Used in Japnaese cooking for centuries, Koji:
♥ contains over 100 enzymes and essential amino acids
♥ aids digestion and absorption of nutrients
♥ adds umami flavour to your cooking
♥ tenderises fish and meat
Koji-kin, Aspergillus oryzae, has been used for centuries as one of the main ingredients in Japanese cooking. It has a special aroma which is often described as reminiscent of the scent of a chestnut flower and in its basic form has a sweet taste. Koji is an essential ingredient in Sake (Japanese rice wine), soy sauce, miso (soy bean paste), mirin (sweet rice wine) and lots of other products which together form the foundation of much of Japanese cuisine. Koji creates complex flavours with plenty of umami (the fifth taste which I will come back to) and has lots of health benefits (possibly being one reason behind Japanese people’s longevity).
The Koji-kin is grown on grains. In Japan steamed rice is commonly used as the growing medium, and this fermented rice with Koji-kin is called Koji. Koji is completely white and has a fur-like appearance. As it grows the Koji-kin produces over 100 kinds of enzymes and essential amino acids. These enzymes, such as amylase, protease, lipase etc., play a prominent role in breaking down starch into sugars, proteins into amino acids, fats and oils into fatty acids thus helping in the absorption of food and the maintenance of a healthy diet. It also contains a number of important vitamins such as vitamin B1, B2, B3(niacin), B5(pantothenic acid), B6, inositol and biotin. All are more easily absorbed since they are naturally rather than synthetically produced.
Now what is Umami? It has been known to the Japanese that there is another taste on top of the basic 4 tastes, sweet, salt, sour, bitter. However it was only a few years ago that western scientists understood that the tongue has a receptor of umami. It’s not easy to describe “Umami” taste, but this gives a depth of flavour to many foods and is the reason why people find that completely ripe tomatoes and long matured Parmesan cheese are so tasty. Umami is a backbone of lots of Japanese seasoning, such as soy sauce and miso (soy bean paste), and Japanese cooks have for centuries used umami flavour to enhance their dishes. Cooking, aging or fermentation is the way to release umami from food. Koji, as you know now, is fermented rice with Koji-kin. Koji-kin produces lots of enzymes when they grow on rice, and when Koji is used for cooking, like marinating fish or meat, those enzymes help convert protein in the food into amino acids, releasing the umami taste. As part of this process it also tenderises fish and meat, so a cheap cut of meat and fish tastes much better by being marinated in it.
If you are interested in Umami, this article on Guardian (http://www.theguardian.com/lifeandstyle/wordofmouth/2013/apr/09/umami-fifth-taste) is very informative.