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Yeast is a living single cell fungi used in the production of beer. Yeast is added to sweet wort after cooling to initiate the fermentation process. During fermentation, yeast cells convert simple sugars such as glucose into carbon dioxide and alcohol. Fermentation can take anywhere from a few days to several weeks to complete.

Yeast Types

Yeasts come in two basic types - top fermenting ale yeast and bottom fermenting lager yeasts. Of the two, ale yeast are most commonly used for homebrewing because they can be fermented at room temperature.

  • Top Fermenting Yeast - Commonly called ale yeast are fermented at or just below room temperature (10-25 C). These yeasts rise during fermentation and form a foamy head at the top of the fermentation vessel. They also produce a strong estery flavor that is a key characteristic of ales. Stouts, Porters and all forms of Ale are made with top fermenting yeast.
  • Bottom Fermenting Yeast - Called lager yeast is fermented at low temperatures in the range of 7-15 C. Lager yeast grows slowly and tends to settle at the bottom of the fermenter because of the cold temperature. Bocks, Pilsners, Marzens and the large popular American lagers are made with this type of yeast.


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See Also

External Links