Fermented onions

fermented onions
Fermenting any food, including onions, is as simple as prepping the food, making the brine, and finding some space on the counter.

Fermented onions were my first foray into lacto-fermentation, and so far they are my favorite. So much so, I started two batches of them. I’ve been eating them every day. I really can’t get enough of my fermented onions. Why ferment? Because the bacteria produced during this preservation process aides digestion and has all sorts of health benefits. Read my blog on what fermenting is to learn more.

Most people start their fermenting journey with cabbage (making sauerkraut). But onions were the thing I had in abundance the day the fermenting bug hit me, so fermented onions were to be my first ferment.

What is remarkable about them is that somehow they become sweeter in the fermenting processes. I almost feel like I’m eating candy as I cover my lunch salad in them every day. I’ve sense fermented green beans, radish, and carrots and all are so tasty. But onions, amazingly, are my favorite.

Many people advocate fermenting with whey. I have not done this for no reason except I haven’t gotten my hands on any. I use a simple spring water and salt brine. It does the trick. I hear the results are a little uneven that way, that the whey helps you have more control how the ferment will turn out. I can see that…each of my batches has been completely different even though I use the same water to salt ratios. But that’s part of the fun, right?

I also ferment is quart size ball jars. There are also varying opinions on that, but they’re working just fine for me so, at least for now, I’ll continue using the jars.

fermented onions
Let the fermenting begin!

Recipe: Fermented onions


  • 1 to 2 onions thinly sliced (any kind of onion)
  • 2 Tbs peppercorns
  • brine made of 3 cups water and 2 tablespoons sea salt
  • 2 tablespoons brine from previous veg ferment (optional)


  1. Sterilize your jar.
  2. Place the peppercorns in the bottom.
  3. Fill the jar about 3/4 full with the onions, pushing them down firmly to get in as many as you can.
  4. Cover with the brine. Drop in a 1/2 cup size ball jar (or something else that fits in the quart jar and can keep the onions submerged. I use the small ball jar and then fill it with the brine as well.
  5. Cover tightly and culture at room temperature for 3-?? days, taking off the top as needed to release gas pressure.
  6. Start tasting on day three until they’re as fermented as you like. I usually ferment for 7 to 14 days, depending on the temperature.
  7. Move to cold storage.

Quick notes

Don’t be alarmed if some mold forms at the top of the jar. This happens. Just scrape it off. Your ferment is fine as long as all the food is submerged.

Preparation time: 5 minute(s)

Cooking time: 3 minute(s)

Diet type: Vegan

2 thoughts on “Fermented onions

  1. melodie reyes

    a friend of mine has to take blood thinners after her surgery. Comidon contains rat poison. I was looking for an alternative and came across fermented black onions. White ones that turn black after 30 days of fermenting. Do I just use the recipe you gave and continue the fermenting process for 30 days? You never did say how often you check the onions and how often you scrape the mold off. Thank you.
    Melodie Reyes

    1. Hi, I've never heard of fermented black onions, so I don't know the answer to that question. Perhaps ask a functional medicine doctor. In terms of scraping off the mold, I simply run a paper towel around the rim to wipe it off. If there is any mold floating on top of the liquid, I just use a spoon to spoon it out.


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