Food & Drink

Everything You Need To Know About Sour Beers

Pucker up!

Sour beers have become huge in the past couple years, which weirdly makes Trappist monks the biggest hipsters in the beer world, considering they've been making them for centuries. Now that most major American breweries are at least dabbling in the sour arts, now's as good a time as any to learn what the hell all these beers are about. For a little lesson in the science of sour -- and, more crucially, a list of the best old- and new-school versions out there -- we hit up resident beer expert Zach Mack of New York's ABC Beer Co. and Governors Island Beer Co with all our sour questions. Pucker up: this lesson is going to be delicious.

What is it that makes beer sour?

As with most food discoveries, you could say that traditional sour beers come around by way of a misunderstanding of the world and sheer accidental luck. Way back when, beers were stored in wooden barrels or open-air vessels known as cool ships while fermenting. This is the same process used to make lambics -- a style of Belgian beer that relies on spontaneous fermentation. The staves of the barrels and the air around them, unbeknownst to the pre-Pasteur brewers of the day, were home to a host of microorganisms, wild yeast, and bacteria that would play their own part in the chemical reactions taking place as the beer aged for months (or years).

So it’s that simple?!

Actually, here’s where things get a little tricky. Sour beers come about by different microflora that are responsible for different sets of resulting tastes: lactobacillus bacteria (lovingly referred to as “lacto” in the beer world) creates lactic acid, which results in the relatively clean lemony-tart puckering sour you recognize in beers; pediococcus bacteria (which also gets a cute nickname: pedio), similarly creates tart lactic acid but also brings funkier side notes; acetobacter is the same bacteria that turns wine into vinegar and creates acetic acid, giving sour vinegar flavors; and brettanomyces, a wild yeast known as “brett” for short that creates a drier, funkier set of flavors.

That’s a lot to remember. And yes, there’s a whole textbook’s worth of microbiology and cell biology jammed into a paragraph there, but what’s most important to know is the basic flavors that each is responsible for. After all, in many cases, these work in conjunction with one another (especially brettanomyces and pediococcus). Remember, it all started by absentmindedly dumping a bunch of beer into barrels that produced a (somewhat unintentional) sour result. And it wasn’t even until the mid-19th century that Louis Pasteur could prove these cells existed, let alone isolated what they did. Kind of puts the whole idea of ordering up cell cultures from a modern lab to brew a batch of beer into perspective.

Why is brewing a sour beer such a big deal?

Brewers FREAK out when they have to brew a sour beer, because these cells can contaminate a “clean batch.” A lot of slightly larger breweries even invest in entirely separate facilities so they can produce and age sours without fear of infecting their hazy IPAs or pilsners.

Why do sours tend to cost a little (or a lot) more than other styles?

Besides tending to come in larger 750ml bottles, sours require a different kind of finesse than brewing, say, a straightforward IPA. Most traditional styles take a lot of time to make, and use blends of different batches suit a brewer’s very specific tastes. Most argue that it’s worth the wait, because the complexity that can be achieved is arguably second to none in the beer world. The stark flavor profiles make them stand out. Take one sip of a Duchesse de Bourgogne and you’ll quickly understand why Flanders Reds have been described as the “Burgundy of the beer world.”

So what are these kettle sours I keep hearing so much about?

Kettle sours forego the wooden barrels of their ancestors for sleek, inert, and (hopefully) sanitized stainless steel and a tweak on the process. Brewers create a “sour mash” by allowing the beer to cool after the boil, adding lactobacillus, waiting for it to sour, and then pitching yeast and going forward as normal. This takes the process down from months to days to complete, which has been huge for producers during the sour craze of the past few years. In fact, there’s a very good chance this process is responsible for the can of Berliner Weisse or gose that you drank from your small local brewer last weekend.

What are some examples of sour styles?

