Beer is a generic word that includes different styles of fermented malt beverage, including lagers and ales, as well as all individual and hybrid styles that are categorized under these headings. Even among the major beer categories, there are some truly unique brews, such as organic beer, kosher beer, extreme beer, wood-aged and barrel-aged beer, real ale, and gluten-free beer, which do not represent different beer styles, but rather different techniques of making and presenting beer.
The two primary classifications of beer are lagers and ales, and every beer lover should know a few basic facts about them, including:
• All beers are made as either ales or lagers, since they are all fermented from grain
• Ales have been around for thousands of years, while lagers are a fairly modern creation that is about two centuries old
• The first difference between ales and lagers is on the types of yeast used. Ale is brewed using top-fermenting yeast – “Saccharomyces cerevisiae” while lager uses bottom-fermenting yeast – “Saccharomyces uvarum”.
• S. Cerevisiae is the most common yeast, with its variants being used in wine making, bread making, and other popular formulations. It was the original beer yeast used in early Babylonian times. It has high tolerance to alcohol, which makes it capable of producing stronger or higher alcohol content beers.
• Saccharomyces uvarum is more fragile. It ferments like its ale counterpart, but settles to the bottom of the vessel at the end of the process. It also attenuates slowly and to a lesser extent compared to ale yeast, leaving a greater remnant of sugar in the beer. This yeast also has lower alcohol tolerance.
• The yeast used, in turn, dictates the temperature at which fermentation takes place. Ales are typically fermented at warmer temperatures, between 12 and 21 degrees Celsius (55 - 70°F), while lagers are fermented at cooler temperatures of between 3 and 10 degrees Celsius (38 - 50°F).
The cooler fermentation and ageing temperatures associated with lager yeast tend to slow down the activity of yeast, resulting in longer maturation time. The cold inhibits the production of esters (fruity aromas), as well as other fermentation byproducts that are common in ales.
This is not necessarily a bad thing, as the slow attenuation results in better clarification, creating the lager’s cleaner taste. This process also gives lagers their crisper and less fruity aroma, compared to the heavy and hoppy ale beer.