Lambics are funky, wood-aged tradition in a glass, but people have come to appreciate quick sour beers for their bright, refreshing tartness. Even though the classic wild-fermented beers often revel in a robust complexity, quick sours offer more than just the shorter time to getting beer in the glass. In particular, with quick sours, brewers have a finer control over the level of sourness with greater predictability. It may seem like a compromise to give up the funk and settle for a cleaner sourness, but that clarity can vary from a mild, focusing tang to a sharp accent. Another bonus is that you don’t generally have to worry about infecting your equipment.
As a homebrewer, you have three main options for getting into the fast lane to sour brewing, moving from easiest-to-control to least-predictable: dosing your wort or finished beer directly with lactic acid, kettle souring, and sour mashing. Although sour mashing is riskiest, none of these is particularly difficult.
Using lactic acid cuts out the indirection of pitching Lactobacillus, reducing the chance of other infection. It’s incredibly simple, but some people claim it leads to a less nuanced, artificial sourness. If you’re aiming for a very tart beer, this is more likely to be true, but I’ve tasted goses where it worked very well.
Lactic acid commonly comes in an 88 percent solution. You’ll add this to your wort or finished beer. Hitting your sour target is straightforward. Start with a measured sample of your wort or a comparable beer. Add drops of lactic acid and taste the sample until you hit the right level of acidity. Once you know how many drops, you may want to start over with a new sample and double check because each sip changed the volume of your sample. Once you’ve settled on the number of drops needed, you can scale that up in proportion to your sample size and batch volume. Add the calculated amount of acid solution to the wort or beer, and then stir it in. If you add the lactic acid before fermentation, be aware that the lower pH may impact yeast health and efficiency, so it’s a good idea to pitch a larger starter.
Kettle souring may not be as predictable as adding lactic acid, but it’s still relatively easy. Here, I’ll give you a quick overview, and then in a future column, we’ll do a detailed walkthrough.
For kettle souring, it’s just a matter of pitching a Lactobacillus culture into your wort and letting it work. As with yeast fermentation, the time required will vary according to the culture’s volume and health. Even though the time is variable, you can still dial in the desired tartness by sampling the wort to see whether it’s ready.
Kettle souring slips right into your normal brewing process. For all-grain brewing, you can do your normal mash and sparge; for extract batches, dilute the extract as usual. You’ll want to adjust the pH to 4.0–4.3 to help with head retention and make the Lactobacillus feel at home.
While not required, it’s a good idea to boil your wort for at least a couple of minutes, then cool it down to pitch the Lactobacillus. This reduces the chance of other contaminants such as Acetobacter or Clostridium competing and adding off-flavors. Your target temperature will depend on the culture you choose. Each culture has its own ideal range. Most of these are between 110 and 120°F (43 and 49°C). Once your wort cools into range, pitch the Lacto culture. As with yeast, it’s a good idea to use a starter and pitch a larger volume, in this case, 300–500 ml.
You should flush your kettle with CO2 to keep out oxygen and then seal it with the lid and plastic wrap. There are a number of ways to hold the wort at the target temperature. A warm water bath with a wand-type sous vide device (such as the Anova Precision Cooker) works great, as does a temperature-controlled fermentation box. As long as you keep an eye on the temperature, you can also use a heating pad, an electric blanket, or even a space heater in a small room.
Then, it’s a waiting game. It should take between one and three days for the Lacto to do its job. You can sample the wort periodically to see whether you’ve hit the desirable sourness, either by taste or by measuring the pH, but be sure to follow sanitary procedures and then flush and seal the kettle again. Once you’ve achieved the right level of tartness, you can slide right back into your normal brewing process: boil the wort, add the hops, chill it down, and then pitch your yeast.
Three things to remember: don’t add any hops to the wort before pitching the Lacto (hops will shut it down); given the acidity, it’s not a good idea to use an aluminum kettle; and (as I mention under “Dropping Acid”) the lower pH may impact yeast health and efficiency, so it’s a good idea to pitch a larger starter.
If you’re going all-grain, you also have the option of adding the Lactobacillus to your mash. The process is similar to kettle souring, and as I did with kettle souring, I’ll provide an overview here and come back in another column with a more detailed walk-through.
You’ll mash as usual, including the mash-out step, then you’ll cool down to your target temperature range and stir your Lacto culture into the mash. Some brewers add a small amount of malt grist instead to let the naturally present Lactobacillus go to town. I’d stick with a culture because the grain likely has a host of microorganisms, perhaps including wild yeast or Clostridium.
As with kettle souring, you’ll want to purge the mash tun with CO2 and press clean plastic wrap into the top layer of malt, then seal everything up to reduce exposure to oxygen and pathogens. Hold the mash tun at the target temperature range for one to three days, checking the pH as desired. After that, you’ll follow your normal procedure: sparging, boiling, etc.
Styles of Twang
All three of these approaches will work; it just depends on your goal. If you want just a light twinge of tart and total control of the level of sourness, try a simple lactic acid addition. If you’re feeling more adventurous and experimental, stay tuned! We’ll cover both kettle souring and sour mashing in detail in future columns.
From Berliner Weisse to Gose and points in between, quick souring is rapidly becoming the time-constrained brewer’s choice for building pleasant tartness on a schedule. In Craft Beer & Brewing Magazine®’s online course, Quick Souring Methods, Funkwerks Cofounder Gordon Schuck explains how to use Lactobacillus bacteria, experiment with sour mashing, test acidity levels, and more. Sign up today!