There’s a lot to unpack, as always, but the best known could be boiled down to a few:

Flemish red

Flanders reds are one of the most storied beers in the brewing world, let alone sours. As we originally said in our guide to Belgian beer, their trademark tartness comes from acetobacter and lactobacillus that were inadvertently introduced to the beer during an aging process in oak barrels that can span all the way up to two years. It’s a medium-bodied beer with fruity flavors (black cherry and currants) that can be bracingly sour, tannic, and complex. Remember when we said it got called the Burgundy of the beer world? That’s why!
A great Old World example: Duchesse de Bourgogne
A great American take: Bruery Terreux Oude Tarte

Geuze lambic

The lambic category is an entire lesson in beer in and of itself. There are the straight lambics, which are so delicate and time sensitive that they aren’t shipped more than mere miles from where they are brewed; the fruit lambics, which vary from traditional examples with fresh ingredients to modern productions made with syrupy sweet fruit concentrates; and the heaviest hitter of all Belgian beers, the geuze lambic, a blend of spontaneously fermented beers (brettanomyces comes into play here!) from batches as far back as three years. Of course, none of these traditionally pack the puckering punch that a Flanders red or oud bruin will, but they are sours, both chemically and flavor profile-wise. We suggest you dive into out Belgian beer guide to get a better run down on what’s at stake with each style here, but suffice to say, the centuries old nickname of “champagne of beers” is not being used sarcastically here.
Great Old World examples: Cantillon Gueuze 100% Lambic (the most sought after example in the game) for geuze, De Cam Framboise Lambiek for fruited lambic
Great American takes: Lost Abbey Duck Duck Gooze for geuze (which is “extremely hard to come by” even in the brewery’s own words), Allagash Coolship Red for a fruited lambic

Oud Bruin

Crassily, you could think of oud bruins as the cousins of Flanders red ales with a few minor differences, but mainly they’re often just a little less fruit-forward and vinegary than their Flemish counterparts. If you’re splitting hairs (or ask a brewer familiar with BJCP guidelines), the big defining differences between the two is that oud bruins today use stainless-steel barrels for aging instead of wood. Oud bruin tends to be one of the harder, more obscure styles to chase down outside of its home country, although this is changing as sour programs take off across the US and elsewhere.
Great Old World example: De Brabandere Petrus Oud Bruin
Great American take: New Belgium La Folie

Anderson Valley Briney Melon Gose sour beer sours beers
Andy Kryza/Thrillist

Gose

Goses hold a special place in the sour world for a few reasons, one of which is their flavor profile. The best examples have a lemony lactic tartness that is balanced out by a subtle saltiness and a dry finish. The second reason is because this beer was out of production for the better part of a century before a brewery was able to track down an old factory worker who just happened to remember the recipe. The story itself kind of has to be read to be believed. These days, you’re  likely to see your local brewer dropping in some fruit to round out the tartness.
Great Old World example: Gasthaus & Gosebrauerei Bayerischer Bahnhof Leipziger Gose... the brewery responsible for bringing the style back from the dead
Great American takes: Lost Nation Gose for traditional, Anderson Valley Briney Melon Gose for a fruited version

Berliner Weisse

It should go without saying that any style dubbed “the Champagne of the North” by Napoleon’s troops is probably worth seeking out to try at least once. Luckily, it has recently become very easy to do just that! Some of the more classic takes have a funky, brett-forward finish, but like gose, there are plenty of breweries who use this wheat-based style to make a bright, easy drinking refresher. Not like that’s breaking too much with tradition: In Germany, it’s common to serve it with along with a shot of raspberry syrup to cut the tartness.
Great Old World example: Professor. Fritz Briem 1809 Berliner Weisse
Great American take: Evil Twin Nomader Weisse

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Zach Mack is Thrillist’s contributing beer writer, the owner of Alphabet City Beer Co. and Governors Island Beer Co. in NYC, a Certified Cicerone®, and absolutely nothing else. Follow him: @zmack.