How to Make Lacto-fermented Red Onions

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Lacto-fermented red onions are not as commonly made as pickled red onions but they're easier to make, tastier and healthier! Learn how here!

I’m going to start out this blog with a genuine question that I’ve been curious about for a while. Why do people make pickled onions when lacto-fermented onions have so many more benefits?

I ask because the reason I made lacto-fermented red onions for the first time was because a friend had made pickled onions using vinegar and sugar.  They were OK but the taste of vinegar was quite apparent.

I knew right away I had to try the lacto-fermented version.

Sure enough, in my opinion anyway, the lacto-fermented red onions were MUCH tastier.  They tasted fresh, pleasantly sour and well, didn’t make my mouth pucker.

But pickling via the use of vinegar and sugar seems to be the far more common home preparation.  The word “pickling” is often used interchangeably with the word “fermenting” but for the most part pickling refers to preserving foods in an acidic medium at a high temperature (often in a water bath) which destroys the enzymes and probiotics.

Lacto-fermentation is a natural preservation process that uses just salt and water. It enhances the probiotic and enzyme content.

I understand that food companies prefer pickling because this method allows for a more uniform product with a longer shelf life.

But why do people do this at home when it’s more time-consuming, less tasty and less healthy?  It’s not like you need to preserve vegetables for three years at home. Lacto-fermentation will also keep foods preserved for long periods.

Did pickling become fashionable at a certain time in American history for some reason? Do people really like the vinegary taste better? Is it just me?

I really don’t know. If you know, please comment below. I’m genuinely curious!

How to Make Lacto-Fermented Red Onions

So if you’ve never made lacto-fermented onions or pickled onions before, make the lacto-fermented version!

Use them on salads, burgers or anywhere you usually use red onions.  Lacto-fermented red onions will have a sour albeit less pungent flavor than raw ones.

Preparing lacto-fermented red onions won’t take you more than ten minutes from start to finish.

Ok, here’s how you do it.

Lacto-fermented Red Onions Recipe
Prep Time
15 mins
Total Time
15 mins

Red onions, water, salt and a starter culture are all it takes to make lacto-fermented red onions. They are not as common as pickled onions but they're easier to make, tastier and healthier!

Course: Side Dish
Cuisine: Any
Servings: 12 ounces
Author: Craig Fear
  • 2 medium red onions, sliced into rings
  • 1/2 - 1 TBSP sea salt
  • 12 ounces filtered water
  • 1 TBSP whey, optional
  • Herbs of your choice, optional
  1. Pack sliced onions firmly into 12 ounce glass jar.  Layer in any herbs you want.
  2. Dissolve salt in 12 ounces of filtered water and add whey.
  3. Pour brine over onions and tilt jar a few times to mix well.  Leave one inch between the top of the jar and the top of the brine. Use a weight (find a good source for fermenting weights here) to keep the onions under the brine, if necessary.
  4. Let sit on counter for three to seven days. Use an airlock lid (find a good source for airlock lids here) or burp the jars (meaning just open them) every day to let out the gasses that are a natural byproduct of fermentation.  If the water level rises, simply pour some out.
  5. Enjoy on salads, burgers or anywhere you usually use red onions.  Fermented red onions will have a sour albeit less pungent flavor than unfermented ones.


Lacto-fermented red onions are not as commonly made as pickled red onions but they're easier to make, tastier and healthier! Learn how here!

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  1. Hi There!
    This look really great and I love the picture!! To me it seems as we moved into the processed foods and methods, the canning with vinegar was considered a “safe” method and we lost the understanding of the traditional wisdom of lacto fermentation. Thankfully, the revival is under way! I love your summer series of fermentation! Trish

  2. When my father was growing up people had to grow most of their vegetables. There were no grocery stores that carried canned goods, fresh fruits/veggies and processed food. Families tended to be larger during that time and you would have to can all of the items you can get out of your garden to last you till the next growing season. Refrigeration was not an option for a long time and foods needed to be stored safely. It was matter of necessity. As technology made our lives easier, we became lazy n began purchasing canned, frozen, and processed foods. Then that way of life became a necessity because of single working mothers and two working parents. Due to the heath crisis we face it has now become a necessity to go back to fresh n healthy foods.

