The German Lager

Compared to the Belgians, German beers are rather monotonous. Instead of using ale yeast, lager yeast (a more chilled out yeast) is used in the brewing process. There are two historical events to thank for all this: a beer purity law and a duke. The law was called the Reinheitsgebot and it said that beer could only be made from barley, water, and hops. As for the duke, well, he really liked predictable beer flavors, so he insisted people only brew between September 29th and April 23rd.

not lagers
I know I wrote a whole post about lagers, but personally, I hate them and have no pictures of them. So here is a double flight of mostly Belgian golden ales. Use your imagination, pretend we’re in Germany.


If you’re a baker, you’ll know that keeping ingredients consistent is important, but not quite as important as baking your bread at the right temperature. So, brewing beer in the colder months of the year (thanks to the duke) meant that the beers were inadvertently being lagered. This process produced beers that had less off-flavors and a more consistent taste. No one knew about yeast back then, but this practice of brewing at lower temperatures meant that when lager yeasts emerged, they became wildly popular in a short amount of time. No longer did brewers have to deal with the temperamental and feisty ale yeast.

S. cerevisiae

The official name for ale yeast is Saccharomyces cerevisiae. They ferment at the top of the barrel and produce nice white foam. They also have a bad habit of sucking in whatever is in the air. It’s fine if the air smells like grass or hay or apples, but not so great if it smells like cow manure. Today, there are hundreds of strains of S. cerevisiae. You can think of them like domesticated dogs: really helpful, though some may bite, and everyone has a favorite breed.

Hybrid Yeast

On one of the trips to South America, someone somewhere picked up a hitchhiker yeast called Saccharomyces eubaynus. Back in Europe, S. eubaynus and S. cerevisiae met, made love (aka: sexually reproduced and sporulated), and produced little hybrid yeast offspring. Scientists isolated and identified them in the 70’s, naming them Saccharomyces pastorianus, after the Father of Germ Theory, Louis Pasteur. We call them lager yeasts. They ferment beer at the bottom of the barrel, tolerate cold temperatures better and produce easy-to-drink, low alcohol, golden brew. Bottom fermenters also don’t suck in weird smells from the air. Commercial beer makers capitalized on these attributes and now, almost all commercial beers are lagers.

A Kölsch in Cologne

The Kölsch and the Altbier

If you visit Cologne and Dusseldorf, make sure to try a Kölsch and Altbier, respectively. These German beers are still made in the traditional way: fermented by S. cerevisiae, twice: the first time at higher temperatures and the second time at low temperatures. The result is a “hybrid” beer that looks like a lager, but tastes fruitier and sweeter. For a fun Cologne bar experiment, order a Kölsch and a commercial lager like the Pilsner Urquell. Drink them side by side (yes, double fist it!), can you taste the difference?