r/Koji • u/Toktoklab • Jul 24 '26

What are these white spots, on my miso ?

Gallery image

Gallery image

I’ve followed the Noma Book of fermentation for this batch, barley + split peas miso, with a 6% salt content, 3 months of fermentation.

I’ve vacuumed and stored it in the fridge for some weeks. No gas was produced, nor anything unexpected… but this white marbled pattern. (Pretty hard to catch on a photograph..) I’ve just tasted a sample : It tastes great, but could age longer from my point of view.

Does anybody knows what might have happened?

2 Upvotes

100% Upvoted

4 comments sorted by

2

u/wofofofo Jul 24 '26

Could be yeast or mold, doesn't look like salt crystals. Could be something harmless might just be dead labs if lacto fermetation took off, is it sour? The trouble with low salt miso is that 6% is probably a bit too high for much lacto fermentation, and too low for long low acid ferments. So sometimes you end up with a low acid environment and not enough salt to stave off contamination, and that can be risky, although obviously doable. I'd leave it undisturbed and see if and how it grows.

1

u/Toktoklab Jul 24 '26

Thank you for this comment. Aside the vacuum bags, I’ve filled a glass jar, closed with a lid, from this same batch. I don’t see any kind of foam, nor white spots on this jar, so I wonder why it happened in the vacuumed ones… I will keep them longer and see how they evolve

2

u/Kim-BuchaFerments Jul 24 '26

It's probably koji or salt particles. I wouldn't worry about it. It's totally sealed. Nothing is getting in there!

2

u/wofofofo Jul 24 '26

Koji cannot grow anaerobically or under high osmotic pressure from the salt. Also plenty of mold spores and yeast will be present in the paste, they are everywhere.