I remember my first mixed-culture fermentation: I was so nervous about infecting my home brewery that I pitched a Lactobacillus culture into my Berliner weisse wort in the open-air environs of my deck, far from my preciously not-bacteria-laden equipment and fermentors.
The resulting beer (my Scared Sour Berliner Weisse) was successful, and I avoided creating a runaway Lacto infection in my brewhouse. That turned out to be an unjustified fear on my part. The biggest lesson I learned is that mixed cultures are nothing to be scared of, while they can be an outstanding way to expand your repertoire of flavor compounds, combinations, and profiles as a brewer.
A few quick hits before we go any further:
- First, don’t assume that when we say “mixed culture” we’re always talking about sour beer. That’s not necessarily the case—though the spectrum can vary from just a pleasant kiss of funk to bracing sourness, via gentle tartness.
- Second, a mixed-culture fermentation is not the same as spontaneous fermentation, where native cultures in the air or wood go to work on the beer. Creating a true “wild ale” entails considerations and risks that we won’t get into here. (For more on that, see Spontaneity: Prospecting for Bugs.)
- Last, and most important, is this: Don’t expect the bugs to do your work for you.