Fermented onions are made using brine (water and salt) and time. Fermenting onions at home is easy and totally worth the effort. The best part is that the health benefits are enormous! Fermented onions are more digestible and higher in nutrients than raw, fresh onions. Fermented vegetables are rich in enzymes and probiotics.

Although there are many health reasons to incorporate fermented foods into your kitchen, many people choose to ferment foods for the delicious flavour. Fermenting onions makes them less pungent but creates a fresh, tangy and sour condiment that is perfect for topping dishes such as stir-fries or salads. I love having fermented onions or fermented leeks in my fridge to add an extra boost of nutrition to my lunch bowls.

It took me a long time to work up the courage to try lacto-fermenting vegetables in my home kitchen. I was convinced of the health benefits and it was painful spending so much of my grocery budget on expensive jars of fermented vegetables from the health food store when I knew I could do it for a fraction of the cost at home. But I was nervous that I wouldn’t know if the fermentation had gone wrong.

After a lot of reading, experimentation and watching videos including this one by Joshua Weissman, I now feel super confident when fermenting vegetables. Here are some of my tips for a successful fermentation.

Tips for Successful Fermentation

• Use a kitchen scale. This method ensures that you’re using enough salt and increases the chance of a successful fermentation. 
• Keep the onions totally submerged. It’s important that the item you’re fermenting is kept in an oxygen free environment. Peek at your fermenting jar once a day to check that everything is still submerged.
• Discard your ferment if you see black or brightly coloured molds.
• Discard your ferment if it smells really awful. If you’re not sure what I mean by this, believe me you’ll know.
• Keep your ferments out of direct sunlight.

Ways To Use Fermented Onions

• Top burgers or sausage. 
• Mix into a Greek salad.
• Use as a condiment to add acidity and brightness to a dish.
• Add colour and nutrition to your plate.
• Top scrambled eggs or an omelette.

How to Ferment Onions

1. Choose a mason jar that is the appropriate size to fit the sliced onion. I used a 16 oz wide mouth style mason jar. Place the mason jar on your kitchen scale and press tare to zero out the weight of the jar.
2.  Fit the sliced onion into the mason jar and pour in enough water to cover the onions. Take note of the total weight in grams of the onion and water combined. To determine the amount of salt you need to add in grams, multiply that number by .02.
3. For example If the weight of the onion and water combined is 800 grams then you will multiply 800 by .02 and get 16. I would add 16 grams of salt to my jar.
4. Tare the scale again and add the amount of salt in grams that you determined in the above step. Put on the lid and shake well to dissolve the salt.
5. It’s very important to keep the onions submerged. To do this you can use fermentation weights, pinch bowls, small mason jar or a plastic sandwich bag filled with a little water. (See photos for examples.)
6. Leave your ferment at room temperature away from sunlight for 4-7 days. Check it once a day to make sure the onions are submerged. Open the lid slightly on a daily basis to prevent pressure from building up in the jar. Close it again tightly.
7. Once your fermented onions have reached the desired flavour, place the jar in the fridge. This will halt the fermentation process. Your fermented onions will now keep for a very long time. Enjoy!

Frequently Asked Questions

What is lacto-fermentation?

Lacto-fermentation is the process of lactic-acid-producing bacteria breaking down the sugars or glucose in fruits, vegetables, or other foods into lactic acid. It does this in an environment free of oxygen. 
You can lacto-ferment many different vegetables or foods including meat or dairy. Some examples of popular lacto-fermented foods would be yogurt, sourdough bread, sauerkraut and cucumbers. 

Does lacto fermentation produce alcohol?

Yes, lacto fermentation can produce trace amounts of alcohol. This happens as the bacteria breaks sugar down into lactic acid. Typically the alcohol content is very minute but the longer a ferment is left out at room temperature, the more risk for the alcohol content to increase.

What salt is best for lacto fermentation?

The best salt to use for lacto fermentation would be either unrefined sea salt or pickling salt.  Avoid using an iodized salt like table salt or a heavily refined salt as this can affect your ferment.

More Recipes to Enjoy Around the Table

Tools You May Need For This Recipe

Kitchen Scale

Mason Jar

Fermentation Weights

Pickling Salt

Noma Guide to Fermentation

Fermented Onions

If you make this recipe please leave a comment and give this recipe a rating! I aim to respond to every single comment. I am so grateful when you trust me and try one of my recipe creations in your own kitchen. I love to hear how it went!  Let’s connect on Instagram and tag me in your food pics!

‘Til next time,

Christy