What do you mean by sour beer?

My trip to Belgium for #EBBC15 has driven home how eclectic the styles termed "sour" truly are. Aside from the fact that not all non-pure-Saccharomyces fermented beers really are sour, the sour/wild characteristics can be imparted by different methods.

These beers fall in to the following broad style groupings

1. Spontaneously fermented (lambic, gueuze etc), e.g. Cantillon
2. Fermented with cultured "wild" strains e.g. Alvinne Morpheus 
3.  Refermented with cultured "wild" strain, e.g. Orval
4.a)Mixed fermentation including bacteria and matured e.g. Rodenbach
b) Mixed fementation using lactobacillus and released young, e.g. Berlinner Kindl Weisse, Ritterguts Gose
5. Pre-soured in the kettle by lactobacillus/lactic acid
6. Refermented/matured in wood
7. Unintentional!

We were fortunate to be able to visit a number of breweries courtesy of both Visit Flanders & the Belgian Family Brewers, plus chat to a lot of the family brewers themselves. I'll use some of these examples to outline the differences, remember if the beers are unpasteurised they can continue to develop over time and can get worse as well as improve! This is not supposed to be an in depth how-to guide on these beers, nor do I want to go too deeply into the science as its pretty complex!  (There are a number of better qualified writers than I on these topics, Including Lars Marius Garshol, with recent posts on yeast and bacteria being particularly informative.)

1. The first "sour" that usually comes to mind are the Belgian lambics. These are brewed as a normal beer (except with the use of aged hops to reduce bitterness impact) then instead of being pitched with yeast are cooled overnight whilst exposed to native flora usually in a coolship with airflow controlled by vents. A number of breweries previously used coolships for cooling only but the lambic brewers specifically intend for wild yeasts and bacteria to inoculate the beer. A complex primary fermentation ensues, where different species including lactobacillus, Saccharomyces, pediococcus and Brettanomyces take the lead at different times. It is then matured in pre-used wooden casks that also contain a mixed culture and add further complexity to the beer. The beer may be released unblended (as jonge lambic <1yr and oude lambic >2yrs) or more often blended as a mixture of 1,2 & 3 year old lambics to produce gueuze. Lambic may also be aged on fruit to produce kriek (cherry), framboise/frambozen(raspberry) or other fruit lambics.

Coolship & open rafters at Cantillon
Recommended: Cantillon Lou Pepe Framboise, Boon Kriek Mariage Parfait, 3 Fonteinen Gueuze, Girardin Oude Lambiek

Sour ales maturing at Struise
2. Some brewers wish to produce beers with similar character to lambic beers but would like to be able to improve consistency/ repeatability of each batch. They may harvest or acquire a wild yeast(s)/ mixture with bacteria, then use this culture to ferment a beer. Often the cultures are not analysed, though in some cases they have been. They are capable of producing equally complex beers, though as they are not often matured/blended can taste quite different to spontaneously fermented beers.

Recommended: Alvinne Wild West, To Ol/ Mikkeller Ov-Ral

Orval mural at Bruges brewing museum
3. Similar to #2, these beers undergo a regular Saccharomyces fermentation then undergo a secondary refermentation either in bottle or conditioning tank. As with culturing wild yeast, these beers can gain complexity but in a more controlled way. That said, there is still variation in maturation "After three months people might say 'This beer is stinking' after 9 months however 'its fantastic'" of Hendrik Wild. 

Recommended: Orval, StraffeHendrik Wild, De Koninck Wild Jo

Forest of foeders at Rodenbach
4. a) Known as oud red/ oud bruin in Belgium, these beers obtain their sour character from a lactobacillus fermentation producing lactic acid. Rudi Ghequire at Rodenbach was a fount of knowledge about how their beer is produced. Undergoing initial fermentation it ends up at a pH around 5.5 whereupon it is aged in virgin (unused for other purposes) wood foeders for two years, reaching a pH of 3.2. The aged beer is then blended back with unaged beer to produce beers of different levels of sourness (regular rodenbach 3:1 new: old (pH 3.5) and grand cru 2:1 old:new (pH3.3)). Hops are not usually used as bitterness does not produce a good flavour profile with lactic acid; this can make the beers susceptible to acetobacter oxidation (producing acetic acid> vinegar) so care must be taken with the recipe design to scavenge (reduce) free oxygen and the beer is usually pasteurised prior to packaging. Like lambics, these beers can also be matured on fruit prior to packaging.

