The word for salt in Japanese is shio [塩], so shio-koji is essentially salt koji. While some call it a koji marinade or a koji cure, it is best to use whatever term comes most naturally to you.

Shio-koji is made by mixing rice koji, salt, and water, then leaving it to mature slowly at room temperature for about one to two weeks. This process allows the sweetness, umami, and enzymes within the rice koji to be released, resulting in a rich and flavourful seasoning.

The Power of Enzymes

While it is a healthier alternative to salt, saying it is just a substitute sells its potential short. When rice koji is used to make shio-koji, some 100 or so enzymes produced during the growing process meld into the water and salt mix. Two in particular are the heavy lifters of your larder:

Protease: This enzyme breaks down proteins to produce amino acids, the building blocks of umami.

Amylase: This enzyme breaks down starch to produce glucose and oligosaccharides, providing a deep, natural sweetness.

Finding Your Level

Having a stock of shio-koji is absolutely essential to making the majority of recipes in this collection. You can access it in three ways depending on your ambition:

Beginner: Buy ready-made shio-koji from a Japanese or Asian grocery retailer.

Intermediate: Buy ready-made koji rice and combine it with salt and water yourself.

Advanced: Make your own rice koji from scratch at home.There is no shame in starting at the beginning; once you see the results, we’re confident you’ll be inspired to move up the levels.