souring beer using InstantPot?

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Dec 19, 2015
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Greetings Zymurgists,
I was recently reading about the technique of "kettle souring." I'm not actually a big fan of sour beer, but I started thinking about going this route to add a bit of "tang" to certain styles, for example an Irish dry stout, à la Guiness. And it occurred to me that I have this handy little device in my kitchen with which I like to ferment yogurt, and wondered whether it might not be helpful. I came up with this:
  • Remove 1 gal of unhopped mash runnings.
  • Boil for a few minutes and cool to around 110°
  • Use lactic acid to reduce pH to 4.5
  • Pitch lactobacillus culture, OYL605 or WLP672
  • Keep warm (80 – 85°) in Instant Pot on Yogurt – “less” program for 12 – 96 hours
  • Target pH: mid – high 3’s for light tartness, low 3s for firm acidity
  • Pasteurize culture at above 170° (slow cook – “less” function) for a short time
  • Cool and add to fermentor
First of all, am I crazy?

Second of all, some of what I read mentions the desirability of covering the souring wort with a blanket of CO2. How important is this? If I can't do this (I'm a bottler, not a keggler, so I can't), does that screw the pooch?

Your thoughts are solicited.
I don't see anything wrong with it. There's been a shift in thinking that sealing the souring wort or pumping CO2 through/over it is not a good idea.

I'm not sure how much use you'll get out of this versus using acid malt but if you want to, go for it.
To sour one gallon its probably gonna sour super fast esp if you pitch the whole package. (I have had a five gallon batch sour in a day and half on a new pitch, I repitched a lacto culture and soured in 8 hours)

I do not ever drop my ph on the wort before pitching lacto. I like to use White Labs WLP 677 for my kettle sour for my Berliner Weisse.

I say go for it! Good Luck!
For some other opinions, I always pre-acidify the wort before souring, somewhere in the range of 4.3 - 4.5. This helps to reduce the risk of something unwanted taking hold of your wort and infecting it.

Is the 1 gal that your souring going to be a standalone beer or are you adding it back to the fermenter with the rest of the wort from that batch? Reason I ask is if you're adding 1 gal of 3.2 pH wort back to 4 or 5 gallons of 5.2 pH wort, how much of that acidity is going to come through? Would you be better off just using lactic acid to slightly bring the pH down?

It'd be an interesting experiment to see how it comes out and if you like it. I always use OYL-605 lacto. That's my go to and always gets me down to 3.2 pH. If you do it, report back how it goes and what you got out of the final beer.