Hopskull’s Guide: Introduction To The Wonderful World Of Sour Beers!

Welcome to an article about some of the best beer styles in the world – The sour beers! A sour beer can easily seem a bit daunting for most beer drinkers, as the flavor profile of sour beer is acidic, fruity, complex and tart!  The Sour beer styles are often pushing to the perception of what beer is? – Especially in the world of ”macro” beer drinkers, as most have drinkers have the mindset that the Lager/pilsner beer is the one and only ”true” beer style in the world, and that sour beer is a weird gimmick.

I’ve had thousands of discussion with people about what beer is? Most beer drinkers don’t even know that the sour beers are in fact the most original beer styles, and came to be long time before the Lager/Pilsner beer!


Prior to the 18th century brewers were aware that something ”magical” happened when they wanted to turn their watery mixture (wort) into beer - well at least if the fermentation went well. – The key word is ”spontaneous fermentation”, and the magic has been unveiled to be a mix of wild yeast and bacteria. Back in the 18th century these yeast and bacteria were either friend or foe! When things went bad, the brewers then dubbed the failure of fermentation as ”The Beer diseases”.

Along with time came a few men, which became really important in the world of beer, and forever changed the face of beer with their pasteurization and purification of yeast, thereby eradicating all the funky sour yeast and bacteria – thanks Louis Pasteur and Emil Christian Hansen! Your work paved the way for ales and lagers!

BUT the discovery and commercialization of pure yeast and thereby consistent beer brewing didn’t mark the death of sour beer, as the different sour beer styles have become highly appreciated and very sought after today! – With some bottles reaching astronomical economical highs, just like fine wine!

If you find yourself getting bored with normal ales and lagers, well I highly recommend that you turn your sight towards some sour beers, and slowly delve into the best beer style in the world. Lets dive in, and uncover the wonderful world of Sour beer


What is a sour beer?


Sour beers were originally invented and brewed hundreds of years ago in Belgium and France. Back then Sour beers contain yeast and bacteria that had been introduced by spontaneous fermentation, or because of spoilage. Fast forward to present day, brewers now intentionally pitched the unfermented wort with single bacteria strains along side the yeast or use mixed cultures of yeast and bacteria.

You’ll still find some brewers still rely on the magical tradition of spontaneous fermentation, a process by which the unfermented wort is exposed to the outside air, and wild yeasts and bacteria are present in the environment are allowed to inoculate (Infect). After a few days, a combination of different strains of bacteria and yeasts begin fermenting the sweet wort for a little year, giving the different yeast and bacteria room to develop and impact with various flavors. After the fermentation is complete, the beer can be aged, sometimes for many years!


But any method of brewing sour beer is unpredictable, and different combinations of wild yeast and bacteria create very different styles of beer throughout the world.

The whole sour beer thing is quite simple, but at the same time really complex!

Lets rewind a bit, and take a closer look upon the yeast and bacteria that are responsible for fermenting wort into that delicious sour, tart, fruity and sometime complex beer. Grab your microscopes and get to know ”The Three SOUR-teers and the odd man out”


The Three SOUR-teers and the odd man out!:


Thanks to work of Antonie Van Leewenhoek ”The father of microbiology” whom work with improving microscopes paved the way for others like Louis Pasteur and Emil Christian Hansen to unveil which yeasts and bacteria play the parts in spontaneous fermentation – thereby ending the whole idea that magical stuff happened.


What was considered magic in the 18th century was in fact caused by an array of different yeasts and bacteria but when it came to souring the beer, the key players have been unveiled to be LactobacillusBrettanomyces, and Pediococcus ohh, and the odd man out Acetobacter! Disclaimer - I got to point out, that Brettanomyces produces acid, but the quantities are to low for the human pallet to pick up! Many think that Brett plays a part of souring beer, that idea lead to the creation of ”Brett Not Sour IPA” by the American brewery Yazoo Brewing Company – simply because they wanted to really stick it in your face, that Brett doesn’t create detectable levels of acid!

