On November 11 (11/11/11) I brewed my first mixed-culture beer (Sour Mistress - full post here). In the subsequent weeks, the brewers yeast (Wyeast 3522) has done its job and converted most of the available sugar into alcohol and carbon dioxide. The resulting beer is a mild but tasty bosch pear colored Belgian ale at around 6.4% abv. This beer was intentionally barely hopped to around 6 ibu's to accommodate the growth of its souring culture, a species of Lactobaccillus bacteria. Unfortunately, the fermentation temperature never got warm enough to really bring out any sourness from the bacteria, so I've come up with a plan.
I did a bit of research on Lactobaccillus and learned a few interesting things. Unlike ale yeast which prefer a fermentation temperature of around 60-75°F, this species of bacteria thrive in much warmer conditions. The temperature of a human intestine, 98.6°F, is ideal for growth and thus ideal for the production of lactic acid (the dominant contributor of acidity in sour beer). Unfortunately, fermenting anywhere near that hot would result in a very harsh, undrinkable beer. With this is mind, I decided to borrow a technique from Germans who use Lactobacillus to sour their Berliner-Weisse, a highly refreshing, tart low-alcohol wheat beer.
I constructed a makeshift incubator using an old submersible heater from my marine aquarium days (properly sanitized) and a 20 litre fermenter. Into this I added 4.75 litres of 10.75°P/1.043 wort (mashed earlier with 2lbs of Munich and 1lb of 2-Row), plus a fresh culture of Lactobaccillus (Wyeast 5335). The heater will ensure that the solution is held above 90°F for the next week. I measured the starting pH at 5.80 and will closely monitor both the gravity and pH of the solution for the next 7 days. This species is known to continue producing lactic acid up until the point at which it becomes fatal to itself - around 3.4 (malt vinegar is 3.5, so we're talking about a significantly tangy substance). I'm not sure what to kind of timeline to expect from this fermentation, so I'll be taking measurements frequently. Once soured, I'll blend this new wort with the original Sour Mistress to my desired acidity.
Munich Malt (Canada)
Two Row Malt (Canada)
Wyeast 5335 Lactobaccillus
OG 10.75°P / 1.043
Original pH 5.80
Holding at 94°F
UPDATE: The lacto culture took this wort from a pH of 5.80 to 3.29 in 3 days. It tastes very tart but surprisingly unoffensive. Going to cool it for a few days and see if I can get any of the cloudiness to dissipate, then blend with the blonde and bottle it.