  3. jackk friend says:

    i’ve wanted to try making fermented foods for a long while. i’m fearful i won’t do it correctly & will poison myself on bacteria. i’ve had my share of food poisoning & wish to avoid it at all cost. thanks for explaining that pickling in vinegar brine removes the ‘good stuff.’ i like vinegar just fine but want the benefits of fermented foods for good gut health. thanks.

    • Hi,

      You can’t miss lacto fermentation of veggies: if the batch is missed, it will smell bad. If the batch of lacto fermentated food is a success, it will have a pleasant sour an vinegar-like smell. I have been doing kimchi, zucchini, carrot, beet (or beetroot if U r from the UK), bell pepper, and I have never missed one for years. This is bull shit to add any ferment. You just need the bacteria that are native to the veggies (it means, try to get organic grown food). It is these bacteria that are going to reproduce and start the lacto fermentation process. Adding too much water in the beginning actually retard this process.

      I give you a clue that you won’t find in most of the post and web site: DO NOT POUR WATER in the beginning. It dissolves too much of the lacto fermentative bacteria. Just slice your veggies and add raw sea-salt in an air tight glass container. Wait for the veggies to “cry” their juice. When it start to make bubbles and smell a little sour, at this time, you can add just the sufficient amount of distilled water to cover the veggies.
      in kimchi for example, you do not add any water. People add too much water, it dilutes too much the good stuff. My kimchi can last for 3 months, and still being eatable….

      pardon my poor English, I am French (and a male 🙂 )

      thierry jeanne

  4. Can you use water kefir instead of whey here, for dairy intolerant people?

  5. Thanks for sharing a recipe for laco fermentation. I have to say that I loveeeeee the taste of vinegar and will eat it whenever I can get my hands on it. So anything that has been pickled taste good to me. However I am not understanding some things about the pickling/fermentation process. #1 I don’t understand why good bacteria would not grow in something that has been pickled. Also is vinegar not good for our digestion? The bi-product of kombucha is a vinegar and from what I have read it is great for our digestion. #2 What kind of whey are you adding to the laco fermented onions? Lactobacillus, from what I understand is a bacteria and it grows in the fermentation process because of the whey added. If the whey is not alive then will the process not happen. If you don’t add the whey the lacobacillus process can still occur?

    • I have been fermenting all sorts of foods for a long time. The lactobacilis culture occurs naturally on the surface of the foods, and therefore the whey is not necessary, but allows a more favourable environment for the laxtobacilis to grow more quickly than without. I never use whey, but sometimes use rejuvilak (liquid from fermented sprouts) as a starter culture (this is also not necessary but gives the fermentation a quick start). As for the vinegar, it is definitely good for our digestion, and kombucha (which I have made for years and drink daily) is even better. The thing is that it is a different process, the vinegar/kombucha provide acids that aid digestion and the fermented vegetables provide probiotic bacteria/enzymes that help maintain healthy gut flora. The acids in vinegar with stop the process of fermentation of lactobacilis in the vegetables, and therefore pickling is not fermenting, it is preserving. Pickles are still good for you because they provide the vinegar acids, but they are not fermented. So in short, the two processes are different but both good for you.

  6. I put some sliced onions, and peppers into a jar, some months ago, with salt, ( I did a sour kraut brine ).
    They have fermented, and now there is a cloudy top, with mold growing on top.

    What do I do with them ?
    Do I cook them? Roll them raw into a tortilla ?

    • Robert, If they are moldy you should not eat them. It’s a shame to throw them away, but mold can be dangerous.

    • Hi Robert, usually mold forms on the surface when your veggies make contact with the surface. A small weight of some sort can help keep the veggies submerged in the brine.

  7. Why do you need whey? And what temperature should the fermentation take place? I live in a tropical country and it can get really hot like 30 degree Celsius hot

  8. Heather says:

    if the top onions turned a grayish color did I do something wrong??

    • Hi Heather, as long as they’re under the brine, they should be fine. I’ve noticed this as well. Over time, as the onions continue to ferment, even in cold storage, they will change color and even taste.

