So, there are a few ways to get a lactobacillus soured beer. Most serious brewers will insist that you allow the lactobacillus to help ferment the beer with the yeast (100% lacto ferments have been tried, though there is much debate about how possible this is given that it cannot attenuate like yeast does), adding it at the same time or shortly after the yeast. This process takes months at best and years at most. This lengthy process produces a lot of depth from the microbes at work, and some brewers (including, rather vocally, two Denver brewers considered some of the best in the game) believe this is the only way to sour a beer.
You can, alternately, sour the mash, or sour the wort before boiling. These have the advantages of being much faster and of improved sterilization. Many brewers who make sour beers will purchase a full set of extra cold side equipment only for their sour beers. Bacteria are tough critters, able to withstand sterilizing techniques that yeast cannot. Many common sanitizers, like Star-San, are acid based. Since lactobacillus are tougher, smaller, and their whole existence revolves around making their habitat more acidic, they tend to survive typical brewery sanitation practices.
Kettle souring involves taking the wort, boiling it just enough to sterilize it, introducing the lactobacillus, giving it some time to sour the wort, and then firing it up again and resuming the brewing process. This means that the only equipment your live lactobacillus touches is your stainless steel (or other impervious metal) kettle, which is then held above pasteurization temperature for 60-90 minutes.
- don’t have a year to wait for one gallon of beer that may or may not be good on my first try
- don’t want to go buy a whole additional set of cold-side equipment
- don’t want every beer I make from now on to possibly contract lactobacillus
kettle souring sounds like the way to go. After pouring over Dr. Lambic’s really great Sour Beer Blog, I come up with a plan.
At the brew shop, Kellin warns me to make sure I really seal oxygen out to stave off butyric acid. We also get to chat a bit about the Mexican Hot Chocolate Stout, which he says the shop hasn’t had a chance to do a tasting of yet. I tell him that’s probably for the best, and fill him in on the details from our tasting observations.
- 1lb US White Wheat malt
- 10oz UK Maris Otter
- 10oz US Pilsner
- 4oz Ger Acid malt
- 1/3pkt WB-06, plus harvested WB-06 fed a starter
- Hallertauer for around 8IBUs
I mash in at 145 with 1.25 quarts to lb, give it a 15 minute rest at 135, kick it to 150 for an hour, mashout to 168. Lauter, recirculate, sparge to 1.75G. I pull off about 200ml into an erlenmeyer flask. I crash cool the kettle in an ice bath to 90 degrees, dump in my lacto culture, cover the surface with saran wrap, put on a lid, and put it in the oven (the oven is off, it just keeps it out of the way and a few degrees warmer than the room because of the oven pilot).
To the erlenmeyer flask I add another 100ml room temp water, to take the gravity down and temp to 80. Into this I add my harvested WB-06, aerate, cap with foil, and put on top of the fridge.
I’ll try to not disturb the wort, and will keep an eye on the WB-06 for signs of fermentation and yeast growth, and will aim for a boil day two days later.