A Big Difference Between Lager And Ale Boils Down To One Ingredient

For casual beer drinkers, the difference between ales and lagers is mostly arbitrary: They're just words on the beer's label. But even if you're not planning to brew beer yourself, it's always good to know more about what you're drinking. Ales and lagers are brewed in different ways, and most importantly, they're brewed with different kinds of yeast.

Yeast is a key ingredient in any beer — alongside other kinds of alcohol — because yeast is necessary for fermentation. The short explanation for brewing beer is that a grain (like wheat or barley) is malted, boiled, and then fermented in yeast, and that final step is where the alcohol comes from. Ales are brewed with top-fermenting yeast at warmer temperatures, and lagers are brewed with bottom-fermenting yeast at colder temperatures. The final result gives ales a more robust, richer taste, especially once you get into IPAs, while lagers have a lighter, cleaner taste.

So, what's the actual difference between top-fermenting and bottom-fermenting yeast? The names refer to how the yeast looks during the fermentation process. Top-fermenting ale yeast looks foamy while fermenting, as if all the yeast has risen to the top. Meanwhile, if there's no foamy head because the yeast settled at the bottom, it's considered bottom-fermenting lager yeast. But it's not just looks; ales and lagers use entirely different species of yeast.

For much of history, we only brewed ales because that's the process that humankind discovered first. Even though we didn't understand the science behind fermentation -– the process where yeast microbes break down sugars and create alcohol –- humans first brewed beer thousands of years ago, using top-fermented wheat at room temperature to create what's now called ale. Lager popped up in Bavaria, Germany, about 500 years ago, where it was made in colder caves and stored for much longer periods. Over time, lager became the world's most popular beer, although ale still thrives in modern craft brewing.

It's tough to generalize ales and lagers too much because there's lots of variety among the two beers — especially ales, which have much more complicated flavors that can often taste fruity or floral. Among ales, for example, you can have citrusy, strong IPAs (India pale ales) and dark, chocolatey stouts that taste and look entirely different. Lagers tend to be slightly more consistent, although you still have lighter flavors with Corona or Budweiser versus spicier, hoppier pilsners.

A beer's flavor is determined by a mixture of its malt, its yeast, and the kinds of hops and other ingredients added during the brewing process. The malt is a grain that's been soaked and heated to prepare it for the fermenting process, and the kind of malt used often determines a beer's color and flavor. Hops are a plant frequently used in brewing to contribute to a beer's aroma and flavor profile, and these are what give beers like IPAs the bitter, earthy taste we call "hoppy."