Lacto-Fermented Vegetable Troubleshooting: Mold

It took me years to be where I’m at with vegetable fermentation – okay with things not being ideal and uniform. You see, vegetable fermentation is not canning. It is not uniform freezing in plastic bags that will be sold behind glass freezer doors in the mega mart.

Vegetable fermentation is part science, part art. Get the science right, and the art comes through in the new and different combinations you create from whatever it is that is being harvested in your garden.

But things can go wrong, and they most likely will. You can have ten great batches of pickles and then one will just not be right. There is, most likely, an explanation for why things didn’t work out. So, I find it helpful to run through some of the possibilities.

Let’s take a look at one of the most common problem we all have with vegetable fermentation: mold.

Mold is actually quite common in vegetable fermentation, but it freaks. people. out. I understand that. I don’t like to eat salsa with a layer of white fuzziness on top either. I do like to remember, though, that there are things I like to eat that do contain “good” molds, like cheese.

If you’re experiencing mold problems, you might want to check a couple of things out:

  1. Are you keeping your vegetables submerged well under the brine? The vegetables need to be kept in an anaerobic environment to avoid contact with air, and thus mold, and to fully ferment properly. This is one of the most important elements of vegetable fermentation.
  2. Are you fermenting at a reasonable temperature? Vegetables fermented in hot weather – 90 degrees or more – tend to have a shorter shelf-life, whereas vegetables fermented in cooler temperatures – 60 degrees or less – tend to not acidify fast enough to deter some molds.
  3. Is everything neat and orderly? There are yeast and mold spores – good and bad – all around us. If a piece of equipment we are using to ferment our vegetables with is not very clean, or there are mold-carrying items nearby when you are fermenting in an open crock, then you could have cross contamination.
  4. Are your vegetables fresh? The very bacteria by which vegetables ferment are already on the vegetable itself, assuming it is a good and fresh piece of produce. As food begins to decay, if there is no measure taken to preserve it, it can begin to carry spoiling bacteria. Always ferment vegetables at their best, this is an act of food preservation after all. Waiting too long will preserve something you don’t want to keep.

Barring these things, and assuming you’ve got a good layer of brine separating your vegetables from the surface mold, you should be able to carefully scrape that mold off and not worry about the vegetables well beneath the layer of the brine.

If you have a health concern, then by all means throw that moldy ferment to the chickens or the compost pile, and consider fermenting with an airlock. I don’t think it’s necessary, but some people find it gives them peace of mind.


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. Mantan Calaveras says

    I made some lacto-fermented pico de gallo. All was well for a week or so, but then I noticed that the vegetable matter had risen to the top of the container. I taste tested it, and while it tasted okay the fluid had become totally carbonated.

    Any tips for such a situation?

    • says

      If you’re getting excessive fizz it could also be because the tomatoes were too sweet. That could make yeast fermentation the dominant process rather than bacterial fermentation. The best way to tell is by smell. If it’s yeasty or alcoholic on the nose, that means there was a bit too much sugar involved in the process. I know this thread is a year old, but I thought any other readers with the same issues might benefit!

      • says

        Amanda – I agree, and thank you for chiming in on this older thread! I would also add that the combination of tomatoes + warm temperatures is a real harbinger for yeasts. We’ve had tomato salsas taste a bit too much like wine after a few days in hotter weather. Love your blog, Amanda! Thanks for commenting.

      • Renee says

        I am on my third batch of salsa. The first one turned out great. The second one I checked it at two days and it had a white film (which I thought was mold) on top so I tossed them. Today I have another batch going and it will be 48 hours at 2:00 but it had a white film on top again. I scraped it off and stirred it up. Do you think this would be the yeast or mold? I loved the first batch I made and really want to get a lot of this stuff made up to last awhile.

  2. Chili Monsta says

    I’d assume the carbonation is the CO2 that is created as the lacto bacteria consumes the existing carbohydrates in your ferment. After the primary ferment is complete and the acidity increases, the “fizz” should dissipate.

    • says

      Chili – That is my understanding as well. The CO2 is primarily released in the earliest stages of fermentation so after a bit it starts to dissipate.

  3. Katherine says

    I’m making some lacto- pickles. One of my jars has some soft spots on the tops of the cukes that weren’t submerged. Can I cut those parts off, and replace the pickles in the jar to keep fermenting or should I toss the whole jar?


  4. Gabriella says

    I have a crock that i recently bought and used cabbage and carrots to ferment its been a week….. I opened up the crock and there is a whitesh film on top is this normal??? HELP I am a first timer!!!

    • says

      Gabriella – If it is just white then it could be a harmless kahm yeast. This is totally normal and not harmful. You can scrape this off and so long as the veggies underneath smell fine, they should be fine.

  5. Dawn says

    I lacto fermented beets and carrots with garlic. The garlic insisted on floating. I just opened the crock and it has molded to a blue color. What to do? Also can I put this in jars and seal if still good?

    • says

      Dawn – Garlic turns blue when fermented, so no need to worry about the color. Mold, though, should be taken on a case-by-case basis. If it is minor, the ferment can be retrieved and the mold discarded.

  6. Lindsay Sharp says

    I made some cultured veggies in cap-lock jars. There is really no liquid (brine) layer at the top of the jars even though I added it as per the instructions. What should I do? It’s looking pretty dry at the top. I’m afraid it’s going to get very moldy.

    • says

      Lindsay – If you’re still looking into this, I would recommend adding some brine to the top in a ratio of 2 Tablespoons per quart of water. Mix that up and then pour in only as much of it as you need to cover by 1-2″. The rest of the brine can be used up within a couple of weeks for another project.

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