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Hakkou Tamanegi (Fermented Onion Sauce)


I am a big fan of fermented foods. I like to try new things, so I decided to make hakkou tamanegi, which is a fermented (salt brined) onion sauce.

The recipe seemed simple enough:

Hakkou Tamanegi (Fermented Onion Sauce)


  • 1 onion (about 200 grams)
  • 6 grams salt (3% of the weight of the onion)
  • 100 ml water


  1. Finely dice the onion
  2. Put it in a ziplock bag
  3. Add salt
  4. Seal the bag
  5. Squish around the onion in the bag until the salt is well distributed
  6. Open the bag and add the water
  7. Close the bag, squish the contents around a bit, push out any extra air, and tightly seal the bag
  8. Lay the bag on a tray and keep at room temperature until the water gets a little cloudy and the sharpness of the onions is gone (1-3 days in spring, or 3-6 days in winter)(do not try this when it is hot, especially in the summer)

Important Notes:
Try this at your own risk.
Wash hands thoroughly and always use clean, sterilized equipment in a clean environment.
Be diligent in checking the sauce as it ferments to detect any unwelcome changes.
If the sauce appears to have gone bad or smells bad, throw it away.


The part of the recipe that states to ferment the sauce “until the water gets cloudy” sounds kind of scary…

That is, there is probably a fine line between “this is nicely fermented” and “this is just plain old rotten”…

In any case, I decided to make the onion sauce, being careful to keep a close watch on its fermentation.

Day 1:
Here is the onion sauce on the first day:

Day 1: hakkou tamanegi, a fermented (salt brined) onion sauce
Day 1: hakkou tamanegi, a fermented (salt brined) onion sauce

Day 6:
And below, here it is on day 6 (@12°-14°C room temperature). It finally fermented into a somewhat mellow sauce.

Day 6: hakkou tamanegi, a fermented (salt brined) onion sauce
Day 6: hakkou tamanegi, a fermented (salt brined) onion sauce


After the onion sauce has reached a nice level of fermentation, transfer it to a sterilized jar and keep it in the refrigerator.

Use a clean spoon to scoop out the sauce.

Finish the sauce within two weeks from the initial date that it was made.

Final verdict:

This onion sauce never reached the level of fermentation that I had hoped for.

The sharpness of the onions was gone, but I had hoped for a much deeper, umami taste.

Dealing with room temperature fermentation is risky and a bit tricky due to a combination of environmental factors. If I make the onion sauce again, I think I will try tweaking the recipe a bit.

Posted in Food, Side dish