Is My Ferment Safe to Eat?

When it comes to food, you want to be safe. And when it comes to food preservation, experience is the best education you can get. When I first started canning our food, I questioned everything. I constantly called my neighbor to run over and look at something to make sure I was doing it right. Abigail has the experience. And in this post, she lets you know if your ferment is safe to eat.

Posted by Abigail

How Can I Tell When a Ferment Has Gone Bad?

When you are new to fermenting, one of the most common questions you are likely to have is this: “How do I know if it’s still good? Is my ferment safe to eat?” After all, fermentation is one of the only food preservation processes in which you are supposed to leave food out at room temperature and it’s supposed to smell and taste strange and strong when it’s done. So how can you tell a fermenting success from a fermenting failure?

While it’s unlikely that a properly controlled ferment will spoil, it is important to know what’s normal and what’s not when you open up a finished jar.

Is my ferment safe to eat?

A Normal Ferment:

  • Pleasantly sour taste. Think sourdough bread or plain yogurt. Now transfer that tangy, potent taste to fermented vegetables or fruits and you’ve got the right idea. Fermented foods can range from slightly tangy to zingy to downright strong, but in a good way! Each fruit or veggie combo has its own fermented flavor profile.
  • Strong smell when you open the jar. If you have to take a deep breath of fresh air when you first open a jar of fermented food, fear not. That’s normal, so long as the smell isn’t that of spoilage. (You’ll be able to tell; spoiled ferments smell quite rotten.) As the food is exposed to air before serving, the smell will become less odorous.
  • White film on top of the liquid in the jar. This is just a natural yeast by-product of the fermentation process. Skim it off the top and you’re good to go.
  • Sediment at the bottom of the jar or cloudy liquid. This is simply the presence of good bacteria and isn’t a cause for concern.
  • Brine overflow. Sometimes the release of carbon dioxide will cause your jar to overflow during fermentation. While it might be messy, it’s not a problem with the food itself. Unpack a little bit of the brine and vegetables to give a bit more headspace in the jar (1-2” is ideal), ensure that the veggies are still under the brine, and proceed as usual.
  • Brightly colored vegetables. Beets and radishes can turn an entire jar pink or purple and garlic can turn green or blue. This is normal.

An Unsafe Ferment:

  • Visible fuzz, or white, pink, green, or black mold. Get rid of it. This means your ferment was exposed to too much oxygen, bad bacteria was introduced during preparation, or it was too warm. Either way, it shouldn’t be consumed.
  • Extremely pungent and unpleasant stink. This differs significantly from the normal smell of fermented veggies. We had a jar of sauerkraut go bad once in our early fermenting days, and while it looked perfectly fine from the outside, the smell quickly told us it was no good. If it makes you want to gag, discard the whole thing and sanitize your jar.
  • Slimy, discolored vegetables. While bright color changes frequently occur during fermentation, very brown or slimy vegetables are a sign of spoilage. (Note that green veggies like cabbage may brown and pale somewhat.)
  • A bad taste. Remember, even though the taste of fermented veggies is unfamiliar to many of us, it shouldn’t be unpleasant. If the food tastes spoiled, spit it out!

Practice Makes Confidence

As you practice, you will become more familiar with the normal tastes and smells of lacto-fermented foods. Soon you will be able to easily identify the full range of fermented-normal!

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When you have a variety of several different foods to ferment, you want to have more fermentation lids for Mason jars on hand. Fermentools lids are made to last a lifetime, of surgical steel. Get a 12-pack in our store!

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Abigail is an aspiring homesteader, homeschooler, and music-maker. She lives with her husband and three children on her acre-and a half homestead in scenic Pennsylvania. You can visit her blog about living the homegrown life (and seeking contentment while doing it) at They’re Not Our Goats.

