Koji is one of the greatest products in the fermentation world. It is the fungus Aspergillus oryzae that produces enzymes and devours everything that gets in his way. Starch breaks down into natural sugars, proteins into umami-flavored amino acids, and fats into tasty fatty acids. It is the start for making your own miso, mirin, saké, shoyu, tamari and amasaké.
Koji is a rice grain that has been introduced with a live culture (Aspergillus oryzae) and is one of the main ingredients in making soy sauce and miso paste. When koji is mixed with cooked beans like soy, the live culture helps break down the carbohydrates, amino acids, simple sugars, and proteins in the soybeans.
Koji fungus conidia are used both in brewing industry production (Koji Starter) and in the manufacture of mold to produce enzymes and antibiotics. Mold can be called a bacillus giving a bad impression. However, Japanese focus on the time-honored koji fungus’s excellent properties which are put to use in the production of traditional fermented foodstuffs such as sake, shochu (white distilled liquor), mirin (sweet sake used for seasoning), miso, soy sauce, vinegar , amazake(a sweet drink fermented from rice) and Shio Koji. These fermented foodstuffs have been at the heart of the Japanese diet for centuries, making a fundamental contribution to the longevity of the Japanese people. Due to world-wide recognition of the value of koji fungus, proposals have been made to designate it the “National Fungus”. Koji fungus is drawing attention as a host in the large-scale manufacture of beneficial products.
While the history of fermented foodstuffs is long, the history of independent production and selling of koji starter is surprisingly short, dating from the end of the 19th century. Until this time koji production and sales were monopolized by a guild of koji craftsmen. They sold koji but did not sell koji starter, jealously guarding the secret of koji. First koji was made from ambient fungus adhering to a cultivation medium (usually rice or barley); the good koji was selected and was used as koji starter. Nowadays there is an established technique for the unadulterated cultivation of superior koji fungus strains.
Koji starter is sown on hydrated and steamed cereals (rice, barley, soy beans) and is cultivated under temperature conditions suitable for the growth of koji fungus. The resulting koji contains such a wide variety and large amount of enzymes that it is called “an enzyme treasure trove”. The enzymes act to break down the cereals. Moreover, koji itself is a nutrient rich food full of sugars, amino acids, vitamins and minerals produced by the koji fungus. The raw materials, the koji starter and environmental factors (heat and moisture) determine the kind of koji produced resulting in a wide variety of tastes in the products (sake, miso, soy sauce etc) which delights the palate.