The first time you try a sour beer can be intense, but once you start acquiring the taste you will notice much greater complexity. The traditional European sours are Berliner Weisse, Flanders Red, Oud Bruin, Lambics, Geuze and Gose. Saisons, pale ales, even porters and stouts can work with some sourness to them, big hoppy beers not so much. The sourness in these beers come from the blends of yeast and bacteria used to ferment them (often referred to as "bugs"). The main souring bugs are Lactobacillus, Pediococcus, and Brettanomyces. Lactobacillus is the bacteria that turns milk bad. Its byproduct is lactic acid which is a smooth, pleasing sort of sour. Pediococcus also create lactic acid but more aggressively. Pediococcus also create a lot of diacetyl (buttery flavor) and a snotty (commonly referred to as ropey) like mouthfeel. It is almost always pitched alongside with Brettanomyces which will clean those flavors up. Brettanomyces (or Brett) is a non-spore forming genus of yeast in the family Saccharomycetaceae. The word Brettanomyces is Latin for British fungus. It is a bit of a misnomer to say that brett sours beer as it adds more funkiness, flavor and tartness than sourness. It's the lactobacillus bacteria that really do the souring.
First time sour beer makers usually start with either a Gose or a Berliner weisse. Our There she Gose is very simple to make as it does not rely on bacteria to sour it. It contains 2 pounds of acidulated malt which has lactic acid on it already that will give a tartness to this beer. With the addition of coriander and sea salt you get a refreshing, tart, slightly salty beer. If you want a little more control over the saltiness of the final beer you can add salt water to your flat beer before bottling to taste, instead of adding it to the boil. If you want to be more adventurous you can omit the acidulated malt and pitch lactobacillus the same time as your yeast. This will take longer to sour and contaminate your equipment but it will be more authentic. And more sour.
When you make Berliner Weisse Guy we recommend pitching yeast, lactobacillus and brettanomyces together. Primary fermentation will be around three weeks and then you’ll rack to a secondary glass carboy for around three months to get all of that brett goodness. This is a refreshing low alcohol beer that will be worth the wait.
If you want to sour right away, the quickest way to sour a beer is to kettle sour. This involves creating your wort, cooling it down to around 120F and either pitching in some Lactobacillus or a handful of crushed malted barley (which contains lactic acid bacteria) and letting it sit at that temp for a day or two until your wort is the sourness you would like. Once it is there you bring you wort to a boil as usual, add your hops and ferment with an ale yeast of your choice. It helps to have a heating blanket to wrap around the wort to maintain the temperature while the souring is taking place. It is also a good idea to purge your wort of oxygen with some co2 and cover it with plastic wrap to keep it from oxidizing. If it oxidizes you can get a cheesy flavor that will not boil or ferment out.
Brettanomyces can eat sugars that other yeasts cannot. Make sure you are done fermenting before bottling to avoid bottle bombs. It is also a good idea to repitch about a gram of fresh dry ale yeast for five gallons at bottling time to ensure carbonation. It is good practice to reserve the fermenters and tubing and such on the cold side of making a sour beer for sour beers. Many of these bugs have a biofilm that makes them hard to clean and sanitize. Using them for non sour beers just might sour them anyway!
For more information on making sour beers check out our friend Michael Tonsmeire’s excellent blog the Mad Fermentationist.
If you are new to sour beers, go to your local bottle shop and try a Berliner Weisse or a Flanders Red (Rodenbach Grand Cru is my favorite) or one of the many new American sours out there (Peekskill Simple Sour comes to mind). You will be pleasantly surprised.