Spontaneous fermentation SOUR TIMES

Blending is a true art form – its here that a brewer puts their palate to the test


Asking when UK drinkers will finally ‘get’ sour and spontaneously fermented beers is a tedious distraction, says Matt Curtis. Instead, we should concentrate on the sheer breadth of characteristics which make up this delightful and poorly understood category

In Ferment #8 I put forward the case for “wild” or “sour” beer becoming a trend within 2017’s evolving beer culture. Andrew Cooper, co-founder and director of Somerset’s The Wild Beer Company disagreed with me, however. 

“Wild beer will steadily grow over the next few years, but the general quality needs to improve, and there needs to be a lot more ageing going on,” he said. “Until there are more breweries really investing in barrel programs I don’t think we will see it become a trend in this country.”

But here’s where I disagree with Andrew and offer my counter argument, because despite his opinion I still think that ‘sour’ beer is going to be big this year. 

The first problem that this expanding genre of beer will have to overcome is the terminology currently used to describe it. The reason I put the word “sour” in inverted commas is because it just doesn’t have the capacity to describe the gamut of flavours and nuances that beers within this broad style can convey. Once the right terminology is in place, then the conversation about them can truly begin.

The first problem with the word “sour” is that it can be used to describe the negative aspect of flavour within food or drink. It also has deep associations with tooth-rottingly sweet and mouth-puckeringly sour kids sweets – hardly something you’d also want to associate with an elegant glass of a beer such as a Belgian Gueuze, right?

If you look to the world of wine, styles are defined by ingredients – or more specifically, grape varieties. By choosing to make the consumer immediately aware of the type of grapes used in the product, it has educated them and with increased consumer knowledge comes its powerful market position.

The beer world has gradually cottoned on to this over the past few years. Beers now often celebrate the inclusion of specific hop varieties, some taking their names directly from the hop itself, such as Oakham Citra or Marble Mosaic Pale Ale. A few breweries have even gone so far as to proudly talk about the malt they use in the beer. You might already be familiar with Maris Otter, but how about Pearl or Chevallier? 

The problem with the ingredients that cause a beer to turn sour is that they are yeasts and bacteria with names that can be a bit of a mouthful. Try explaining to a customer standing three deep at a busy bar that a beer contains “Brettanomyces”, “Pediococcus” or “Lactobacillus” and you’ll likely pick up a few disgruntled stares from fellow patrons. Even brewers tend to shorten them to things like “Brett”, “Pedio” and “Lacto” respectively. 

For me, the best way to describe beers that are fermented with a mixture of yeasts and bacteria is either “mixed fermentation” or “spontaneous fermentation”. 

The first is ideal for most beers that fit under this umbrella because it immediately indicates to the customer how this beer has been fermented and gives them the option of delving deeping into which specific cultures were used if they wish. The second describes a specific set of beers, which are inoculated by capturing yeast and bacteria that naturally occur in the environment. Beers such as Belgian lambic are made in this way and we’ll get deeper into that a little later on. 

If the wine world can convince drinkers to freely describe grape varietes such as “Pedro Ximenez” or even mouthfuls such as “Gewürztraminer” (an aromatic German white wine variety) then I have every confidence that we, the beer lovers, can talk about yeast, bacteria and oak ageing in much the same way. 

The Wheel of Sour

There are many different types of beer that can fall under the “wild” or “sour” bracket. In fact wild is often used instead of sour to describe a beer fermented with Brettanomyces (literally translated from Greek this means: British Yeast) because Brett doesn’t actually make a beer sour. It makes it tart, funky and fruity – but it does not make a beer sour. 

The simplest way of making a beer sour is to lower its pH – the base acidity of the beer – using Lactobacillus when mashing in the grains to extract their sugar for fermentation. This technique is commonly known as “kettle souring”. This adds about 24 to 48 hours to a beer’s production time, incurring little extra cost to the brewer. An advantage of this process is that, once soured, the beer is boiled – killing off the bacteria and protecting the brewery from becoming contaminated. The last thing a brewery wants is for its clean fermented beers to become sour beers too. 

The resulting beers have a very one-dimensional sourness, lacking the complexity that mixed or spontaneous fermentation beers possess. I would say that it’s acceptable to badge this specific style of beer as “sours.” 

There are some great examples out there too. Some recent highlights for me have included the intensely flavoured dry-hopped sours from Manchester’s Chorlton Brewing, especially its Amarillo Sour. Tzatziki Sour from Liverpool’s Mad Hatter is another excellent example. It’s soured using the naturally occurring bacteria in Greek yoghurt before receiving additions of mint and cucumber. It’s about as far removed from a traditional beer as you can imagine. 

Mixed fermentation beers take significantly longer to make and typically cost a lot more money. This is not just because of the varied and complex method of fermentation, but because of the amount of time they need to mature into a finished product. Once they’ve completed an initial fermentation period, mixed fermentation beers are typically aged in oak barrels for anywhere from a few months to several years. 

