Differences of bottom and top fermentation. Bottom fermentation.
Bottom fermentation — a method of producing beer using yeast species Saccharomyces pastorianus*. Bottom fermentation is more modern and more common than top fermentation.
Bottom fermentation. The main stage of fermentation takes place at a lower temperature, from 4 to 10 °C. In this case, other yeast is used, not like in top-fermented beer, therefore, a “cap” does not form on the surface of the beer vats - the yeast accumulates at the bottom of the tank. The risk of wort infection during bottom fermentation is much less. And beer is more stable, has a longer shelf life and a pronounced hoppy taste. This type of fermentation is used in our production.
Top fermentation. Top fermented beer is born at a temperature between 15 and 20 °C, using special yeast. At the end of the main stage of fermentation, yeast forms a “cap” on the surface of the beer - hence the name. The top fermentation method makes mainly wheat beer (mainly from Belgium and Bavaria, but also the farther, more often, from the Czech Republic), as well as, for example, beer such as ales, stouts or porters. The top fermentation method mainly produces beers with a higher alcohol content.
Lager - from the German "Lagerbier" and means " beer made for storing." It is believed that the lagers were invented by German monks who first guessed to leave beer for ripening in the cool cellars of the monasteries.
Production of bottom-fermented beer - lagers
Bottom-fermented beer matures longer than top-fermented beer, has less alcohol, but at the same time has a bright expressive taste and a long shelf life. It is produced using bottom fermentation technology followed by fermentation at low temperature. The brewed beer wort is cooled and the wort is pumped over by a fermentation tank, where it ferments for about a week at a temperature of 4–10 °C.
Then the yeast is separated, and the beer is sent to lagering, which occurs at an even lower temperature (2–5 °C) and can last from 20 to 120 days. Then the beer is filtered and poured into vessels. Most of the sugar contained in the wort is converted to alcohol during the main fermentation. During fermentation, the residual sugar breaks down, the yeast settles to the bottom, and the beer becomes transparent.
* Saccharomyces pastorianus – a hybrid of baker's yeast and tartar yeast Saccharomyces bayanus. The genome of these and several dozen other fungi has been fully studied. Thanks to this, modern microbiologists can correct and improve the properties of yeast, which are important for the beer industry.