Shio Koji: The Secret Weapon In Japanese Cuisine Is Simple, Versatile and Alive!

Also known as Aspergillus oryzae, kōji is the national fungus of Japan. It is also the powerful little microbe responsible for many of the ingredients that make up the foundation of Japanese cuisine like miso, mirin, shōyu, and sake.

When speaking of kōji, however, the term kōji is used when referring to both the microbe itself as well as the kōji-cultured grains used in fermentation. Rice and barley, and even sometimes soy beans, are first inoculated with the kōji mold and then fermented to create the mother kōji culture. That culture is used to create many delicious fermented ingredients.

One of the most common mother cultures, responsible for the likes of miso and shoyu, is called kome-kōji (米麹/米粉) or rice kōji.

Along with shōyu and miso, kome-kōji is a key ingredient in the production of mirin, sake, and another lesser-known traditional staple of Japanese cooking called shio kōji (塩麹), or salt kōji. 

Like shōyu and miso, shio kōji is a powerfully rich seasoning agent that can be used as a marinade or a substitute for salt. It can also be used to cure and preserve foods as well.

There are some differences between shio kōji and shōyu and miso, however, namely being the way in which it’s produced and the way it flavors the ingredients it’s combined with.

Unlike the laborious process of creating shōyu, shio kōji is a simple a mixture of kome kōji, salt, and water. The mixture is then left to ferment and develop its flavor as the microbes do their work, turning something that was once dominantly salty into something mildly briny with a faint sweetness.

It is the rich umami flavor that shio kōji develops as it ages that makes it such a versatile seasoning. In fact, it has experienced a resurgence in popularity in Japan in recent years where shoyu and miso reign supreme.

One key characteristic working towards shio kōji’s resurgence is its versatility and the health benefits it’s purported to offer. 

Both of these factors are tied directly to the fact that shio kōji is a living, natural ingredient. When it’s added to a recipe, shio kōji works to deepen the richness of the other ingredients as the active enzymes break down starches and proteins, releasing sugars and amino acids. Additionally, the enzymes produced through fermentation make it a great tenderizer and marinade for ingredients, while also offering some probiotics to aid in digestion. 

The simplicity and versatility shio kōji offers makes it a necessity in any kitchen, and not just when working with Japanese recipes. There aren’t any complicated steps to incorporating it into a recipe, all one needs to do is substitute one teaspoon of salt for two teaspoons of shio kōji. The rest is up to the cook to explore and experiment with the ways they enjoy introducing it into their cooking.

So give making shio kōji a try if you want try your hand at some simple fermentation, or just use some pre-made shio kōji. Incorporating it into your next recipe might even help you to get closer to defining your wa.

To find out more about what washoku is and what that might mean to you, check out our previous article Washoku: Japanese Cuisine. And to try creating your own Japanese dishes at home, try our Creative Beginnings: Redefining "Wa" Care Package.

About the author

The spark that lit Kevin Kilcoyne’s interest in Japanese culture began in elementary school through a friendship with his then classmate Keisuke. Since then, that passion has evolved and bloomed to encompass more than just video games and manga, leading Kevin to live in Japan as a participant of the JET program. During his time in Japan, Kevin sought out as many foods as he could, the experiences and taste memories lingering long after they had gone. Now he is forging a path to link his passions for Japanese food, history, and visual culture and is planning for his return to live in Japan once again. For now, you can find Kevin on Instagram (@kevinjkilcoyne) where he posts his photography and illustration work. Keep an eye out for more posts and updates as Kevin delves more deeply into his passions for writing and food.