Lager & Pilsner

'Lager' says something about the yeast and the way of maturing: bottom-fermenting yeast and cold lagering. 'Pilsner' is one particular style within that family: pale and with a clear hop bitterness.

The BJCP distinguishes numerous European lager styles, from Münchner Helles and märzen to Vienna lager, Münchner Dunkel, schwarzbier, (doppel)bock and baltic porter. The Bavarian food agency LGL, too, names among the bottom-fermented beers Hell, Dunkel, Kellerbier, Pils, Export, Märzen and Doppelbock, among others.

Even pilsner is not one thing. A Czech pilsner is maltier, fuller and more softly bitter than a dry German pilsner. And in the Czech Republic only Pilsner Urquell and Gambrinus are called 'Pilsner'; the BJCP describes the style as a group of beers 'of the Pilsen type' (pivo Plzeňského typu).

The image comes from the big international brand beers. The BJCP classes those as 'International Pale Lager' and describes them as highly attenuated pale lagers without pronounced flavours.

But the family is much broader. A Czech pilsner has rich malt and 30–45 IBU. Märzen and Vienna lager are about rich, toasted malt. Münchner Dunkel has notes of bread crust and chocolate, schwarzbier soft roasted notes, and baltic porter has up to 9.5% alcohol, with dark fruit and liquorice.

Lager is, moreover, not a 'simple' beer. In Bavaria, people worked on cold fermentation and lagering cellars for centuries, and in 19th-century Munich brewers and scientists together laid the foundations for the industrial brewing of lager beer.

According to the Historisches Lexikon Bayerns, cold fermentation became widespread in Bavaria from the 16th century, and bottom fermentation was by then already generally known. Pilsen built its Burgher Brewery partly because in 1839 the town was already being 'flooded' by bottom-fermented beer in the Bavarian style.

What was new in Pilsen in 1842 was the colour. With malt kilns on the English model, which were heated indirectly, pale malt was easier to make, whereas Bavarian lagers were still fairly dark at that time. Even that 'first pale lager' is not entirely certain: the BJCP notes that there may already have been earlier pale lagers in Bohemia.

How old lager exactly is, is not settled. What we do know is that before 1883, when Emil Christian Hansen isolated pure culture yeast, brewers always worked with mixtures of top- and bottom-fermenting yeasts, wild yeasts and lactic acid bacteria. Bottom fermentation in the strictly modern sense therefore did not exist before that.

The 'skunky' or 'lightstruck' smell is a well-known beer defect with a chemical cause. According to research by, among others, Ghent University (Huvaere et al., 2006), it comes mainly from the compound 3-methylbut-2-ene-1-thiol (MBT), which stinks at just a few nanograms per litre. MBT forms because light breaks down the bitter compounds from hops (iso-alpha acids). Riboflavin (vitamin B2) in the beer absorbs the light and starts the reaction; a sulphur fragment, from amino acids among other things, completes the compound. Blue light (350–500 nm) proved the most effective.

That is why the packaging matters. According to the Brewers Association (BA), brown glass protects somewhat, green glass less and clear glass hardly at all. A Molson patent from 1981 confirms with measurements that clear glass lets through the most harmful light and brown glass the least. But even brown bottles do not belong in bright light according to the BA, and according to a guide from CraftBeer.com (also from the Brewers Association) the skunk smell can then form within a few seconds. The BA calls cans 'mini kegs' that protect beer from light.

Heat is bad for beer, but it causes other defects. According to the Brewers Association, lagers stored at 25 °C tended towards caramel-like notes, and at 30–37 °C towards a cardboard taste (ageing through oxidation). A skunk smell is not part of that.