for an altbier. Use a single strain and write down the fermentation temperature every day. When you taste the finished beer, compare it with what the temperature log shows. That habit, tying a flavour to a number, is what turns homebrewing into brewing.
Common questions
Is Kolsch an ale or a lager?
Kölsch is an ale, fermented with top-fermenting yeast. It is fermented cool and stored cold, which gives it a lager-like crispness.
What temperature should I ferment a Kolsch at?
Around 13 to 16 °C for the classic liquid strains. Warmer fermentation makes it fruitier.
Why is my Kolsch still cloudy?
Kölsch strains are low flocculating. Several weeks of cold storage near 0 °C usually clears the beer.
Can I use the same yeast for Kolsch and altbier?
Many brewers do. Dry K-97 is a common choice for both, though dedicated strains give a more authentic result.
