Supermarkets of mystery - Koji ~ Japanese rice mold

Fermentation. Umami. Mold. Now that we've got all the buzzwords out of the way, we can freely talk about the moldy Japanese rice grains called koji that create all the flavour in the soy sauce, miso and sake products we love.

Koji is high up on the food buzzword bingo along with most fermentation, preservation and natural food curing processes. We are interested in the use of it as an additional way of adding flavour to our cooking. Our dabbling in Japanese cooking techniques is fairly limited but our enthusiasm for Japanese flavours is endless. After reading Preserving the Japanese Way: Traditions of Salting, Fermenting, and Pickling for the Modern Kitchen by Nancy Singleton Hachisu and fan-girl squealing when she turned up in the cooking show Salt, Fat, Acid, Heat, we were interested in exploring more about this technique for preserving and adding flavour to food. Finding some koji at Tokyo Mart we took the plunge to try it out.

Out of the pack koji looks like rice that has powdered up and clumped together. It is rice indeed, and the white powder is a mold that has formed on the rice and holds all the flavour power.

There's two types of koji we are keen to make - a shoyu and and shio base, one soy one salt. We used guidelines from the website Cooking with Koji, an excellent resource for all things miso and mold. 

First step, we split the whole packet between two large clean jars.

To make Shoyu-koji: Pour the soy sauce (about 200ml, we used Japanese Yamasa brand) into the first jar with the koji rice until it looks like a jar of soggy coco pops. Stir the grains and soy sauce together, put lid on jar and wait.You can use in about a week, better after a month and even better the longer you can wait.

To make Shio-koji: We mixed about 3 tablespoons of salt in with the grains in the second jar. It's about a 30% ratio to the amount of koji grain you use, we weren't that exact. Pour in 200ml of plain water and wait. And wait. It will slowly change flavour after a couple of weeks. Keep in the fridge until you are ready to use it. It didn't seem to keep as well as the shoyu-koji so use up within a couple of months.

We find the best salt for pickling and general cooking use to be a Coles supermarket no name cooking salt. Other supermarket generic brands have added extras. The Coles brand doesn't have any anti-caking agent in it that can make pickle juices go cloudy. Check the ingredients list on the salt packet you want to use, it should just be 100% salt. Don't bother with fancy sea salts, good old cooking salt is fine here or just use what you fancy, as long as it is pure.

After a couple of days just check in with the jars as the contents will start to bubble as the mold spores do their work. Its alive! 

The shoyu-koji we use as a flavouring on cooked vegetables or on raw cucumber or fresh cold tofu. The shio-koji was a lot saltier and need only be used sparingly, mostly on pan fried chicken or a little on steamed vegetables, maybe a dab or two on stir fried strips of pork.

We bought our koji spores from the fridge at Tokyo Mart in Northbridge, about $4.00 a 200g pack.

We love Supermarkets of Mystery!