From kitchen to health: The wonders of Onion Koji

Discover the remarkable fusion of flavour and wellness with onion koji! In our previous article on Shio Koji recipes, we explored the fascinating enzyme-rich condiment that breaks down protein into amino acids. Now, imagine combining the power of shio koji with the incredible health benefits of onions. The result is a transformative blend that not only enhances your meals but also nourishes your body from within.

Onions, known for their high fibre, mineral, and vitamin content, become even more extraordinary when paired with shio koji. The oligo sugar found in onions, along with the magic of shio koji, acts as a gentle cleanser for your stomach, promoting better digestion and leaving you with radiant skin. Additionally, this dynamic duo supports healthy blood circulation, ensuring your body stays in prime condition. The best part? Creating these incredible onion koji condiments is a breeze, allowing you to effortlessly embark on a journey towards better health and exquisite flavours. Get ready to unlock the secrets of onion koji and savour a world of wellness and culinary delight!



  • 200g rice koji (you can find it on Amazon but also in Japanese supermarkets)
  • 2 onions (about 300g)
  • 70g sea salt



  1. Blend chopped onions with a blender. You can also finely chop it with your knife or use a food processor or grate with a box grater.
  1. Mix rice koji and salt in a bowl.
  1. Add blended onion into the bowl and mix well. Add water little by little if necessary. (Depending on the water content of the onion. I added about 150ml of water to make this consistent in the photo.)
  1. Pour the mixture into a sterilised container.
    Leave the lid lightly open to remove the gas during the fermentation. Keep it in a dark place.
  2. Mix it with a clean spoon every day to enhance the fermentation process. It takes about a week or ten days to be ready to use. Once prepared, keep it in a fridge and use it within two months.

I took some photos of the fermentation process, so let’s look at how it evolves.

Day 2

The dried rice koji sucks the moisture and expands. I mixed the onion koji with a clean spoon and added some water to bring it back to the right consistency. I mixed it well again and left it on my kitchen counter.

Day 3

The water content seemed enough, so I mixed and left for the day. Same for the days 4 and 5.

Day 6

The colour is entirely different! It’s getting brown, and the smell is sweeter now.

Day 9

The onion koji seems softer, and the smell is even sweeter! I think it’s ready, so let’s move it to the fridge. Yippee!

If you prefer, blitz the onion koji into a puree to have a smooth texture.

If you have a yoghurt maker,

I recently bought a yoghurt maker to make amazake – which I will write about soon! This equipment is ideal since we can keep a specific temperature to help with fermentation. So if you have one, set the temperature to 58 degrees Celsius and keep it for roughly 10 hours. Then it’s done! It makes it much easier to make any fermented food.

Lakeland Multi Yoghurt and Soft Cheese Maker

I love using this to make

  • Homemade vegan kimchi
  • Soup
  • Stew
  • Marinade
  • Dressing

I made some vegetable curry recently and added this onion koji at the end to season it. I used it as an alternative to salt, but it also got some umami! It was delicious!

Closing words

So there you have it, my new favourite healthy condiment, “Onion Koji”. Hopefully, this method makes it easier for you to try. If you have any questions, get in touch via our social media, and we’ll get back to you shortly; Instagram, Pinterest, and Facebook pages. Don’t forget to subscribe to our newsletter,