Keep Calm, It’s Only Kahm Yeast!


One of the most distressing parts of vegetable fermentation is when one goes bad. There are no mysteries in this case, though people often ask how they can know for sure that a ferment is okay to eat. In my experience, you will know. It will stink like you wouldn’t believe and often has various colors that should definitely not exist in that ferment.

If those things do not exist – the stench and funny colors – then what you might be seeing on the surface of your vegetable ferment is a harmless yeast called kahm. This is often indicative of things that could have gone better, but is certainly not poisonous or harmful. I actually have no idea whether kahm rhymes with calm, but in either case kahm yeast is nothing to freak out about. Here’s a peek at what it looks like.


I recently opened up a batch of fermented jalapeno slices and found a thin layer of white. I looked at the sides and it didn’t seem to be putting any tendrils down into the ferment itself.

It was merely a thin layer of white yeast that I could easily skim from the top. The jalapenos were perfectly edible and tangy, though quite spicy as I left the seeds in.


Have you ever encountered kahm yeast?


Shannon is a mama to four small children, homesteader, freelance writer, and picture-taker. She lives with her husband on their off-grid homestead where they make and eat kefir, kombucha, sourdough, and fermented vegetables.

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  1. ColleenF says

    I think this is what was on my pickles. It didn’t smell bad but looked scary so I threw them out. I was really disappointed because I was really looking forward to eating those pickles!

  2. Leanda says

    In regards to the Kamh on the Jalapeno’s it might be starter I read that in India chili’s – the part with stem I think – are used as a culture starter in making yogurt: I haven’t tried it so can’t confirm it.

  3. Lynn says

    I recently found this white stuff on my preserved lemons. I was using the preserved lemons (just salt added) but not storing the jar in the fridge. So, because I couldn’t bear to even consider tossing the jar of preserved lemons, I just put the jar in the fridge and the white stuff that had been covering the top of the fruit and juice disappeared.

  4. Bronwyn lyman says

    Hi Shannon,

    I too live off the grid, in northern New Mexico and make kombucha, kefir, gluten free sourdough, and fermented veggies. Have a passive solar greenhouse, too. Children are all grown. Tutor students with reading problems. Where do you live? Am always interested in chatting with other people off the grid.

    Blessings, Bronwyn

  5. says

    I’m interested in what kahm yeast actually uses as a substrate. I once had a batch of fruit kimchi that, toward the end and with enough exposure to oxygen, developed a strong secondary kahm ferment. the kahm yeast seems to break down the pectins in the fruit and added a flavor and textural profile similar to cheddar cheese. Spicy cheddar cheese. It was actually delicious in its own way.

    I’ve *heard* that some (mostly older?) Koreans appreciate batches of kahm-infected kimchi as a delicacy, but that preference seems to be disappearing with younger generations. Just a rumor, though.

    I wonder if it’s similar to the “flower” surface yeast bloom in sherry making:

    • says

      Ethan – That is very interesting! I haven’t gone out of my way to taste the kahm on its own, but its certainly been present within ferments and I’ve never noticed anything unpleasant about it. I suppose it’s a bit like growing fungi in that way, if one were to produce it as its own food entity. Thanks for sharing your thoughts!

    • Sarina says

      I believe it’s the higher sugar content from the fruit or root veggies (radish, carrots) that encourage the yeast. I had fermented a batch of radishes this spring that got very mushy and yeasty and tasted like cheese. I just couldn’t handle the texture/flavor (and knew no-one else would eat it) and ended up giving them to my chickens. They sure loved it!

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