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Cultured Guru is an Educational Health & Wellness Brand and a Fermentation Company.

Created and Operated by Microbiologist Kaitlynn Fenley and Photographer Jon Scott Chachere II.

Fermented Foods | Better than Pickled Red Onions

Fermented Foods | Better than Pickled Red Onions

I LOVE fresh and pickled red onions... a lot. We always have red onions in our house and we never, ever run out. We put them in quinoa bowls, in burrito bowls, on avocado toast, and pretty much any savory meal. Want to know what we love more than pickled red onions though? Fermented Red Onions! It's the same great taste of pickled red onions, but with an awesome benefits fermented foods provide: gut health! We PROMISE they are worth the wait! 

Pickled Red Onions are Good, BUT Red Onions as a Fermented Food are Even Better!

We fermented some for two weeks and some for four weeks, and they are delicious! I prefer the four week fermented batch because they are just a bit more tart. Four weeks allows for the Lactobacillus in stage three of the fermentation to make more lactic acid, dropping the pH a bit more, and allowing the flavor to develop. 

If you are curious what the elusive probiotic Lactobacillus look like, here is a picture from my microscope:


Fermented Foods | Better than Pickled Red Onions

This is a diluted sample of the two week fermented red onion brine. It's rich in probiotic Lactobacillus and there are still a few Leuconostoc bacteria remaining. The chain of rod shaped bacteria in the middle is Lactobacillus. The two little round bacteria to the right are Leuconostoc bacteria. The big blob to the left is a piece of onion.  I love using microscopy, because it validates the safety and probiotic quantity of everything we ferment.  When developing recipes we always keep the focus on the microbes, what's best for selecting just friendly species of microbes, and what allows for a high population of those friendly microbes. Then we share recipes like this based on science and facts! 

Fermented Foods | Better than Pickled Red Onions
Fermented Foods | Better than Pickled Red Onions
Fermented Foods | Better than Pickled Red Onions

Mastering Fermented Foods

If you're going to master fermentation you'll need to use weight measurements for your fermentation ingredients. That means you need a kitchen scale. In order to select for the best probiotic bacteria (the ones that are actually beneficial) in your ferments, you must weigh salt to create a specific salt concentration. Weighing salt is the only way to create a salt concentration that will select for only probiotic microbes to thrive. You can read more about why you must weigh your salt here.

This is the scale we use in our home kitchen to weigh salt.  

We Recommend either one of these scales:


Supplies You Need to Make Better Than Pickled Red Onions:

Fermented Foods Better than Pickled Red Onions

Better Than Pickled Red Onions




  1. Wash your fermentation equipment (jar, weight and lid)
  2. Peel then wash your red onions in cool water. Using a knife, slice your onion to desired thickness.
  3. Place your kitchen scale on the counter. Turn it on and set it to weigh in grams.
  4. Place a mixing bowl on your kitchen scale and tare/zero the scale. Note: Taring/zeroing the scale with a container on it subtracts the weight of the container, allowing you to weigh only what is added to the container. After taring/zeroing the scale, the scale should read 0.0 with the container on it.
  5. Add chopped onion into the bowl on your scale until the scale reads 200 grams.
  6. Remove the bowl from your scale and set aside. Place your empty, clean mason jar on the scale, and tare/zero the scale. Make sure your scale is still set to grams and add 200 grams of filtered water to your mason jar.  
  7. Add the 200 grams of onions from your bowl, into the mason jar with water.
  8. Place a small bowl on your scale and tare/zero the scale. weigh out 10 grams of salt. Then add the 10 grams of salt to the jar of onions and water.
  9. Place your standard mason jar lid on the jar, and secure. shake the jar vigorously for 2 minutes.
  10. Remove the silver standard mason jar lid. Place your fermentation weight in the jar making sure to submerge the onion pieces and weight fully in the liquid.
  11. Secure the standard mason jar lid, or your airlock lid to the mason jar.

How to Care for Your Fermented Foods 

Better than Pickled Red Onions Tips

During the first few days of fermentation: carbon dioxide and bubbles will be produced. Sometimes Jars will become very full with liquid, and this liquid can seep out. 

  • If using a standard mason jar lid: remove the lid and tamper everything back down using a gloved hand, tamper or spoon. Make sure everything is still submerged below the brine.

  • If using a silicone airlock lid: If liquid comes out of the top of the lid, you can remove the lid and tamper everything back down, or you can leave the lid on and just rinse the top off in the sink.

Always Trust your sense of smell: Fermented onions should smell pleasantly sour and a bit oniony. Never eat anything that smells repulsive. 

Never eat anything that had mold growing on it: By following directions you should not encounter this problem. 

Taste test at two weeks: If you prefer the onion to be more tart and sour, let them ferment for two more weeks. 

What Temperature Should I Keep My Fermented Foods At?

Keep your fermenting red onions at a temperature between 70-80 degrees F. Keep out of direct sunlight

How Long Should I Ferment My Better than Pickled Red Onions 

After 2-4 weeks, remove the fermentation weight and smell and taste test. Your fermented onions should smell oniony and pleasantly sour. They should taste tart and full flavored. 

Do I Need to Refrigerate My Better than Pickled Red Onions

After fermenting for 2-4 weeks, place a regular mason jar lid on the jar and refrigerate. Consume within 6 months for full probiotic benefits


Better than Pickled Red Onions Fermentation Timeline

We tracked our onions throughout the fermentation process. By checking the progress of microbial stages under the microscope we have provided you with this handy timeline! If you follow our recipe and directions, your timeline of red onion fermentation should approximately match ours! 

24 - 72 hours: all contents in the jar should be submerged beneath the brine. At this time there are still Gram negative bacteria and possible pathogens present. 

72 hours - 5 days: After 72 hours you should start to see lots of bubbles being produced. This is the stage in which you will burp the jar. This is when the ferment enters stage two of vegetable fermentation. Leuconostoc bacteria begin to thrive and produce a lot of carbon dioxide. Gram negative organisms die off. 

5 - 14 days: The bubbles in the brine will decrease, as the ferment leaves stage two and enters stage three. The red onions will become cloudy and start to develop a pleasant sour smell. The onions will also start to turn fully pink. Lactobacillus species are most abundant during this time period.

14 - 28 days: Lactobacillus make up majority or all of the microbial population. They produce copious amounts of lactic acid, and make the ferment smell even more pleasantly sour. This is the time in which the vegetable mixture becomes preserved. This is when you want to smell and taste test.
 30 days: Wait for the onions to smell and taste as you like, and refrigerate when you find the smell and taste most pleasant! We like ours best when we refrigerate at about 30 days, but they are also good at around 15-20 days. The longer the red onions ferment, the more the flavors develop.

Best Tea for Gut Health

Best Tea for Gut Health

Vegan Sandwich Recipe | Vegetable Sandwich with Probiotic Fermented Dill Pickles

Vegan Sandwich Recipe | Vegetable Sandwich with Probiotic Fermented Dill Pickles