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Yeast are single-celled microorganisms that reproduce by budding. They are biologically classified as fungi and are responsible for converting fermentable sugars into alcohol and other byproducts. There are literally hundreds of varieties and strains of yeast. In the past, there were two types of beer yeast: ale yeast (the "top-fermenting" type, Saccharomyces cerevisiae) and lager yeast (the "bottom-fermenting" type, Saccharomyces uvarum, formerly known as Saccharomyces carlsbergensis). Today, as a result of recent reclassification of Saccharomyces species, both ale and lager yeast strains are considered to be members of S. cerevisiae.

Top-Fermenting Yeast

Ale yeast strains are best used at temperatures ranging from 10 to 25°C, though some strains will not actively ferment below 12°C (33). Ale yeasts are generally regarded as top-fermenting yeasts since they rise to the surface during fermentation, creating a very thick, rich yeast head. That is why the term "top-fermenting" is associated with ale yeasts. Fermentation by ale yeasts at these relatively warmer temperatures produces a beer high in esters, which many regard as a distinctive character of ale beers.

Top-fermenting yeasts are used for brewing ales, porters, stouts, Altbier, Kölsch, and wheat beers.

Bottom-Fermenting Yeast

Lager yeast strains are best used at temperatures ranging from 7 to 15°C. At these temperatures, lager yeasts grow less rapidly than ale yeasts, and with less surface foam they tend to settle out to the bottom of the fermenter as fermentation nears completion. This is why they are often referred to as "bottom" yeasts. The final flavour of the beer will depend a great deal on the strain of lager yeast and the temperatures at which it was fermented.

Some of the lager styles made from bottom-fermenting yeasts are Pilsners, Dortmunders, Märzen, Bocks, and American malt liquors.

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Related Questions

What is the difference between top fermentation and bottom fermentaion yeast?

Bottom fermenting yeast, which produce Lager beers, are fermented at lower temperatures (around 0-5 degrees C), and take roughly twice as long to ferment as ales, which are procuced with top fermenting yeast Top fermenting yeast produce Ales and are fermented at higher temperatures (around 10-15 degrees C), and have a shorter fermentation time.


What is the difference in production processes of ale beer and lager beer?

The main differences between ale and lager production are in temperature and type of yeast used. Lager is fermented at a lower temperature than ale and uses a bottom fermenting yeast whereas ale uses a top fermenting yeast.


True or False the main difference between a Lager and an Ale is the type of yeast used?

True Lager is distinguished from ale by its yeast. Lager yeast ferments at lower temperatures and flocculates on the bottom of the fermenting vessel, while ale yeast ferments at higher temperatures and settles on the tops of fermentation tanks.


What is lager and clarification in brewing beer?

A lager is fermented at relatively cooler temperatures using bottom-fermenting yeast. Compare to an ale, which uses top-fermenting yeast at warmer temperatures. Clarification is the precipitation of the yeast from the finished brew.


Where is lager from?

Lager is a type of beer that has been fermented using yeast that prefers a cooler temperature than ale yeast. It is made of the same ingredients as beer, namely barley, water, hops, and yeast. The only difference between Lager and Ale is the type of yeast used and the temperatures that it is fermented at. Lagers are a "bottom fermenting" beer that prefers cooler temperatures. Ales are "top fermenting" beers that prefer warmer temperatures.


What is brewers yeast?

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Boiled yeast has been heated to a high temperature, which kills the yeast cells and deactivates the enzymes. Unboiled yeast is live and active, capable of fermenting sugars and producing carbon dioxide. Boiled yeast is typically used in recipes that do not require fermentation, such as bread recipes that call for instant yeast.


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What sentence can you use for the word yeast?

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