Overview of yeast in beer brewing

yeast in beer photo

With all of the attention that is often given to grain and hops in homebrewing, the important part played by yeast in beer brewing is often overlooked. When we really think about it though, yeast actually plays the most significant part in the process.
The yeast takes the sugar within the wort and converts it into alcohol, carbon dioxide and various other flavors.

There are a range of factors that are important when choosing which yeast to use in your brew. Although I will cover this in more detail in another post, it is important to be aware that different strains of yeast will perform in different ways.

Most homebrewers will be aware that there are two principle strains (species) of yeast in beer making; lager yeast and ale yeast. The main differences between these two different species of yeast are in the way that they ferment the alcohol.
Ale yeast is generally referred to as being ‘top fermenting’ as it raises to the top of the wort and create a thick head called krauzen. Lager yeasts work at cooler temperatures and are referred to as ‘bottom fermenting’ as they settle towards the bottom of the fermenter.
Within these there is also a range options that have been taken from various sources and selected for their ability to work well to ferment beer of the appropriate style.

Yeast attributes

There are a few other factors when selecting the type of yeast you will use.


This refers to the amount of sugar that the yeast will be able to ferment. Highly attenuating yeast will result in a drier, less sweet beer while a low level of attenuation will finish with a more malty and sweeter beer.


This level indicates the yeasts natural tendency to clump together. This is an important consideration in some styles of beer as it will impact on the speed and final amount that the beer becomes clear.
A high level of flocculation means that the yeast will settle ‘out of solution’ faster. This is desirable for many brewers as it means that the final beer will also be clearer. In some instances this means that there is little need for a secondary fermenter as the yeast and other particles will settle out almost completely in the primary.

Fermentation Temperature

Each yeast will perform best within a certain temperature range.
Although it is generally accepted that lager yeast will work at a cooler temperatures, it is also critical that these temperatures are maintained. If these temperatures are not maintained, a range of undesired flavors may find their way into your beer.
Temperature control when making ales is also important but slightly more forgiving and accessible to homebrewing. This is because the optimum fermentation temperature is closer to regular room temperature. It is due to this that many people start their journey in homebrewing with ales.

Selecting the right yeast

When deciding what yeast you will use in your homebrew beer, you should have the desired characteristics of your finished product in mind. It is important that the yeast that you use has the attributes that you are looking for.
Each yeast producer publishes information about the attributes of the yeast in their range. It is often easier to do some research on the more common types used for the style of beer that you are making. In most cases, these will only be a few varieties and will often include the name of the style in their name.
If you are looking for more information or guidance, I am always happy to help and can be reached through the comments section below or on social media.

Photo by ecstaticist

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