Koji, my favorite mold

Today, I’d like to write a post about my favorite mold, Koji or Aspergillus oryzae. Koji is a mold that has been used by the Chinese for over 2,000 years and about 1,500 in Japan. In Chinese, it takes the name Qu麴 or QuJun 麴菌. Because Japanese is so much easier to pronounce, along with the western world being obsessed with Japanese food the last decade, the Japanese pronunciation is used.

What is Koji?

Simply put, Koji is a mold which possesses a ton of different enzymes which break down starches(amylase), proteins(protease), and fats(lipase). It is prominent in foods all around Asia, but is most integral in Japanese food. If you have ever eaten Japanese cuisine, you are certain to have consumed multiple products made using koji. From soy sauce and miso soup, to a koji salt mixture used in marinating or even sake, almost every aspect of Japanese food will be intertwined with koji’s influence.
For those who need a refresher on how important enzymes are, consider someone who is lactose intolerant. Lactose is the sugar in milk, that is broken down by the enzyme lactase. The enzyme lactase breaks down lactose into one glucose and one galactose molecule, both easily digested. If someone doesn’t have that enzyme, they will have a lost of gastrointestinal distress after consuming a dairy product. Because of the necessity of lactase to break down milk sugar, milk stouts are often quite sweet. I will write another post about that in the future.

How does koji affect flavor

Koji breaks down many components of food, bringing out a much richer flavor as a result. Starches are broken down into many kinds of sugars, fats are broken into different fats, and proteins are broken down into amino acids. This will add a depth of flavor complexity that the original ingredient would not possess. Many will note that it largely brings out umami, or savoriness. Additionally, Koji will act as a tenderizer to most things it is put on, because it breaks down parts of food that may be tough.

How is Koji used

Koji is used in an immense number of ways all around Asia. It is used in both foods and drinks. Soy sauce, rice wine, miso, and even beer. I have even tried to use it with coffee, but it is too dense for the mold to penetrate the outer layers. If you want to play with enzymes and coffee, adding amylase to an arabic style boiled coffee at low temperatures gives very interesting flavors.

How to get koji

It is important to note that Koji can be one of two things. Koji can be used to refer to an inoculated grain, most commonly rice or barley, or the spore itself. If you want to grow the spore yourself, stay tuned as I will write a guide all about how to grow it. If you want to save some time and effort, you can also buy pre inoculated and dried rice koji easily on amazon. This will work for most applications, but you wont be able to try out as many new applications as you would with the spores. Koji spores are also available on amazon. Naturally there are many different varieties, which I will write about in the future, but to begin with simplicity is key.

More about Koji

If you like Koji, there are a couple books I recommend. The first is a bit old, and more about miso than koji, but it is an amazing resource. The Book of Miso is excellent if you care at all about Japanese food culture. The second book is newer, The Noma Guide to Fermentation, which has a great section dedicated only to Koji. It is an excellent book if you like food in general. Finally, if you want to brew sake, read this.

As this is my first blog post, I don’t want to get too carried away with it. I would like to end with some questions. Have you ever heard of koji before? If so, have you used it? What kind of foods would you like to try using it on? Please leave your thoughts in the comments, and have a great day.