Sour Beer, Vault City and Edinburgh Craft Beer Festival

If a pint of brown, foamy ale is the liquid equivalent of a big hug from a grandad in a thick cable-knit jumper, and a lager is akin to a reassuringly straightforward catch-up with a pal, sour beers are a bit more like an extremely enthusiastic high-five. Enjoyable, invigorating, a bit different, and they only occasionally leave you writhing on the ground in agony.

The beer world’s embrace of the sour continues, with more and more breweries adding sharp, tangy and funky beers to their line-ups. You can expect to see a whole host of the blighters at this month’s Edinburgh Craft Beer Festival, but more on that shortly. First, we need to take a quick trip to the laboratory.

In the normal course of brewing, the plan is to keep things under control. Carefully measure your ingredients, work to a precise recipe, get all your ratios spot on, and use a yeast that’s going to give you predictable results. The trick is not to let random stuff into the beer as it’s brewing, say, by leaving the door open...

Lambic beers are created by leaving the door open. This Belgian variety is the original sour beer style, and understanding how it comes together is helpful in getting your head around sour beer in general.

Essentially, there are wild bacteria and yeasts occurring in the environment all around us, and in certain conditions they can be quite useful in building flavour and character into food. They can also destroy your food if they completely overrun the scene, but by allowing just some of those interlopers to get into a batch of beer, it’s possible to get a drink that has a sharpness and funk that can’t be achieved with standard ingredients. As such, a good lambic has a Champagne-like fizz and a dry, sharp finish that comes from the wild yeasts that spark its fermentation. Gueuze beers are made up of blends of different lambics, which are then re-fermented once they’ve been buddied up. Gueuzes tend to be a bit on the farmy side, so be ready for big musty aromas and strong tangy flavours – if you like the faint smell of hay and cattle with your half-pint, you’re in business.

Then there are two big words that will be helpful in your understanding the new breed of sour beers – Brettanomyces or Brett for short, and lactobacillus or lacto. Brett is a non-standard form of yeast that works more slowly than a standard brewing option, and helps to send beer fermentation in strange and interesting directions.

Lacto is a bacterium that converts sugars into lactic acid rather than alcohol; put some of it in with your batch of beer, and you get a sour beer. It’s also responsible for the lactic funk of yoghurts, kimchi, and many other fermented goods. It is, as the Yakult advert once said, a good bacteria. Berliner Weisse makes use of lacto, adding the bacteria to a standard German-style wheat beer; gose works along similar lines but is noted for featuring coriander and salt, just to make things even more interesting.

‘Interesting’ is very much the word to describe the beers coming out of Edinburgh’s Vault City microbrewery. The brewery is an all-sour operation, using wild fermentations and a whole host of hop blends and fruit additions to give their beers a genuinely unique edge. Their Yuzu Sour is a lip-smacker of the highest order, and their Strawberry Sour is a remarkably well-rounded and refreshing drink. The brewery has won a host of plaudits since launching last year, and earlier in 2019 Vault City won the Edinburgh Craft Beer Festival’s Raise the Bar competition to feature at this year’s festival alongside some of the biggest hitters in craft beer.

The Festival’s official beer is another sour-ish effort, this time from Leith brewers and full-time Twitter shit-stirrers Pilot. It’s a Watermelon, Mint and Hibiscus Semi-Sour, described by Pilot’s Matt Johnson as a drink with a “nice, refreshing tartness” and one that “festivalgoers can enjoy without getting their heads blown off by a high ABV.”

Losing one’s head thanks to an unexpectedly high number on the back of a can is something most of us can sympathise with (drink responsibly, folks), but taking a full force shot to the taste buds from the lacto fairy might not be as familiar. If this sour beer lark sounds like it’s for you, we have some pre-festival tips to impart.

First, head to the experts. Breweries like Wild Beer Co and the aforementioned Vault City are full-timers at the funky fermentation game, so they’re the ideal place to start. Try anything and everything they have, and work out which styles suit you. You might like beers with a distinctly farmhouse vibe, but you’ll never know if you don’t give them a go.

Next, move up through the gears. Hit up the Berliner Weisses – these are super-refreshing beers that won’t put you off the concept for good. Expect light, floral smells and crisp flavours from breweries like Whiplash and To Øl. After that, move on to the goses for a more savoury vibe, then to the more traditional styles or heavily Bretted beers. Also, Cromarty have brewed a milk sour called Udder Madness and it’s a bit like a fizzy, mildly alcoholic milkshake. Very weird, but strangely enjoyable, so pop along and see if they have any lying around. These kinds of ‘experiments’ are pretty rife when it comes to sours – give them a bash once you have your lacto legs.

Finally, remember that when it comes to sour beer, fruit is your friend. Tropical fruit and berries are used in many of the best of the new wave of sours, amplifying the hop flavours and helping your addled mind make sense of what it’s drinking. ‘This is a beer, so I don’t quite get why it’s so tangy,’ you think to yourself. ‘But then I suppose a guava does have a bit of a kick to it, so I’ll play along.’

Beers like 71 Brewing’s Passion Killer (lots of passion fruit puree, as many thumbs up as we can manage) and Amundsen’s Raspberry and Lime Berliner Weisse, Lush, are both good examples of fruity beers that end up as more than the sum of their parts. Intriguing, exciting, and probably somehow contributing to your five-a-day – looks like sour beers are here to stay.

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Edinburgh Craft Beer Festival, The Biscuit Factory, Edinburgh, 24-25 May