Fact: all beer is either lager or ale.

Within those categories, you’ll find all the different varieties – stouts, lambics, porters, IPAs, sessions, pale ales, bitters, and more.

But how do you know which is which? Is there a fundamental difference between lager and ale, or is it just beer nerds making things awkward for the rest of us? Let’s have a look.

What is the definition of beer?

First, let’s define beer. Beer – as we’re sure you’re aware – is a delightful drink that humans have been enjoying for many centuries. It’s made up of four main ingredients – grains, hops, yeast and water.

The grains, which are usually malted barley, contribute colour, flavours, proteins and maltose (the sugars which ferment into alcohol).

Hops come from the hop plant, give the drink its bitter taste (to counter the sweetness of the grain sugars), and help stabilise the body of the brew.

Water makes it all into a refreshing drink.

And the yeast is what makes the difference between lager and ale.

Yeast is a key part of the fermentation process. Yeast is a fungal microorganism that does one job, and does it well. It’s super important for making bread, wine, and even biofuel.

What yeast does is metabolise. The yeast that brewers put into the wort (the liquid made from boiling malted grains, ie. barley) eats up the carbohydrates (sugars) from those grains. It then metabolises them to produce alcohols. So yeast turns grains into alcohol. Magic.

The difference

The difference between lager and ale lies in how this yeast metabolism (the fermentation) is done.

Ale is top-fermented, which means the yeast is put into the top of the grainy wort mixture, at higher temperatures. Ale normally uses yeast called ‘Saccharomyces cerevisiae’ (also referred to as Brewer’s Yeast). This is the older method, and tends to bring out more flavour, due to it helping produce esters and phenols. Esters are types of alcohol that provide fruity, sweeter flavours, like apple, pear, and pineapple. Phenols are a type of organic compound that offer a wide range of earthy, natural, smokey flavours.

Lager on the other hand usually makes use of ‘Saccharomyces pastorianus’ or ‘Saccharomyces eubayanus’, which are bottom-fermenting (colder temperature) yeasts. The yeast in lager works its magic at the bottom of the wort mixture, at lower temperatures than those of ale. It takes longer for the chemical reaction to complete when cold-fermenting, and results in a crisper, less complex-tasting beer.

This yeast doesn’t affect the flavour as much as that in ale, and provides more of a blank canvas for the flavours of the hops and barley to come out. This means that lagers can be brewed to have a less intense taste – usually better for pairing with food, or working as cold refreshment on a hot sunny day.

This method of brewing became popular in the 15th century, and became widespread around Europe as folks stored their lagers in cold cellars and caves to keep them cool.

Lagers don’t have the sweet flavours that esters produce in ale, but sweeter flavours can be added after the fermentation process.