valentine sour

Sour beer

So, as February is here, I’m going to make a very public statement, I couldn’t give a hoot, a damn or a tinker’s cuss for Valentine’s Day.

I’m not bitter, i’m sour

Sure, I could make lots of statements about how any display of love is positive and that it’s good for pubs and restaurants and blah, blah, blah but I find it excruciating and I am happy to excoriate it for what it is - a venal money grab with its roots in beating women and murdering saints.

And with all this adorable information in mind, this month’s jolly column is about sours and the definition thereof!

Sour beer: what is it?

But what is a sour beer? What makes a beer sour? And are we frequently getting it wrong when we talk about them?

We perceive sour when hydrogen ions are split off by an acid dissolved in a watery solution and the main souring agents in beer are bacteria, which turn up in different forms in different beers.

Lactobacillus (Lacto) and Pediococcus (Pedio) are the two most important bacteria in sour beer production and, pernicious little buggers that they are, will find their way via a number of different ways.

Lacto is the most straightforward one to address, and probably the predominant acidic note in modern beers at the moment as it’s what is used in beer styles like gose and Berliner Weisse - like Magic Rock’s Salty Kiss - which particularly when brewed with additional fruit or dry-hopped can be really accessible and refreshing.

Introduced in a few different ways to the brewing process: it can be introduced into the mash, which is then kept warm for a few days by the brewer until it reaches the desired pH of 4.5, or introduced in the kettle, which tends to be a little more reliable and controllable or it can also be added afterwards, although this is less common and, I find personally, a bit more harsh on the palate.

Mixed fermentation

Lacto is also present in mixed fermentation beers and traditional styles like lambic, there it takes a lot longer to make its presence felt, as it has to wait its turn after the standard fermentation with Saccharomyces yeast has achieved its level of attenuation (basically eaten all the sugars it can) leaving behind complex carbohydrates.

Pedio is also a lactic acid producing beast but, the problem is, it also produces enough diacetyl to keep a cinema popcorn company in business and can also produce a quite disgusting gloop called exopolysaccharides, which in extreme cases can produce ropey strands in the beer, which are exceptionally unpleasant, trust me on this.

However, in mixed fermentation beers, you will find that it’s Brettanomyces to the rescue, as it will happily slurp up all the nasty diacetyl and exopolysaccharides and many brewers stand by the fact that this ropey beer early on will lead to a more complex sourness later on.

Wild Beer Co makes some of the finest mixed fermentation beers you’ll find on our shores, but if you would like to find one from the spiritual home of funky fermentation, then I cannot recommend Liefman’s Goudenband enough (and stick one in your cellar or a dark cool cupboard and forget about it for at least five years and go back to it, it ages sublimely well in my opinion).

The smallest contributor

The smallest sour contributor in the beer world is acetobacter, the stuff that makes vinegar (this isn’t the only way for acetic acid to turn up in beer Brettanomyces also produces it in the presence of oxygen).

If you want to experience probably the most iconic iteration of this in beer then Duchesse de Bourgogne is the best example to my mind, it’s like cherries and balsamic had a big old party in an oak barrel but you can also pick up some in Rodenbach Grand Cru from time to time.

It’s also worth noting that a lot of brewers are moving beyond just using a measurement of pH for sourness to acidic titration, which is something altogether different, as it is a far more accurate measurement of ‘perceivable’ acidity as opposed to the straight up ‘physical’ acidity that pH gives you (and that’s about as far as my science extends in this matter!).

Recipe: Sour beer and tingly oysters

This month’s recipe could, of course, be used as a supposed aphrodisiac but, and maybe it’s just me, I’m not exactly at my sexiest when I’m trying to slurp an oyster out of its shell, but this does taste damn good... so maybe just lock yourself in for the night with a dozen oysters and a few great glasses of beer.


  • 12 fresh oysters
  • 2tsps rice wine vinegar
  • 2tsps cider vinegar
  • 1/2 tbsp finely-minced shallot
  • 1tsp wasabi (or more to taste)
  • 3tbsps Magic Rock Salty Kiss
  • 1tsp chilli flakes

Mix all the ingredients together apart from the oysters.

Open oysters, serve on a bed of ice with your mignonettes in the middle and a glass of Salty Kiss on the side.

Download recipe

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Sour beers available at Beerwulf