Sour beers are an old beer that’s quickly coming into fashion once again. Traditionally they were sour because the brewers didn’t know any better. “God is goode” took this sweet substance and turned it into something that tasted kinda weird but was safe to drink and you also felt kinda good. Since Pasteur we know what makes our beers the way they are and over time that sourness was considered to be a flaw. Several commercial breweries from the new world are starting to embrace old world styles, and are developing new ways to make these beers in shorter periods of time.

Sours also have a reputation of being a little bit unforgiving to a brewer. The bacteria responsible for many of the sour flavours we enjoy can wreak havoc on our clean (Saccharomyces cerevisiae) beers. A small mistake in cleaning could result in batches with flavours that don’t match what you were going for. Though, there is a place where brewers can experiment with making sour beers that doesn’t involve risking any of your fermentation equipment. One of the easiest bugs to start brewing sours with is Lactobacillus along with a brewing technique called “Kettle Souring“.

When doing the kettle sour approach you’ll need to have some kind of vessel that you can be without for a few days. This could be your brew pot or cleaned out mash tun. You’ll do a regular mash the put all your wort in whichever vessel you choose. It’ll sit in there for a few days at optimal temperature for your bacteria to sit at. For Lactobacillus that range is around 35 – 48 degrees C, so if you are doing the souring in your brew kettle be sure that you can easily maintain temperature. For us, we wrapped the kettle in a blanket and set a low heat to bump up the worts temperature.

Building up your Culture

There’s plenty of vendors that sell Lactobacillus strains or blends, though if you are feeling a little bit more adventurous you can play around with probiotics. If you are a Canadian though, getting your hands on any of the probiotics listed on Milk the Funk can be a bit difficult. Your main interest for brewing is in collecting the right strains of Lactobacillus. For myself I used the Natural Factors Ultimate Multi Probiotic and added 4 capsules to a 1L starter (consisting of 900ml of 1.040 wort, 100ml of Minute Maid Apple juice, 20g chalk, 1/4tsp 88% lactic acid).

When doing your starter you need to ensure that you maintain the perfect breeding ground for your Lacto babies. If you are interested in playing around with Sous-Vide, then an immersion circulator might be something to look into. I don’t have one so instead I took a 18 quart cooler and simply replaced the water every 12 hours or so. Replacing water shouldn’t be too involved since your taps hot water should give you temperatures at the upper range of Lactobacillus’ tolerance.

Souring the Wort

The Berliner Weisse is an excellent beer to start off with because you simply don’t need to worry about any other additions you could be doing to your beer. You’ll create a very low gravity wort, sour it with your Lactobacillus and throw in a couple IBUs during pasteurization.

My target was a 1.030 gravity wort that I’d make with 77% Pilsner Malt and 23% Wheat Malt. According to the Bavarian Purity law, this isn’t a valid wheat beer, but… fuck the police. Follow whatever mashing targets and schedule you’d like; I planned a 60 minute mash at 62 degrees C.

Once you’ve finished your lauter, collect all your wort in the vessel you’ll be souring in and boil it for 10 minutes. This is simply because grains are pretty dirty and contain a bunch of other nasties on them as well. By boiling you are ensuring that no poop and vomit scent producers are in your wort before you add your own bacterial culture. After the boil, cool your wort down to at or a little below 48 degrees C and pitch your Lactobacillus culture.

Some other procedures you might want to do after pitching is covering your wort with plastic wrap (over the top of the kettle+CO2 or with the plastic film covering the wort). Lactobacillus doesn’t require oxygen in order to propagate, while some of the nasties do. Something else to consider is wrapping your souring vessel in blankets to help prevent the temperature from dropping too rapidly.

Testing Acidity

There’s a couple of ways you can check to see how sour your wort is and if you want to let it sit for longer. You can go the scientific (and more repeatable/controlled route) and get your hands on a PH Meter or you can just go by your tastebuds and try a small sample of the wort every few hours.

Don’t let the lack of a pH meter prevent you from attempting to make a Berliner. If you are on top of everything and checking the sourness often enough, you shouldn’t have to worry about it getting super sour. If you have an in house brewing partner, have them double check the sourness.

Pasteurization and Fermentation

The only difference between a regular brew day and the one you’ll be doing for finishing up your Berliner is that your boil time will be far shorter than normal. Berliners aren’t very bitter, so all you really need to do is boil to kill of all the Lactobacillus and add a few IBUs. If you feel like being traditional, use a typical German hop such as Hallertau or Perle though it really doesn’t matter all that much. For my batch I just used what I had available, which was 7 grams of Amarillo (10.5% AA).

Something to keep in mind when brewing a sour beer like this, is that you are putting your yeast in an environment that they weren’t really designed for. The acidity of your wort is quite a bit higher than they are used to, so you’ll want to be sure that you are pitching sufficient yeast. For example, if you normally pitch a single pack of US-05 to regular wort, consider pitching 2 packs instead.

Wait.

That’s all there is to it. Now you just wait until fermentation is complete then package it up as you normally would. Something you might want to consider is making flavoured syrups to add to the base beer. Ours is sitting in the fermenter but there are plans to make a few syrups such as one using cranberries and orange zest.

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Resources

1. Milk the Funk – Lactobacillus
2. Milk the Funk – Alternative Bacteria Sources
3. Milk the Funk – Berliner Weissebier
4. American Sour Beer