Lacto-fermentation not only preserves food, it enhances the flavour as well. There are also occasions when the food is almost completely transformed in appearance and taste.  This is very apparent in lacto-fermented red onions.  It is a favourite condiment I like to make in the summer as it pairs so well with BBQ!

I use red onions in a lot of my cooking- slightly blackened in Mexican dishes, stir-fried in Asian recipes and thinly sliced in salads, tacos and burgers.  Red onions have a pungent, complex flavour; sweet at first with a slight after-burn.  lacto-fermented red onions

When lacto-fermented, onions lose the bite and take on a more mellow tang.  They also lose their bright crimson colour and become a more festive hot pink.  

I love to use them on burgers, wraps, guacamole, salsa, anywhere you would use a red onion.

Lacto-fermented red onions with dill sauerkraut on burger
Lacto-fermented red onions with dill sauerkraut on burger

Try making some today and amp up the flavour and presentation of your next dish with these beautiful onions!  This is an easy ferment, and can be ready in 2 weeks.  I personally like to let mine ferment for a month to get maximum flavour and colour.


Fermenting Time: 2 weeks-1 month


  • Red onions (peeled and sliced)
  • 2% brine (20 grams/approximately 4 teaspoons of salt + 1 litre filtered water)
  • fermentation container
  • fermentation weight


  1. Slice onions and pack into fermentation container.
Slice red onions, pack in container
Slice red onions, pack in container

2. Fill with 2% brine, leaving a ?” space from the top of the container.  Add a fermentation weight.img_1843

3. Lid container, and place out of direct sunlight for at least 2 weeks.  For optimal flavour, leave to ferment for a month.  

add brine, lid contaner
add brine, lid contaner

4. Refrigerate to decelerate fermentation.

Lacto-fermented red onions after 1 month
Lacto-fermented red onions after 1 month

2 Responses

  1. Hi,
    What was the weight of the onions?
    Did you use the whole quart of brine?
    My understanding is that you need to take into account the weight of the onions AND the weight of the water, then calculate the 2% salt addition.
    Otherwise, the salt content would be less than 2%.
    Just something I read somewhere by someone who studied advanced microbiology lab classes at Louisiana State University.
    P.S. Just found the link….

    1. Hi Hank, thanks for your interest, question and link. I read the link, and found the content very interesting, however I never use this method, and don?t know many who do. The extra step of weighing the produce isn?t really necessary. I have never weighed my produce and have had repeated success using the correct brine percentage method. You don?t need to weigh the produce, it is the salt concentration (% ) in the brine that is important for the success of different vegetable ferments. Most vegetables can be fermented using a 2% brine, while cucumbers and peppers do best with a 3-3.5% brine, and pepper mashes, meat cures and olives with a 10% brine. The easiest way to calculate the salt amount is to use the metric system (1 litre= 10000ml). The formula to find the salt amount for a 1itre of 2% brine: 1000 x 2%= 20 grams (of salt). It is also advisable to add as little brine as you can get away with ? just enough to cover the vegetables.

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