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Fermented Onions: How to Make and Store!


Reading Time: 8 minutes

Instead of eating fresh or pickled onions, you can make your meals more flavorful and nutrient-filled with fermented onions. After fermentation, onions have a fresher, sour taste that’s more refreshing than the natural onion flavor.

You don’t need to train for a prolonged period to master the fermentation process. Fermenting onions is almost similar to pickling with sugar and vinegar, which you lust have tried by now.

That’s why some people often confuse “pickling” for “fermenting,” thinking that the two words mean the same thing.

This article discusses the meaning, process, and importance of fermenting onions, providing several easy-to-implement recipes. If you want to learn more about why fermented onions are the best, keep reading to the end.

Is Pickling the Same as Fermentation?

No. pickling is not the same as fermentation. That’s because the preparation of pickling onions involves pouring a spice-enhanced vinegar over preprepared onions and letting it sit for some time until the onions have absorbed all the included flavors.

The acidity of the vinegar-preserve onions creates a long shelf-life, especially when kept in the fridge. However, pickled onions do not contain probiotics or live enzymes.

With fermented vegetables, you need more time and the action of good bacteria to consume the sugars in the onions, converting them into alcohol, carbon dioxide, and acids to preserve the vegetables.

You can catalyze the process using sea salt and create a conducive environment for lactobacilli, a bacterium that speeds up the fermentation process.

Both pickling and fermentation involve adding ingredients to raw onions and waiting for some time for the process to end successfully. While both result in a salty, tangy taste, fermentation creates several layers of complex flavors together with healthy bacteria. It’s also less acidic than vinegar-pickled onions.

What Is Lacto-Fermentation?

It can be challenging to associate fermentation with anything else other than the production of beer or wine. Specialized yeast is the main active ingredient when producing beer or wine, converting the sugars in grains or grape juice into alcohol.

On the other hand, lacto-fermentation involves using tiny bacteria that are naturally present on the surface of the onions to convert the sugars to lactic acid, alcohol, and carbon dioxide.

Lactic acid is a natural preservative inhibiting the growth of harmful bacteria. Lacto-fermentation also effectively maintains or improves the vitamin and enzyme levels, enhancing the digestibility of food.

Reasons to Ferment Onions

Apart from the apparent reasons for fermenting onions, there are so many more benefits of fermenting onions, including the following:

  • Easy Recipes: There are several easy recipes to help you learn how to ferment onions for the first time. You do not have to go through an intensive cookery class to learn the process.
  • Health Benefits: Lacto-fermented vegetables contain lots of beneficial bacteria, creating optimal digestive system conditions.
  • Excellent Preservation Method: By fermenting onions, you trigger a natural preservation method that doesn’t require the use of other acids such as vinegar. The naturally occurring lactic acid gives the food a long shelf-life.
  • Flavorful Condiments: After lacto-fermentation, onions change their texture and flavor profile. Instead of the raw onion pungent smell, the onions create more delicious meals.

How to Make Fermented Red Onions?

Red onions are some of the best to ferment due to their sweetness combined with the natural lacto-fermentation process to provide tangy, delicious umami-packed condiments.

In addition, fermented red onions are easier to make, creating a texture that tends towards cooked onions rather than their raw counterparts.

You should choose fresh, firm onion bulbs to produce red onions successfully. Usually, fermentation takes place at room temperature. That’s because high temperatures can kill the bacteria behind the fermenting process, curtailing your efforts to create healthy, delicious onions.

Here is a simple process to help you to produce fermented red onions quickly:


  • Two medium-size red onions
  • 1.5 tablespoon sea salt
  • 12 ounces filtered water
  • One tablespoon whey
  • Herbs of your choice


Step 1: Slicing Onions

Cut off the woody ends from the onion bulbs and remove the dried cover. Next, cut the red onions in half and thinly slice them. You can also use pearl onions, white onions, or yellow onions. Essentially, you should end up with nice onion strings. Therefore, you shouldn’t dice the onions in any way.

Step 2: Salting Onions

Put the sliced red onions in a big bowl and sprinkle with 1.5 tablespoons of salt. Massage the salt into the onions until they start releasing their juices and sweating. As you keep massaging the onions, they will become soft and less crispy.

Step 3: Transferring to a Fermentation Jar

Once the onions have adequately broken down, use fermentation weights to press down the onions and add ½ cup of filtered water. Close the lid to the jar until it is completely airtight.

Step 4: Topping Up Water in the Jar

The following day, check the water level in the jar and top it up to submerge the weighted onions. Close the jar once more, ensuring it’s airtight. Keep the onion jar at room temperature, away from direct sunlight.

Step 5: Waiting for Fermentation to Take Place

The fermentation process takes five to seven days. Therefore, you can remove the onions sooner or later, depending on the taste you wish to achieve and your personal preferences. Regardless of how long you want it to take, keep the onion jar at room temperature.

Step 6: Transferring to Jars and Storing

Keep tasting the onions to measure their tang and flavor depth until you’re satisfied with the results. Once you’re sure the fermented onions are delicious, store the container in the fridge and use the onions to make great food whenever you need to. Fermented onions can last in the fridge for at least two months.

How to Make Lacto-Fermented Red Onions with Salt Brine

Instead of massaging salt over sliced onions, you can use salt brine for fermentation. With this recipe, you’ll have fermented onions perfect for use on burgers, with cheese, and for storing in mason jars.

The good thing is that onions lacto-fermented in this manner do not require a starter culture. Here is how to get lacto-fermented red onions using salt brine.


