Discover the world in your own language!


Yeast is added and a beer is born


BB BeerBasics Ferment1 small

Fermentation space is always an issue at an expanding brewery like Milwaukee Brewing, where new tanks were about to be added to these three.

By: Stephen Beaumont


After the boil, the hopped wort is sent to a heat exchanger, where it will be cooled to a temperature suitable for fermentation. This is an essential step, since yeast added to boiling hot liquid will simply die. (Prior to the introduction of modern refrigeration technology, wort had to be sat out and exposed to the air in order for it to cool to a suitable temperature, which of course exposed it also to airborne bacteria, wild yeast and other microflora and made it open to possible infection.)


Once cooled and transferred to the fermenter, yeast will be added and fermentation begun.

Top-fermenting yeasts will work best when they are added to the hopped wort at warmer temperatures, normally between 15-25 ºC/50-77 ºF, hence the reason they are sometimes also known as warm-fermenting yeasts, or simply ale yeasts. Bottom fermenting yeasts function better at cooler temperatures, typically between 5-10 ºC/41-50 ºF, which is why they are also known as cool-fermenting yeasts or lager yeasts. (See What’s in a Beer: Yeast.)


BB BeerBasics Ferment2 small

Housed in a heritage building, Toronto’s Steam Whistle Brewing must make efficient use of every square meter for fermentation.

Fermentation is the process during which yeast consumes fermentable sugars and expels carbon dioxide – the bubbles in beer – and alcohol. While all brewer’s yeasts will do this, each will also contribute different flavour and aroma characteristics to the beer, with top-fermenting yeasts generally yielding fruitier tastes and bottom-fermenting yeasts usually contributing leaner, more streamlines flavour profiles.


Initial, or primary fermentation will generally take from two or three to several days, depending on how much sugar is contained in the hopped wort. Once primary fermentation has completed, the beer will undergo what is called secondary fermentation, or sometimes conditioning or lagering, which may take place in the same vessel or a different one. This process, during which the flavours of the beer will harmonize and mellow, will normally take from two to six weeks, although some breweries will speed through this step in a matter of days and others, especially in the case of very strong beers, might continue it for months. Normally, lagers require significantly longer periods of conditioning than do ales.


See also: