Beer yeast is a crucial ingredient in brewing, often referred to as the unsung hero of beer production. This microscopic organism, a type of fungus, is responsible for fermenting sugars present in the wort (the liquid extracted from the mashing process during brewing) into alcohol and carbon dioxide, giving beer its alcohol content and characteristic fizz. While hops, barley, and water get most of the attention, yeast is the key component that turns a sugary liquid into the beer we enjoy.
In the world of brewing, there are many types of yeast, each playing a pivotal role in crafting different styles of beer. Whether you’re sipping on a crisp lager or indulging in a hoppy IPA, the type of yeast used significantly influences the beer’s flavor, aroma, and mouthfeel.
Why do you need yeast to make beer?
Yeast is indispensable in beer making because it facilitates fermentation, the biological process where sugars are converted into alcohol and carbon dioxide. Without yeast, you wouldn’t have the alcohol or the bubbly texture that defines beer. Essentially, it is what transforms wort into beer.
During fermentation, yeast consumes the sugars extracted from the malted grains during the mashing process. As it metabolizes these sugars, it produces ethanol (alcohol) and CO2. Additionally, it contributes to the overall flavor profile of the beer by producing various by-products, such as esters and phenols, which add complexity and distinct character to the final brew.
Different strains of yeast can produce different results. Some are clean fermenters, contributing minimal flavors, while others generate fruity, spicy, or other complex notes that add unique layers to the beer’s taste.
How is yeast used to make beer?
The process of using yeast in beer making involves carefully introducing the yeast into the wort, which is the liquid extracted from grains that contains all the necessary sugars for fermentation. Once the yeast is added, it’s time to sit back and let the magic happen.
- Pitching the Yeast: After the wort is boiled and cooled, yeast is “pitched” into the fermenter. This term simply means that it is added to the wort, initiating the fermentation process.
- Fermentation: The yeast begins consuming the sugars, producing alcohol and carbon dioxide as by-products. This process can last anywhere from a few days to several weeks, depending on the type of yeast and the style of beer being made.
- Conditioning: After primary fermentation, the beer may be conditioned, which involves allowing the yeast to continue working at a slower pace. During this phase, the beer’s flavor and carbonation levels can continue to develop, and any unwanted by-products from fermentation are reabsorbed by the yeast, leading to a cleaner-tasting beer.
- Bottling: Once fermentation and conditioning are complete, the yeast can be filtered out, or in some cases, left in for bottle conditioning, where it continues to carbonate the beer in the bottle.
What yeast is used in beer? Beer yeast types
Beer yeast can be categorized into two primary groups: Saccharomyces cerevisiae (ale yeast) and Saccharomyces pastorianus (lager yeast). These two species are responsible for producing the vast majority of beer styles in the world.
However, within these two categories, there are various strains, each with distinct characteristics that can dramatically affect the beer’s taste, aroma, and mouthfeel. Let’s dive into the main types of beer yeast:
Saccharomyces yeasts
Saccharomyces is the genus of yeast primarily used in beer production, with two key species:
- Saccharomyces cerevisiae – Commonly known as ale yeast, it’s used for top-fermenting beers, where yeast ferments at warmer temperatures and typically floats on top of the beer during fermentation.
- Saccharomyces pastorianus – Known as lager yeast, it’s used for bottom-fermenting beers, fermenting at cooler temperatures and settling at the bottom of the fermenter.
Both of these species are vital to modern brewing, but each is used in different ways to create a wide variety of beer styles.
Top-fermenting yeast
Top-fermenting yeast, or Saccharomyces cerevisiae, is used in ales and ferments at temperatures between 15-24°C (59-75°F). This yeast works quickly, completing fermentation within a few days, and produces a range of fruity and spicy flavors, making it ideal for many beer styles, such as IPAs, stouts, and Belgian ales.
Ales brewed with top-fermenting yeast are often more robust, complex, and higher in alcohol content compared to lagers. This yeast also produces more esters, which give ales their signature fruity aromas and flavors.
Bottom-fermenting yeast
Bottom-fermenting yeast, or Saccharomyces pastorianus, is used in lagers and ferments at cooler temperatures, typically between 7-13°C (45-55°F). It ferments more slowly than ale yeast, often taking several weeks to fully convert the sugars to alcohol.
This yeast produces cleaner and crisper beers, with fewer fruity esters and phenols. Lagers, Pilsners, and Bocks are all examples of beer styles brewed with bottom-fermenting yeast. Because of the longer fermentation process and cooler temperatures, lagers tend to be smoother and more subtle in flavor than ales.
Lager yeast
Lager yeast is a specific strain of bottom-fermenting yeast, Saccharomyces pastorianus, and is responsible for the creation of various lager beers, which are known for their clean, crisp flavors. The fermentation process for lagers happens at lower temperatures, and they often undergo a longer conditioning period.
Lager yeast produces fewer esters and phenols, resulting in beers with a neutral, smooth flavor profile. This is ideal for brewing beer styles like Pilsner, Bock, and Märzen, which are popular for their refreshing, light taste.
IPA beer yeast
IPAs (India Pale Ales) are known for their hop-forward character, but yeast plays an equally important role in shaping the beer’s overall flavor profile. Most IPAs are brewed with top-fermenting yeasts, specifically strains of Saccharomyces cerevisiae. These complement the hop bitterness with fruity esters, which can bring out tropical, citrus, or stone fruit flavors in the beer.
The yeast strain used in an IPA can have a significant impact on the final product. For example, English IPA yeasts tend to be more expressive, adding a layer of sweetness or fruity complexity, while American IPA yeasts often produce cleaner, more straightforward flavors, letting the hops shine through.
Conclusion
Yeast is a crucial player in the beer-making process, responsible not just for fermentation, but also for influencing the flavor, aroma, and texture of the beer. From top-fermenting yeasts used in ales and IPAs to bottom-fermenting yeasts used in lagers, each strain contributes unique characteristics that shape the final brew.