What is koji?

Traditionally made koji

The Japanese cuisine is deeply rooted in fermentation and the koji is very centre of it. No koji means no sake, nosoy-sauce, no miso. All condiments which characterise much loved Japanese cuisine wouldn’t have existed. In the long history of Japan, koji has been a major driver in the development of its food culture.

So, what is koji, then?

“Koji” refers to koji microbes (The scientific name is Aspergillus oryzae) grown on steamed grains such as rice, soybeans or barley (In my house, when bread becomes mouldy, its colour is green, meaning koji is grown on the bread as the koji making is so intertwined with my daily life). Koji is essential for the fermentation processes used to make sake, soy sauce and miso.

Let’s see the historic side of it.

Japan is a beautiful mountainous country with lots of active and dormant volcanoes and is surrounded by the ocean. However, because of these unique geographical settings as well as the fact that it is located on the pass way of tropical typhoon, it has often been struck by major natural disasters from ancient times. The Japanese ancestor believed these disasters were underlined by the god’s anger and made offering of foods (typically rice) to shrines. As Japan is a country of high-temperature and humidity, it is not hard to imagine that the rice quickly became mouldy and then turned into sake. This very mould is koji.

As in many other culture, then Japanese regarded sake being special medium to communicate with gods (because when you drink, your mind is freed from reality and you see different world as if you trance to spiritual world) and hence believed this holy mould, which turns rice gratefully into sake, was a gift from them. Sake is deeply intertwined with the concepts of Japanese religion, which in turn led to the development of traditional performing arts and music. From this sense, you could say that the whole of Japanese culture has been nurtured by koji.

What does it do? What’s so special about it?

In the turn of modern time, koji’s power was scientifically analised and various fact was revealed. The results were probably far more astonishing than Japanese ancestors would have thought. Koji is nothing like any other creature on this planet. It is sensitive, friendly and unselfish, yet capable. I will go into detail about this in my workshops, but in one word, koji produces numerous kind of abundant enzymes when it grows which is very useful in culinary, medical and environmental application.

In culinary application, the enzymes create new flavours and taste which didn’t exist in the original ingredients while they break down the larger molecules into smaller one. As a result, sweetness is created, umami is created. Because of the sweetness, yeasts are attracted and start producing alcohol. Lactic bacteria are attracted and start producing sourness.

Apart from sake, miso, soy sauce, rice vinegar, in Japan, koji is used to make shio-koji (it is called koji cure in Noma’s book) and amazake.
Shio-koji is called a miracle condiments as it makes the food tastier. By simply marinating, value chicken will be turned into premium chicken!
Amazake is a very healthy sweet rice drink made from rice, koji and water. Without a single crystal of sugar, it makes sweet refreshing drink with myriad of good nutrition (vitamin B, all essential amino acids, dietary fibres, oligosaccharide).

These are just a few of koji application. The possibility is limitless. Why don’t you discover your own use of koji’s robust power? 

Welcome to the wonderful world of koji!

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Latest News

11 May 2021

Will be back in Stroud Green

We will be back in Stroud Green. Koji natto, Pink shiokoji, Spicy soy dressing, Miso sesame dressing, Wild garlic pesto
11 May 2021

Koji for Life 6 copies remaining

Only 6 copies left in stock. Order now to avoid disappointment
11 May 2021

Koji starters restocked

Premium koji starters from Hishiroku restocked - 40 bags for rice and 20 bags for protein substrates

Koji Making - Online

The online koji making class takes place over the span of 10 days. The class structure is as follows.

Day 1       Guidance session (Zoom 1 hour):

What is koji?   Koji making overview Tools & equipment required

Day 7-9 Practical (Zoom & Facebook Live):

Day 7  Steam Inoculation Zoom 4 hours) Day 8  Mixing (Facebook Live) Day 9  Drying(Facebook Live)

Day 10     Wrap up (Zoom 1.5 hour)

        Review, Troubleshooting, QA         Koji application

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