One of the most annoying (and intimidating) aspects of brewing sour beers is how long they take to ferment. Sure there are shortcuts, like sour mashing, but rarely do the results approach the nuances of long-aged mixed-fermentation beers. One of the last things I did while I was at Modern Times in August was to taste the four versions of a beer I brewed with an experimental souring technique two weeks earlier.
Souring a beer before the alcoholic fermentation is a good idea, but a sour mash presents three major issues:
1. After souring the mash, it can be difficult to separate the wort from the spent grain.
2. Exposure to air during souring can lead to the growth of unwanted aerobic microbes that produce off-flavors.
3. Allowing the pH to drop too low can cause fermentation issues for most ale yeasts.
To remedy problem #1, I dipped into my bag of tricks and pulled out the sour worting technique I used a few years ago. After a single-infusion mash, I collected the reddish wort and heated it in the kettle to near boiling to ensure any microbes from the grain were dead. With this method the wort is drained with a standard temperature and pH, so there are no issues lautering as usual.
To address problem #2, I ran the wort through the plate chiller (aiming for 115F), and into four plastic carboys, each of which had been flushed with carbon dioxide (back at home I miss the plumbed CO2 lines at the brewery). Flushed kegs would work equally well.
To achieve the acidity, I pitched one carboy each with a starter of Wyeast Lactobacillus, a starter made from the microbes living on pale malt, a starter from the microbes living on acid malt, and a small hop-sock of crushed acid malt. For the grain starters I followed a similar protocol to the one used for that previous sour worting batch. My goal was to determine which of these microbial sources produced the best results.
To maintain the temperature in Lactobacillus’s ideal range, I placed each carboy in one of the pilot system’s vessels, filled with 120F water. At the start and end of each day for three days I removed the carboys, reheated the water, and replaced them. I also insulated the rig with blankets to help maintain temperature. Usually they'd be down to about 100F by the time I reheated. I didn’t have room for the fourth (pale malt starter) so I left it under the blanket.
The results were surprising. After three days, the least sour of the bunch was the Wyeast Lacto, clean and pleasantly tart. The two grain-starters were next (despite the temperature difference), they were still clean, but a bit more lactic. The grain bag was the most acidic, but also had a slightly stranger aroma that was more in line with what I expect from a sour mash but luckily not as cheesy or intense. With acid production complete (pH 3.4-3.5), I boiled each in turn with a small dose of hops and yeast nutrient. During each boil I cleaned and sanitized the fermentor, refilling it with 68F wort post-boil.
To resolve problem #3, rather than fermenting with pH sensitive Saccharomyces, I opted for a 100% Brett fermentation with the BSI Brett Drie we had on hand for production brews of Neverwhere, Roraima, and Southern Lands. Brett works quickly at a pH as low as 3, and produces interesting flavors too.
My last day working in San Diego I racked each of them to a Corny keg, and shook in carbonation. The pale malt starter and the steeped acid malt were my favorites. Each had a nice acidity with a pleasant Brett character. I had skipped boiling the Wyeast Lacto portion and the result was a subtle raw graininess similar to what I taste in my no-boil Berliner weisses. The acid malt starter had an unpleasant aroma not present before the Brett fermentation, just sort of rough. With that interesting range of characters, we decided to blend the three we liked to make 15 gallons of beer to serve at the Tasting Room Grand Opening.
Reviews were mostly positive on Untappd, "I'm not one for sour beets, but this is fantastic! Tickles the taste buds in the back of your mouth in just the right way." - Stephanie P. "Had it 3 times so far might get another" - Heather H. Both included pictures of the finished beer as well, something I never got to see for myself!
I had a beer at GABF from TRiNiTY Brewing (7 Day Sour) that used a similar technique, but fermented with a mixture of Brett strains post-kettle-souring. The result was terrifically funky, and brightly acidic. I think I’ll have to try something similar, integrating a strain like Brett Drie/Trois which ferments quickly, with others that produce more classic Brett aromatics.