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Fermented Onions in a Jar

Fermented Onions Recipe

  • Author: Gigi Mitts
  • Prep Time: 15 minutes
  • Total Time: 15 minutes
  • Yield: 2 quarts 1x


Simple and easy fermented onions recipe.



  • 4 large red onions, sliced thin or made into rings
  • 6 cups water
  • 2 tbsp kosher salt


  1. Pack the onion rings or slices into 1-half gallon or 2-quart size jars.
  2. In a separate bowl, combine the water and salt together and stir until dissolved.
  3. Now pour the brine into the jars until the onions are completely submerged. Prepare more brine if needed.
  4. Close the lids and leave the jars in a cool, dry place away from direct sunlight.
  5. There will be CO2 build-up in the first week. Release the bubbles by slightly loosening the lid and closing it right away. Do not open the lid completely.
  6. When fermentation stops, test the brine with pH strips. Do not consume the onions if there is a strong, rotten egg-like aroma or if the brine pH is over 4.0
  7. If there is surface mould (known as Kahm yeast) there is nothing to be concerned about. Simply skim the top mouldy layer and test the pH. Harmful bacteria cannot survive in brine with pH below 4.0.
  8. When fermentation is to your liking, move the jars to a refrigerator.


These onions can last anywhere between 6 months to 1 year. Note that after a few months, they are still edible despite their dull, faded appearance.