3.2 Bottom fermented beers: lagers
Lagers are the most commonly consumed beers worldwide taking their name from the German lagern (meaning ‘to store’). Fermentation occurs at lower temperatures than for the top fermenting beers (7–12°C), with the beer then being stored at 0–4°C (the ‘lagering phase’). During this time the lager clears and mellows. With modern improved fermentation control, most lager breweries use only short periods of cold storage, typically 1–3 weeks. The cooler conditions also inhibit the natural production of esters and other by-products, resulting in a crisper tasting beer. The yeast used in the fermentation of lagers is known as bottom fermenting yeast as it sinks to the bottom during the fermentation process.
Most of today’s lager is based on the original Pilsner style, pioneered in 1842 in the town of Pilsen (Plzeň), in an area of the Austrian monarchy now located in the Czech Republic. As you learned in Section 1, this area has very soft water.