Traditional beer lovers might turn up their nose at the idea of a sour beer, but that’s only because it’s a polar opposite taste sensation to what they’ve become used to. Conversely wine lovers and other drinkers who often struggled with beer’s bitter dimension are enjoying a flavour experience that transcends what they thought beer could be.
It’s easy to understand why people who normally hate beer, love sours. While humans have evolved to be wary of bitter (it can indicate toxicity) we’re pretty good with acidic flavor…think old-fashioned lemonade, acid drop lollies and, of course, wine.
Sour was beer’s natural state dating back thousands of years when no-one knew anything about yeast and all fermentation came courtesy of bugs from the air, plants or barrels – all of which impart a funky, tart flavour. It wasn’t until breweries learned more about yeast, in the past 200 years, that beer came to resemble the beverage it is now.
Despite technological change, sour beers remained popular in Belgium and Germany and many modern brewers riff of these traditional styles.
How is sour beer made?
There are many ways of creating sour beers but the main three are:
- exposing raw beer (wort) to the elements and letting wild yeasts do their job
- fermenting a beer normally and then putting it in a wooden barrel where other microbes and oxygen get to work on it
- or using a lactobacillus culture to sour the beer before it’s boiled.
Fruit can be added at various stages, bringing with it some added flavour dimensions, tartness and its own set of bugs, and brewers can also blend different “vintages” to create a more complex and layered beer.
In the first example, wild yeast exposure creates what the Belgians call a Lambic. But like Champagne, anyone else making such a style outside a specified region in Belgian can’t call it that. Instead they use the term wild ale. The barrel-aged beers are called just that, while the pre-soured beers are known as kettle-soured (because the beer is soured inside the brew kettle). Sometimes the term quick-soured is used. That’s because kettle-souring is relatively quick and done in a day, whereas a barrel-aged beer can take two years or more to make.
In a kettle-sour, lactobacillus (as in the bug that makes yoghurt) is added to the raw beer before its boiled in a brew kettle. Left overnight the beer develops an acid tang and brewers can refine the acidity level before they carry on and brew the beer as usual, with the boil process killing off the bacteria so it doesn’t have any further effect. The result is an effervescent, slightly tart, very dry beer.
The addition of fruit to kettle-sours – raspberry, blueberry, peach, feijoa – enhances the flavour and acidity to create beers with a refreshing, dry quality and a depth of flavour that can beautifully mask a lower ABV. Another term you’ll hear that’s in the same ballpark as kettle-sour is Gose. This traditional east German style – from the town of Gosler – has gone through a renaissance in recent years as modern brewers rediscovered an almost extinct style. The traditional method was a salty beer brewed with coriander and lemon. The salt works in the same way it works with salt and vinegar chips! Again breweries are going for fruit additions to this style.
Not many brewers make wild ales, but Garage Project, 8 Wired, North End, Hallertau and Moa are among the industry leaders. Wild ales are very much about taking what nature you gives you in terms of the yeast in the air that gets into the exposed beer. The flavours are often quite “funky” – with barnyard, silage-like aromas. But the complexity and refreshing nature of these beers can be mind-bending.
Barrel-aging is a more common practice – this is because the process can be controlled to an extent. There are two types of barrel-aged beers. One method is to use “clean” barrels that don’t have any microbes lurking in the wood. Here brewers are often trying to get a vanilla flavour out of the wood, as well as letting some oxygen in to mellow the beer.
The other method with barrel-aging is to use a barrel full of all sort of microbes and let them go to work on the beer – these barrels are often old wine or whisky barrels that bring other flavours with them.
While all these variants are classed broadly under “sour” the breadth of flavour is quite remarkable, but what they all have in common is a refreshing, tart, dry and spritzy personality. In fact, they’re often more like cider or wine than beer and are great to pair with food or have as an aperitif.