Lets quickly run thru ”The Three Sour-teers and the odd man out”



Lactobacillus is in fact a normal bacteria found in humans - mouth, stomach, intestinal tract, and the vagina. Like Yeast, Lactobacillus is able to ferment sugar.

Lactobacillus is important in production of cheese, and yogurt, and Lactobacillus is also used to acidify food and produces a “sour” flavor. Lactobacillus metabolizes sugar and produce lactic acid which supplies a sour taste. Beer styles in which a sour taste is desirable are e.g. Lambic, American sour beers, Berliner weisse, Flanders, Gose, and Belgian witbier.

Ohhh Bonus fact! There exists a beer, which is made with Lactobacillus from a vagina! Yep, that’s a thing!

A company named The Order of Yoni have isolate and prepared Lactobacillus from The vagina of Czech model Alexandra Brendlova and brewed a sour beer named “Bottled instinct” which has a 2,99 Points on Untappd.

If you want a beer flavored with your girlfriend’s vagina bacteria, you can in fact get it! The order of The Yoni offers to brew a batch specially with your girlfriends flavor - you just have to pay them the small amount of 10.000 €



Brett is a all eating strain of Wild yeast genus - found primarily on fruit skin BUT Can occasionally become airborne by Wind, or get carried around by insects, thereby contaminating Wooden structures or objects such as barrels, wooden walls and beams. It’s also possible to buy packages of Brett from a yeast manufacturer.


Brett can brake down complex sugars such as the sugar “cellubiose” found in wooden barrels, Lactose, dextrins, glucose and fructose.

The genus Brett has a total of 6 different species, but for beer fermentation, there are 4 specific species of Brett, which are superstars! And here are a few words on them:

“Brettanomyces claussenii”: This strain was The first one found and isolated by Danish scientist N. Hjelte Claussen, the lab director for the New Carlsberg Brewery. In 1903 he discovered the yeast while investigating the causes of spoilage in English beer. The Brett yeast was discovered in oak barrels previously used to transport British Ale. The Brett genus was immediately named; British Fungus (Brettano-myces) by Claussen.


“Brettanomyces bruxellensis”: Strains within this species can offer the classic horse blanket and barnyard funk associated with Brett, but also nuances of grass, leather, pie cherry and citrus.

“Brettanomyces lambicus”: as its name suggests, it is closely associated with lambics! This is actually just a specific strain of Brett Brux, one that can tend to be supremely funky and earthy.

Brettanomyces anomalus: Strains within this species tend to be less funky than those of the Brux variety; bold pineapple and ripe fruit flavors dominate here.

Lambic and Gueuze owe their unique flavor profiles to Brett, the some goes for Saison/Farmhouse styles! Sometimes Brett it is also found in Oud Bruin and Flanders red ale!



Pediococcus (Often just called Pedio) is a genus of lactic acid bacteria. Like other lactic acid bacteria, these organisms have the ability to ferment sugar into lactic acid. – Pediococcus produces a deeper acidity and mouth feel then Lactobacillus.

Pedio is often found in various foods including pickles, sausages, and milk products.

There are 16 recognized strains of Pedio, and the ”Pediococcus damnosus” is by far the most common in sour beers. This strain has evolved into a super bacteria, with the ability to tolerate the iso-alpha acids in hops (Which act as a antibacterial preservative).

When using Pedio in beer, brewers will often encounter the fermentation by-product ”Diacetyl” which is characterized by a buttery aroma and flavor.

Diacetyl is considered an off-flavor, but brewers have uncovered a little trick to get rid of the Diacetyl – Brettanomyces has the ability to break down the Diacetyl, and the two are often used/found together when brewing sour beer.



 The reason I call Acetobacter the odd man out, is because I think – and know, that most sour beer lovers don’t like too much presence of him! Acetobacter produces acetic acid and is referred to as the  ”vinegar bacteria”. Acetobacter is a genus of aerobic bacteria, which can turn ethanol into acetic acid during fermentation if Acetobacter gets enough aeration/oxygen during fermentation it will thrive, and unfortunately turn most beers into salad dressing.