  • Two medium-size red onions
  • 1.5 kosher salt
  • 12 ounces filtered water
  • One tablespoon whey
  • Herbs of your choice, such as garlic


Step 1: Peeling and Slice the Onions

Once you have bought your red onions, slice off the woody part. Next, cut each red onion in half and thinly slice it. Alternatively, you can use pearl, yellow, or white onions.

It should take a few minutes to have onions strings you can use in the fermentation process. In this step, avoid dicing the onions, rendering them unsuitable for fermentation.

Step 2: Pouring Onions into a Glass Jar

Put the sliced onions in a 12-ounce glass jar. Add a layer of your favorite herbs, such as cilantro or garlic. That should get the onions ready for the addition of salt brine.

Step 3: Preparing Salt Brine

Brine is a salt solution. It would help if you prepared it by dissolving the 1.5 tablespoons of salt into 12 ounces of water. Then, add the whey and stir until all the salt crystals dissolve in the water. Once the brine is ready, you can pour it over the sliced onions.

Step 4: Adding Brine to the Onions

Now is the time to pour the brine over the onions. Tilt the jar several times as you do it, ensuring that the onions and brine mix well. Remember to leave a one-inch space at the top of the jar from the highest level of the liquid brine.

Use fermentation weights to push the onions under the brine. In most cases, some of the onion pieces might rise above the liquid and not ferment as adequately as you expect.

Step 5: Waiting for Fermentation to Happen

Allow the glass jar to sit on the counter for five to seven days for fermentation. Where possible, use an airlock lid, which releases any excess air that could have built into the container.

If you use an ordinary jar, keep burping it every day to release carbon dioxide and other gases resulting from fermentation. Then, if the liquid level rises, pour some out to have what you need.

Step 6: Pack the Fermented Onions in Jars

After waiting for the fermentation to happen, you can go ahead and pack the onions jars. Alternatively, you can use fido jars. Fill each jar with fermented onions and keep in cold storage. In a refrigerator, fermented onions can last for up to two months if you don’t decide to use them in between.

Fermented onions create great food and create perfect burgers, salads, cheese, and other foods. They have a sour, less pungent flavor than their raw counterparts.

How to Make Fermented Pickled Onions

For a simple process of making fermented onions, use this pickled onion recipe. Fermented onion pickles are great on sandwiches, tacos, and when served over fish. Here is the simple process of fermenting pickled red onions:


  • Two large red onions (yellow onions, pearl onions, or white onions)
  • ½ teaspoon whole black peppercorns
  • One bay leaf
  • Two cloves crushed garlic
  • One tablespoon coarse kosher salt
  • 2 cups of water


Step 1: Prepare the Ingredients

Before you can start fermenting red onions, you should prepare all the ingredients. For the onions, you’ll have to peel and slice them into thin, long strings. Next, remove the dry cover, cut the onion bulbs in half, and thinly slice them.

Step 2: Add Ingredients to a Quart Jar

Put the peppercorns and garlic in a clean mason jar, followed by the sliced onions. Tack the bay leaves on the sides of the jar. Let it sit for a few minutes as you prepare the salt brine.

Step 3: Prepare Salt Brine

Put the two cups of water in a separate jar and add salt to prepare the brine. Gently stir the solution until all the salt crystals have dissolved in the water.

Step 4: Adding Brine to the Onions

Now is the time to add the brine to the onions. Pour the brine over the onions until the liquid completely covers them. Leave one to two inches of headspace between the brine level to the jar’s rim.

Step 5: Adding a Fermentation Jar Weight

It could be necessary to add a fermentation weight on top of the onions to push them below the surface of the liquid. So, do it if you have such a weight.

Step 6: Closing the Lid to the Jar

Now that you have added all the ingredients and the brine add a mason jar canning lid and ring. Tightly screw the lid onto the jar. It should take up to seven days for the onions to ferment at room temperature, between 60°F to 75°F (or 15°F to 23°F). Avoid direct sunlight by all means.

Step 7: Checking the Fermentation Jar

Making fermented onions is a process that requires constant monitoring. Check the setup daily to ensure the onions are consistently below the brine level.

If you notice any onions rising above the brine, push them using a clean spoon. Burp the jar daily to remove any accumulated gases.

Step 8: Transferring to Mason Jars

After one week, taste the onion pickles to check that the flavor is what you want. If it’s okay, transfer the onions to mason jars and onwards to the fridge. Alternatively, you can keep the entire onion jar together with the brine in the fridge. Then, feel free to use the onions in your favorite recipe whenever you need them.

How to Use Fermented Onions

Lacto-fermented onions have a variety of uses and can find themselves in a recipe that requires you to use onions. However, you should avoid recipes that require heating, boiling, broiling, or frying since that can destroy the probiotics in the onions. Here is how to incorporate fermented onions in your recipes:

  • Onion Butter: Crush some fermented onions and mix with softened butter. Spread the mixture on fresh bread.
  • Caprese Salad: Use fermented onions to top the classic tomato and mozzarella salad.
  • Savory Cocktails: The fermented version is the best if you’re looking for great cocktail onions.
  • Onion Salad Dressing: Why don’t you use fermented onions instead of fresh ones on your favorite vinaigrette?
  • Cheese and Charcuterie: Take some Lacto-fermented onions and add them to a charcuterie board or celebratory cheese.
  • Pizzas and Burgers: You can stuff a juicy burger or a homemade pizza with fermented pickled onions. The contrasting sour flavor tastes great.

If you’re looking for an easy way to preserve onions, fermentation is the best way to prolong their shelf life and improve their flavor. In addition, unlike pickling, fermentation improves the onions’ health benefits due to their high probiotic content. Besides, fermented onions are great for use in a variety of recipes. So, why don’t you go ahead and ferment your onions?









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