The barrels themselves can vary too: from virgin oak to barrels that once held wine or spirits such as bourbon to large oak vats commonly referred to as foudres. Sometimes the beers may even be aged with fruits such as cherries or raspberries in the barrel. Brewers must perform the arduous task of regularly tasting the aging beer to know when it’s ready to be blended. 

Blending is a true art form – it’s here that a brewer puts their palate to the test to create something delicious that has both nuance and balance. At Colorado’s New Belgium Brewing there are in 64 foudres in its mixed fermentation program that each contain around 20000 litres of beer. Its master blender, Lauren Salazar, will blend slightly sweet six month old beer with much more tart and sour two year old beer to create its flagship sour red, La Folie. Its flavours of overripe stone fruit and tart cherries are the result of Salazar carefully monitoring how the flavours of the beer progress before eventually fusing it into one complete whole. 

Spontaneously fermented beer is aged and blended in much the same fashion as mixed fermented beer – but there are a few crucial differences between the two. Most importantly, a brewer does not inoculate this type of beer. Instead the freshly brewed wort is poured into a large, flat metal tray known as a coolship. Here it is left to cool overnight – and when it does, the locally occurring wild yeasts present in the air will inoculate the beer. The following morning the beer will be transfered to oak barrels for fermentation, followed by its lengthy maturation period.

The most prominent examples of spontaneously fermented beers are Belgian lambics, which once blended and bottle conditioned become Gueuze. This style of beer can range from being intensely sour, such as those from Hanssens or Cantillon, to soft, balanced and subtly tart, such as the beer produced by Boon or Tilquin. From flavour to presentation, these beers have a depth and complexity that can easily match a great bottle of wine. 

The Future of Flavour

There’s more to mixed and spontaneously fermented beer than that brief summary, but it should give you an idea of how challenging these beers are to make, and the possibilities they present brewers to experiment with.

One of these brewers is Mark Tranter, who founded Burning Sky brewery in the village of Firle, Sussex, in 2013. Alongside an accomplished range of pale ales and IPA, Tranter produces an impressive range of mixed fermentation beers. These include the softly tart and complex Saison a la Provision and the deep and tannic Monolith; a strong, dark beer aged in foudres that once held red wine. 

Tranter isn’t content with merely producing mixed fermentation beer, however. In January he announced Burning Sky would be commissioning a coolship of its own, featuring a canopy fashioned from barrel staves already inoculated with a range of yeasts and bacteria in order to help guide the flavours he desires from fermentation and aging. 

“I’ve long been a fan of gueuze, lambic and saison from Belgium and spent a lot of time poking my nose around breweries, getting little bits of information here and there and generally going from enthusiastic to semi-obsessive about these beers,” Tranter says. “The first ever brew we did here was a mixed fermentation Saison and to say I was happy with our first foray into the world of ‘bugs’, would be an understatement.”

I believe that, along with The Wild Beer Co, Burning Sky are at the forefront of a quiet revolution led by millions of yeast and bacteria, silently fermenting beer in oak barrels. Both London’s The Kernel and Brew By Numbers are already flexing some serious brewing muscle in the mixed fermentation department. Manchester’s Cloudwater and London’s Beavertown are also investing heavily in barrel ageing projects and both already have foudres in place. This new wave of wood-aged beers will not be a mere flash in the pan – this is really happening.

Unlike The Wild Beer Co’s Andrew Cooper, Burning Sky’s Mark Tranter tends to agree with me that UK-produced mixed and spontaneously fermented beer is a trend that’s set to skyrocket. 

“For me it shows a growing maturity in the marketplace. Certainly, if you look at the ‘new’ UK beer scene, which started a decade ago and has exploded in the last five years, it’s a natural progression,” he says. “As the drinkers’ palate develops, people will look for the sort of subtle depth that is only achievable with spontaneous or mixed fermentation.”

If you look at the ‘new’ UK beer scene, which started a decade ago and has exploded in the last 5 years, it’s a natural progression

It’ll be several years before we experience the results of Burning Sky’s foray into spontaneous fermentation, but judging by its current output it’ll almost certainly be worth the long wait. By the time it arrives on the market, I imagine things will look very different. We’ll not just have more UK producers brewing mixed fermentation beers. 

The Belgians will want more market share as lambic, gueuze and other styles such as Da Brabandere’s oak aged sour pale ale grow in both production volume and popularity. In the US, the mixed fermentation beer market is becoming ever more established, with producers from Maine’s Allagash Brewing to California’s The Rare Barrel releasing some of the most exquisite beer you haven’t tasted yet. It has to be, for me at least, the most exciting sector in craft beer in a world full of so many copycat pale and hoppy beers. 

It could also be how beer well and truly enters the restaurant market and finally takes its rightful place alongside wine when paired with food. These beers aren’t going to replace the hoppy, pale beer at the heart of craft beer. That is theirs for evermore. What it is going to do is broaden the spectrum of the great beer available, demonstrating the scope beer has for flavour, nuance, balance and innovation for many years to come. 

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