In Lambic beers and some other sour beer styles, acetic acid can be a desirable component that adds to the complexity of the flavor and aroma profile.

If you want to try a beer with a quite high acetic acid profile, I recommend The ”Duchesse de Bourgogne from Brewery Verhaeghe” – I’m not that big of a fan, as I tend to think, that it’s almost like a Malt vinegar salad dressing.



Quick summery: Types of acids

Acetic (vinegar flavor – just think vinegar!)

Lactic (sour milk-like flavor – yogurt like character)

Malic, and Citric acid (strong tartness like lemon)


PH Scale and Titradable Acidity


Remember what your chemistry teacher told you about the concept of pH? – if not, lets quickly run thru this subject! pH was invented and first introduced by the Danish chemist Søren Peder Lauritz Sørensen at the Carlsberg Laboratory in 1909 – Yep, Carlsberg paved the way for a lot of things!

pH stands for “potential of hydrogen, and is a simple tool/scale used to specify how acidic or basic/ alkaline a aqueous solution is. (Things, which are Soluble in water) 


pH is measured on a logarithmic scale from 0 (the most acidic) to 14 (the most alkaline), with 7 being neutral like regular water


Why do I tell you all this? This isn’t telling you much about which beers you should buy or taste, as there aren’t many beer labels with the pH level written on them – pH really only maters to the brewers.


Brewers manage their pH values mostly to enhance enzyme performance in the mash and give the yeast the best performance possibilities in the fermenter – which of cause will impact quality of the finished beer.


But brewers have found a way, to tell their consumers a little about how acidic – or at least how many grams of acid is Soluble in the beer, thereby giving the consumers a hint about how acidic the beer might feel on the taste pallet. pH only tells about disjointed hydrogen from stronger acids, but the acids made by yeast and bacteria fermentations are weak acids and cat be measured as easily as strong acids. What now you might ask? well the key word is Titradable Acidity (TA).


TA and pH are related in that they are associated to acidity. Titratable Acidity (TA) is a measurement of the amount of acid present in a solution. It is expressed as grams/liter (g/L).  The pH simply tells how strong the acid is, and TA tells how much acid is present in the solution – I also have to point out, that two solutions with the same g/L of acid may have very different pH readings if one solution’s acid is weaker than the other’s. This also means that the perception of acidity will often differ, acids made by yeast and bacteria fermentations are weak acids – complicated? Yes! But no one said that understanding acid chemistry should be easy. Another thing I also must point out is that other factors also change the perception of sourness in beer; include carbonation levels, alcohol levels, flavors from fruit or barrels the beers have aged in.


But in the case of TA, it may also give some drinkers a better idea of what to expect when they order a beer. Mikkeller Baghaven Beers showcase the TA on the side of the logo, which is a tremendous help!


Also the pH and TA measurement tools, helps the brewers with a good chance of re-creating the sour beer!


So remember! Next time you stand in the bottle shop, or order a beer – ask about the Titradable Acidity, as the acid grams/liter (g/L) is a really good guide when selecting the right sour beer for your preference.


Where to start your sour beer journey?

Ok, time to get down and dirty! We have gone over the subjects, what is a Sour beer? , The Three SOUR-teers and odd man out and pH Scale and Titradable Acidity– I think you’re ready to dive into some sour beers, and hopefully find something you’ll like – or learn about new ones to try!


I’ve put together a list of different beer styles, and rated them on a scale from 1-5 HopSkull’s whereas 1 is for the sour beer novice, and 5 is for the sour beer veteran.

Berliner Weisse / Kettle Sour (1 HopSkull)

Berliner Weisse is variety of sour wheat beer. The style originated in Germany and was once hugely popular. The style probably dates to the 16th or 17th century and was so renowned that Napoleons troop supposedly called it the “Champagne of the North.”

The Berliner Weisse is very low in alcohol - around 3 or 4 % ABV. The beer is mildly tart, clean, fruity characteristics and a dry finish. Traditional Berliner Weisse is accompanied by fruit syrup, such as raspberry or green woodruff that’s added when serving the beer. The syrup adds both sweetness and additional complexity.

