What is the difference between ale and lager?

The core difference is the yeast

Every beer is either an ale or a lager, with a small number of hybrids and spontaneously fermented beers in between. The split depends on the yeast. Ale yeast, Saccharomyces cerevisiae, is the same species used for bread and wine. Lager yeast, Saccharomyces pastorianus, is a hybrid of S. cerevisiae and the cold-tolerant Saccharomyces eubayanus, a wild species first identified in Patagonia in 2011.

Ale yeast is often called top-fermenting because many strains rise to the surface during fermentation and were skimmed off the top. Lager yeast is called bottom-fermenting because it settles at the bottom of the vessel. Modern cylindro-conical fermenters blur this distinction, so brewers now classify beers by yeast species and fermentation temperature rather than by where the yeast sits.

Fermentation temperature and time

Ales ferment warm, usually between 15 and 24 °C, and primary fermentation often finishes in three to seven days. Lagers ferment cold, typically between 7 and 13 °C, which slows the yeast down to one or two weeks. After fermentation, lagers are stored near 0 °C for several weeks. This cold storage, called lagering from the German lagern, to store, lets the beer clarify and lets the yeast reabsorb off-flavors such as diacetyl.

Warm fermentation makes ale yeast produce more esters and phenols, the compounds behind banana, pear, clove or stone fruit aromas. Cold fermentation suppresses them, so lagers let malt and hops speak with less yeast character. Lagers therefore need more time, more tank space and refrigeration, which is why large-scale lager brewing only spread after artificial cooling arrived.

A short history

Ale is the older tradition. Lager developed in Bavaria from the 15th century, when brewers stored beer in cool caves and cellars over summer; a 1553 Bavarian rule banned brewing between late April and late September, which favored cold-fermenting yeast. The lager breakthrough came with Munich and Vienna brewers in the 1830s and 1840s and with the first pale pilsner, brewed in Plzeň in 1842 by Josef Groll.

Two inventions made lager global. Carl von Linde's refrigeration machines, adopted by breweries from the 1870s, freed lager from cold caves. In 1883 Emil Christian Hansen at the Carlsberg Laboratory in Copenhagen isolated a pure lager yeast culture, giving brewers consistent fermentations. Today pale lager is the most consumed beer type on earth, while ales dominate in the United Kingdom, Belgium and the craft beer scene.

How they taste, with examples

Color and strength do not separate ale from lager. A lager can be black and an ale can be pale. A stout like Guinness and a Belgian tripel are both ales; a schwarzbier and a doppelbock are lagers. In general, ales show more fruit and body, and lagers show a cleaner, drier, more refreshing profile. Some hybrids, such as Kölsch and altbier, use ale yeast fermented cool and then lagered.

• Ales: IPA, pale ale, stout, porter, bitter, German wheat beer, saison, dubbel, tripel
• Ale examples: Guinness Draught, Sierra Nevada Pale Ale, Duvel, Weihenstephaner Hefeweissbier, Fuller's London Pride
• Lagers: pale lager, pilsner, helles, Märzen, bock, dark lager, Vienna lager
• Lager examples: Pilsner Urquell, Heineken, Budweiser, Augustiner Lagerbier Hell, Corona Extra, Asahi Super Dry
• Hybrids: Kölsch, altbier, California common (Anchor Steam), cream ale