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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DISCLAIMER: Because we are not able to see or smell your ferments, we are not able to tell you that your particular food is safe to eat. The best motto to follow is “When in doubt, don’t.” Please use your own best judgment.

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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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29 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

      • Chris Jennings on July 26, 2020 at 11:29 pm

        Hi Cassie,
        I am trying to torment Armenian cucumbers from a recipe on you tube. It calls for grape vinegar salt and water mixed not cooked as a brine. Just poor over the packed jar and screw on lid and put away in Hubbard for 15 days. Now the 4th day and one jar lost all its brine somehow so I threw it out. Another jar bent the lid so I slowly unscrewed it causing the brine to release gases and lots of bubbles. I put a new lid and put back in the Hubbard. The temps in my house are fairly warm due to summer and no AC. I have now put the jars in a brown bag in the fridge? The recipe warns if too hot they can explode so I’m assuming this is what was happening. Do you think these will be safe to eat still lol.

        • Chris Jennings on July 26, 2020 at 11:31 pm

          I’m sorry I forgot to mention I used high end balsamic vinegar since I could not find grape vingar

  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 🙂

  6. Alex on June 11, 2020 at 3:37 pm

    My mixed vegetable ferment developed a small piece of black mold early on. I removed it and haven’t seen any more since. Most of the positive signs are there. Would you recommend throwing the the ferment out? Thanks!

    • Carol Alexander on September 5, 2020 at 9:45 pm

      Hi Alex,
      My motto is “when in doubt, don’t.” Your eyes and nose are your best defense. I can’t see it or smell it.

  7. Val McArthur on June 17, 2020 at 12:38 pm

    Hi Cassie. Thanks so much for the article and helpful fermenting tips.

    Can you give me some advice on the following ferment please? I have fermented some carrot sticks but I didn’t put a weight on top to keep them submerged beneath the brine. Silly me! Initially they were well under the brine but they have bobbed up and have been exposed to some oxygen since when I last checked. The top 1cm has turned white. I have chopped this off and tasted one of the carrots. It has a strong sour taste but doesn’t taste off, the brine has turned cloudy and there’s a sediment at the bottom of the jar – which I believe is OK – and there is no foul smell or other signs of mould. I’ve returned the carrots to the jar and put a cabbage leaf on top with some weights. Do you think it’s OK to eat the rest? Or should I start again to be sure? Thanks, Val

    • Carol Alexander on September 5, 2020 at 9:39 pm

      Hi Val!
      Cassie is no longer with Fermentools so I will try to answer your question. My motto is “when in doubt, don’t.” Though I would like to be able to tell folks to go ahead and taste or try, without seeing and smelling, that is a dangerous call. You really have to do what you think is best here.

  8. Cameron on July 9, 2020 at 6:03 pm

    I recently made a batch of sauerkraut (in a pint jar). After about a week I had to leave town for a few days, so I topped it off with brine before I left. When I got back after 2 or 3 days, the top layer was a bit darker than the rest and there was no liquid on top for about an inch; however, it didn’t smell bad or anything. I scooped off the top layer (as much as I could). I think the jar was too full. What can happen if it’s exposed to the air out of the brine too long? Now, a week later, it smells and tastes fine and there’s no (visible) mold. There were a few small pieces of cabbage that had shriveled up and turned brown that were on the top of the lid and the side of the jar from when there was less brine, but like I said there was no mold and I removed that stuff before putting it in the fridge. Is it alright to eat?

    • Carol Alexander on September 5, 2020 at 9:04 pm

      Of course, without being able to see or smell it, I advise you to do what you feel comfortable with. But from your description, I would probably try it.

  9. Htoo on July 28, 2020 at 5:43 pm

    I wanna ask one thing. Doni have to rinse out all the fermented vegetables water? It’s my first time doing it so I am kind of unsure about the smell too.

    • Carol Alexander on September 5, 2020 at 8:48 pm

      No, Htoo. After the ferment is complete, place the jar in the fridge as is without rinsing. That brine is healthy, too. It should smell fresh and slightly sour.

  10. Heather on August 3, 2020 at 10:31 pm

    Hi! I just made a batch of sauerkraut (it sat for about a week). I just opened it up and it looks/smells/tastes good, but it’s soft. Is it ok to eat? I’ve been trying to find a definitive answer about whether it’s ok. The brine is milky, but not slimy. My assumption is it was a little too hot so it fermented too quickly. It’s not total mush, but definitely way softer than I’d like it to be, but I think it could still be good mixed into certain dishes. Just want an educated opinion before I eat a bunch of it! Thanks!

    • Carol Alexander on September 7, 2020 at 2:49 pm

      Hi Heather,
      Without seeing and smelling, I’m really not able to tell. If it were mine, I might taste a small bit first. But you need to use your own best judgment.

  11. Jenny R on August 30, 2020 at 8:24 pm

    I have a mason jar full of very well rinsed and packed wild blackberries that I left in the back of the fridge for about a month. I’d like to still use the berries if possible. Any recommendations? They were foraged and are so delicious…Northern CA. I hate to waste!

    • Carol Alexander on September 3, 2020 at 4:12 pm

      Not sure, Jenny. I would think they’d be all moldy by now. Or do you mean they’re fermented? If they’re fermented, they should still be good.

  12. Tim on September 12, 2020 at 11:06 pm

    I made a batch of sour pickles in a large crock using 2 tablespoons of salt per quart of water. In addition to the cucumbers which were small and firm, I added dill, garlic cloves, and black peppercorns. I weighted down the cucumbers with a plate to ensure all were submerged. On about day 4 nearly 2/3s of the cucumbers began to balloon and rot in the middle of the cucumber (the ends were still hard but the middle portion had turned to mush). What a disaster. What could have caused this? I’ve had success in the past following similar practice. It’s humbling!

    • Carol Alexander on September 26, 2020 at 4:11 pm

      That is so disheartening! Were the cucumbers fresh? Did you cut the blossom end off? Was that the right brine solution? I’d check a trusted recipe for the correct brine strength. What was the ambient temperature? There are just so many variables! But, please check out this post, and others in our pickle section. https://fermentools.com/5-tips-for-lacto-fermented-crunchy-pickles/

  13. B. Ebert on September 26, 2020 at 10:05 pm

    I made a jar of fermented spicy pickles and they have a slight smell of rotten eggs. Everything else looks perfect about them. I have made other jars just like this one but have never smelt the egg smell?? Are they ok to eat? Thanks so much!

    • Carol Alexander on October 10, 2020 at 3:30 pm

      I haven’t heard of that before, B. Did you use a different water than usual? I really can’t advise you about whether you should eat it or not. I say use your own best judgement.

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