Traditionally the Lactic acid sour profile was primarily created by adding Lactobacillus, either in the fermentation vessel or by bottle conditioning. Legends have it, that brewers traditionally buried the bottles in warm earth for several months thereby creating the best environment for the acidification and conditioning.

Fast forward to present day, most brewers create Berliner weisse by the kettle-sour technique.

The kettle-sour method is quite simple! Brewers follow a traditional mash schedule then transfer the unfermented wort to the boil kettle, then pitch Lactobacillus into the wort and let it sit (the time in the kettle varies depending on the level of intended sour, from a few hours to a few days). They then boil to kill off the Lactobacillus, and ferment with brewers yeast – voila! Instant Sour beer - additions of different flavors like fruit are done, to balance out the lactic acid.

Gose (1 HopSkull)

Gose pronounced "Go-zuh," is a very traditional German beer style that’s in fact it's many centuries older than e.g. German Pilsner or Kölsch.

The history of the Gose beer style traces back to late 15th century, and The town of Goslar,

Eastern Germany, which historians believed the beer got its name from.
Another theory is that the name Gose is really derived from the Gose River which has been providing the Goslar villagers with fresh brewing water.

Once a very popular beer style which Unfortunately, meet a decline during World War I, and by the end of World War II, Döllnitz brewery, the remaining Gose brewery at that time was finally closed.

Luckily the beer style has once again risen, and is being brewed by a lot of different breweries across The Globe.
Traditional Gose is spontaneously fermented, however most brewers now brew Gose by using the kettle-sour technique, similar to Berliner Weisse

The Gose beer is a cloudy yellow, top fermented unfiltered wheat beer, that’s flavored with coriander and salt. It’s crisp with a low IBU and a has a subtle dry’ness, Sometimes additions of different flavors like fruit are done, to balance out the lactic acid.


Saison/ Bière de Garde (2 HopSkull’s)

Both farmhouse Ales – one Belgian, one France! The main thing they have in common is that they both are pale ales, which are highly carbonated, fruity, spicy, and often bottle conditioned.

These beers were originally brewed in farmhouses (they are also known as farmhouse ales) during the winter and spring where  – for consumption during the summer. The reason the beers weren’t brewed during the summer was because a fear of uncontrollable yeast and bacteria, which would lead to spoiled beer.

The Saison is a lower % ABV beer, which got its name after the main consumers of the beer style – the seasonal workers (”saisonniers”)

The Bière de Garde - meaning ”beer for keeping", is a stronger farmhouse ale style, which similar to the Saison was brewed during the winter and spring, and consumed during the summer. The Bière de Garde is a higher % ABV beer.

Both styles share the ability to become mildly sour/tart over time - or intentionally soured by the brewer. The historical reason theses beer often became sour, was because wild yeast and bacteria often where present in the staves of the wooden beer barrels, which often sparked a secondary fermentation/acidification process.


The Saison and Bière de Garde isn’t the sourest beer in the world, but a great intro to other styles such as American wild ale and Lambic! – You must learn to crawl before you can walk


Flanders Red Ale (3 HopSkull’s)

Flanders Red Ale - "the Burgundy of Belgium"! Is a style most commonly brewed in West Flanders, Belgium.


Many consider this to be one of the most wine like/vinous beer styles. Why this you might ask? – Simply due to higher amount of tannins, mostly the woody oaky tannis and the beer has almost zero to non-presence of hop characteristics. As a matter of fact, Flanders Red Ale is usually aged for up to three years in oak barrels – This is where the magic happens, with naturally occurring bacteria, and yeast in the barrel give the ale a mild sour/tart flavor.


Flanders red ale has a fruity flavor profile, with plum, black cherries, raspberries and even dried fruit like cherry, raisins, prunes and plums being present in the beer.


Those flavors, along with the tannins present from the barrel aging and that fermentation with lactic acid, contribute to the wine like /vinous character.


