Koji is prepared by adding koji mold to steamed grains (rice, barley, soybeans, etc.).
It is then carefully cultured in warm, humid conditions that promote propagation.
Koji mold spores are just 3 to 10 μｍ (micrometers) in size.
* 1 μｍ = 0.001mm.
In 2006, the Brewing Society of Japan designated koji as "a valuable asset carefully nurtured and used by our ancestors," and certified koji as Japan's "national mold". Ancient people recognized koji mold from among various molds as valuable, and used it for miso, soy sauce, Japanese sake, etc.
Mainly used in the production of miso, soy sauce, and refined sake.
The spores are yellow, light green, or yellowish brown.
Mainly used in the production of shochu. The spores are brown.
Mainly used in the production of “awamori” (Okinawa liquor).
The spores are blackish brown.
Used in the production of tofu-yo, Chinese red wine, and Shaoxing wine. This mold produces bright red koji.
Use in the production of katsuobushi (dried bonito).
This mold absorbs residue moisture from the katsuobushi, produces umami components, and breaks down fats and oils.
Ingredient for rice miso, Japanese sake, mirin, vinegar, and amazake.
Ingredient for barley miso and shochu.
Ingredient for soybean miso.
Koji contains many enzymes. The role of enzymes is to break down the nutrition in food, and aid in digestion and absorption. They also help in converting absorbed nutrition into energy.
Koji is said to contain more than 30 types of enzymes including amylase, protease, lipase, and pectinase. Koji is a treasure trove of enzymes. Since it can generate vitamins beneficial for women and aids in digestion, it has gained popularity in the beauty and health fields.
Enzymes break down nutrients so they can be easily digested and absorbed. They create amino acids that produce umami, and aids in the tenderizing of food.
Amylases found in koji breaks down starch into glucose, and proteases break down protein into amino acids. Foods are eaten after the nutrients have been partially broken down by the enzymes, so nutrients are easily digested and absorbed in the body.
Good bacteria, such as lactic acid, love the oligosaccharides and dietary fiber* produced by koji enzymes. They consume these substances and produce more good bacteria.
*Dietary fiber is a component originally found in the koji.
As the bacteria metabolizes, it releases vitamins necessary for skin metabolism, such as vitamin B1, B2, B6, niacin, biotin, pantothenic acid, and inositol.
The pressure required to cut pieces of chicken, beef, and pork that have been marinated in shio koji for 30 minutes at 86F was measured using a stress rupture test.
Compared to meat that had not been marinated in shio koji, the pressure required to cut the chicken and beef was 38% less, and 18% less for pork.
* Stress rupture test ... Measurement of pressure needed to cut meat.
Lightly coat the fish with shio koji, and let marinate for 30 minutes to overnight. Lightly wipe off the shio koji before cooking.
Lightly coat the meat with shio koji, and let marinate for 20 to 30 minutes. Lightly wipe off the shio koji before cooking.
For cucumber pickles, rub koji all over the cut vegetable for approx. 15 minutes.