Wars of the Yeast

All beers have four ingredients in common: water, malt, hops, and yeast.

About yeast

The genus of yeast used primarily in the fermentation of food product is the saccharomyces.
If the word bears a resemblance to saccharine it is because it is a Latin term for sugar. Sugar is the primary food for yeast.
In either case the one-celled critters do two things: they eat and …well…. they create by-products. I’ll call the by-products …well…. gas (namely CO2) and alcohol.

Back to the battle of the two yeast species namely cerevisiae and uvarum.
The two species of the yeast are what divide the world of beer.
Wow, who would know that microscopic, one-celled organisms called yeast could make such a difference in a beer?

Saccharomyces cerevisiae is known as a top-fermenting yeast, so called because during the fermentation process flocs ( the white floaty things) adhere to CO2 and rise to the top of the fermentation vessel.

Some beers that use top-fermenting yeast are called ales, and for that reason these yeasts are also sometimes referred to as "ale yeast". Top-fermenting yeasts are often fermented at temperatures between 50 and 75 degrees farenheit. The resulting beers are normally "fruitier."

Saccharomyces uvarum is known as a bottom-fermenting yeasts, so called because during the fermentation process flocs stay toward the bottom.

Some beers that use bottom fermenting yeast are called lagers, and for that reason these yeasts are referred to as “lager yeast”. Bottom fermenting yeasts work best at temperatures between 32 and 55 degrees farenheit.

Lagering is a german term for cellar or storage. This refers to the long cool storage time required to ferment the beer. Additionally, these yeasts ferment more sugars, leaving a crisper smoother more refined taste.

Not all lagers are fermented at cool temperatures. A classic example of this stye of beer is referred to as california common. This is a lager yeast fermented at ale temperature. This beer style was made famous by Fritz Maytag and his brewing company,Anchor.

Not all ales are fermented at warm temperatures. An example of this style is Alaskan Amber brewed by Alaskan Brewing Co. This beer is a commercial example of the Northern German altbier.

This is not an exhaustive profile of yeast. Commercially there are literally dozens of different yeast strains for each species. Each yeast has a very distinctive aroma or ester profile that is sought after by the brewer to create a signiture beer.

I refer to the yeast as the soul of the beer. I believe that when all is said and done it is the yeast that puts the final stamp of creativity on a brewers' beer.