Everybody Kahm Down!

It’s not mold, it’s yeast, commonly called Kahm, which is a sort of catch-all term for a variety of yeasts that can form a film, or pellicle, on top of ferments.1 It’s harmless. No one is going to get hurt here. It’s alright, no need to panic. It’s incredibly common. It can, however, negatively affect taste. Our lid system prevents the yeast from coming in contact with the ferment. You can just scrape it off. Covering your ferment with cheesecloth makes it easier to remove.






1- In an early version of this post, I inadvertently named the yeast as Saccharomyces cerevisiae. Thanks to those who pointed it out and to Ben Wolfe for clarifying.


6 thoughts on “Everybody Kahm Down!

  1. I recently had a fantastically tasty batch of cabbage and bok choy with ginger and garlic bubbling away in a fermenting crock (with a lip on the lid to seal with water as an airlock). When it tasted “done” after about three weeks, I added the kimchi spices (which slow fermentation) and figured I’d let it brew for a bit. I foolishly neglected to check daily, and when I lifted the lid – horrors! – mold. Not the bloom, not the scum, but blue-green explosions of fuzzy mold growing all over the interior of the lid and the sides of the crock above the brine. A ruined batch. Live and learn. In the future, diligent scrutiny will replace my “ah give it a few days it’ll be fine” approach. I have read, though, that mold spores can be present without any visible detection, and only lab sampling will reveal that the mold has roots into the bottom of the fermentation vessel.

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