February 10, 2022


Fermentation is essential to the creation of the magical elixir known as beer. Lagers go through a unique cold fermentation process that many people don't know about. This process is essential to this beer style and gives the beer its iconic characteristics. Whether you're just curious about the brewing process or interested in home brewing yourself, we'll help you gain a better understanding of cold fermentation and the science behind brewing.


What is Cold Fermentation?

Generally, lager yeasts are best fermented at temperatures between 48 and 58 degrees Fahrenheit. This initial fermentation period for a lager is typically about a week, depending on the gravity of the beer. You can learn more about fermentation in our beginner's guide here.

After the first fermentation phase, is the cold fermentation stage, also known as lagering or cold conditioning. This secondary fermentation phase can last anywhere from two to three weeks at a temperature of 32 degrees Fahrenheit. During this unique cold aging process, yeasts and other proteins are precipitated out, producing the crisp, smooth lager that is iconic to the beer style.


The Right Equipment

This process is essential to the lager brewing process, which means that when brewing a lager, it will require a dedicated temperature-controlled space for the lagering process. To save space in your home and for convenience, a homebrew kegerator is the ideal piece of equipment to do it all! That's right, if you find the right homebrew kegerator with a wide temperature range, you can use it for every stage of the process. From your first fermentation stage all the way to dispensing, this kegerator will do all the work for you and more! The Kegco Homebrew Kegerators are designed with a temperature range from 35 to 42 degrees Fahrenheit, which is wide enough for first fermentation, second fermentation, and beer storage and dispensing! These are the ultimate homebrewer's kegerators because they are designed to do it all and take up as little space as possible. With digital temperature controls, you can precisely set the temperature you need for every step of your brewing process. The spacious cabinet interior allows you to store up to three 5 gallon Cornelius ball lock homebrew kegs or a large fermentation vessel. This dedicated brewing space will prevent your brews from taking up precious space in your home or refrigerator. Plus, the temperature is much more precise, which we all know is essential for fermentation. We have a dedicated article on fermentation basics here. Maintaining strict temperatures with your kegerator ensures your yeasts will behave as intended and your resulting brew will be perfect!


Understanding The Process

As you may already know, during fermentation yeasts consume sugars that produce carbon dioxide and a variety of aroma and flavor molecules. When fermented at room temperature, yeasts consume sugars rapidly and are exhausted quickly, preventing the production of additional gases and flavor compounds.

When fermented at cold temperatures, yeasts produce carbon dioxide and other molecules more slowly and steadily. This much slower process results in a more complex combination of flavor compounds. Heat accelerates the chemical reactions and the faster the sugar is converted into alcohol. This is also why lagers have a lower alcohol content than ales. If you want to learn more about the difference between ales and lagers read our in-depth article here.


The Benefits of Cold Fermentation

Since so much of the flavor and characteristics of the beer is developed during fermentation, brewers go through great lengths to ferment their beer. Cold fermentation is such a prized and valued process by brewers because it is known to:

  • a more notable mouthfeel
  • excellent foam
  • a nobler taste
  • lower alcohol content
  • improved clarity
  • a fuller body
  • mellower to the palate

During lagering, the beer undergoes subtle, but significant, flavor-altering biochemical processes that are responsible for the crisp and clean characteristics we associate with a good lager. This cold fermentation process reduces any acetic and lactic acids whose effects on beer flavor tend to be marginal because they have a much higher taste threshold to humans. Instead, the prolonged fermentation period that these lagers go through develops more desirable and impactful flavors.

Traditionally, when the beer reaches the lagering stage it frequently still contains a small fraction of the sugar that was originally present at the start of fermentation. Approximately, four-fifths of this residual sugar is made up of easily fermentable maltose; the rest is mostly maltotriose. During cold fermentation, the total residual sugar content of the beer usually drops by as much as 50%. The beer slowly carbonates as the yeast processes the remaining fermentable sugar and if any oxygen was introduced during the transfer to the lagering tanks, it is possible for yeast to scavenge, limiting potential damage to beer flavor and appearance.

When done properly, only the desirable flavors and characteristics will be in the resulting lager. These characteristics that are developed during this process are cherished by brewers because not only are they signs of a well-crafted beer but it greatly affects the resulting taste of the beer.


What Is Cold Crashing?

A result of cold fermentation is clearer beer due to the rapid chilling of the liquid, which allows the solid particulates to separate from the liquid. Cold crashing is a similar process, prior to packaging, the fermented beer is rapidly chilled. This allows the brewer to easily remove the liquid from any yeast particulates.

Rapidly decreasing the temperature of a colloidal solution encourages the coagulation of particulates such as proteins and yeast, and as these particulates coagulate, they become heavy enough to drop out of the solution. Then, the brewer can easily extract the liquid without the solids creating a foggy and hazy appearance to the beer. This is how lagers can appear so crystal clear.

While cold fermentation is a slower process than cold crashing, it still results in a crystal clear beer and a light mouthfeel. The prolonged lagering stage not only encompasses the benefits of cold crashing your beer but also helps develop the flavor and the distinct characteristics of a lager.


Why is Cold Fermentation Needed to Brew Lagers?

Since lagers are known for their light texture and their very clear appearance, a warm fermentation will not do. A warm fermentation will keep the yeasts incredibly active and it will cause the yeasts to consume the residue sugars rapidly, preventing the further development of flavor and aromas. It also causes a higher alcohol content and an excessive release of bitter proteins, which make the beer less enjoyable.

Crisp, clean, and light mouthfeel of a lager can be directly attributed to this cold fermentation process. Additionally, warm fermentation will reduce volatile acids and increase fixed acids, which throws off the delicate flavor balance of the beer. Since this beer is known for its subtle flavors, any disruption of the flavor balance is significant in the resulting beer.


Homebrew Helpers

From your first brew attempt to your fiftieth brew, Beverage Factory will be here to supply you with the right equipment and advice to achieve your perfect brew! Contact our homebrew experts at 800-710-9939 for help with all your homebrew needs! Lagers, ales, or kombucha, our knowledgeable team can answer all your questions.


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