Why is Lager Fermented Cold?

If you’ve ever looked into how beer is brewed, you may have noticed that lagers are fermented at much colder temperatures than most other beers. This raises an obvious question: why is lager fermented cold in the first place?

The answer largely comes down to the type of yeast used to brew lagers and the flavours brewers want to create. Cold fermentation slows the activity of the yeast and helps produce the clean, crisp taste that lager beers are known for.

In this guide, we’ll explain why lagers are fermented at lower temperatures, how lager yeast behaves during fermentation, and how cold fermentation affects the flavour and character of the finished beer.

Lager Fermentation Temperature

Lager beers are typically fermented at temperatures between 7°C and 13°C (45°F–55°F). These temperatures are significantly cooler than those used when brewing ales.

Ale fermentation usually takes place at warmer temperatures, often between 18°C and 22°C (64°F–72°F). The cooler temperatures used for lagers slow down the fermentation process, meaning the yeast works more gradually to convert sugars into alcohol.

Because fermentation happens more slowly, lagers generally take longer to brew than many other types of beer.

The Role of Lager Yeast

One of the main reasons lagers are fermented cold is the type of yeast used in brewing them. Lagers are brewed using a strain of yeast known as Saccharomyces pastorianus, commonly referred to as lager yeast. Unlike ale yeast, which works best at warmer temperatures, lager yeast performs most effectively in cooler conditions.

This yeast is also often described as bottom-fermenting yeast, meaning that during fermentation it tends to settle toward the bottom of the fermentation vessel rather than rising to the top like ale yeast. These characteristics make it particularly suited to colder fermentation temperatures.

Why Cold Fermentation Produces a Cleaner Taste

Fermenting beer at colder temperatures has a significant impact on flavour. When yeast ferments beer at warmer temperatures, it tends to produce more esters and other flavour compounds. These can create fruity, spicy, or complex flavours that are common in many ale styles.

Cold fermentation slows the yeast down, which means fewer of these flavour compounds are produced. The result is a beer with a cleaner, smoother and crisper flavour profile. This clean character is one of the defining traits of lager beers and is part of the reason they are so widely enjoyed around the world.

Cold Fermentation vs Ale Fermentation

One of the main differences between lagers and ales is the temperature at which they are fermented. Ales are brewed using top-fermenting yeast that thrives at warmer temperatures. This warmer fermentation encourages the production of fruity and aromatic compounds, giving many ales their bold and complex flavours.

Lagers, on the other hand, are brewed using bottom-fermenting yeast that works best in colder conditions. Because fermentation happens more slowly and produces fewer flavour compounds, lagers typically have a lighter, cleaner taste. While both types of beer follow the same basic brewing process, fermentation temperature plays a major role in shaping the final flavour.

What Happens After Fermentation (Lagering)

After fermentation is complete, most lagers go through another important stage known as lagering. During lagering, the beer is stored at near-freezing temperatures for several weeks or sometimes months. This cold storage allows yeast and other particles to settle out of the beer, helping to improve clarity and smoothness.

Lagering also allows flavours to mellow and balance out over time. This step is one of the reasons many lagers have such a clean, crisp finish. If you want to learn more about how this process works and why it gave lager its name, you can read our full guide explaining why lager is called lager.

Why Lagers Take Longer to Brew

Because lagers are fermented at colder temperatures and often undergo a long lagering period, they generally take longer to produce than many ales. Cold fermentation slows down yeast activity, meaning fermentation itself takes more time. After that, the beer may spend additional weeks maturing during the lagering stage. While this slower process requires more patience, it helps create the clean, smooth character that makes lager one of the most popular beer styles in the world.

Cold fermentation is one of the defining features of lager brewing and plays a major role in creating the smooth, crisp character that these beers are known for. If you’d like to learn more about how lagers are brewed, the different styles of lager, and what makes them unique, be sure to check out our complete guide to lager beer.