Wednesday, September 8, 2010

The difference between an ale and a lager

Here's a question I get all the time when I'm describing one of my newest creations. What's the difference between an ale and a lager?

Sometimes I'm a little surprised when people I know who are burgeoning beer enthusiasts are unaware of the difference between the two houses of beer, ale and lager. The essential difference is simply the type of yeast used to ferment the wort (beer before it's beer).

Ale yeast is the so-called top-fermenting (or top-cropping) yeast. Ale yeasts are so called because they float to the surface and ferment (and form a foam) at the top of the wort. Ale yeast typically ferment at ambient room temperatures (approximately 70 - 80 degrees). Ales typically are characterized as beer high in esters, which lends to the fruitier flavors. Ale yeast strains are used for brewing porters, stouts, IPAs, pale ales (pretty obvious), and much much more.

Lager yeast is the so-called bottom-fermenting (or bottom-cropping) yeast. They are best fermented at temperatures ranging from 45 to 55 degrees approximately. At these temperatures, lager yeasts grow less rapidly than ale yeasts, and with less surface foam they tend to settle out on the bottom of the fermenter. This is why they are often referred to as "bottom-fermenting" yeasts. Lager beers are usually characterized by a crisp clean finish, but the final flavor of the beer will depend on the strain of lager yeast used. Now there is also a process called lagering which is usually employed when brewing lagers, but is sometimes used when brewing ales as well. Lagering a beer involves dropping the temperature of the largely completed fermenting wort close to freezing for an extended period of time (weeks to months) in order to round out the flavors and lends to the crisp finish of most lagers. Some lager styles made from bottom-fermenting yeasts are Pilsners, Märzens, Bocks, and much much more.

I hope this was helpful.


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