A Stroll on the Sour Side: Understanding Sour Beer

Tart, sour, wild. Lacto, brett, pediococcus. How about koelschips, kettle sours, and krieks? In an age of craft beer enlightenment, the terminology around sour beers can still read as inscrutably as the side of a prescription drug bottle.

More importantly, the odd words belie a legitimate concern for sour consumers: with all the confusion around what a sour is, it can be damn near impossible to know what the next beer you try will smell or taste like, let alone whether it’s worth the often steep price tag.

If you’re anything like me, you’re tired of being left in the dark when it comes to sours. So let’s charge up the flashlight, scatter a few shadows, and take a stroll on the sour side.

What is sour beer?

When talking about or labeling this type of beer, brewers often lean on two very broad terms: sour and wild. These terms actually categorize in completely distinct ways, and neither refers to a specific beer style.

Confused? At a high level, it can be summed up simply. “Sour” is a taste: a sour beer presents tart and acidic flavors, as opposed to a beer that is more hoppy or malt-forward.

“Wild” refers to the fermentation style, that is, the yeast. The vast majority of non-sour beers are fermented by a strain from one of two yeast types, one for ales and one for lagers. Wild beers are different—they’re either exposed to whatever yeast appears naturally in the environment or deliberately fermented with a yeast that behaves unpredictably, like Brettanomyces. The result might be sour-tasting, but it could just as easily be funky, hoppy, boozy, or a complex melange of sensations and aromas resulting from the brewer’s imagination and nature’s whim.

Take this point home: not all sour beers are wild, and not all wild beers are sour.

If that’s the case – as hard to wrap one’s head around as it might be – how does a sour beer become sour, tart, fruity, or whatever whirlpool of flavors end up on the drinker’s tongue?


The biological toolbox

Here’s where brewers really get to have fun (and where some novice brewers get overwhelmed). Most commonly, they’ll look at one or more of these ingredients:

Brettanomyces. I mentioned this one earlier. It’s a type of yeast, and it’s cultivated for use in a wide variety of Belgian and American-style beers. Brett makes things funky: if you see descriptors like barnyard, horse blanket, tang, hay, dirty, or sweaty, there’s a good chance this yeast was involved. And if some of those qualities don’t sound like things you’d like to put in your mouth, know that they’re often the result of Brett gone wild—well, I guess, too wild. But as balanced accents in a layered brew, they can actually do wonders.

Lactobacillus. This one’s bacteria, and it converts sugars to lactic acid instead of alcohol, which means that it needs to be used in combination with yeast to ferment the beer. That lactic acid results in a clean, relatively pure sourness that works well in low-alcohol brews and keeps things mild enough to be refreshing.

Pediococcus. Like lactobacillus, pediococcus is a type of bacteria that converts sugars to lactic acid, but it produces a harsher and stronger sourness that can get out of control for even experienced brewers. Batches that get a good dose of pediococcus are often blended with other batches to smooth out the rough edges.

Putting the tools to work

With these three biological tools at their disposal, sour brewers develop a wide range of recipes and rely on significantly different brewing techniques. One of the oldest is the koelschip, an open fermentation vessel traditionally made of wood that exposes cooling wort (pre-fermentation beer) to anything in the local air. Non-wild beer styles sometimes use koelschips, but wild ones can depend on them.

Even in traditional fermentation vessels, bacteria, Brettanomyces, and its wild cousins behave in a less predictable fashion than ale and lager yeast strains. As a result, sour beers can not only take a long time to ferment, but they also usually require aging, typically in oak or stainless steel barrels, to balance out extreme flavors and achieve the final outcome that the brewer wants.

Some sour beers also get fruit flavor by introducing fruit in secondary fermentation. Yeast from the fruit’s skin or interior brings new flavors to the beer as the fruit breaks down. Note that this is different from another common practice associated with sours: the introduction of fruity, herbal, or spiced syrups to sweeten or counter extreme sourness. Such syrups are not typically part of the brewing process and can be added to a finished beer.

What about kettle souring?

Many of you have probably seen a label, menu description, or review that referred to a particular brew as “kettle soured.” Just as likely, you’ve heard or read someone use the term derisively.

While kettle sour is currently the most common term, the relevant distinction is really between two key styles:

Aged sours are produced using methods that require significant time, such as barrel-aging, wild fermentation, and blending.

