There are a lot of options when it comes to brewing a Berliner Weisse. When I made my first one a few months ago, I did a lot of research and landed on the one that was the quickest, because, well, it was the quickest. This process also allows you some freedom to sour your beer as much or as little as you want.
The more traditional way that Berliner Weisse is fermented is with a mixed culture containing Lactobacillus and ale yeast together. The ale yeast is much more vigorous than the Lacto, though, so it takes over and does the bulk of the fermentation before getting out of the way. The Lacto then cleans up the scraps that the ale yeast isn’t interested in. This can take several months to get sour.
By pitching the Lactobacillus on it’s own first, you can not only achieve the sourness you want in only a few days, but you can also then pasteurize the wort before racking to a fermenter and pitching your ale yeast. I have mentioned this process in the post about my first Berliner Weisse, and I’ll get into it more tomorrow on my post about my second one, but today I’ll just explain how to get that Lactobacillus culture.
You can buy commercial cultures of Lacto, but it’s very easy to culture your own. This bug lives everywhere, but one of it’s favorite places is on the husks of brewing malt. For this project, you’ll need a pint size mason jar (or something similar), a cup of uncrushed brewing malt (or, y’know… and handful), a cup of water (or just enough to fill the rest of the space in the mason jar) and some aluminum foil.
The water should be boiled, or be from a reliably sterile source. It should be warm, somewhere just north of 100ºF. When your water is ready, add the uncrushed malt to the mason jar, then fill it, with a quarter to half an inch of headspace, with the water. Cover the jar with the aluminum foil and keep the jar somewhere warm. The aluminum foil will keep dirt and insects out, but allow some air to pass, which is what you want.
Check the jar every day, preferably a couple times a day. It should start to smell sour pretty quickly. I’ve seen it described as a sour apple aroma. I wasn’t sure what that meant, but when I smelled it, I knew. You should then start to see some thick, white foam form on top. The aroma will continue to evolve and honestly, get a little unpleasant. That is okay. When it goes from strange to outright bad smelling, it is probably ready to go.
The first time I did this was in the middle of Winter. It took a week to get a good starter. This time, it’s much warmer and I think I could have pitched it in about three days. I moved up my brew day by two days to accommodate. This is the only issue. As with yeast, the Lacto can be a bit unpredictable.
Once the starter is ready, you can just dump the whole thing into your wort. I do it in the brew pot for several reasons. My pot is stainless steel, so it’s easy to pasteurize and sanitize without infecting my fermenters. It’s also easy to get samples, it is important to monitor your sourness to get the level you want and not a big pot of vinegar. Lastly, Lactobacillus likes it warm and this way, I can leave the pot on my stove top and turn it on low once in a while to goose to the temperature.
This is a very easy way to dip your toe into the sour beer pool without any extra investments, long time commitments or threat of infection to your other beers. When you achieve the level of sourness you want, just bring the wort to a boil briefly, chill it, rack it and pitch your ale yeast, just like a normal batch.
I have only done this for my two Berliner Weisse beers, but I’m anxious to try it with other styles. I’d like to try it on a stronger wort and see what kind of results I’d get. Another idea I have is to add hops during the pasteurizing step to get some nice flavor and aroma. There are all kinds of things you can do and other ways to do them. This is what has worked for me, but I’m always happy to try something new.