Lager beer is a popular style of beer known for its crisp and clean taste. One of the key factors that contribute to the unique characteristics of lager beer is the type of yeast used in the fermentation process. Lager yeast, scientifically known as Saccharomyces pastorianus, is the primary yeast strain used in the production of lager beer.
Lager yeast is a bottom-fermenting yeast, which means that during fermentation, it sinks to the bottom of the fermentation vessel. This is in contrast to top-fermenting ale yeast, which floats on the surface of the wort. The bottom fermentation process of lager yeast is one of the factors that contribute to the distinct flavors and aromas found in lager beers.
Saccharomyces pastorianus is a hybrid yeast strain that is believed to have originated from the wild yeast strains found in Bavaria, Germany. It is a cross between Saccharomyces cerevisiae, the yeast used in ale production, and a wild yeast strain. This hybridization is thought to have occurred naturally over centuries of brewing.
The physiological characteristics of lager yeast differ from ale yeast in several ways. Lager yeast can ferment at lower temperatures compared to ale yeast, typically between 45-55°F (7-13°C). This cool fermentation process is crucial in the production of lagers as it helps to develop the clean and crisp flavors associated with this beer style. Ale yeast, on the other hand, typically ferments at warmer temperatures, around 65-75°F (18-24°C).
Another notable difference between lager yeast and ale yeast is the production of certain flavor compounds during fermentation. Lager yeast tends to produce fewer fruity and estery flavors compared to ale yeast. This is due to its lower fermentation temperature and slower fermentation process. The result is a beer that is often described as having a cleaner, more neutral flavor profile.
In my personal experience as a brewer, working with lager yeast requires careful temperature control and patience. The fermentation process for lagers can take much longer compared to ales, often several weeks or even months. This extended fermentation time allows for the yeast to slowly metabolize sugars and produce a well-rounded and balanced beer.
To summarize, lager yeast, specifically Saccharomyces pastorianus, is the yeast strain used in the production of lager beers. Its bottom-fermenting nature, lower fermentation temperatures, and slower fermentation process contribute to the unique flavors and characteristics found in lagers. Working with lager yeast requires attention to temperature control and a longer fermentation period, but the end result is a refreshing and enjoyable beer style.