Some kettle sour technical questions

[andyg55]

Hi all

I'm making my first kettle sour and have a few questions about the process:

1. The recipe I'm using calls for 5% acid malt. Would the purpose of this be to drop the pH of the wort? I have lactic acid to do this, but the method I'm following does not include the addition of lactic acid.

2. When cooling the boiled wort to pitching temperature for the lacto (35 degrees celcius), do people generally leave the kettle to cool on its own, or use a wort chiller?

3. Why do some people cling wrap the wort, other people cling wrap the lid, and others do not cling wrap at all?

4. What are the benefits / drawbacks of souring in the kettle versus souring after racking into a fermenter?

5. Is there a consensus on whether to boil again after the lacto souring stage?

Cheers,
Andy

 

[strange-steve]

1. It's probably there to give the pre-souring a head start. It's a good idea to acidify the wort after the mash down to about pH 4 or 4.5 because this inhibits the growth of unwanted organisms. The acid malt won't drop it that far but it will give it a kick start for sure.

2. If you have a wort chiller then use it.

3. The cling film is to reduce the oxygen contact with the wort because this reduces the risk of something unpleasant growing, such as acetobacter. Ideally you want to place the cling film directly onto the top of the wort, it is possible if you're careful. Some don't bother because they feel it's unnecessary, which it may be, but why risk it?

4. The benefit is that it's much quicker to brew a sour beer this way (a couple of weeks verses months) and that you don't have to worry about contaminating your cold side equipment with bugs. As for drawbacks, some say a quick sour beer lacks the complexity of a long term sour beer though I don't know how much truth there is to that (when comparing like for like that is, something like a lambic isn't a fair comparison.)

5. Yep definitely boil it.

 

[andyg55]

Thanks Steve, that clears a lot up for me!

For questions 4, I didn't explain well enough. What I meant is that some protocols say to add the lacto directly to wort sitting in the kettle, whereas other protocols suggest adding the lacto to the wort in the fermenter first. I find this counterintuitive as you're going to boil it anyway, so you'd just have to remove it from the fermenter and add it back to the kettle again. Milk the funk explains to add lacto to wort in the fermenter not the kettle. I just wondered why some people do this.

 

[strange-steve]

other protocols suggest adding the lacto to the wort in the fermenter first

This isn't technically kettle souring then, it's just souring in the primary before pitching the yeast which may give a more complex flavour because it's unpasteurised, however it does carry the risk of introducing a contaminant to your equipment. The beauty of kettle souring is that everything is pasteurised before it gets near your FVs. The other possible advantage of kettle souring (depending on your setup) is that it might be easier to maintain 40° or so in the kettle compared to the FV.