Homebrewing has exposed me to styles of beer and methods of brewing that I would not have even suspected of existing. Just before I started brewing, my sister and brother-in-law took me to New Belgium for a tour and tasting. During the tour, I tried and enjoyed my first sour beer. The flavor was totally outside of what I thought was possible with beer. (Interesting note – my brother-in-law, Adam Valuckas, made a short film for their release party of the 2013 La Folie and Transatlantique Kriek, both sours.)
While reading another brewing blog, Brew Science, I came across a post detailing a beer that was low alcohol, citrusy, tart, and has champagne-like carbonation: the Berliner Weisse. It sounded like a beer that would be especially well-suited to summer, but it can require significant time to age. Some brewers report going from grain to glass in as little as a month, while for some as much as 6 months of aging is required for the beer to develop.
The most critical part of brewing a weisse is developing the sourness with lactobacillus. There are essentially two possible approaches to this step, although the variations and tweaks are endless: sour mashing or souring the wort.
A sour mash is simply an extension of a regular mash – after the saccharification rest, the grist is allowed to cool to about 120 degrees F. Commercial lactobacillus or just a handful of (unmashed) grains are added to the mash, and the lacto goes to town eating sugar and producing lactic acid sourness. The only complication of sour mashing is that two competing strains of bacteria can be particularly problematic: acetobacter which produces acetic acid (vinegar) and clostridium butyricum which produces butyric acid (which smells like vomit). If your beer is infected with acetobacter, it will convert the alcohols into vinegar, but fortunately the bacteria is inhibited by purging the mash vessel of oxygen. Unfortunately, the clostridium genus is anaerobic, just like lactobacillus, and so trying to inhibit acetobacter by purging the vessel of oxygen may increase the viability of clostridium. Obviously, pitching unmashed grains will increase your risk of introducing acetobacter or clostridium, but is often done successfully.
Souring the wort is just like a regular fermentation, but pitching lacto with the yeast. There are many different ways of souring the wort just as there are to sour mash. One popular way to sour the wort is to pitch a lacto starter, incubate the wort in the 100-120 degree F range for 24 to 48 hours, then put the wort into a kettle and boil it for 15 minutes, making any hop additions you might want to make. At this stage yeast should be added to ferment the rest of the sugar, and the beer can be handled just like any other.
Boiling will kill the lactobacillus, giving you greater control over the sourness of the beer. If you don’t care to hop your weisse, you can also simply raise the beer to about 160 degrees F and hold it there for about a minute to pasteurize it (note that this source refers to pasteurizing milk, not beer, so exercise caution). Fortunately, this is also below the boiling point of ethanol, so in the event that your lacto is heterofermentive and produces alcohol in addition to lactic acid, you won’t lose any alcohol during this process. This shouldn’t be a great concern even with boiling, as homofermentive lacto doesn’t produce alcohol at all (so there is none to boil off), and the USDA studies on removing alcohol from food products with heat report that simmering for 15 minutes only removes 60% of the ethanol. Boiling may also be advantageous for driving off DMS, though I’ve not read of many brewers having problems with DMS whether they boiled or not.
I still don’t have a kettle capable of boiling a large volume of wort, so I am going to split the brewing into two parts. I’ll mash half of the grains to make 2.5 gallons of wort, into which I will pitch a grain-derived lacto starter. Once this wort is sufficiently sour, I’ll put it into my kettle and pasteurize it. I will then put this back into the (cleaned and sanitized) fermenter and inoculate it with S-04. I’ll then mash the rest of the grain and boil it to add a half ounce of hops (leftover EKGs from the recent brown ale), which will help inhibit any reappearance of bacteria. The hops I’ll be using aren’t to style, but in such a small amount they won’t be noticeable.
There is also the option of pasteurizing with Campden tablets (potassium metabisulfite). My last contact with sulfites was when I tried making a spontaneously fermented mead and added a little lemon juice. The lemon juice was from a bottle rather than a lemon, and listed in the ingredients is sodium metabisulfite as a preservative. The fact that spontaneous fermentation failed in that case is possibly a proof of principle that Campden could be used instead of heat to knock out the lacto.
The recipe itself is extremely simple (per Jason Rodriguez of Brew Science) :
- 3.5 lbs pale wheat malt
- 3 lbs Bohemian pilsner malt
This is my most exciting brew yet, and I’m eager to see how it turns out. Hopefully this approach will yield something good on a shorter timeline. Tonight I begin my starter.