Lager yeast, also known as Saccharomyces pastorianus, is the specific type of yeast used for brewing lager style beers. Lager yeast is distinct from ale yeast, which is a top fermenting yeast that forms a thick foam at the top of the wort during fermentation.
The name “lager” actually comes from the German word “lagern,” which means “to store.” This is because lagers are typically brewed at lower temperatures and undergo a longer fermentation and conditioning process compared to ales. Lager yeast is specifically chosen for its ability to ferment at these lower temperatures, which allows for a clean and crisp flavor profile in the finished beer.
Lager yeast is a hybrid yeast strain that was first discovered in the 19th century. It is believed to be a cross between two different yeast species, Saccharomyces cerevisiae and Saccharomyces eubayanus. This hybridization gives lager yeast its unique characteristics and ability to ferment at cold temperatures.
One of the key differences between lager yeast and ale yeast is the temperature at which they ferment. Lager yeast works best at temperatures between 45-55°F (7-13°C), whereas ale yeast prefers slightly higher temperatures in the range of 60-75°F (15-24°C). This lower fermentation temperature contributes to the smooth and clean flavor profile that is characteristic of lagers.
Another important distinction is the fermentation process itself. Lager yeast is a bottom fermenting yeast, which means that it tends to sink to the bottom of the fermentation vessel during fermentation. This is in contrast to ale yeast, which rises to the top and forms a thick foam. The bottom fermentation process results in a slower and more gradual fermentation, allowing for a smoother and more refined flavor development in lagers.
Lager yeast also has a different flavor profile compared to ale yeast. It tends to produce fewer fruity and estery flavors, instead emphasizing more subtle and malt-focused characteristics. This makes it well-suited for beer styles that prioritize clean and crisp flavors, such as pilsners, helles, and bocks.
In terms of brewing process, lagers typically require a longer fermentation and conditioning period compared to ales. After the initial fermentation, lagers undergo a cold conditioning phase known as “lagering.” This can last anywhere from a few weeks to several months, depending on the beer style and desired flavor profile. During this time, the beer is stored at near-freezing temperatures, allowing for further flavor development and clarification.
Lager yeast, scientifically known as Saccharomyces pastorianus, is the specific type of yeast used for brewing lager style beers. It is a bottom fermenting yeast that works best at lower temperatures and contributes to the clean and crisp flavor profile of lagers. Lager yeast undergoes a longer fermentation and conditioning process compared to ale yeast, resulting in a smoother and more refined beer.