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11 Comments

  1. Skylar on March 28, 2020 at 4:28 am

    I am still pretty new to fermenting and been doing cabbage awhile now, so I decided to expand and go with broccoli. I fermented it on my counter, just as with the saurkraut and then put it in my refrigerator. But I noticed it has turned cloudy on top and a little tannish rim around the mason jar? I also fermented it along with fennel and rosemary for seasoning. I opened it and it is strong, but I think that is due to the smell of the broccoli fermenting. But I’m not really sure. I don’t want to waste it, but I sure don’t want to get sick either 🙁 Does the broccoli do that way after going in the fridge? And the date is 3/15 of this month….it is now 3/28

    • Cassie Deputie on April 6, 2020 at 6:37 pm

      My general rule of thumb is this:
      (1) If there is visible mold – green or black – then it’s bad
      (2) If it tastes sour and like any other ferment – then it’s fine
      (3) If it smells sour but not repulsive – then it’s fine

      Broccoli will give off a very strong smell when fermented. As long as it’s not a repulsive smell, it should be fine!

      Hope that helps!
      Happy Fermenting
      – Cassie Deputie

  2. Nicole Spitzer on April 13, 2020 at 8:50 pm

    Hello! Thank you for this article, if you have time I wondering if you could tell me if I’ve gone wrong with my sauerkraut.. here is this situation: Yesterday I began my first attempt at fermenting my own sauerkraut; I followed a basic recipe and used savoy cabbage. I ended up having to add some filtered water as my cabbage did not create enough liquid to be fully submerged. I then sealed the jar. A couple hours later I got fussy and ended up adding thick slices of carrots to attempt keeping the cabbage from floating above the brine and left it there for the night. But this morning I woke up very anxious about it and read that adding a layer of olive oil can help keep oxygen, and therefore the growth of bacteria, out. So i went ahead and added a layer and sealed the jar up again. Now i am worried i’ve ruined it.. does any of this (the filtered water, the oil, opening it up) sound dire? should i discard the whole thing? any help is appreciated!

    • Cassie Deputie on April 14, 2020 at 10:11 pm

      In my opinion, it is very hard to ruin a batch of sauerkraut if you just follow the tried by true process. If you have some cabbage that is floating up out of the brine, that is quite alright. It usually will not mold as long as you have added an adequate amount of salt. I have never added oil on the top of my kraut.

      You can rest assured that the good bacteria will out number the bad bacteria and it will be completely safe to eat if you follow simple recipes that include salt.

      If you purchased more than one airlock, I would recommend making a second batch following a basic recipe and leaving them both to ferment. See which one you like better. Did the carrots and oil affect the flavor? Which taste do you prefer? Let us know what you find out!
      You can always email at contact@fermentools.com

      – Cassie Deputie

      • Nicole Spitzer on April 15, 2020 at 10:32 am

        Thank you!

  3. Olga on May 7, 2020 at 3:30 pm

    Hi there! I just fermented about 400g of garlic and ginger in a mason jar in a cabinet for a week. (followed a recent Bon Appetit video) When I opened it, it smells horrible; like worse than really bad gas. What does a good ferment smell like? How can I know if mine is safe to eat? I’m afraid to eat it and get sick.
    Thanks for any help.

    • Cassie Deputie on May 8, 2020 at 10:04 pm

      General rule of thumb is this:
      Ferments should be sweet, sour and acidic in smell. They should not be repulsive or rancid. They should not have any visible mold (blue, green, black).

  4. Chiara on May 12, 2020 at 9:18 pm

    This is so helpful! I am wondering if it has a sort of tingle on the tongue effect (which is generally my rule for knowing something is bad but unsure with fermenting) but still smells good/tastes good (its hawthorne berries in honey) whether I should still throw it out?

    • Cassie Deputie on May 19, 2020 at 6:15 pm

      Yes! That tingle on your tongue is one of the sensations that makes ferments so unique and so delicious 🙂

  5. Nicole on June 2, 2020 at 11:43 am

    Hi! I am so glad to find your site I am new to fermenting and want to make sure I do it safely. I would love your opinion on some fire cider I just finished. I think it fermented around 6 weeks. Though, I didn’t turn it the whole time it fermented. It looks fine and smells like The apple cider bony. But one of the jars did have some of the yeast at the top I canned it anyway because I didn’t know until after reading your article I should have skimmed it off. Thoughts? Is it still ok to drink despite the yeast being mixed back in?

    • Cassie Deputie on June 4, 2020 at 3:35 am

      Absolutely! Yeast is on everything we eat. It’s in the air we breathe. It’s fine to eat 🙂

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