Brewing Yeast is one of the main four main ingredients in beer brewing and is also the most essential. Yeast is
a unicellular fungus and is also a living organism which possesses the rare ability to live with or without oxygen.
In the presence of air, the yeast organisms multiply but in the absence of oxygen, they ferment sugars into alcohol
which is what makes beer brewing possible. Ale Beer and Lager Beer are differentiated by the two main types of
brewing yeast used to ferment the wort. Wort is the liquid made from water and malt, flavored with hops that is
used to make ales or lagers.
Ale Beer Yeast
Ale beer yeast is said to be top fermenting since the yeast cells tend to flocculate or gather at the top. Lager
yeast on the other hand migrates to the bottom of the tank during fermentation and so is called bottom
In the case of ale yeast, some interaction with oxygen takes place during fermentation. Ale yeast ferments
within a few days to two weeks and at a temperature of around around 21oC/70oF although this
can vary from as low as 10oC/50oF to as high as 25oC/77oF . Brews made
from it also tend to store longer and have a higher alcohol content.
Lager Beer Yeast
Lagers take up to a month to ferment and do so at lower temperatures, sometimes as low as near freezing.
Historically, lagers were often brewed in the winter when the air temperature was lower and then consumed later.
Temperature ranges vary, though, and can easily be in the higher
45oF-59oF/7oC-15oC range. Along with the advent modern refrigeration
came the option of having lager all year round.
There is also a third type of yeast, called Lambic Yeast, which was originally used almost exclusively in
Belgium. The name derives from the West Flanders area in Belgium where Lambic yeasts grow wild. Today, as a result
of importing, it is used in many parts of the world.
As well as converting malt sugar or maltose into alcohol and carbon dioxide yeast also adds distinctive flavors
to the brew during the fermentation process
Many ale yeasts have a full bodied, fruity aroma and taste, whilst others possess a more nutty or mineral taste
which are more suited to stouts, Belgian ales and other strong brews.
One variety is used in Weizen, or wheat beer. The primary ingredient in beer is malt from the cereal grain
barley. Wheat beer is not named after the grain used, but after the yeast used to ferment it. Wheat beer yeast goes
into this ale style brew, where it helps produce a fruity, intense character.
Lager yeasts are usually smoother and dryer, with the taste of cloves, vanilla or a wide variety of other hints.
Pilsner, for instance, is a type originating in the Czech Republic in the town of Pilsen from which the brew gets
At one time Pilsner formed the basis of 90% of the lagers consumed around the world. But with the increase of
micro breweries and the growth of variety in the U.S. and elsewhere, lagers now come as Dortmunders, Marzens, Bocks
to name but a few.
Though carbon dioxide and alcohol are the two leading products of fermentation, yeast produces secondary
products as well. The different types of beer brewing yeast can add tastes or aromas as varied as sweet corn, green
apple and butterscotch. The downside is that they can also produce sulfur, or phenolics, which have a medicinal
Control of the added flavor is as much an art as the control of fermentation is a science.