Quick sours typically take less time and money, and they can be made in a few different ways. Most commonly, lactobacillus is introduced either during the mashing process or in the kettle during the boiling process. (The former option is not really a “kettle sour,” which is why “quick” is a better catch-all term.) Either way, beers produced using the quicker method tend to be less nuanced than aged sours, but there’s nothing inherently wrong with them. Styles such as gose and Berliner weisse have almost always been made in a “quick” way, using lactobacillus added during the boil, acidulated malt in the malt bill, or both.

If quick souring can lead to good beer, why is it an issue in the current beer community? In addition to the less-layered, more one-note nature of quickly produced sours, the quick methods introduce a greater likelihood for off flavors or unpleasant aromas.

In addition, although they’re cheaper to make than aged sours, they’re often marketed in the same way and at the same price point as the much more expensive and delicate aged versions. This marketing or branding practice confuses consumers and can hurt the overall sour market. For this reason, it’s well worth a conversation with a knowledgeable brewer, bartender, or bottle shop employee to get a handle on whether that $30 bomber earned its price tag honorably.

Sour beer styles, and some picks

To reinforce your newfound sour knowledge, survey the most common sour styles and sample at least a few of each type. I’ve listed  one or more examples of each style that’s pretty easy to find in most states, followed by others that are worth a try if you spot them.

Berliner weisse. This German style is tangy, very light in color, and low in ABV. It’s a refreshing summer beer and only slightly sour. As its name implies, it uses wheat malt.

Start with: Dogfish Head Festina Peche

Then try: Smuttynose Smutt Labs Smoked Peach Short Weisse or others in the Short Weisse series

Gose. Another German-style sour, the gose uses a higher percentage of wheat malt than its brother from Berlin. It’s distinguished by the addition of salt and coriander, which makes it slightly fuller in body, though it’s still very light overall.

Start with: Sierra Nevada Otra Vez

Then try: Uinta Ready Set Gose, Victory Kirsch Gose


Lambic. Moving to Belgium, this style is also wheat-based, but it’s much more complex – arguably one of the most complex and least understood styles in modern beer production. Lambics use a “spontaneous fermentation” involving many bacteria and yeast, some of them wild or even unknown. With so much mystery surrounding the brewing process, lambic producers change as little as possible about their brewing conditions, going so far as to avoid dusting barrels or cleaning away cobwebs!

Because of the lack of control and harshness of the many varied yeasts, lambics are aged in barrels. Because even the resulting batches are then very different from each other, brewers taste from each one and create blends and combinations to get the desired results, discarding output that is too extreme even in blended form. The end result can be complex, fruity, slightly sweet, and almost as acidic as vinegar.

A side note: the lambics most commonly found in US craft beer stores are fruit lambics, which are a distinct varietal that includes the whole-fruit additions referenced earlier. Beyond fruit lambics, you might also see lambic varietals like gueze (blended old and newer lambics) and faro (lambic sweetened with syrup, with spices added, or both).

Start: Lindeman’s Framboise

Then try: Cantillon Kriek , Hanssens Oude Gueze

Flanders red/Oud bruin. Originating in Flanders, both styles have reddish to brown color. They might exhibit a bit of bitterness and more malt presence than other styles in this list. Oud bruins can have woody notes, sometimes from aging in oak. Some varieties are also exposed to actual vinegar bacteria, lending a very tangy, almost savory component.

Start with: Rodenbach Grand Cru, New Belgium La Folie

Then try: Duchesse De Bourgogne, Liefman’s Goudenband

American wild. This label is a bit of a catchall, as breweries have only embraced the wild styles relatively recently. These beers draw influence from all of the other styles listed here and embrace all varieties of bacteria, yeast, and souring techniques, including kettle souring, oak aging, and blending. Until breweries volunteer or consumers insist on better labeling, you don’t really know what you’re going to get here. But don’t let that stop you –amidst the tremendous variety are some tremendous beers.

Start with: whatever you can find!

Then try: Russian River Temptation, Allagash Emile, Wicked Weed Recurrant or Black Angel

Also look for offerings from: Jolly Pumpkin, Jester King, Cascade, Crooked Stave, Lost Abbey, The Bruery




Julian Cantella

Julian Cantella

Professional writer based in Delaware. On the lookout for brain-altering music, beer, film, food, and people.
Julian Cantella

One thought on “A Stroll on the Sour Side: Understanding Sour Beer”

Comments are closed.