what is a sour beer

What Is A Sour Beer And How Is It Made?

I don’t know what is more intimidating, the initial taste of a sour beer or trying to pronounce what is in it. Lactobacillus, pediococcus and brettanomyces are not the most friendly of terms. However, answering the question; “What is a sour beer” helps us understand these beers better and appreciate the vocabulary used to describe them.

If you do not like sours, these words sound a bit crazy but hold on and keep reading. There was a time not that long ago that I didn’t like or understand sour beers. While there are still some that overpower me; I am now a fan of sour beers and love getting to know more about them.

What is a sour beer?

Sour BeerAt one time, almost all beer was sour in some way because of poor sanitation and the use of wooden barrels for storage. Through decades of improving the brewing process, sour beer was eliminated. And through this process we also learned how to make intentionally sour beer in a controlled manner.

The use of specific yeast and bacteria cause the beer to become sour, tart, funky or  add other unique flavors. Quite often, these yeast and bacteria are referred to “bugs”. Here are the most common:

Brettanomyces – Often called Brett -This yeast is commonly used in sour ales. It produces rustic or “horse blanket” flavors. I know that sounds disturbing and it does take time to develop a taste for it. Pairing this yeast with bacteria produces complimentary flavors.

Lactobacillus – Often called Lacto – This bacteria makes the beer tart through the production of lactic acid. This is typically found in low ABV and low hop beers.

Pediococcus – Often called Pedio – This bacteria makes lactic acid as well but also produces diacetyl which has a buttery taste. This is almost always paired with Brettanomyces.

There are other yeast and bacteria that can be used but these are the most common. Some breweries use open fermenters which allow local bacteria in the air to “infect” the beer and provide a unique flavor profile that can only be produced in that location.

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How A Beer Becomes Sour

Urban Artifact Warmug Golden Fruited Coffee SourCreating a sour beer follows a similar process as any other beer but along the way, specific steps are taken to alter the final flavor. Since I am not a brewer, I enlisted some help from my friends over at Rivertown to help me understand how a beer becomes sour and they provided some great info. Basically, a beer must be “infected” with the wild yeast or cultures to make it sour. This normally is done to the wort prior to fermentation. There are three ways to do this.


Just as this sounds, this is the process of knowingly inoculating a beer with bacteria and yeast that cause sour characteristics.

Unrestrained Inoculation; aka Open Fermentation, is one form of doing this. This format exposes the beer wort to the open air where microbes naturally find their way to the beer. Many classic styles of sours use this method.

A brewery could also employ Restrained Inoculation to sour the beer. This is the process of adding specific cultures to the beer so they can produce a consistent flavor time after time.


This process adds lactic acid the wort to produce sour flavors. It does not use wild cultures in the form of microbes. The downside is these beers might lack the complexity of using actual bacteria to sour the beer. However, it also eliminates the risk of microbes from contaminating other beers in the brewery.


This is the least favorable way to achieve a sour beer. For this to happen, bacteria has to get into a beer that was not supposed to be sour. In most cases, these beers are destroyed since they are not what was intended by the brewery.

Many sour beers are barrel-aged where additional bacteria in the barrels can impact the final flavor of the sour beer. So each batch of the sour beer is unique and for that reason breweries often blend multiple batches and vintages together to produce the desired flavor.

Related Post: Five Barrel-Aged Stouts To Try

New To Sour Beers?

Single Tree Hickory Sour BeerI know that many have avoided sour beers or have not enjoyed the few that that they have tried. And I completely understand but I encourage you to keep trying them. Like many unique food flavors; it will take time to learn to like them.

Also, stayed tuned to my future articles. I have a few more planned that will discuss sour beer styles and how you can learn to like them. The best way to ensure you don’t miss a post is to subscribe. You can also follow me on your favorite social media platform.

Do You Like Sour Beers? If So, Comment Below And Tell Me Your Favorite

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