Oud bruin (3 HopSkull’s)

Oud bruin (Old Brown) is a beer style, which originate in East Flanders, Belgium. The style has its roots back to the 1600th century. Legend has it, that it was brewed as a “provision beer” that would then develop some sourness as it aged.


Oud bruin is characterized by having an dark red’ish-brown to brown in color, malty caramel, with fruity complexity of dried fruits - prune, plum, and black cherry and of course some sour notes. Somewhat sherry-like character like “sweet-and-sour” profile is coming fourth as the beer ages.

Unlike Flanders red ale, Oud bruin is aged in steel tanks and fermented with a mix of yeast and bacteria.


American Wild Ale (5 HopSkull’s)

Most American wild ales are brewed by relying either on mixed fermentation, where a special blend of yeast and bacteria is pitched to the unfermented wort.


Some breweries like Allagash brewing company or Mikkeller Baghaven use two methods when they create their beers.

Other than utilizing mix fermentation, these mentioned breweries also create spontaneous fermented beer by the help of a koelschip (More about that down below, in the section about Lambic – Most brewers don’t call their wild ale Lambic, in respect of the Belgian brewers and traditions! The method of koelschip inoculation bears a few names – Méthode Gueueze, Méthode Lambic or Méthode traditional are a few of the way the brewers categorizing their Lambic and Gueuze inspired beer made outside of the traditional region of Belgium.  


The style of American wild ale varies greatly depending on the malt, old hops, adjuncts, how long the beer is aged, what kind of vessel it's aged in (wood or steel barrel), and of course the types of wild yeast and bacteria that has been used.


The flavor profile can include sour/tart, funky/barnyard, earthy, fruity, vinous and woody notes. It’s quite popular to blend different varieties of fruit into the beer, and make fruited sours.


Lambic (5 HopSkull’s)

Lambic is the name of a Belgian beer produced by spontaneous fermentation.
Lambic is produced in a very limited geographical area, Payottenland in Zennedalen near Brussels, as there is the right composition of microorganisms in the air.

Instead of adding yeast to start the fermentation, the unfermented wort goes into a Koelschip (Coolship) after the boil is done. A koelschip is a broad, open-top, flat vessel in which wort cools down, thereby initiating spontaneous fermentation – by being inoculated (infection) by the wild yeasts and bacteria in the air or surfaces in the building in which the koelship is standing.

The fermentation of Lambic is only started from mid October to mid May, where the average temperature in the area is approx. 15 degrees Celsius. In the summer, there are too many unwanted bacteria in the air.

Lambic has a crisp, sour taste, acidic scent, funky, fruity dry, woody, and vinous taste – in other words complex

Lambic is often Serving as a base for different beers, Kriek (Cherry Lambic), fruit Lambics and “The Champagne of Belgium” - Gueuze.

Gueuze is a type of Lambic. It is made by blending (gestoken in Flemish) 60 % young (1-year-old), 30 % (2 -year-old) and lastly 10 % (3-year-old) lambics, which is bottled for a second fermentation.

Because the young lambics are not fully fermented, the blended beer contains fermentable sugars, which then allows a second fermentation to occur. Older Lambic brings more Brettonomyces and complexity while Gueuze blended with younger Lambic will often be softer in character



It may be hard to imagine that sour beers are one of the hottest things on the crafter beer scene, as flavors and describers like - sour, tart, acidic, funky, fruity, dry, woody, vinous and complex are something which people go nuts about!

But thing is, when delicately balanced, these beers can hold their own against fine wines for their depth and complexity. The first sip of a sour is an exciting and for some a strange new world to delve into.


This is not unlike the IPA when it began achieving accessibility and renown; sours are daring and challenging people to step outside their comfort zone and head deeper into the rabbit hole of this type of craft beer – be carful, you might not climb up again!


I hope you learn a thing or two, and that I got around all the important things – this was perhaps the most lengthy blog entry I’ve ever done! Hope it will help you on your craft beer journey!


Yours truly,