Recommended: Rodenbach foeder beer, Verhaeghe Duchesse de Bourgogne, Petrus Aged Pale, Rodenbach Caractere Rouge

b) Similar to the above beer styles are goses and berlinner weisses, though their pre-fermentation brewing process differs. Both include wheat in the mash, which is mashed at the higher acidity level conducive to the growth of lactobacillus in fermentation. The fermentation is often finished with other yeast strains and beer sare mor elikely to be drunk fersh rather than aged. Some details here.

5. Another method for producing lactic acid sourness without the need for lengthy ageing process is to sour the mash prior to boiling. This is also known as kettle souring. This is often employed by breweries without the space to mature beer and prevent the risk of contaminating equipment with organisms that could cause contamination of non-soured beers (the soured beer is boiled which kills the bacteria). Some breweries may also use food grade lactic acid, which is frowned upon by some as a cost saving measure (but then so is kettle souring).

Recommended: Galway Bay Heathen, Kernel London Sour

Bush de nuits slumbering
in Dubuisson's cellar
6. The final category is a bit of a catch all, which depending on the previous contents of the wood may or may not have sour character (and may or may not have been intended). The beer may have been fully fermented by one of the above methods prior to entering the barrel or undergo a refermentation in the barrel. Often the beer takes on the character of the wood/ barrels previous contents to a greater or lesser extent dependent upon the length of time in the wood. The use of wood for maturation is a complex topic; which I'll not go in to here.

7. Beers can also become sour unintentionally and sometimes unscrupulous brewers will release these on the market as intentional sour brews! Usually the result of an infection prior to leaving the brewery, they can also be picked up by poor pub hygiene or improper packaging. I'll not give examples here but sometimes unintentional souring can produce interesting results!

The diversity in the world of "sour" beers is only just beginning to be (re)explored by British brewers, with the majority of those released to date being of types 5+6. As brewers begin to invest in separate brew-plants to keep potential contaminants separate from their core ranges we will see more sour and wild beers produced in the UK. Already Elgoods have released a range of lambics inoculated using their old rooftop coolship and Wild beer co have produced Somerset Wild, inoculated in the orchards of Somerset. These beers can have a true sense of place, being tied intimately to their environment by their fermentation flora. Burning Sky and Brodies have produced sour red/brown ales and Fullers occasionally continue to produce the wood-matured Gales Prize Old Ale. Recently Redchurch have begun experimenting and Brewdog hope to invest in separate kit after this round of share-selling to boost their wild credentials. Unlike Nate, I think there is still a long way to go and I'd like to see sour beers more widely available out of the craft beer "geek" bars...of course there should always be a variety available, it is possible to have too much of a good thing!  I look forward to seeing how these breweries and others develop in the coming years. 

Northern Ireland is hosting what (I think) is the first of probably many sour beer competitions in the UK: Sourfest is on Saturday 26th September at Boundary Brewing in Belfast. I will be amongst the judges assessing both commercial and home brew efforts.

Left handed giant in Bristol will be launching their taproom next Sundayat the start of Bristol beer week with a sour beer festival; which has some great beers available, including some one offs; so do head along and check it out.

Do you know of any other UK breweries producing sour/ wild beers? Let me know in the comments below.

The idea for this post was driven by De Brabandere's very good presentation on how they make their Petrus range. Many free samples were provided during the beer bloggers conference, but I also bought plenty of beers.There may be some errors; so please feel free to correct me!


  1. The first pH value for Rodenbach looks too high.

    1. What should it be? when I checked for pHs of common liquids it did seem too high but that's what I heard from Rudi. maybe it was 5-5.5?

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