The term “Koji” can refer to the “Koji-kin” fungus which is sprinkled onto rice and propagated or the resulting “Koji-mai” the “Koji rice” which is the resulting saccharified rice from this propagation as the fungus breaks down the starches in the rice into the smaller sugars. Its technical name is “Aspergillus Oryzae”.
Nowadays, in the West, the term “Koji” tends to refer to the Koji rice and it is fast becoming the latest new and exciting ingredient in top restaurants.
So, what is Koji rice and why is it such an interesting ingredient?
Traditionally, Koji rice is the first stage in the fermentation process to make four of the main, traditional Japanese condiments used in cooking; miso, soya sauce, sake and vinegar. It is added to other ingredients for a second stage of fermentation; soya beans and salt to make miso; roasted wheat, soya beans, salt and water to make soya sauce; steamed rice, water and yeast to make sake.
Koji is a micro-organism that creates enzymes which transform the flavour and texture of food creating fermentation. It creates the enzymes responsible for umami, the fifth taste which has been described as savouriness and deliciousness.
In Japan, Koji rice is used to make home-made miso, Amazake (a sweet rice drink), Shio-koji pickles and more recently to make roasted Koji tea which has lovely caramel aromatics. In non-Japanese cuisine, Koji rice has been used to cure meat increasing the umami content, in ice cream, bread, a parmesan style ricotta and to make butternut squash miso. Furthermore, meat and fish are marinated with Shio-koji (a salted Koji rice paste) and Amazake.
In Japan, Koji is revered due to its ability to create umami and the traditional condiments without which Japanese cuisine would not take the form it currently has. 12 October has been named as National Koji Day and there is even a very popular Koji manga character called “Moyashimon”.
During my research into koji I came across this podcast on Koji from the US which may be of interest.