  9. Craig, Thanks for this recipe! The fermented onions are excellent. I’ve been using them on salad daily. Perfect for burgers and sandwiches. This is a great way to maximize onions, essentially keeping them fresh when you don’t want a whole onion. I really enjoy all that you share.
    ~Julie From NH.

  10. Since you said you were honestly curious… I’m going with vinegar pickling over lacto-fermentation simply because I suck at planning. I’m planning a dinner for tomorrow – fermentation won’t be ready in time (despite vigorous Googling for some magical way to speed it up), but I can make quick vinegar-pickled onions. When I try to plan meal components far in advance, something usually comes up to change the plans, but mostly I’m just too excited about what’s happening soon and don’t start planning for meals a week out.

  11. Sounds delicious! Does it make them taste less spicy? I find raw red onions hard to eat.

  12. lydia hays says:


    • Hi Lydia, yes you can use Himalayan salt. Basically, any unrefined salt will be adequate. And yes, your filtration system is certainly a type of filtered water.

  13. Kymbreli says:

    Hello! I appreciate your response in advance!! I am fermeting red onions. I used filtered water from a Pür filtered water jug. I used himalayan pink salt, and an organic red onion that was cut already and sitting in the fridge. Q1: I used a glass jar with a lid that seaps water when shook (old pasta jar) but I sealed with two layers of plastic wrap. It doesnt seap water at that point. Is that ok? Q2: Also, I made the mistake of adding chopped cilantro and dried dill spice. My reason for calling it a mistake is because I read this forum much later. You answered someone by saying floating bits touching the surface will cause Mold to grow. Then I saw to use a weight to manage this. So, i filled a 2″x2″ ziplock bag with coins and held down the onions and some of the cilantro and dill, and managed to get all if the diced pieces of cilantro stem out, but there is still dill floating atop and pry small bits of onion and cilantro. Will this cause an issue? Should I have used a full spring of cilantro and dill instead? Q3: will you please be more specific with everything as though you were speaking to Sheldon from Big Bang Theory? Because I tend to have a question for every sentence you write. I’d appreciate a new recipe with hints, avoidances, and clear specifics for perfection. Q4: what are red flags for “do not eat” if we were to make mistakes, other than mold of course? Thank you thank you! Much Appreciated!

  14. Sherry says:

    Hi, if I iodized salt, will it mess things up??

  15. I absolutely adore pickled red onions, so I’m curious how much different the fermented red onions hold up in comparison! Hopefully they are pretty similar, because I would love to be able to get the same great taste as pickled red onions but also get the benefit of probiotics! Thank you for sharing this recipe, and I can’t wait to try it at home!

  16. Mary Ann says:

    What is meant by “pure water”? I live in town and have to rely on tap water.

    • Hi Mary Ann, it just means filtered water. If your only option is tap water, you can use it but sometimes there are things in tap water which are not conducive to fermentation (such as chlorine).

      • Jack Friesner says:

        If you plan ahead, you can often strip much of the free chlorine by either leaving your water set out in an open container for a day or two, or you can boil the water (allow to cool before using).

  17. Hi, Where can whey be purchased? In the grocery store?

  18. Excited to try this out myself!

    Question: Why the whey? Can you go into the added health benefits for me?

    Thanks, cheers.

    • Hi Anna, the whey is used as a starter culture because it’s rich in good bacteria. However, since I wrote this post many years ago I’ve learned that whey is not 100% necessary for fermentation. The natural bacteria present on the onions (and all vegetables) should be enough to kickstart the process.

  19. mike hurcum says:

    anyone used pickling spices in ferments

    • Hi Mike, you could certainly try pickling spices in any type of vegetable ferment besides cucumber pickles. I think it would be interesting with onions though I’ve never tried it.


  1. […] You can check out my posts for how to make lacto-fermented pickles and lacto-fermented red onions. […]

  2. […] vegetables via natural fermentation, here’s a great post I found from Fearless Eating on How to Make Lacto-fermented Red Onions. I love the idea of fermenting vegetables because the natural vitamins, minerals, yeast, and […]

  3. […] bulbs. To one-up the health benefits of an onion, try your hand at lacto-fermentation. That is, making pickled red onions that are irresistible and rich in probiotics. […]

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