How to Make Fermented Onions

I’ve recently been asking myself the question, “Why do people make pickled onions when lacto-fermented onions have so many more benefits?”

If you have a tradition at home in preparing pickled onions why not try adding the healthful benefits of lacto-fermentation? The resulting fermented onions taste more fresh and have a seductive sourness that doesn’t make your mouth pucker.

Ingredients you'll need to prepare fermented onions.
Ingredients you’ll need to prepare fermented onions.

Are Pickled Onions Fermented?

The term pickling is often used synonymously with the word fermenting. This is wrong.

Today pickled onions are most commonly preserved in vinegar with sugar, salt and spices. Pickling refers to the preservation of foods in an acidic solution at a high temperature. Therefore vinegar-preserved onions do not contain live enzymes or probiotics. You’ll enjoy more health benefits when canning onions in the kitchen by ditching the pickling method and adopting lacto-fermentation.

What is Lacto-Fermentation?

At some point, thousands of years ago, early humans learned to use the process of fermentation to enjoy its tasty results. The most familiar fermented foods, like Korean kimchi, Jewish pickles and German sauerkraut are made using lacto-fermentation.

Most people think about beer or wine when they hear the word fermentation. While specialized yeasts are used to convert sugars in grape juice or grains into alcohol, it is tiny bacteria that are responsible for lacto-fermentation. Various strains of these bacteria are naturally present on the surface of plants, especially those growing in or close to the ground such as garlic, carrots, and jalapeños.

The naturally occurring bacteria convert sugars into lactic acid. This acid is a natural preservative that inhibits the growth of harmful bacteria. Lacto-fermentation also increases and preserves the beneficial vitamin and enzyme levels, and digestibility of fermented food.

Peeling cipollini and pearl onions.
Peeling cipollini and pearl onions.

Why Make Fermented Onions?

  • if you’re keen to try fermentation for the first time it’s best to start with an easy recipe. Fermented onions are one of the easiest fermentation recipes you’ll find.
  • lacto-fermented vegetables are rich in beneficial bacteria, which have been proven to encourage healthy gut flora.
  • fermenting onions allows you to naturally preserve raw onions to enjoy over a long period of time.
  • onions that has gone through the process of lacto-fermentation changes its flavour profile and texture over time. Many foodies find onion ferments to be more delicious than the more pungent raw variety.
Raw, peeled onions waiting for the fermentation process to begin.
Raw, peeled onions waiting for the fermentation process to begin.

Get Creative with Fermented Onions

Lacto-fermented onions can be used in any recipe that calls for onions. You ideally want to avoid using it in recipes that require cooking, as the heat will destroy the beneficial probiotics. Here are some of our favourite ways to use fermented onions when cooking at home:

  • Onion Salad Dressing: prepare your favourite vinaigrette and replace raw onions with your homemade ferment.
  • Caprese Salad: top a classic tomato and mozzarella salad with your new favourite fermented condiment.
  • Onion Butter: whip crushed fermented onions into softened butter and spread on fresh bread.
  • Pizza and Burgers: top a homemade pizza or stuff a juicy burger with pickled onions for a contrasting sour flavour profile.
  • Savoury Cocktails: swap out cocktail onions for fermented onions in your favourite savoury cocktail.
  • Cheese and Charcuterie: add your favourite lacto-fermented vegetables to a celebratory cheese and charcuterie board.
A jar of fermented onions ready to enjoy after a month long fermentation.
A jar of fermented onions ready to enjoy after a month long fermentation.

Tips on Making Fermented Onions

Our recipe for fermented onions looks very easy based on the short ingredients list. Since lacto-fermentation is a science, it’s best to ensure you understand how fermentation works. Here are our favourite tips and tricks to prepare fermented onions:

  • do not fill the onions and brine all the way to the top of the jar. You want to have just enough brine to cover the onions.
  • You can speed up the fermentation process by adding a teaspoon of organic apple cider vinegar or “sauerkraut juice.”
  • ensure the onions are always submerged under the liquid to prevent mould growth.
  • open your lid each day to burp the jar, releasing a build up of carbon dioxide. This will help you avoid an unwanted explosion in your cupboards.
  • use a variety of white and red Pearl and Cipollini onions as they offer a beautiful colour contrast in the jar.

How To Make Lacto-Fermented Onions

A jar of fermented onions ready to enjoy after a month long fermentation.
Print Recipe
5 from 3 votes

Fermented Onions

Lacto-fermented onions taste better and have more health benefits than pickled onions. Enjoy with a charcuterie and cheese board or in a savoury cocktail. 
Prep Time30 mins
Cook Time30 mins
Total Time1 hr
Course: Condiment
Cuisine: American
Keyword: Fermented Onions
Servings: 1 jar
Calories: 138kcal


  • 3 cups Pearl and Cipollini onions peeled
  • 4 cups water
  • 2 tbsp salt


  • Once your onions are peeled add them to a mason jar so they are 1 inch from the top. 
  • Prepare a salt brine by dissolving salt in water. 

  • Pour brine into the mason jar until the onions are covered. 

  • Optional: add any additional flavourings such as pickling spices or fresh oregano or basil. 
  • Put the lid on the jar and store at room temperature in a dark place like your closet or cupboard.
  • Open the jar once a day to release carbon dioxide. Fermentation fans call this "burping."

  • Continue this process for 3-4 weeks until fermentation bubbles no longer form. 
  • Move the fermented onions to your fridge once fermentation has completed and enjoy for the next 3-6 months. 


Serving: 1jar | Calories: 138kcal | Carbohydrates: 32.2g | Protein: 3.8g | Fat: 0.4g | Sodium: 13995mg | Potassium: 516mg | Fiber: 7.4g | Sugar: 14.6g | Vitamin C: 7.4mg | Calcium: 90mg | Iron: 0.9mg

You May Also Enjoy Reading…


Leave a reply

Receive Updates When New Stories Are Posted