Ask Mr. Wizard

Kettle Souring with a Heating Element


Kevan McCrummen - Coeur d’Alene, Idaho asks,

I want to try kettle souring but am concerned about contamination. I have a 10-gallon (38-L), three kettle, indoor electric brewery. I’m wondering if it’s possible to transfer the sweet wort to my boil kettle for souring instead of a separate heated fermentation vessel. Is it reasonable to maintain 100 °F (38 °C) via electric heating element in the kettle over the 24 to 72 hours, or would the element kill Lactobacillus every time it cycled on? Other than keeping bottling/ kegging/ dispensing equipment funk free (don’t get me wrong - that’s great), I don’t see the benefit to the brewery of transferring the wort to a fermenter to sour. The fermenter, pump and hoses would be exposed to Lactobacillus as the wort travels back to the boil kettle. If I could avoid that contamination by leaving the wort covered in a well-sanitized boil kettle, blanket with CO2, and use a heterofermentative Lacto (which would continue producing CO2), then no other equipment would have contact and I could simply bring it to a boil when target pH was reached.

Kettle sours have become quite popular with commercial craft brewers who want to brew sour beers without turning their breweries into funk factories and the technique really works quite well. It’s also
Response by Ashton Lewis.